2011
Manual for Railway Engineering
1
Volume 2
Structures
Chapter 7
Timber Structures
Chapter 8
Concrete Structures and Foundations
Chapter 9
Seismic Design for Railway Structures
Chapter 15 Steel Structures
General Subject Index
3
Copyright © 2011
by the
AMERICAN RAILWAY ENGINEERING AND MAINTENANCE-OF-WAY ASSOCIATION
All rights reserved
No part of this publication may be reproduced, stored in an information or data retrieval system, or
transmitted, in any form, or by any means—electronic, mechanical, photocopying, scanning, recording, or
otherwise—without the prior written permission of the publisher. Photocopying or electronic reproduction
and/or distribution of this publication is a violation of USA and International Copyright laws and is expressly
prohibited.
Correspondence regarding copyright permission should be directed to the Director of Administration, AREMA,
10003 Derekwood Lane, Suite 210, Lanham, MD 20706 USA.
ISSN 1542-8036 - Print Version
ISSN 1543-2254 - CD-ROM Version
7
CHAPTER 7
TIMBER STRUCTURES1
FOREWORD
The material in this chapter is written with regard to typical North American Railroad Timber Trestles and other
timber structures mentioned herein with
• Spans up to 16 feet,
• Standard Gage Track,
• Normal North American passenger and freight equipment, and
1
• Speeds of freight trains up to 80 mph and passenger trains up to 90 mph.
Special provisions for longer spans and/or higher train speeds should be added by the company as necessary.
This chapter is presented as a consensus document by a committee that comprises railroad engineers, engineers in
private practice, engineers involved in research and teaching, and other industry professionals having substantial
and broad-based experience designing, evaluating, and investigating timber structures used by railroads. The
recommendations contained herein are based upon past successful usage and are periodically updated to ensure
future successful usage. Therefore, as an ongoing concern, the recommendations printed herein are updated in
response to changes in the operating environment, changes in the designations and availability of material and
material systems, advances in design and maintenance practices, and advances in the state of knowledge overall.
These recommendations have been developed and are intended for routine use and might not provide sufficient
criteria for infrequently encountered conditions. Professional judgement must be exercised when applying the
recommendations of this chapter as part of an overall solution to any particular problem.
In general, this chapter is revised and printed anew on a calendar-year basis. The latest printed revision of the
chapter should be used, regardless of the age of an existing structure. For purposes of determining historical
recommendations under which an existing structure may have been built and maintained, it can prove useful to
examine previous printed editions of the chapter. However, when historical recommendations differ from the
recommendations contained in the latest printed revision of the chapter, the recommendations of the latest printed
revision of the chapter should be used.
1
The material in this and other chapters in the AREMA Manual for Railway Engineering is published as recommended practice to
railroads and others concerned with the engineering, design and construction of railroad fixed properties (except signals and
communications), and allied services and facilities. For the purpose of this Manual, RECOMMENDED PRACTICE is defined as a
material, device, design, plan, specification, principle or practice recommended to the railways for use as required, either exactly as
presented or with such modifications as may be necessary or desirable to meet the needs of individual railways, but in either event, with
a view to promoting efficiency and economy in the location, construction, operation or maintenance of railways. It is not intended to
imply that other practices may not be equally acceptable.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-i
3
TABLE OF CONTENTS
Part/Section
1
Description
Page
Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber
Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood . . . . . . . . 7-1-1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
Structural Grades of Softwood Lumber and Timber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Grading Rules for Hardwood Structural Timbers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications for Engineered Wood Products (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ordering Structural Lumber, Timber and Engineered Wood Products . . . . . . . . . . . . . . . . .
Specifications for Timber Piles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications of Fasteners for Timber Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications for Timber Bridge Ties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommendations for Fire-Retardant Coating for Creosoted Wood (1963) R(2008) . . . . . . .
7-1-3
7-1-3
7-1-3
7-1-6
7-1-7
7-1-13
7-1-16
7-1-20
2
Design of Wood Railway Bridges and Trestles for Railway Loading . . . . . . . . . . . . . . . .
2.1 Design of Public Works Projects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 General Features of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4 Designing for Engineered Wood Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5 Allowable Unit Stresses for Stress-Graded Lumber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6 Details of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.7 Recommended Practice for Design of Wood Culverts (1962) . . . . . . . . . . . . . . . . . . . . . . . . . .
2.8 Recommended Practice for Simple Stress Laminated Deck Panels. . . . . . . . . . . . . . . . . . . . .
7-2-1
7-2-3
7-2-4
7-2-7
7-2-11
7-2-20
7-2-38
7-2-39
7-2-40
3
Rating Existing Wood Bridges and Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1 Rules for Rating Existing Wood Bridges and Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-3-1
7-3-2
4
Construction and Maintenance of Timber Structures. . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Handling of Material (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3 Storage of Material (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4 Workmanship for Construction of Pile and Framed Trestles . . . . . . . . . . . . . . . . . . . . . . . . .
4.5 Framing of Timber (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6 Substructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.7 Superstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.8 Support, Repair, Preserve, or Replace Damaged Portions of the Structure (2010) . . . . . . . .
4.9 Methods of Fireproofing Wood Bridges and Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.10 Use of Guard Rails and Guard Timbers (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.11 Typical Plans for Timber Railway Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-1
7-4-2
7-4-3
7-4-3
7-4-3
7-4-4
7-4-5
7-4-14
7-4-14
7-4-18
7-4-20
7-4-21
5
Inspection of Timber Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1 General (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 Details of Inspection (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-5-1
7-5-1
7-5-2
6
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1 Materials Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2 Design Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3 Rating Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4 Construction and Maintenance Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5 Inspection Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-6-1
7-6-2
7-6-5
7-6-13
7-6-13
7-6-13
Chapter 7 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-G-1
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-ii
AREMA Manual for Railway Engineering
TABLE OF CONTENTS (CONT)
Part/Section
Description
Page
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-R-1
Appendix 1 - Contemporary Designs and Design Aids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-1
Appendix 2 - Temporary Structures . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A2-1
Appendix 3 - Legacy Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-1
INTRODUCTION
The Chapters of the AREMA Manual are divided into numbered Parts, each comprised of related documents
(specifications, recommended practices, plans, etc.). Individual Parts are divided into Sections by centered
headings set in capital letters and identified by a Section number. These Sections are subdivided into Articles
designated by numbered side headings.
Page Numbers – In the page numbering of the Manual (7-2-1, for example) the first numeral designates the
Chapter number, the second denotes the Part number in the Chapter, and the third numeral designates the
page number in the Part. Thus, 7-2-1 means Chapter 7, Part 2, page 1.
1
In the Glossary and References, the Part number is replaced by either a “G” for Glossary or “R” for References.
Document Dates – The bold type date (Document Date) at the beginning of each document (Part) applies to the
document as a whole and designates the year in which revisions were last made somewhere in the document,
unless an attached footnote indicates that the document was adopted, reapproved, or rewritten in that year.
3
Article Dates – Each Article shows the date (in parenthesis) of the last time that Article was modified.
Revision Marks – All current year revisions (changes and additions) which have been incorporated into the
document are identified by a vertical line along the outside margin of the page, directly beside the modified
information.
Proceedings Footnote – The Proceedings footnote on the first page of each document gives references to all
Association action with respect to the document.
Annual Updates – New manuals, as well as revision sets, will be printed and issued yearly.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-iii
4
THIS PAGE INTENTIONALLY LEFT BLANK.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-iv
AREMA Manual for Railway Engineering
7
Part 1
Material Specifications for Lumber, Timber, Engi-
neered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for FireRetardant Coating for Creosoted Wood
— 2011 —
1
TABLE OF CONTENTS
Section/Article
Description
Page
1.1 Structural Grades of Softwood Lumber and Timber. . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.1 Grading Rules (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.2 Preservative Treatments (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-1-3
7-1-3
7-1-3
1.2 Grading Rules for Hardwood Structural Timbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2.1 General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-1-3
7-1-3
1.3 Specifications for Engineered Wood Products (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3.1 Structural Glued Laminated Timber - Glulam (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-1-3
7-1-3
1.4 Ordering Structural Lumber, Timber and Engineered Wood Products . . . . . . . . . . . .
1.4.1 Inquiry or Purchase Order (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-1-6
7-1-6
1.5 Specifications for Timber Piles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5.1 General Provisions (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5.2 Classification of Piles (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5.3 General Requirement for All Piles (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5.4 Special Requirements for First-Class Piles (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5.5 Special Requirements for Second-Class Piles (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5.6 Inquiries and Purchase Orders (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-1-7
7-1-7
7-1-7
7-1-10
7-1-11
7-1-12
7-1-13
1.6 Specifications of Fasteners for Timber Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6.1 Material (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6.2 Types of Fasteners (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6.3 Use of Protective Coatings for Steel Fasteners on Timber Bridges (2008) . . . . . . . . . . . .
7-1-13
7-1-13
7-1-13
7-1-15
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-1-1
3
Timber Structures
TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
1.7 Specifications for Timber Bridge Ties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.1 Material (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.2 Physical Requirements (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.3 Design (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.4 Inspection (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.5 Delivery (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.6 Shipment (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.7 Dapping or Sizing Bridge Ties (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.8 Bridge Tie Installation (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.9 Preservative Treatment of Bridge Ties (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.10 Spike or Bolt Holes (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.11 Tie Plugs (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.12 Tie Branding (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.13 End Splitting Control Devices (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-1-16
7-1-16
7-1-16
7-1-16
7-1-16
7-1-17
7-1-17
7-1-17
7-1-18
7-1-19
7-1-19
7-1-19
7-1-20
7-1-20
1.8 Recommendations for Fire-Retardant Coating for Creosoted Wood (1963) R(2008) .
1.8.1 Scope (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.8.2 General Product Requirements (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.8.3 Application Requirements and Instructions (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.8.4 Testing (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-1-20
7-1-20
7-1-20
7-1-21
7-1-22
LIST OF FIGURES
Figure
7-1-1
Description
Page
Measurement of Short Crook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-1-12
LIST OF TABLES
Table
Description
Page
7-1-1 Typical Net Finished Glulam Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-1-4
7-1-2a Friction Piles – Specified Butt Circumference with Minimum Tip Circumferences for Coast Douglas Fir
Piles and Other Species, Except Southern Yellow Pine (See Note 1) . . . . . . . . . . . . . . . . . . . . .
7-1-8
7-1-2b Friction Piles – Specified Butt Circumference with Minimum Tip Circumferences for Southern Yellow
Pine (See Notes 1, 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1-9
7-1-3a End-Bearing Piles – Specified Tip Circumferences with Minimum Butt Circumferences for Piles of
Coast Douglas Fir and Other Species Except Southern Yellow Pine (See Note 1) . . . . . . . . . . . 7-1-9
7-1-3b End-Bearing Piles – Specified Tip Circumferences with Minimum Butt Circumferences for Piles for
Southern Yellow Pine Piles (See Notes 1, 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1-10
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-1-2
AREMA Manual for Railway Engineering
Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
SECTION 1.1 STRUCTURAL GRADES OF SOFTWOOD LUMBER AND TIMBER1
1.1.1 GRADING RULES (2010)
It is recommended that structural lumber and timber be purchased in accordance with the grading rules of the
industry’s agency publishing rules for the species. For allowable stresses for stress graded lumber and timber
generally used refer to Article 2.5.6.
1.1.2 PRESERVATIVE TREATMENTS (2010)
Pressure preservative treatments are listed in American Wood Preservers Association (AWPA) Standards.2
Retention and penetration levels are specified in AWPA Standards (C2, C4, C14 or C24 as applicable) in units of
pounds of retained perservative per cubic foot of wood and depth of penetration in inches. Creosote retentions
in the range of 8 to 12 pcf are common in railroad applications.
It is strongly recommended that all fabrication, trimming and boring of glulam members be performed prior to
the pressure treating process. If field fabrication is needed, surface damage, cuts and holes must be field
treated to protect any exposed wood. Field treatments in accordance with AWPA Standard M4 should be
specified.
1
SECTION 1.2 GRADING RULES FOR HARDWOOD STRUCTURAL TIMBERS3
1.2.1 GENERAL (2009)
Hardwood structural timbers shall comply with the requirements of Northeastern Lumber Manufacturers
Association, Inc. (NELMA), Chapter 6, Timber, Beams and Stringers, Posts and Timbers for the species and
grades listed in Part 2 of this Manual.
SECTION 1.3 SPECIFICATIONS FOR ENGINEERED WOOD PRODUCTS4 (2006)
4
1.3.1 STRUCTURAL GLUED LAMINATED TIMBER - GLULAM (2006)5
1.3.1.1 General and Appearance
a.
General
For allowable stresses for Glued Laminated Timber generally used refer to Article 2.4.1.2.
b. Appearance Classifications6
1
See Part 6 Commentary.
See Reference 7.
3 References, Vol. 65, 1964, pp. 393, 756; Vol. 89, 1988, p. 106.
4 References, Vol. 55, 1954, pp. 568, 1005; Vol. 56, 1955, pp. 641, 1071; Vol. 62, 1961, pp. 512, 848; Vol. 69, 1968, p. 362; Vol. 84, 1983, p. 81;
Vol. 89, 1988, p. 106. See Part 6 Commentary.
5 See Part 6 Commentary.
2
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
3
7-1-3
Timber Structures
For railway bridge stringer, pile cap, deck panel, and rail tie applications, the Industrial or Framing
appearance classifications should be considered.
Industrial Appearance: Voids appearing on the edges of laminations need not be filled. Loose knot
holes appearing on the wide face of the laminations exposed to view shall be filled. Members are
required to be surfaced on two sides only and the appearance requirements apply to these sides.
Framing Appearance: The Framing appearance classification permits "hit or miss" surfacing to
provide specialized finish widths of 3-1/2, 5-1/2 and 7-1/4 inches. This appearance classification may be
suitable for pile caps or bridge deck panel applications.
1.3.1.2 Layup Combinations1
For glulam members stressed primarily in bending, such as for railroad bridge stringers, layups of graded
Douglas fir (DF) and Southern pine (SP) lumber are used throughout the member depth based on the "Stress
Groups" shown in Table 7-2-7, selected specifically for the most commonly used applications. Stress Group
options for bending members shown in this table are defined by bending-stress/Modulus of Elasticity (MOE)
categories selected specifically as "Balanced Combinations" for railroad applications.
1.3.1.3 Balanced
These members are manufactured with symmetrical grade zones above and below mid-depth. Balanced beams
are used in applications such as continuous stringer applications, where the top and bottom of the member is
stressed in tension. Balanced beams are recommended for railroad use since preservatives may make it difficult
to distinguish the tension side.
1.3.1.4 Hardwoods
Hardwoods may be specified by special order in accordance with the Standard Specification For Structural
Glued Laminated Timber Of Hardwood Species, AITC 119.
1.3.1.5 Adhesives
Adhesives must be in conformance with specifications included in ANSI A190.1 for wet-use. Wet-use adhesives
may be specified for all moisture conditions and are required when the in-service moisture content is 16 percent
or higher for repeated or prolonged periods, or when the wood is treated with preservatives before or after
gluing.
1.3.1.6 Finished Sizes2
Table 7-1-1. Typical Net Finished Glulam Sizes
Nominal Width
3”
4”
6”
8”
10”
12”
Western Species
2-1/2”
3-1/8”
5-1/8”
6-3/4”
8-3/4”
10-3/4”
Southern Pine
2-1/2”
3”
5”
6-3/4”
8-3/4”
10-1/2”
Depths can be provided in multiples of nominal 1-1/2 inch for Western species or 1-3/8 inch for Southern Pine
laminations, or for special depths to be compatible with existing solid sawn installations.
6
See Part 6 Commentary.
See Part 6 Commentary.
2 See Part 6 Commentary.
1
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-1-4
AREMA Manual for Railway Engineering
Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
1.3.1.7 Preservative Treatments1
Pressure preservative treatments listed in American Wood Preservers Association (AWPA) Standard C28 for
glulam include creosote, pentachlorophenol and waterborne inorganic arsenicals. Waterborne treatments such
as ammoniacal copper arsenate (ACA) and chromated copper arsenate (CCA) are not recommended for western
species but may be used to treat glulam manufactured with Southern Pine. Waterborne treatments are
typically applied to lumber prior to the laminating process. Waterborne treatments applied to glulam after the
laminating process can cause dimensional changes such as warping, and twisting, in addition to excessive
checking as the result of the necessary re-drying process. Fire-retardant coatings may be used for glulam
railroad structures in accordance with Part 6 Commentary.
Species listed in AWPA Standard C28 for preservative treatment include Pacific Coast Douglas fir, Western
hemlock, hem-fir and southern pine. Other species may also be available by specification in agreements with
the glulam manufacturer.
Retention and penetration levels are specified in AWPA Standard C28 in units of pounds of retained
preservative per cubic foot of wood and depth of penetration in inches. Creosote retentions in the range of 8
to12 pcf are common in railroad applications.
It is strongly recommended that all fabrication, trimming and boring of glulam members be performed prior to
the pressure treating process. If field fabrication is needed, surface damage, cuts and holes must be field
treated to protect any exposed wood. Field treatments in accordance with AWPA Standard M4 should be
specified.
1
1.3.1.8 Fire-retardant coatings
Fire-retardant coatings may be used for glulam railroad structures in accordance with Article 1.8.
1.3.1.9 Certification, Wrapping and Shipping
When specified by the engineer or customer, Certificates of Conformance shall be supplied by the glulam
manufacturer to indicate conformance with industry standard ANSI A190.1.
3
1.3.1.10 Storage and Handling
Loading & Unloading: Glulam stringers are commonly loaded and unloaded with forklifts. Greater
stability can be achieved when the sides of the beams rest on the forks. Moving long beams on their
sides, however, can cause them to flex excessively increasing the risk of damage. If a crane with cable
slings or chokers is used to load, unload, or install glulam members, adequate blocking shall be provided
between the cable (or strap), and the members. Wooden cleats or blocking should be used to protect long
edge corners. Use of spreader bars can reduce the likelihood of damage when lifting beams in excess of
30 feet in length.
Storage: To minimize possible degradation that can result from excessive seasoning checks or splits
(checks that develop into openings across the member width), glulam members should be stored off of
the ground on blocks in a level, well-drained location and covered. If members are to be stacked, spacer
blocks should be placed between members to allow for ventilation and to protect against water
entrapment on surface areas.
1
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-1-5
4
Timber Structures
SECTION 1.4 ORDERING STRUCTURAL LUMBER, TIMBER AND ENGINEERED WOOD
PRODUCTS
See Commentary Article 6.1.4 for an Example.
1.4.1 INQUIRY OR PURCHASE ORDER (2010)1
An inquiry or purchase order for structural lumber or timber should clearly stipulate:
a.
Quantity in board feet or number of pieces.
b. Thickness, width and length.
c.
Whether rough or surfaced, and extent of surfacing.
d. Stress-grade. Use the complete designation as given in the rules. Paragraph or page numbers may be
used as additional identification.
e.
Species of wood.
f.
The name and date of the grading rule book and the name of the organization issuing it. It is preferable
to use the most recent rule book but the designation “current grading rules” should not be used because
confusion may result due to changes in grade names and/or paragraph or page numbers.
g.
Any exceptions to or modifications of the grading rules such as:
(1) Lumber or timber to be free of wane.
(2) Seasoning if desired, stating the method and acceptable moisture content. (Note that mills do not
ordinarily season beam and stringer or post and timber sizes.)
(3) Special heartwood requirements.
(4) Special shear grades.
(5) Special provisions to make joist and plank or beam and stringer grades suitable for continuous
spans.
(6) Special provisions to make joist and plank or beam and stringer grades suitable as columns or
tension members.
(7) Special inspection provisions.
(8) Provisions for treatment.
1
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-1-6
AREMA Manual for Railway Engineering
Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
SECTION 1.5 SPECIFICATIONS FOR TIMBER PILES1
1.5.1 GENERAL PROVISIONS (2007)
1.5.1.1 Scope
This specification covers the physical characteristics timber piles to be used either untreated or treated by
approved preservative process.
1.5.1.2 Species of Wood
Piles may be of any species which will satisfactorily withstand driving and support the superimposed loads.
1.5.2 CLASSIFICATION OF PILES (2007)
1.5.2.1 Classes
Piles are classified in this specification under two general classes according to quality, First-Class Piles and
Second-Class Piles. First-Class Piles are divided into two size groups as follows:
1.5.2.2 First-Class Piles
a.
Butt Circumference – The butt circumference is specified and minimum tip circumferences are in
accordance with Table 7-1-2a and Table 7-1-2b. (friction piles) .
1
b. Tip Circumference –The tip circumference is specified and minimum butt circumferences are in
accordance with Table 7-1-3a and Table 7-1-3b. (end-bearing piles).
1.5.2.3 Second-Class Piles
Piles which do not meet the requirements of First-Class Piles but which are suitable for use in cofferdams,
falsework, temporary work and light foundations or other light construction. Second-Class Piles may also be
specified by butt circumference or tip circumference.
3
1.5.2.4 Sizes
a.
The ratio of “out of round” maximum to minimum diameter at the butt or the tip of any pile shall not
exceed 1.2.
b. All circumference measurements must be taken under the bark.
c.
1
The circumference at the butt may not exceed the circumference at 3 feet from the butt by more than
8 inches.
References, Vol. 10, 1909, part 1, pp. 541, 603; Vol. 29, 1928, pp. 506, 1301; Vol. 34, 1933, pp. 66, 760; Vol. 37, 1936, pp. 668, 1036; Vol. 40,
1939, pp. 376, 789; Vol. 406, 1945, pp. 185, 802; Vol. 54, 1953, pp. 945, 1329; Vol. 61, 1960, pp. 587, 1095; Vol. 89, 1988, p. 106.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-1-7
4
Timber Structures
Table 7-1-2a. Friction Piles – Specified Butt Circumference with Minimum Tip Circumferences for Coast
Douglas Fir Piles and Other Species, Except Southern Yellow Pine (See Note 1)
Required
Minimum
Circumference,
(inches),
3 feet from Butt
22
25
28
Length (feet)
31
35
38
41
44
47
50
57
Minimum Tip Circumference (inches)
20
16.0
16.0
16.0
18.0
22.0
25.0
28.0
30
16.0
16.0
16.0
16.0
19.0
22.0
25.0
28.0
16.0
17.0
20.0
23.0
26.0
29.0
16.0
17.0
19.0
22.0
25.0
28.0
60
16.0
16.0
18.6
21.6
24.6
31.6
70
16.0
16.0
16.0
16.2
19.2
26.2
80
16.0
16.0
16.0
16.0
21.8
90
16.0
16.0
16.0
16.0
19.5
100
16.0
16.0
16.0
16.0
18.0
16.0
16.0
40
50
110
120
16.0
Note 1: Where the taper applied to the butt circumferences calculates to a circumference at the tip of
less than 16 inches, the individual values have been increased to 16 inches to ensure a minimum
of 5 inches tip diameter for purposes of driving.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-1-8
AREMA Manual for Railway Engineering
Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
Table 7-1-2b. Friction Piles – Specified Butt Circumference with Minimum Tip Circumferences for Southern
Yellow Pine (See Notes 1, 2)
Required
Minimum
Circumference,
(inches),
3 feet from Butt
22
25
28
Length (feet)
31
35
38
41
44
47
50
57
Minimum Tip Circumference (inches)
20
16
16
18
21
25
28
31
34
37
40
47
30
16
16
16
19
23
26
29
32
35
38
45
17
21
24
27
30
33
36
43
19
22
25
28
31
34
41
60
20
23
26
29
32
39
70
18
21
24
27
30
37
19
22
25
28
35
40
50
80
Note 1: Where the taper applied to the butt circumferences calculates to a circumference at the tip of
less than 16 inches, the individual values have been increased to 16 inches to ensure a minimum
of 5 inches tip diameter for purposes of driving.
Note 2: Southern Yellow Pine piles are generally available in lengths shorter than 70 feet or girth of less
than 50 inches at 3 feet from butt. A dark horizontal line in each column designates pile sizes
(above the line) which are generally available. The purchaser should inquire as to availability of
sizes below the lines.
1
Table 7-1-3a. End-Bearing Piles – Specified Tip Circumferences with Minimum Butt Circumferences for
Piles of Coast Douglas Fir and Other Species Except Southern Yellow Pine (See Note 1)
3
Required
Minimum Tip
Circumference,
(inches)
Length (feet)
16
19
22
25
28
31
35
38
Minimum Circumferences 3 feet from Butt (inches)
20
21.0
24.0
27.0
30.0
33.0
36.0
40.0
43.0
30
23.5
26.5
29.5
32.5
35.5
38.5
42.5
45.5
40
26.0
29.0
32.0
35.0
38.0
41.0
45.0
48.0
50
28.5
31.5
34.5
37.5
40.5
43.5
47.5
50.5
60
31.0
34.0
37.0
40.0
43.0
46.0
50.0
53.0
70
33.5
36.5
39.5
42.5
45.5
48.5
52.5
55.5
80
36.0
39.0
42.0
45.0
48.0
51.0
55.0
58.0
90
38.5
41.5
44.5
47.5
50.5
53.5
57.5
60.5
100
41.0
44.0
47.0
50.0
53.0
56.0
60.0
110
43.5
46.5
49.5
52.5
55.5
58.5
120
46.0
49.0
52.0
55.0
58.0
4
Note 1: Piles purchased as “8-inch and natural taper” have a required minimum
tip circumference of 25 inches and are available in lengths of 20 to 45 feet.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-1-9
Timber Structures
Table 7-1-3b. End-Bearing Piles – Specified Tip Circumferences with Minimum Butt Circumferences for
Piles for Southern Yellow Pine Piles (See Notes 1, 2)
Required
Minimum Tip
Circumference,
(inches)
16
Length (feet)
19
22
25
28
31
35
38
Minimum Circumferences 3 feet from Butt (inches)
20
19
22
25
28
31
34
38
41
30
21
24
27
30
33
36
40
43
26
29
32
35
38
42
45
50
31
34
37
40
44
47
60
33
36
39
42
46
49
70
35
38
41
44
48
51
80
37
40
43
46
50
53
90
39
42
45
48
52
55
40
Note 1: Piles purchased as “8-inch and natural taper” have a required minimum
tip circumference of 25 inches and are available in lengths of 20 to 45 feet.
Note 2: Southern Yellow Pine piles are generally available in lengths shorter than
70 feet or girth of less than 50 inches at 3 feet from the butt. A dark
horizontal line in each column designates pile sizes (above the line) which
are generally available.
1.5.3 GENERAL REQUIREMENT FOR ALL PILES (2007)
1.5.3.1 General Quality
Except hereinafter provided, all piles shall be of sound wood, free from defects which may impair their strength
or durability as piles such as decay, red heart, marine borer attack, or insect attack. Cedar and cypress piles
may have a pipe or stump rot hole not more than 1-1/2 inches in diameter. Cypress piles may have peck
aggregating not more than the limitation for holes. Piles having sound turpentine scars not damaged by insects
shall be permitted. Piles shall be cut above the ground swell and have continuous and reasonably uniform taper
from butt to tip.
1.5.3.2 Knots1
a.
Sound knots shall be no larger than one sixth the circumference of the pile located where the knot
occurs. Cluster knots shall be considered as a single knot, and the entire cluster cannot be greater in size
than permitted for a single knot. The sum of knot diameters in any 1 foot length of pile shall not exceed
one third of the circumference at the point where they occur. Knots shall be measured at a right angle to
the length of the pile.
b. Piles may have unsound knots not exceeding half the permitted size of a sound knot, provided that the
unsoundness extends to not more than a 1-1/2 inch depth, and that the adjacent areas of the trunk are
not affected.
1
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-1-10
AREMA Manual for Railway Engineering
Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
1.5.3.3 Heartwood
Piles specified to have high heartwood content, for use without preservative treatment, shall exhibit a
heartwood diameter at the butt not less than eight-tenths the diameter of the pile.
1.5.3.4 Sapwood
Piles for use with preservative treatment shall have sufficient sap wood to meet minimum penetration
requirements.
1.5.3.5 Close Grain
If close grain is specified for softwood piles, the pile shall show on the butt end not less than 6 annual rings per
inch, measured radially over the outer 3 inches of the cross section. Douglas-fir and pine averaging from 5 to 6
annual rings per inch shall be accepted as the equivalent of close grain if having one-third or more
summerwood.
1.5.3.6 Cutting and Trimming
Butts and tips of piles shall be sawed square with the axis of the piles and shall not be out of square by more
than 1/10 inch per inch of diameter. All knots and limbs shall be trimmed or smoothly cut flush with the surface
of the pile.
1.5.3.7 Peeling
a.
1
Piles are classified according to the extent of bark removal as clean-peeled, rough-peeled or unpeeled.
b. Clean peeled piles require the removal of all outer bark. In addition, at least 80 percent of the inner bark,
well distributed over the surface of the pile shall be removed. Piles for preservative treatment shall have
no strip of inner bark larger than 1 by 6 inches.
c.
3
Rough-peeled piles require the complete removal of all outer bark.
d. Unpeeled piles require no bark removal.
e.
The sapwood of piles shall not be unnecessarily scarred or injured in the process of peeling.
f.
Piles for preservative treatment shall be clean-peeled.
4
1.5.3.8 Lengths
Piles shall be furnished cut to any of the following lengths as specified: 16 feet to 40 feet, incl., in multiples of 2
feet; over 40 feet in multiples of 5 feet. Individual piles may exceed the length specified as much as plus 1 foot in
piles 40 feet and shorter, and plus 2 feet in piles over 40 feet.
1.5.3.9 Twist of Grain
Spiral grain shall not exceed 180 degrees of twist when measured over any 20 foot section of the pile.
1.5.4 SPECIAL REQUIREMENTS FOR FIRST-CLASS PILES (2007)
a.
A straight line from the center of the butt to the center of the tip of First-Class piles shall lie entirely
within the body of the pile. First-Class piles shall be free from short crooks that deviate more than 2-1/2
inches from straightness in any 5 foot length (see Figure 7-1-1).
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-1-11
Timber Structures
b. Holes less than 1/2 inch in average diameter shall be permitted in First-Class piles provided that the sum
of average diameters of all holes in any square foot of pile surface does not exceed 1-1/2 inch, and the
depth of any hole does not extend to more than 1-1/2 inch and provided that holes are not caused by
decay or marine borer attack. Internal holes or damage to the cross-section (bearing) surfaces caused by
decay, marine borers, or insects are not permitted.
c.
Splits in First-Class Piles shall not be longer than the butt diameter. The length of any shake or
combination of shakes, measured along the curve of the annual ring, shall not exceed one-third the
circumference of the butt of the pile.
Figure 7-1-1. Measurement of Short Crook
1.5.5 SPECIAL REQUIREMENTS FOR SECOND-CLASS PILES (2007)
a.
A straight line from the center of the butt to the center of the tip of Second-Class piles may lie partly
outside the body of the pile, but the maximum distance between the line and the pile shall not exceed 1/2
percent of the length of the pile or 3 inches, whichever is the smaller. Second-Class piles shall be free
from short crooks that deviate more than 2-1/2 inches from straightness in any 5 foot length. (See
Figure 7-1-1).
b. Holes less than 1/2 inch in average diameter shall be permitted in Second-Class piles provided that the
sum of the average diameters of all holes in any square foot of pile surface does not exceed 3 inches and
the depth of any hole does not extend to more than 1-1/2 inch and provided that the holes are not caused
by decay, or marine borer attack. Internal holes or damage to the cross-section (bearing) surfaces caused
by decay, marine borers, or insects are not permitted.
c.
Splits in Second-Class piles shall not be longer than 1-1/2 times the butt diameter. This length of any
shake or combination of shakes, measured along the curve of the annual ring, shall not exceed one half
the circumference of the butt of the pile.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-1-12
AREMA Manual for Railway Engineering
Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
1.5.6 INQUIRIES AND PURCHASE ORDERS (2007)
Each inquiry or purchase order for piles purchased under this specification should clearly state:
a.
The number of pieces of each length.
b. The species of wood.
c.
Whether the piles shall conform to the requirements for First Class or Second Class piles.
d. Whether the piles shall be specified by butt circumference or tip circumference.
e.
Whether the piles shall be clean-peeled, rough peeled, or unpeeled.
f.
If close grain is wanted (in softwood piles).
g.
If heartwood content is wanted.
h. Whether piles shall be treated or untreated, and if treated, the type of preservative and minimum
penetration.
i.
Any exceptions to this specification such as the entire removal of all inner bark for clean-peeled piles.
j.
Instruction for inspection, marking, acceptance and shipment.
1
SECTION 1.6 SPECIFICATIONS OF FASTENERS FOR TIMBER TRESTLES1
3
1.6.1 MATERIAL (2008)
a.
Malleable Iron. Malleable iron castings shall conform to current ASTM Specifications, designation A47,
Grade 35018, with minimum yield point of 35,000 psi.
b. Cast Iron. Cast iron shall conform to current ASTM Specifications, designation A48, Class No. 30.
c.
4
Rolled Steel. Rolled steel plates, bars and shapes shall conform to current ASTM Specifications,
designation A36.
d. Cast Steel. Cast steel shall conform to current ASTM Specifications, designation A27, Grade 65-35, full
annealed with minimum yield point of 33,000 psi.
1.6.2 TYPES OF FASTENERS (2009)
a.
1
Nails, Spikes and Drift Bolts. Nails, spikes and drift bolts shall be made of rolled steel, square or round,
as called for on the plans. Where special heads are not specified, the manufacturer’s standard heads will
be acceptable. Nails used for fastening timbers shall be of a type having grooved, barbed or otherwise
deformed shanks for greater holding power.
References, Vol. 7, 1906, pp. 692, 719; Vol. 11, 1910, part 1, pp. 178, 228; Vol. 37, 1936, pp. 667, 1036; Vol. 48, 1947, pp. 386, 938; Vol. 54,
1953, pp. 942, 1329; Vol. 61, 1960, pp. 587, 1095; Vol. 89, 1988, p. 106.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-1-13
Timber Structures
b. Through Bolts. Through bolts shall be made of rolled steel with U.S. standard square or hexagon heads
and nuts unless otherwise specified on the plans.
c.
Washers.
(1) Ogee washers shall be made of cast iron and conform with ASTM A48.
.
A
Bolt Size
Top Outside
Diameter
1/2
5/8
3/4
7/8
1
1-1/8
1-1/4
1-1/2
1-3/8
1-5/8
1-7/8
2
2-1/2
2-1/2
2-1/2
3
B
Bottom
Outside
Diameter
2-3/8
2-3/4
3
3-1/2
4
4-1/4
4-1/2
5-1/2
T
Thickness
1/2
5/8
3/4
7/8
1
1-1/8
1-1/4
1-1/2
(2) Malleable cast iron round washers shall be made of malleable or cast iron. Finish may be black or
hot dip galvanized.
Bolt
Size
3/8
1/2
5/8
3/4
7/8
1
1-1/8
1-1/4
1-1/2
A
T
Outside
Diameter
Thickness
2-1/2
2-1/2
2-3/4
3
3-1/2
4
4-1/2
5-1/2
6
1/4
1/4
5/16
7/16
7/16
1/2
1/2
9/16
3/4
(3) Round plate washers shall be made of rolled steel. Finish may be black or hot dip galvanized.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-1-14
AREMA Manual for Railway Engineering
Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
Bolt
Size
3/8
1/2
5/8
3/4
7/8
1
1-1/4
1-1/2
B
A
C
Outside
Diameter
2
2-1/4
2-1/2
3
3-1/2
4
5
5
Inside
Diameter
7/16
9/16
11/16
13/16
15/16
1-1/16
1-3/8
1-5/8
Thickness
3/16
3/16
1/4
1/4
5/16
3/8
3/8
3/8
d. Lag Screws. Lag screws, including steel drive dowels and spikes with spirally grooved shanks shall be
made of rolled steel. Heads for lag screws shall be U.S. standard unless otherwise specified.
e.
Special Castings. Special castings, including such parts as gib plates, angle blocks, etc., shall be made of
cast or malleable iron. They shall be true to pattern, free from wind, without injurious defects and of the
size and shape specified on the plans.
f.
Cap - Stringer Fasteners. These include such types of fastenings as shown on Appendix 3 - Legacy
Designs; Figure 7-A3-64. They shall be made of rolled steel of the size and shape specified on the plans.
g.
1
Metal Joint Connectors.
(1) Spiked grids, cast shear plates and claw plates shall be made of malleable iron.
(2) Split rings, toothed rings, bull dog types, pressed shear plates and clamping plates shall be made of
rolled steel.
3
(3) They shall be of the size and design specified on plan.
h. Brace Plates and Washer Plates. Brace plates and washer plates or similar items shall be made of rolled
steel to the size and details specified on the plan.
1.6.3 USE OF PROTECTIVE COATINGS FOR STEEL FASTENERS ON TIMBER BRIDGES
(2008)
a.
Plain iron or steel fastenings will ordinarily outlast untreated timber. Creosote oil, whether straight or in
coal-tar or oil mixtures, will retard corrosion of embedded metal fastenings.
b. Galvanizing or other protective coating on iron or steel fastenings is not warranted if the fastenings are
to be entirely embedded in untreated or creosote treated timber or if metal is to be exposed only to
ordinary weathering.
c.
When metal fastenings are not to be completely embedded and are to be exposed to salt water or an
unusually corrosive atmosphere, consideration should be given to the use of galvanizing or to some other
protective coatings on the exposed metal. As the limits within which protectively coated metal is
economical are not well established, local experience should be investigated.
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SECTION 1.7 SPECIFICATIONS FOR TIMBER BRIDGE TIES
1.7.1 MATERIAL (2009)
1.7.1.1 Kinds of Wood
Before manufacturing ties, the railway or end user shall determine which species of wood are acceptable.
1.7.2 PHYSICAL REQUIREMENTS (2009)
1.7.2.1 General Quality
The general quality of bridge ties shall conform to the appropriate grading rules. All ties shall be sawn from
live, sound, straight timber free of defects that may impair strength or durability; such as decay, splits, shake,
excessive slope of grain, or numerous holes or knots, bark, wane, etc.
1.7.3 DESIGN (2009)
Also see Article 1.7.4.
1.7.3.1 Support Conditions
Depending on the intended service conditions, bridge ties may be classified as structural or bearing ties.
Structural ties are normally used for open deck bridges having steel girder spans. Under these conditions the
strength of the ties is governed by flexure or horizontal shear. Bearing ties are normally used for open decks of
timber trestle spans or on open decks of steel beam spans having multiple beams where the strength of ties is
governed by bearing on the top of the stringer flange.
1.7.3.2 Dimensions
a.
The minimum cross-section for structural and bearing type bridge ties shall be based on the applicable
clauses of Chapter 7, Part 2.
b. The minimum width of bridge ties shall be eight (8) inches nominal.
c.
When ties are dapped, the minimum depth of the tie shall be the net depth as calculated in
Article 1.7.3.2a.
d. The minimum length of bridge ties shall be ten feet (nominal) or center-to-center of outer supports plus
three times the depth of tie, whichever is greater.
1.7.4 INSPECTION (2009)
1.7.4.1 Place
Before accepting ties for installation, the bridge ties shall be inspected at locations specified by the railway.
1.7.4.2 Manner
Prior to treatment, inspectors shall make a close examination of the top, bottom, sides and ends of each bridge
tie with regard to its manufacture and compliance with respect to the grading rules. Each bridge tie shall be
judged independently, without regard to decisions on other ties in the same lot.
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Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
1.7.4.3 Handling
Bridge ties are to be handled with care to prevent damage. Damaged ties will not be accepted.
1.7.4.4 Quality
Bridge ties shall be treated No. 1 Grade in the following species:
• Douglas Fir - Costal Species, Beams and Stringers, WCLIB, WWPA or NLGA.
• Oak, Timbers - Beams and Stringers, NELMA.
• Southern Yellow Pine, Timbers, SPIB.
1.7.4.5 Dimensions
The following finished dimensional tolerances of sawn or machined bridge ties are to be followed unless
otherwise specified by the railway.
Depth: Sized or dapped areas: ± 1/16”
1.7.5 DELIVERY (2010)
1.7.5.1 Location
1
Bridge ties delivered for acceptance shall be stacked at suitable and convenient locations meeting individual
railway safety requirements and as approved by the railway. Bridge ties delivered on the premises of a railway
for inspection shall be stacked on blocking placed on firm ground.
1.7.5.2 Risk, Rejection
3
All bridge ties remain the property of the supplier until accepted. All rejected ties shall be removed from
railway premises by the supplier at his expense within a time frame specified by the railway; for example within
thirty (30) days after the date of rejection.
1.7.6 SHIPMENT (2009)
Bridge ties shall be separated into bundles therein according to bridge locations for which they are intended,
and also according to the location on the bridge spans, unless otherwise stipulated in the contract, on the
railway order form or on the accompanying plans for the ties.
1.7.7 DAPPING OR SIZING BRIDGE TIES (2009)
Dapping or sizing of ties is to be performed in a framing mill properly equipped to perform such work. Dapping
or sizing is to be performed before treatment.
a.
When dapped bridge ties are used, the width of dap shall be the width of flange plus 1/2 inch and the
minimum depth of dap shall be 3/8 inch or such that the undapped portion will not bear on gusset plates,
bracing, etc.
b. When sized ties are required, the railway may specify surfacing on 1 or more sides or edges.
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c.
On curved tracks, superelevation may be provided by tapered ties, which may be dapped or sized. An
approved tie plan must be provided to the framing mill and the ties should be uniquely and individually
numbered to identify ties having different dapped dimensions. The method of numbering shall comply
with the requirements of the railway.
1.7.8 BRIDGE TIE INSTALLATION (2010)
1.7.8.1 Bridge Tie Spacing and Spacers
a.
The maximum recommended nominal clear distance between ties shall be:
• six (6) inches for structural ties,
• six (6) inches for bearing ties on steel beams or girders and
• eight (8) inches on timber stringers.
b. Bridge tie spacers may be a minimum 4" x 8" wood, or 3" x 5/8” steel bar having predrilled holes for
fasteners, or of other design as specified by the railway.
c.
A tie spacer shall be fastened to each bridge tie with 5/8” diameter drive spikes, lag screws or lag bolts
and shall be long enough to engage a minimum of one half the depth of tie. To avoid splitting, it is
recommended to pre-bore holes in the ties.
1.7.8.2 Rail Fastening
The type of rail fasteners to be used will be determined by the railway.
a.
For spikes refer to Chapter 5, Part 2.
b. For spiking refer to Chapter 5, Part 4.
c.
For other fastening systems refer to manufacturer’s specifications.
1.7.8.3 Tie Plates
a.
For tie plates refer to Chapter 5, Part 1.
b. Suitably sized double shouldered tie plates shall be used taking into consideration species of wood, axle
loads, predominant train speeds, track curvature, etc.
c.
The minimum recommended size of tie plates is:
Main line bridge decks: 7¾” x 15"
For other bridge decks: 7" x 12"
d. The railway may use tie plates of special design providing the requirements of Article 1.7.8.3c are met.
1.7.8.4 Bridge Tie Pads
a.
Tie pads may be used to minimize plate cutting and to reduce impact and vibration effects on the bridge
structures.
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Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
b. Tie pads may be made of a plain or reinforced elastomeric material, impregnated fibrous material or any
other suitable product, provided they are strong enough for the loading, are water repellent and stay
firm in shape during service.
c.
The size of tie pad shall conform to the tie plate used and shall be of suitable thickness.
d. Many special design tie plates do not permit the use of tie pads. The suitability of specific tie plates for
use with bridge tie pads shall be verified with the tie plate manufacturer.
e.
Refer to Chapter 30, Section 2.5 for material requirements and testing.
1.7.8.5 Bridge Tie Fastening
a.
For fastening bridge ties to timber stringers, one of the following anchoring systems may be used:
(1) Bolts or drive spikes.
(2) Machine bolts with adequate washers and nuts.
(3) A combination of (1) and (2).
b. For fastening bridge ties to steel beams and girders, one of the following anchoring systems may be used:
(1) Machine bolts with a plate or spring washer and standard or lock type nut.
1
(2) Hook bolts with a plate or spring washer and standard or lock type nut.
(3) Machine bolts with a clip and plate or spring washer and standard or lock type nut.
(4) Other systems may be used if approved by the railway.
(5) Ties installed on the rivet or bolt heads of built-up girders should have the fasteners re-tightened
after traffic has set the new deck down on the girder flange.
c.
3
The size and the spacing of the anchoring system should be such as to provide adequate stability for the
open deck considering the loads and forces as described in Chapter 7 and Chapter 15.
d. Refer to Chapter 7, Part 1 and Chapter 15, Section 8.3 of the latest revision of this Manual for additional
guidelines.
1.7.9 PRESERVATIVE TREATMENT OF BRIDGE TIES (2009)
Refer to Chapter 30, Section 3.6 and Section 3.7.
1.7.10 SPIKE OR BOLT HOLES (2009)
Refer to Chapter 30, Part 3.
1.7.11 TIE PLUGS (2009)
Refer to Chapter 30, Article 3.1.5.
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1.7.12 TIE BRANDING (2009)
Refer to Chapter 30, Article 3.1.4.5.
1.7.13 END SPLITTING CONTROL DEVICES (2009)
Refer to Chapter 30, Articles 3.1.6 and 3.1.7.
SECTION 1.8 RECOMMENDATIONS FOR FIRE-RETARDANT COATING
FOR CREOSOTED WOOD1 (1963) R(2008)
1.8.1 SCOPE (1988)
These recommendations are intended primarily for use with coatings of the film-forming classification, such as
paints and mastics. Any material other than film-forming type shall conform to these recommendations except
where film-forming qualities are required for fulfillment of the recommendations and apply to:
a.
Performing requirements of fire-retardant coating compositions for use with wood treated with creosote
or mixture of creosote with coal tar or petroleum, and
b. Methods for the acceptance testing of such fire-retardant coatings.
1.8.2 GENERAL PRODUCT REQUIREMENTS (1988)
1.8.2.1 Uniformity
a.
All component raw materials of the product shall be thoroughly mixed and dispersed during its
manufacture, unless the product is a multi-component system which sets or polymerizes rapidly and
requires mixing immediately prior to application.
b. The formulation and quality of the product shall be maintained constant by the manufacturer and shall
not be varied without notice.
1.8.2.2 Stability in Storage
The product shall maintain stability at temperatures above 32 degrees F, shall not require unusual storage
conditions, and shall conform to the requirements of the following:
a.
In a freshly opened container the product shall reveal no curdling, livering, lumping, decomposition,
gelling or any other objectionable characteristic within 12 months after delivery.
b. Separated, settled, caked or thickened materials shall be easily and adequately dispersible with a paddle
without change in the quality or properties of the product.
1.8.2.3 Applied Coating
A dry film of the product shall exhibit the following properties:
1
References, Vol. 64, 1963, pp. 374, 621; Vol. 89, 1988, p. 106.
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Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
a.
Adhesion: The product shall be cohesive and shall adhere to the primary surface or to any secondary
supporting surface.
b. Durability: The product shall resist water, brine, creosote, mixtures of creosote with petroleum or coal
tar, sunlight, freezing and thawing, and general temperature extremes.
c.
Foot Traffic: The product shall resist damage when applied on traffic areas.
d. Fire Retardancy: The product shall withstand heat or flames originated by miscellaneous heat sources,
including ignited fusees, hot brake shoe splinters, sparks, hot coals or cinders, drops of molten metal,
and burning debris.
1.8.2.4 Flammability of Wet Films
a.
The evaporation of solvents or other materials from a wet film of the product shall cease to constitute a
flammable hazard within 4 hours after application.
b. A film of the product, applied so as to achieve the minimum total dry thickness recommended by the
manufacturer, shall cease to support combustion within 48 hours after application of the final coat.
1.8.2.5 Drying Time
A film of the product, applied at the maximum wet thickness recommended by the manufacturer, within 36
hours after application and without forced drying, shall be hard enough to allow firm pressure of the thumb
against the coated object without rupture of the film or adherence of coating to the thumb.
1
1.8.3 APPLICATION REQUIREMENTS AND INSTRUCTIONS (1988)
1.8.3.1 Handling Instructions
All precautions for storage and handling prior to and during application of the product shall be stated clearly in
an accompanying instruction leaflet prominently displayed on each container, together with complete
information and instructions for recommended equipment and materials for surface preparation, thinning, and
application.
3
1.8.3.2 Product Information
All information and physical measurements not specified elsewhere in these recommendations, which might
assist in the proper handling or testing of the product, shall accompany the instructions and shall include the
following:
a.
Specific gravity, and weight in pounds per gallon, or weight to the nearest 0.1 g of 1 pint of the coating.
b. Recommended maximum wet thickness and calculated coverage of a single-coat application of the
coating, unthinned and thinned with recommended proportions of thinner.
c.
Measured resultant dry thickness of the recommended maximum wet thickness of a single-coat
application.
d. Recommended minimum dry thickness required for fire-retardancy effectiveness.
e.
Drying time required between applications, thinned and unthinned.
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Timber Structures
f.
Duration of solvent fire hazard during the drying lime of a single-coat application, thinned and
unthinned.
g.
Drying or curing time required to attain maximum fire retardancy.
h. Recommended spray equipment (gun type, orifice size, spray pattern, pressure, etc.).
i.
Solvents and materials which may be used to clean application equipment.
j.
Corrosiveness of product to container and spray equipment.
k. Toxicity to humans and animals of the product in the wet and dried conditions.
1.8.3.3 Working Properties
a.
The product shall be applicable by brushing, spraying and, if it is a mastic, by trowelling, or it shall be
adaptable for spraying, without loss of quality, by addition of a thinner recommended by the
manufacturer.
b. A wet film of the product, when applied at the thickness recommended by the manufacturer, shall not
show sagging, running, pinholing or other objectionable features.
1.8.3.4 Surface Preparation
Timber surface preparation or treatment shall not be extensive and shall not require unusual equipment,
materials or operations.
1.8.4 TESTING (2011)
1.8.4.1 Specimen Preparation
a.
Wood Selection. The wood shall be selected from well-seasoned nominal 2 inches by 6 inches boards of
Grade B & Btr edge-grained southern yellow pine containing no more than 10 percent heartwood, at
least 14 feet in length, dressed on four sides and free from knots, stains, pitch pockets and bark. The
maximum width of the annual growth rings shall be no greater than 1/16 inch. Edge-grained shall mean
that at both ends of a board, where the wood has been cut cross sectionally, at least half of the acute
angles between lines drawn tangential to the annual rings and lines drawn perpendicular to the broad
surfaces of the board shall be no greater than 45 degrees.
b. Sectioning. The first 6 inches of the ends of each board shall be discarded, and the remainder shall be cut
laterally into 18 inch sections. Each section shall be identified by the board number and by its own
number from one end of the board. Each section shall be tested for moisture content at 6 inch intervals
along its longitudinal axis with an electrical moisture meter employing metal probes which are no
shorter than 1/4 inch. The moisture content of a section shall be greater than 8 percent and less than 15
percent. The sections shall be protected from checking or loss of moisture, preferably by storage in a
cold, humidified atmosphere. A section which has checked shall not be used as a test specimen.
c.
Preservative Treatment. The dimensions of an 18 inch section shall be measured to the nearest 0.01 inch
and the volume calculated to the nearest 0.001 cubic foot. Each section shall be weighed to the nearest
gram before preservative treatment. The creosote solutions and treating methods employed for
impregnation of the sections shall be prescribed by the purchaser. After preservative treatment, each
section shall be allowed to drain freely for 24 hour, wiped clean, and weighed to the nearest gram. The
preservative retention shall be calculated in pounds per cubic foot to the nearest 0.01 lb per cubic foot,
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Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
using the previously obtained dimensions and volume calculations, and the resultant figure shall be
called “initial retention.” The treated sections shall be stored for a minimum of 30 days or a maximum of
60 days, at approximately 75 degrees F and 50 percent relative humidity, prior to a coating application or
any form of testing. Immediately prior to preparation of a section for use in testing procedures, the
section shall be weighed to the nearest gram, the net preservative retention shall be calculated: the
resultant figure shall be called “test retention.” The test retention of any specimen shall be no less than
10 lb per cubic feet. All treated or untreated specimens used in a test shall be subjected to identical pretest storage conditions.
1.8.4.2 Fire Tests
1.8.4.2.1 Testing in Fire-Test Cabinet
a.
Apparatus. The fire-test cabinet shall be a rectangular insulated chamber measuring 31 inches high, 10
inches wide and 12 inches deep. In order to suspend the specimen in the fire-test cabinet, a supporting
rod shall be affixed horizontally 1 inch from the tops of opposite walls of the cabinet. For draft control,
the 2-inch bottom section of the cabinet shall consist of louvers which can be raised 90 degrees. Two
pairs of ungalvanized iron pipe with 3/8 inch internal diameter, each pair vertically parallel and
separated by 3 inches between their longitudinal axes, shall be fastened to opposite sides of the cabinet.
Orifices of 1/32 inch diameter shall be located in a straight line at 1-inch intervals, for 20 inches along
each pipe, beginning at 1/2 inch from the cap (Figure 7-A3-1). The cabinet shall be equipped with a
removable door fitted with viewing ports covered with mica sheet (Figure 7-A3-2). A pilot-flame orifice
shall be installed at the bottom of one pipe at each side of the cabinet (Figure 7-A3-3 and Figure 7-A3-4).
b. Fuel. Bottled liquid-petroleum gas, with a minimum propane content of 95 percent, shall be supplied to
the burner pipes at the rate of 0.4 cubic foot per minute or approximately 60,000 Btu per hour during the
course of a specimen ignition. The flames shall extend approximately 4 inches horizontally from the
orifices and shall be a definite yellow color.
c.
Specimen Section and Position. The test specimen shall be selected by the procedures specified under
Article 1.8.4.1a coated with a film of uniform thickness, allowed to dry or cure completely, and shall be
suspended vertically in the fire-test cabinet at the initiation of the test. The broad faces of the specimen
shall parallel the two pairs of burner pipes at a distance of 3 inches from the orifices, with the top end of
the specimen on a level with the top orifices.
d. Test Procedure. A specimen shall be positioned in the fire-test cabinet with the door closed and the pilot
flames lit. The ignition of the specimen shall be effective by quickly opening the fuel valve to the
required setting and allowing the flames of the ignited gas to be directed against the specimen for 5
minutes. The duration of self-sustained flaming after ignition shall be recorded and designated as “freeburning time.” The period after which flaming has stopped and glowing occurs shall be recorded and
designated as “glow time.” The free-burning interval shall be terminated for one of the following
reasons:
(1) A maximum free-burning time of 30 minutes shall have passed.
(2) During the 30-minute free-burning period it is judged that the flames are merely flickering or
flashing and constitute practical self-extinguishment, or that small flames are being sustained only
at the ends of the specimen.
If at the end of the 30-minute free-burning period, flaming continues at a rate requiring the use of an
accessory extinguishing agent, the flames shall be extinguished with a fire-extinguishing gas.
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The test may be conducted in a well insulated laboratory fume hood or on a table placed under an
insulated canopy. Both the fume hood and the canopy shall be equipped with efficient, safe, smokeexhaust fans. The exhaust fans shall be operating prior to ignition of the specimen.
e.
Observations. The specimen shall be attentively observed during the ignition and the free-burning
periods, and specimen appearance, coating condition and flame activity shall be recorded. Relative flame
activity during the free-burning period and at its termination shall be described with the following
terminology:
(1) Vigorous – Entire specimen flaming with little or no apparent diminishment of combustion rate.
(2) Very Strong – Approximately 75 percent of specimen flaming, with apparent combustion rate slowly
decreasing.
(3) Strong – Approximately 50 percent of specimen flaming, with apparent combustion rate decreasing.
(4) Mild – Approximately 25 percent of specimen flaming, with apparent combustion rate decreasing
rapidly.
(5) Scattered – Areas of flaming where creosote wicking may be occurring or a heat trap may be located.
(6) Torching – Flames occurring with jet-like activity at points of coating rupture or specimen checking.
(7) Flickering – Small, virtually extinguished, flames at a few discrete points.
(8) Flashing – Spontaneous extinguishment and reignition of an area.
After the free-burning period, the specimen shall be allowed to remain in the fire-test cabinet, with the
door removed, until glowing has ceased. The time required for the cessation of glowing shall be recorded
as “glow time.”
The burned specimen shall be weighed to the nearest gram, with the coating removed and wood char
intact, not less than 24 nor more than 36 hours after the free-burning period. The specimen shall be
cleaned of char immediately, without damage to the wood, and weighed again. The differences between
the two weighings shall be recorded as the weight of the char, and shall be calculated in pounds per cubic
foot of volume of the unburned specimen. The difference of weight of the specimen before burning and
after being burned and cleaned shall be recorded as its total weight loss, and shall be calculated in
pounds per cubic foot by volume of the unburned specimen.
The thickness of the burned, cleaned specimen shall be measured to the nearest 1/64 inch on its
longitudinal axis at a point 6 inches from the end which was topmost in the fire-test cabinet. The
difference between the thickness of the specimen before and after cleaning shall be divided by two and
recorded as char depth.
Other observations which shall be recorded are:
(1) Coating thickness and weight, wet.
(2) All defects found in a coated or uncoated specimen before a fire test.
(3) Blistering, fissuring, rupturing, intumescence, sloughing or other effects exhibited by a coating
during a test and the elapsed time before their occurrence.
(4) Relative extent of preservative bleeding during a fire test.
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Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
(5) Relative amount of smoke production during a fire test.
f.
Acceptance Criteria. The specimen shall be totally self-extinguished within the 30-minute free-burning
period or shall exhibit only flickering flames.
(1) The total weight loss of the specimen, with char removed, shall not exceed 30 percent, or 15 lb per
cubic foot by volume of the unburned specimen.
(2) The char depth shall not exceed 1/8 inch. The char shall be evenly distributed with no occurrence of
cupped areas.
(3) The quality of char shall not exceed 2.5 lb per cubic foot by volume of the unburned specimen.
(4) Glowing shall cease within 1 hour after termination of the free-burning period.
(5) The coating shall remain intact upon the specimen throughout the ignition, free-burning and glow
periods, and shall exhibit no sloughing, spalling or peeling.
(6) The performance of a minimum of three specimens, prepared in an identical manner, shall conform
to the stipulations of the acceptance criteria.
1.8.4.2.2 Fusee Test
a.
Construction. The fusee test apparatus shall consist of two specimens selected by the procedures
specified under Article 1.8.4.1a and a section of gypsum or other fireproof insulating board measuring 18
inches by 16 inches by 1 inch. The two wood specimens shall be coated uniformly with the same
thickness used for specimens tested in the fire-test cabinet, and allowed to dry or cure completely. The
coated specimens shall be joined together lengthwise in the shape of an “L”, forming one side and the
bottom of a flat-bottomed trough. The trough shall be completed in a “U” shape by joining the insulation
board to the bottom specimen. The specimens need not be nailed or fastened together. The bottom
specimen may be laid flat, with the other coated specimen and the insulation board standing on their
edges and placed flush against the edges of the bottom specimen.
1
3
b. Procedure. The trough shall be situated in a laboratory fume hood, with the exhaust fan operating. A 10minute fusee shall be ignited and laid snugly in the corner formed by the junction of the two coated
specimens. When the fusee has been consumed the duration and intensity of residual flame activity shall
be recorded.
c.
4
Acceptance Criteria.
(1) Flames shall be totally or virtually self-extinguished within 10 minutes after the fusee has stopped
burning.
(2) The coating shall not flake, peel, crumble, slough or exhibit any other effects which result in the
exposure of the wood substrate.
(3) Glowing shall have ceased within 30 minutes after flaming has stopped.
1.8.4.2.3 Accelerated Weathering Test
a.
Apparatus and Specimens. When a coating shall have conformed to the standards of the first tests during
initial testing, it shall be used to prepare five additional specimens which shall be approximately
identical to those which had been tested. After thorough drying or curing, the specimens shall be exposed
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to artificial sunlight and simulated rainfall in a weathering device described in ASTM Specifications,
designation E42.
b. Procedure. Each specimen shall be positioned vertically in the weathering device, with one of its broad
surfaces facing the light source. The same surface shall face the light throughout the test. The test shall
be terminated after an accumulated light-exposure time of 1,000 hours or when, at any prior time, the
coating is judged to have failed. The decision of apparent coating failure shall be subjective and shall be
based on the appearance of excessive blistering or softening, or exposure of wood by sloughing, peeling,
flaking, cracking or other effects. The test shall be conducted in accordance with the following program:
(1) The specimen shall be exposed to artificial sunlight at all times during the operation of the
weathering device, except for such time as shall be required for the restriking of the carbon arc.
(2) The specimens shall be mounted, with a face-to-face diameter of 30 inches, on a circular rack which
rotates at the rate of 1 rpm. A water spray in the weathering device shall operate for 18 minutes at
intervals of 102 minutes, so that during each 2 hours of light radiation the specimens shall be
exposed to water for 18 minutes. In this manner each specimen shall receive approximately 2.5–3.0
minutes direct water spray during each 2-hour radiation period.
(3) Exposure in the artificial weathering device shall be undertaken daily, for a total of 90 hours within 5
days. At the end of each 90 hours of exposure, the specimens shall be allowed to cool at room
temperature for a minimum of 2 hours and then placed for 65 hours in a cold chamber adjusted to
maintain a temperature of –20 degrees F. At the end of the cold period, the specimens shall be
observed during all handling and transfer operations involving a specimen so as not to modify its
condition.
c.
Acceptance Criteria. At the termination of the weathering program, if failure has not occurred, the
specimens shall be subjected to the fire tests and shall be rated by the acceptance criteria of those tests.
1.8.4.2.4 Brine Resistance Tests
a.
Apparatus. An assembly shall be arranged consisting of a stop-cock-controlled funnel and a small
container equipped with an overflow outlet. The container shall measure 4 inches on all sides, with an
overflow tube of a minimum 1/8 inch diameter leading out from a point 1 inch below the top edge, and
shall be composed of waterproof and chemical-resistant materials, such as glass, rubber or plastics. The
funnel shall be large enough to contain a minimum of 500 ml of liquid and shall be placed vertically over
the container.
b. Specimen Selection and Preparation. An 18 inch preservative-treated specimen shall be selected by the
procedures outlined under Article 1.8.4.1a discarding 4-1/2 inches of each end of the specimen. The
remainder of the specimen shall be sawn laterally at 2 inch intervals, yielding four sections, each of
which shall be weighed to the nearest 0.1 g. A uniform continuous coating film of the same thickness
used for the fire-test specimens shall be applied to all surfaces of the section, beginning at a point 1 inch
from one end. The thickness and weight of the wet coating application shall be recorded, and the coating
shall be allowed to dry or cure completely.
c.
Test Procedure. The container shall be filled to the overflow outlet with a 10 percent sodium chloride
brine solution. The funnel also shall be filled with the brine solution. The test shall be conducted at room
temperature, 75 to 80 degrees F, and the brine shall be maintained at that temperature throughout the
test. The coated end of a specimen shall be immersed at approximately a 45 degree angle in the
container, with the wider side facing upward, and with the uncoated area of the opposite side resting on
the edge of the container. No more than 4 nor less than 3-1/2 inches of a coated side shall be below the
surface of the solution. The tip of the funnel shall be positioned 1 inch above the center of the line
between the coated and uncoated areas of the specimen. At the start of the test, the stop cock shall be
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-1-26
AREMA Manual for Railway Engineering
Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.
opened sufficiently to allow drops of brine to fall at the rate of approximately 10 drops per minute,
striking the specimen at the midpoint of the line between the coated and uncoated areas. Dripping and
immersion shall be continuous for 300 hours. The effluent from the specimen container shall be collected
in any suitable container and discarded. At the end of 300 hours, the brine solution in the specimen
container shall be examined for discoloration and for materials which have separated from the coating.
The specimen shall be observed for blistering, fissuring, crumbling or other effects.
d. Acceptance Criteria. The specimen shall be examined immediately at the end of a test and at a time one
week after the test. Fissures in the coating shall be no wider than hairline cracks. Blisters shall be no
larger than 1/8 inch in diameter. Gentle teasing of the coating with knife point shall not result in easy
dislodgement of coating particles. The dry thickness of the coating at any location on the specimen shall
not have decreased by more than 1/4 of the original dry thickness. Discoloration of the brine solution and
the presence of coating particles in the container shall indicate possible leaching or solvation of the fireretardant constituents of the coating.
1.8.4.2.5 Foot Traffic Test
A specimen shall be selected and prepared in the same manner as the specimens used for the fire tests, with the
same thickness of coating applied. The coating shall be allowed to dry or cure completely.
a.
Procedure. The specimen shall be heated for 1 hour at 140 degrees F in an electric oven. The specimen
shall then be removed from the oven and immediately laid flat on one of its broad surfaces on a protected
area of the floor, The uppermost surface shall be stepped upon with one foot by a person weighing no less
than 150 lbs. His entire weight shall be concentrated on the specimen for 1 minute, at the end of which
time he shall execute a 45 degree twisting movement of the ball of his foot upon the coating and then
step off the specimen.
1
b. Acceptance Criteria.
(1) The coating shall not exhibit tearing and shall not be lifted from the wood substrate by adhesion to
the shoe used to exert pressure. Should these or other objectionable effects occur, the test shall be
repeated, using mineral aggregate or similar material spread over the specimen surface while the
coating is still wet.
3
(2) When a surfacing material is used in conjunction with a coating, it shall not be sufficiently dislodged
to require resurfacing the specimen.
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-1-27
Timber Structures
THIS PAGE INTENTIONALLY LEFT BLANK.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-1-28
AREMA Manual for Railway Engineering
7
Part 2
Design of Wood Railway Bridges and Trestles for
Railway Loading1
— 2011 —
FOREWORD
This specification covers the design of wood structures subject to railway loading, and it assumes each
structural member to carry its own load, competent design and fabrication, reliable stress grading of timber
material, and adequate maintenance of structures.
1
TABLE OF CONTENTS
Section/Article
Description
Page
2.1 Design of Public Works Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.1 General (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-2-3
7-2-3
2.2 General Features of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.1 Materials (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.2 Clearances (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.3 Stringers (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.4 Ties (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.5 Bents (1998) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.6 Piles and Post Footings (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.7 Contemporary and Legacy Designs and Design Aids (2010). . . . . . . . . . . . . . . . . . . . . . . .
2.2.8 Temporary Structures (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-2-4
7-2-4
7-2-4
7-2-5
7-2-6
7-2-6
7-2-7
7-2-7
7-2-7
2.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.1 Loads and Forces (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.2 Dead Load (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.3 Live Load (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.4 Centrifugal Force (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.5 Other Lateral Forces (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-2-7
7-2-7
7-2-7
7-2-8
7-2-8
7-2-9
1
References, Vol. 44, 1943, pp. 362, 670, 691; Vol. 51, 1950, pp. 433, 866; Vol. 52, 1951, pp. 428, 847; Vol. 58, 1957, pp. 676, 1169; Vol. 70,
1969, p. 219; Vol. 76, 1973, p. 232; Vol. 84, 1983, p. 88; Vol. 89, 1988, p. 106; Vol. 91, 1990, pp 57, 62.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-1
3
Timber Structures
TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
2.4 Designing for Engineered Wood Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4.1 Design Values for Glued Laminated Timber (Glulam) (2006) . . . . . . . . . . . . . . . . . . . . . .
2.4.2 Design Equations (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-2-11
7-2-11
7-2-17
2.5 Allowable Unit Stresses for Stress-Graded Lumber. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.1 Working Unit Stresses (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.2 Form Factor (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.3 Deflection, Permanent Set (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.4 Compression Parallel to Grain or Centrally Loaded Columns (2009) . . . . . . . . . . . . . . . .
2.5.5 Bearing (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.6 Allowable Unit Stresses for Stress-Graded Lumber (2010) . . . . . . . . . . . . . . . . . . . . . . . .
2.5.7 Bearing at Angle to Grain (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.8 Combined Axial and Bending Loads (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.9 Horizontal Shear (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.10 Notches (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.11 Shearing Stress (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.12 Bearing on Bolts (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.13 Connectors (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5.14 Round Sections (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-2-20
7-2-20
7-2-20
7-2-20
7-2-20
7-2-21
7-2-21
7-2-29
7-2-29
7-2-30
7-2-30
7-2-31
7-2-31
7-2-38
7-2-38
2.6 Details of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6.1 General (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6.2 Net Section (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6.3 Bolted Connections (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6.4 Notched Beams (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-2-38
7-2-38
7-2-38
7-2-38
7-2-39
2.7 Recommended Practice for Design of Wood Culverts (1962) . . . . . . . . . . . . . . . . . . . . .
2.7.1 Wood Culverts (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.7.2 General Notes (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.7.3 Design Data (Tangent Track) (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-2-39
7-2-39
7-2-39
7-2-40
2.8 Recommended Practice for Simple Stress Laminated Deck Panels . . . . . . . . . . . . . . .
2.8.1 Material (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.8.2 Fabrication (2000). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-2-40
7-2-40
7-2-43
LIST OF FIGURES
Figure
7-2-1
7-2-2
Description
Page
Tangent Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cooper E 80 Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-2-5
7-2-8
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-2
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
LIST OF TABLES
Table
Description
Page
7-2-1
7-2-2
7-2-3
7-2-4
7-2-5
7-2-6
7-2-7
7-2-8
7-2-9
7-2-10
7-2-11
7-2-12
7-2-13
7-2-14
7-2-15
7-2-16
7-2-17
Lateral Clearance for Curved Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Centrifugal Force for Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Applicability of Adjustment Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Effective Column Length for Various End Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Specific Gravity of Lumber for Design of Connectors in Timber Structures . . . . . . . . . . . . . . . . . .
Applicable Adjustment Factors to Fasteners for Trestle Design . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Design Values for Structural Glued Laminated Softwood Timber - Railroad Applications. . . . . . .
Design Values for Structural Glued Laminated Softwood Timber -- Railroad Applications . . . . . .
Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)1 . . .
Unit Compression (Column) Stresses for Standard Stress Grades. . . . . . . . . . . . . . . . . . . . . . .
Basic Unit Stresses for Bearing on Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Percentage of Basic Stress for Various L/d Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bearing Value for Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Spacing of Prestressing Bar, SP (Inches) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bulkhead Channel Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bearing Plates Sizes For Channel Bulkhead Anchorage Configuration . . . . . . . . . . . . . . . . . . .
Bearing Plates Sizes For Bearing Plate Anchorage Configuration . . . . . . . . . . . . . . . . . . . . . . .
7-2-5
7-2-9
7-2-12
7-2-14
7-2-16
7-2-17
7-2-18
7-2-19
7-2-22
7-2-28
7-2-31
7-2-32
7-2-33
7-2-41
7-2-42
7-2-42
7-2-43
1
SECTION 2.1 DESIGN OF PUBLIC WORKS PROJECTS
2.1.1 GENERAL (1990)
a.
The design, plans, special provisions and specifications for railroad bridges to be built as a public works
project and paid for with public funds administered by a public agency shall be prepared by the
engineering staff of the railroad involved or by a consulting engineer whose selection has been mutually
approved by the railroad and the public agency. The intention of this requirement is that if a consultant
is selected, it shall be one who is familiar with the design of railroad bridges, and particularly with the
special requirements and operating conditions of the railroad concerned so that the time involvement of
the railroad’s engineering staff will be minimized.
b. If a consulting engineer is engaged, the contract for his services may be administered by the public
agency or by the railroad if it so desires. In either case, the technical aspects of the work of the consulting
engineer shall be under the direction of the railroad and the final plans and specifications must meet
with the approval of the railroad.
c.
Specifications and Recommended Practice for Overhead and Other Wood Highway Bridges (2009)
It is recommended that the current edition of Standard Specifications for Highway Bridges adopted by
the American Association of State Highway and Transportation officials be used as a guide for overhead
and other wood highway bridges. Clearances, foundations, construction practices and details should be
with approval and in accordance with individual railroad practice.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-3
3
4
Timber Structures
SECTION 2.2 GENERAL FEATURES OF DESIGN1
2.2.1 MATERIALS (1988)
a.
Wood piles shall conform to AREMA specifications see, Part 1, Material Specifications for Lumber,
Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations
for Fire-Retardant Coating for Creosoted Wood.
b. Structural lumber shall be stress-grade and shall conform to AREMA specifications see, Part 1, Material
Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge
Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood.
c.
Where portions of the structure consists of structural steel, reinforced concrete or masonry, the current
AREMA specifications relating to structures of these materials shall apply, with the allowance for impact
provided for in those specifications.
2.2.2 CLEARANCES (1988)
a.
The clearances on straight track shall be not less than those shown in Figure 7-2-1. On curved track, the
lateral clearance each side of track centerline shall be increased 1-1/2 inches per degree of curvature.
When the fixed obstruction is on tangent track, but the track is curved within 80 feet of the obstruction,
the lateral clearance each side of track centerline shall be increased as shown in Table 7-2-1.
b. Where legal requirements specify greater clearances, such requirements shall govern.
c.
1
The superelevation of the outer rail shall be specified by the Engineer. The distance from the top of rail
to the top of tie shall be assumed as 8 inches, unless otherwise specified by the Engineer.
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-4
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
1
Figure 7-2-1. Tangent Track
3
Table 7-2-1. Lateral Clearance for Curved Track
Distance from Obstruction to
Curved Track in Feet
Increase per Degree of
Curvature in Inches
0-21
1-1/2
21-40
1-1/8
41-60
3/ 4
61-80
3/ 8
4
d. Where there are plans for electrification, the minimum vertical clearance shall be increased to that
specified in Chapter 28, Clearances.
e.
The clearances shown are for new construction. Clearances for reconstruction work or for alterations are
dependent on existing physical conditions and, where reasonably possible, should be improved to meet
the requirements for new construction.
2.2.3 STRINGERS (2009)
a.
The span length, for the purpose of computing bending stresses in the stringers, shall be assumed as the
clear distance face to face of bearings plus 6 inches; except that, if continuity is figured on, the
intermediate support shall be taken at the center of the support.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-5
Timber Structures
b. Stringers shall be selected to provide:
(1) Depth, preferably, not less than one-twelfth of the span.
(2) Width, not less than one-third of the depth.
c.
Stringers shall comprise a group placed to effect, as nearly as practicable, equal distribution of track
loads. On open deck timber bridges, each stringer chord shall be centered as nearly as practicable
beneath the rail it supports.
2.2.4 TIES (2010)1
a.
Cross ties shall be of adequate size to distribute the track load to all stress-carrying stringers.
b. Each tie shall be designed to carry not less than one-third of the maximum axle load, as well as to provide
sufficient stiffness to properly distribute loads to the stringers. Ties shall be secured against bunching,
and the maximum clear space between them, on open deck timber bridges, shall be 8 inches.
c.
On open deck timber bridges, timber bearing ties shall be selected to provide:
(1) Depth, nominal, not less than the following, rounded to the nearest half-inch:
The larger of:
8”
or
( b – N ) 3 – 6t
-------------------------------------6
(which can be approximated as 0.2887 (b - N) - t)
Where:
b = total nominal width of a single stringer chord centered beneath a single rail, in inches.
N = width of rail base, in inches.
t = minimum thickness, in inches, of rail seat: i.e. the portion of the tie plate in direct contact with
the rail base
(2) Width, not less than 8 inches.
(3) Length, not less than 10 feet.
2.2.5 BENTS (1998)
a.
1
Bents shall consist of a sufficient number of piles or posts, so that no member in any bent will be
overstressed under any condition of loading. For the purpose of computing stresses in the bents their
spacing shall be considered as the distance center to center of caps thereon. An approximate analysis to
determine the division of load among the several piles of a bent is given in Appendix 3 - Legacy Designs.
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-6
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
See Table 7-A3-1 thru Table 7-A3-4. The application of this analysis to bents of various typical
dimensions is given in Appendix 3 - Legacy Designs. See Figure 7-A3-5 through Figure 7-A3-57.
2.2.6 PILES AND POST FOOTINGS (1988)
Piles shall be driven to the required bearing capacity in accordance with AREMA specifications see, Part 4,
Construction and Maintenance of Timber Structures and Part 5, Inspection of Timber Structures. Posts shall
be provided with adequate foundation to support the loads superimposed upon them.
2.2.7 CONTEMPORARY AND LEGACY DESIGNS AND DESIGN AIDS (2010)
See Appendix 1 - Contemporary Designs and Design Aids and Appendix 3 - Legacy Designs.
2.2.8 TEMPORARY STRUCTURES (2010)
See Appendix 2 - Temporary Structures.
SECTION 2.3 LOADS, FORCES AND STRESSES1
2.3.1 LOADS AND FORCES (1988)
1
The following loads and forces should be considered:
(1) Dead load.
(2) Live load.
3
(3) Centrifugal force.
(4) Lateral force due to wind load and nosing of locomotives.
(5) Longitudinal force.
4
(6) Impact.
2.3.2 DEAD LOAD (1988)
The dead load shall consist of the estimated weight of the structural member, plus that of the tracks, ballast
and other portions of the structure supported thereby. The weight of material shall be assumed to be as
follows:
Track, rails, inside guard rails, and fastenings . . . . 200 lb per linear foot of track
Ballast, including track ties. . . . . . . . . . . . . . . . . . . . 120 lb per cubic foot
Timber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 lb per foot board measure
Protective coverings. . . . . . . . . . . . . . . . . . . . . . . . . . Actual weight
1
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-7
Timber Structures
2.3.3 LIVE LOAD (2010)
a.
The recommended live load is Cooper E-80 loading with axle loads and axle spacing as shown in Figure
7-2-2. The Engineer shall specify the live load to be used, and such load shall be proportional to the
recommended load, with the same axle spacing.
Figure 7-2-2. Cooper E 80 Load
b. On bridges with ballasted deck the live load shall be assumed as distributed laterally over a width equal
to the length of track ties, plus twice the depth of ballast below the base of tie, unless deck planks are
designed to effect greater distribution of the load.
c.
For members receiving load from more than one track all tracks contributing load shall be assumed fully
loaded.
2.3.4 CENTRIFUGAL FORCE (1988)
a.
On curves, the centrifugal force in percentage of the live load is:
0.00117 S2 D
where:
S = Speed in miles per hour
D = Degree of curve
(Because of the limited duration of the loads, centrifugal force need not be considered in the design of
stringers.)
b. It shall be assumed to act 6 feet above the rail. Table 7-2-2 gives the permissible speeds and the
corresponding centrifugal force percentages for curves with the amounts of superelevation shown. It is
based on a maximum speed of 100 mph and a maximum superelevation of 7 inches, resulting in a
maximum centrifugal force of 17.5 percent.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-8
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
Table 7-2-2. Centrifugal Force for Curves
D
E
S
C
D
E
S
C
0°-10¢
100
1.95
2°-30¢
7
77
17.5
0°-20¢
100
3.90
3°-0¢
7
71
17.5
0°-30¢
0.33
100
5.85
3°-30¢
7
65
17.5
0°-40¢
1.44
100
7.80
4°-0¢
7
61
17.5
0°-50¢
2.56
100
9.75
5°-0¢
7
55
17.5
1°-0¢
3.67
100
11.7
6°-0¢
7
50
17.5
1°-15¢
5.33
100
14.6
8°-0¢
7
43
17.5
1°-30¢
7
100
17.5
10°-0¢
7
39
17.5
1°-45¢
7
93
17.5
15°-0¢
7
32
17.5
2°-0¢
7
87
17.5
20°-0¢
7
27
17.5
2°-15¢
7
82
17.5
C = .00117 S2 D = 1.755 (E+3)
D = Degree of curve.
E = Superelevation in inches.
2
S = Permissible speed in miles per hour.
2
E = --3
C = Centrifugal force in percentage of live load.
1500
S2 = ------------- ( E + 3 )
D
c.
S D
C – 5.265
------------- – 3 = ------------------------1000
1.755
1
If the conditions at the site restrict the speed to less than that shown in the table, the centrifugal force
percentage shall be taken for the greatest speed expected.
3
d. The effect of centrifugal force may be reduced by the compensating effect of the actual amount of
superelevation provided.
2.3.5 OTHER LATERAL FORCES (2009)
2.3.5.1 Wind on the Structure
4
The lateral force due to wind shall be assumed as 30 lb per square foot acting in any horizontal direction as a
moving load:
a.
on 1-1/2 times the vertical projection of the floor system for trestles.
b. for truss spans, on the vertical projection of the span, plus any portion of the leeward trusses not
shielded by the floor system.
c.
on the vertical projection of all bracing, posts, and piles of trestles and towers.
2.3.5.2 Wind on the Train
The wind force on the train shall be taken as 300 lb per linear foot on the track applied 8 feet above the top of
rail. This force shall be considered as a moving load acting in any horizontal direction.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-9
Timber Structures
2.3.5.3 Nosing of the Locomotive
a.
The lateral force due to the nosing of the locomotive shall be a moving concentrated load of 20,000 lb
applied at the top of the rail in either horizontal direction at any point of the span. The resulting vertical
forces shall be disregarded.
b. Because of the limited duration of the loads, the lateral forces from wind and nosing of the locomotive
need not be considered in the design of stringers.
c.
In computing the stability of towers and trestle bents, the structure shall be considered as loaded on the
leeward track with a live load of 1200 lb per linear foot and subjected to a wind force of 300 lb per linear
foot applied 8 feet above the top of rail.
2.3.5.4 Longitudinal Force1
a.
The effect of starting and stopping of trains shall be considered as a longitudinal force, acting 6 feet
above top of rail, and taken as the larger of:
• Force due to braking, equal to 15 percent of the live load.
• Force due to traction, equal to 25 percent of weight on the driving wheels.
b. Design of bridges shall ensure the adequate transfer of longitudinal forces from the structure to ground.
c.
For bridges where by reason of continuity or frictional resistance of rails and floor system, much (or all)
of the longitudinal force will be carried directly to the abutments or embankment, longitudinal force
need not be considered in the design of piles, posts or bracing of bents, (Such bracing is to be designed to
give the necessary L/d stability to the posts).
d. The longitudinal forces shall be considered as being carried by the stringers and deck of the bridge to the
abutments or embankment or other locations providing specifically designed restraint to transfer the
longitudinal force from the bridge to the ground. Intervals of such restraint shall not exceed 550 feet for
material meeting the requirements of Number 1 Douglas Fir or Number 1 Southern Yellow Pine or
better. For other timber materials use 400-foot intervals of restraint to ground unless an evaluation
shows that a larger interval may be used. The design shall ensure the adequacy of timber stringers and
foundation materials to carry this load.
2.3.5.5 Combined Stresses
For stresses produced by longitudinal force, wind or other lateral forces, or by a combination of these forces
with dead and live loads and centrifugal force, the allowable working stresses may be increased 50 percent,
provided the resulting sections are not less than those required for dead and live loads and centrifugal force.
2.3.5.6 Impact
The dynamic increment of load due to the effects of speed, roll and track irregularities is not well established
for timber structures. Its total effect is estimated to be less than the increased strength of timber for the short
cumulative duration of loading to which railroad bridges are subjected in service, and is taken into
consideration in the derivation of allowable working stresses for design.
1
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-10
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
SECTION 2.4 DESIGNING FOR ENGINEERED WOOD PRODUCTS1
2.4.1 DESIGN VALUES FOR GLUED LAMINATED TIMBER (GLULAM) (2006)2
Design values for glulam are derived based on ASTM D3737, Standard Practice for Establishing Allowable
Properties for Structural Glued Laminated Timber, using data from ASTM D2555, Standard Test Methods for
Establishing Clear Wood Strength Values, and full-scale bending and shear tests.
2.4.1.1 Allowable Stresses3
Selected Douglas fir and Southern pine layup combinations intended specifically for railroad stringer
applications -- members to be stressed primarily in bending -- as balanced combinations, are provided in
Table 7-2-7 (see Part 6 Commentary, Article 6.2.4.1.2). Properties for the selected Stress Groups are listed in
Table 7-2-7 based on the loading direction as well as the specific gravity for connection design. Stresses are
listed based on Bending about the X-X Axis, Bending about the Y-Y Axis, for Axially Loaded, and for Fasteners.
1
3
Bending About X-X Axis – The design values to be used when loads are applied perpendicular to the wide
faces of laminations, causing bending about the X-X axis, are designated in Table 7-2-7 by the subscript X. For
example the "Fbx" column in Table 7-2-7, lists allowable bending stresses when members are stressed primarily
in bending with loads applied perpendicular to the wide faces of the laminations.
For balanced layups, the allowable bending stress values with "Tension Zone Stressed in Tension (positive
bending), Fbx+" and “Compression Zone Stressed in Tension (negative bending), Fbx-” are the same.
Bending About Y-Y Axis – The design values to used when loads are applied parallel to the wide faces of
laminations, causing bending about the Y-Y axis, are designated in Table 7-2-7 by the subscript Y. Glulam
members stressed in the Y-Y orientation, such as for ballast deck panels, shall be designed using values with the
Y subscript.
Axial Loading – Glulam members to be designed as columns or truss members shall be designed using values
Ft for tension loading, and Fc for compression loading, under the Axially Loaded heading. For lateral or
eccentric loads on columns, either Fbx or Fby values may be applicable, depending on the loading direction.
Layup combinations made up from all one grade of laminations are listed in Table 7-2-8.
1
See Part 6 Commentary.
See Part 6 Commentary.
3 See Part 6 Commentary.
2
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-11
4
Timber Structures
Fasteners -- For specialized applications including trestle designs, the specific gravity values shall be used in
conjunction with the information in Sections 2.4.1.5 and 2.5.12.
2.4.1.2 Tabular Design Values1
[See Tables 7-2-7 & 7-2-8]
2.4.1.3 Adjustment Factors2
Design values tabulated in Tables 7-2-7 and 7-2-8 shall be adjusted based on the adjustment factors defined
below. Table 7-2-3 indicates the applicability of the various factors to specific design properties.
Railroad Application Adjustment Factors
Table 7-2-3. Applicability of Adjustment Factors
Note: Railroad Use and Wet-Use adjustments are included in Tables 7-2-7 and 7-2-8.
Design Properties Temperature
Beam
CT
Stability CL
Volume
CV
Column Chemical
Stability
(fireCP
retardants)
CR
-------------
Fb’ = Fb x
1.0
1.0
CV
none
none
Ft’ = Ft x
1.0
none
none
none
none
Fv’ = Fv x
1.0
none
none
none
none
Fc^’ = F^ x
1.0
none
none
none
none
Fc’ = Fc x
1.0
none
none
CP
none
E’ = E x
1.0
none
none
none
none
CRR: Railroad Use Factor:
Tabular design values listed in Tables 7-2-7 and 7-2-8, except for Fv, E and Fc perp, include a 0.9 RR Use Factor.
The shear values shown include adjustments that are not cumulative with the RR Use Factor.
Note: The appropriate Railroad Use adjustment factor has been applied to the values listed in
Tables 7-2-7 and 7-2-8 with the exceptions noted in this section and in footnotes to the tables.
CM: Wet Service Factor
Wet-use adjustment factors are applicable when glulam members are subject to in-service equilibrium moisture
content of 16 percent or higher.
Note: The appropriate Wet-Use adjustment factors have been applied to the values listed in Tables
7-2-7 and 7-2-8.
CT: Temperature Factor
1
2
See Part 6 Commentary.
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-12
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
Design values listed in Tables 7-2-7 and 7-2-8 need not be adjusted in railroad use for temperature effects
unless glulam members are subject to sustained exposure to temperatures greater than 100oF (without cycling
intermittently to lower values). Engineers must use judgment when considering the applicability of
temperature adjustment factors (See Commentary).
Cv: Volume Factor
Allowable bending stresses of glulam are affected by geometry and size. Generally, larger sizes have a
correspondingly lower allowable bending stress than smaller members. To account for this behavior, a volume
factor, Cv, shall be applied. Cv shall not exceed 1.0 and is computed as follows:
p
p
p
æ 5.125 ö æ 12 ö æ 21 ö
Cv = ç
÷ ç ÷ ç ÷ £ 1.0
è b ø è dø è  ø
where:
b = width of bending member in inches. For multiple piece width layups, b = width of widest piece in
the layup. For practical purposes, b £10.75 in.
d = depth of bending member in inches
 = length of bending member between points of zero moment in feet
1
p = 1/20 for Southern pine and 1/10 for other species
Cp: Column Stability Factor
Tabulated compressive stresses parallel to grain (Fc) shall be multiplied by the column stability factor, Cp.
CP
=
ìï1 + ( F /F * )
cE
c
í
2c
ïî
é1 + ( FcE /F * c ) ù
ê
ú
2c
ë
û
2
3
ü
( FcE /F * c ) ï
ý
c
ïþ
where:
Fc* = tabulated compression design value multiplied by all applicable adjustment factors except CP
FcE = KcE E’/(e/d)2
KcE = 0.418 for glulam
E’ = tabulated E value multiplied by all applicable adjustment factors
e = effective column length in inches, which shall be determined in accordance with principles of
engineering mechanics or using the unsupported column length multiplied by an appropriate buckling
length coefficient as shown in Table 7-2-4
c = 0.90 for glulam
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-13
4
Timber Structures
Table 7-2-4. Effective Column Length for Various End Conditions
When a compression member is supported throughout the length to prevent lateral displacement in all
directions, Cp = 1.0. In addition, the slenderness ratio, e/d, shall be based on the larger ratio in both
directions, and shall not exceed 50 except that during construction e/d shall not exceed 75.
CL: Beam Stability Factor
The beam stability factor is not applicable when the compression edge of a bending member is supported
throughout its length to prevent lateral displacement, and the end points of bearing have been laterally
supported to prevent rotation. CL = 1.0 under these conditions. This condition is typical for stringer
applications. The beam stability factor shall not apply simultaneously with the volume factor. Beam stability
considerations for other conditions are beyond the scope of this document. The National Design Specification
(NDS) includes information on special cases.
CR: Chemical Treatment Factor
Glulam industry standards do not specify reductions in "dry" design values for glulam preservative treated in
accordance with AWPA Standard C28. Use of adjustments to account for wet-use in service conditions
(moisture content of 16 percent or higher) are considered adequate to include possible effect from the treating
process, including incising. Fire-retardant coatings that may be specified in accordance with Section 1.8
require no additional adjustment in design properties. Adjustment for the tabulated design values, including
connection design values, may be necessary with some fire-retardant treatments. Values for these adjustments
may be obtained from the company providing the treatment and redrying services.
2.4.1.4 Other Design Considerations
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-14
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
Notches and Holes
Field modifications of glulam members such as notching, tapering or drilling not shown on the design or shop
drawings shall be avoided and never done without a thorough understanding of their effects on the structural
integrity of the members involved. This understanding shall include knowledge of how affected members are
expected to perform in the design application.
Notches: Notching of bending members shall be avoided whenever possible, especially on the tension faces, for
both simple span and continuous span applications. Notching of bending members on the tension face results
in stress concentrations that can induce tension perpendicular-to-grain stresses that can propagate into splits.
Normal adjustments used to account for notching in building structures are not applicable to railway bridge
applications.
Horizontal Holes: Holes drilled through width of bending members should be limited to locations away from
shear and moment critical zones as determined by the design engineer. Field-drilled horizontal holes shall not
be used as attachment points for brackets or other load bearing hardware unless specifically designated in the
design. Any horizontal holes required for support of significant weight, such as water mains, must be located
above the neutral axis of the member in zones stressed to less than 50 percent of the design flexural stresses.
Vertical Holes: Vertical holes drilled through the depth of a glulam beam cause a reduction in the capacity at
that location directly proportional to the ratio of 1-1/2 times the diameter of the hole to the width of the beam.
For example, a 2-inch vertical hole drilled in a 8-3/4 inch wide beam may be assumed to reduce the allowable
capacity of the beam by approximately (2 x 1.5)/8.75 = 34%. For this reason when it is necessary to drill
vertical holes in glulam bending members, the holes should be positioned in areas of the member stressed to
less than 50 percent of design stress in bending.
1
Holes for Support of Suspended Equipment: Heavy equipment or piping suspended from glulam beams
shall be attached such that loads are applied to the top to the member to avoid introducing tension
perpendicular-to-grain stresses.
Storage & Handling: Glulam members should be stored on evenly spaced blocks to minimize ground contact
and to prevent warping or permanent-set in bending (Y-Y axis). Physical damage such as gouges and splits
should be reviewed for possible structural significance by the Engineer of Record prior to installation. Also see
Article 1.3.1.10.
3
2.4.1.5 Connections and Fasteners
4
Glulam Simple or Continuous Span Bridges and Bridge Decks Panels:
Timber railway bridge components are generally designed to take high rail loads in full bearing as loads are
transferred through bridge ties to stringers, pile caps and pile ends. Where connections are used to maintain
alignment and resist lateral loads, stresses developed at the connections can be amplified by dimension changes
inherent in structural components subject to in-service cyclic wetting and drying conditions. Structural
performance and serviceability of any glulam or solid sawn timber structure is dependent on proper design of
connections. Larger sizes and longer spans made possible with glulam components make the proper detailing
of connections critical. Careful consideration of moisture related expansion and contraction characteristics of
wood is essential in detailing glulam connections to prevent introducing tension perpendicular-to-grain
stresses.
Wood expands and contracts as a result of changes in its internal moisture content. While expansion in the
direction parallel to the grain in a wood member may be slight, dimensional changes in the direction
perpendicular to the grain can be significant and must be accounted for in connection design detailing. A 24
inch deep beam can decrease in depth through shrinkage by approximately 1/4 inch as it changes from 12 to 8
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-15
Timber Structures
percent in equilibrium moisture content. Connections should be detailed to allow for such changes by over
sizing or slotting bolt holes in steel connectors.
In addition to moisture-induced tension perpendicular-to-grain stresses, similar failures can result from a
number of factors associated with poor connection detailing. Improper beam notching, application of eccentric
(out of plane) loads, and loading beams in tension perpendicular to the wide face of the laminations can induce
internal moments and tension perpendicular-to-grain stresses.
The following seven basic principles will provide guidance for efficient, durable and structurally sound
connections:
a.
Transfer loads in compression/bearing whenever possible.
b. Allow for dimensional changes in the glulam due to potential in-service moisture cycling.
c.
Avoid the use of details that induce tension-perpendicular-to-grain stresses.
d. Avoid moisture entrapment in connections.
e.
Do not place glulam in direct contact with masonry or concrete (use steel plates at the interface).
f.
Avoid eccentricity in joint details.
g.
Minimize exposure of end grain.
Table 7-2-5 contains a partial list of specific gravity that may be used for connector design in accordance with
the National Design Specification (NDS) published by the American Forest and Paper Association. Also
tabulated in Table 7-2-5 are species groups for split ring and shear plate connectors.
Table 7-2-5. Specific Gravity of Lumber for Design of Connectors in Timber Structures
Species
Specific Gravity
Species Group for Split Ring
and Shear Plate Connectors
Alaska Cedar
0.42
C
Douglas fir
0.50
B
Douglas fir (North)
0.49
B
Engleman Spruce-Lodgepole Pine
0.38
D
Hem fir
0.43
C
Hem fir (North)
0.46
C
Mixed Oak
0.68
A
Mixed Maple
0.55
B
Redwood (open grain)
0.37
D
Redwood (close grain)
0.44
C
Southern Pine
0.55
B
Spruce-Pine-Fir
0.42
C
Spruce-Pine-Fir (South)
0.36
D
Western Hemlock
0.47
C
Western Woods
0.36
D
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-16
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
Glulam Trestles:
Details on connector and fastener design needed for glulam or timber trestle design require specialized
application of connection design principles. This information is covered in detail in the National Design
Specification (NDS), for Wood Construction available through the American Wood Council (www.awc.org).
Details on design values for the use of bolts, screws, nails, spikes, shear plates and split rings are provided in
the NDS.
Consider the following items when determining design values for mechanically fastened joints in glulam or
timber trestles:
a.
Lumber species, specific gravity, dowel bearing strength
b. Critical section or net section
c.
Angle of load with respect to the grain
d. On center spacing and pitch spacing of fastening groups
e.
Edge and end distances
f.
Conditions of loading
g.
Eccentricity, and
1
h. Adjustment factors applied to tabular design values.
Adjustment factors applicable to fasteners for trestle design may include:
Table 7-2-6. Applicable Adjustment Factors to Fasteners for Trestle Design
CD - Duration of load
CS - Spacing
CM - Moisture content
Cd - Depth of embedment
CT - Temperature
Cg - Group action
Ce - Edge distance
Cst - Steel sideplate
3
4
Cn - End distance
The tabulated design properties for connection designs in wood are tied directly to specific gravity. Species
groups and specific gravity values to be used in conjunction with the Tables 7-2-7 and 7-2-8 are given in
Table 7-2-5.
2.4.2 DESIGN EQUATIONS (2006)1
Equations from Articles 2.5.7, 2.5.8, and 2.5.9 are applicable to the design of glued laminated timbers. Use
appropriate design stresses from Tables 7-2-7 and 7-2-8.
1
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-17
Timber Structures
7-2-18
AREMA Manual for Railway Engineering
© 2011, American Railway Engineering and Maintenance-of-Way Association
See Part 6 Commentary.
1
1
Table 7-2-7. Design Values for Structural Glued Laminated Softwood Timber - Railroad Applications
1 See Part 6 Commentary.
7-2-19
Design of Wood Railway Bridges and Trestles for Railway Loading
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
Table 7-2-8. Design Values for Structural Glued Laminated Softwood Timber -- Railroad Applications 1
Timber Structures
SECTION 2.5 ALLOWABLE UNIT STRESSES FOR STRESS-GRADED LUMBER1
2.5.1 WORKING UNIT STRESSES (1988)
a.
Working unit stresses to be used for design shall be those shown in Table 7-2-9 for the appropriate
condition of use and species.
b. In locations of more extreme exposure than “occasionally wet but quickly dried,” and where serious
depreciation is more apt to occur, a further reduction in the working stresses for extreme fiber and
compression should be made.
c.
Where timber is treated by creosoting or other process rendering it decay resistant, the working stresses
for continuously dry may be used except in compression perpendicular to the grain and for joists and
planks continuously submerged.
2.5.2 FORM FACTOR (1988)
The size and shape of a beam affects the modulus of rupture. This effect is called the form factor. A factor of
0.90 has been assumed in arriving at allowable stresses, so that for rectangular beams of ordinary size no form
factor need be figured. The form factor for beams of all sizes and for round and box or I-section are given in the
Wood Handbook.
2.5.3 DEFLECTION, PERMANENT SET (1988)
The modulus of elasticity given in Table 7-2-9 gives the deflection which will occur immediately on application
of load. Under long continued load there will be an additional sag or permanent set which will be approximately
equal to the elastic deflection.
2.5.4 COMPRESSION PARALLEL TO GRAIN OR CENTRALLY LOADED COLUMNS (2009)
a.
Stress values in Table 7-2-9 are to be used for posts and struts where the unsupported length is not
greater than 11 times the least dimension, and for end bearing of compression members.
L
b. For columns where ---- is more than 11, the allowed working stresses are:
d
1 L 4
P
---- = c 1 – --- æ --------ö for L/d less than K
3 è Kdø
A
0.274E
P
---- = ------------------- for L/d greater than K
A
Lö 2
æ --è Dø
E
K = 0.641 ---c
p E
K = --- -----2 6c
or
where:
P = total load in pounds
1
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-20
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
A = area in square inches
c = working unit stress in compression parallel to the grain for short columns
L = unsupported length in inches
d = least dimension in inches (also see Article 2.5.14)
E = modulus of elasticity (Table 7-2-10)
P
Table 7-2-10, gives values of allowed ---A
L
Columns should be limited to ---- = 50
d
2.5.5 BEARING (1988)
a.
The working stresses for compression perpendicular to grain apply to bearings 6 inches or more in
length located anywhere in the length of a timber and to bearings of any length at the ends of beams or
other members. For bearings shorter than 6 inches located 3 inches or more from the end of a timber the
stresses may be increased in accordance with the following factors:
Length of bearing, inches
1/ 2
1
1-1/2
2
3
4
6
Factor of increase
1.75
1.38
1.25
1.19
1.13
1.10
1.00
b. For stress under a washer or other round bearing area, the same factor may be taken as for a bearing
whose length equals the diameter of the washer.
1
2.5.6 ALLOWABLE UNIT STRESSES FOR STRESS-GRADED LUMBER (2010)
2.5.6.1 Working Stresses (1990)
3
Recommended working unit stresses for most commercial stress-grades of lumber have been determined in
accordance with the principles set forth in the ASTM D245 for several conditions of use. These stresses are
shown in Table 7-2-9. For other conditions the stresses should be adjusted as recommended in Section 2.7,
Recommended Practice for Design of Wood Culverts (1962).
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-21
Timber Structures
Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)1
(See Notes)
Railroad values wet conditions (over 19% MC)
Grade
Size
Classification
Fb
psi
Ft
psi
Fv psi
Fc^
psi
Fc
psi
E
ksi
235
615
1400
Grading
Agency
Rules
Eastern Spruce
Select Str.
No. 1
Select Str.
No. 1
Beams and
Stringers
Posts and
Timbers
945
565
115
810
385
115
235
510
1400
880
610
120
235
635
1400
720
495
120
135
555
1400
Select Str.
995
520
120
200
865
1170
No. 1
670
360
120
200
755
1080
595
315
120
200
720
990
345
180
120
200
520
900
670
360
120
200
865
900
385
205
120
200
720
810
460
250
120
200
565**
900
No. 2
No. 3
Construction
Standard
2” to 4” thick
by 2” and wider
(use dimension
lumber
adjustment
factors)
Stud
NELMA
Hem-Fir
Select Str.
No. 1
Select Str.
No. 1
Beams and
Stringers
1170
675
125
245
760
1300
945
475
125
245
615
1300
Posts and
Timbers
1080
720
125
245
800
1300
880
585
125
245
695
1300
1070
835
130
245
1080
1440
Select Str.
No. 1 & better
840
655
130
245
970
1350
750
565
130
245
970
1350
650
475
130
245
935
1170
385
270
130
245
655**
1080
750
540
130
245
1115
1170
Standard
420
295
130
245
935
1080
Stud
520
360
130
245
720**
1080
No. 1
No. 2
No. 3
Construction
1
2” to 4” thick
by 2” and wider
(use dimension
lumber
adjustment
factors)
WCLIB
WWPA
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-22
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)1
(Continued)
Railroad values wet conditions (over 19% MC)
Size
Classification
Grade
Fb
psi
Ft
psi
Fv psi
Fc^
psi
Fc
psi
E
ksi
Grading
Agency
Rules
Douglas Fir (See Note 4)
Dense Select Structural
1710
990
150*
440
1065
1700
Select Struct.
1440
855
150*
380
900
1600
1700
Beams and
Stringers
Dense No. 1
1395
700
150*
440
900
No. 1
1215
610
150*
380
760
1600
Dense Select Structural
1575
1035
150*
655
1215
1700
Select Struct.
1350
900
150*
565
1035
1600
1260
855
150*
655
1080
1700
No. 1
1080
745
150*
565
900
1600
Select Struct.
1150
900
155
380
1225
1710
No. 1 & better
920
720
155
380
1115
1620
765
610
155
380
1080
1530
690
520
155
380
970
1440
405
295
155
380
700**
1260
Dense No. 1
No. 1
No. 2
No. 3
Construction
Posts and
Timbers
2” to 4” thick
by 2” and wider
(use dimension
lumber
adjustment
factors)
765
585
155
380
1190
1350
Standard
440
340
155
380
1010
1260
Stud
535
405
155
380
610
1260
WCLIB
WWPA
NLGA
1
3
4
1
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-23
Timber Structures
Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)1
(Continued)
Railroad values wet conditions (over 19% MC)
Size
Classification
Grade
Fb
psi
Ft
psi
Fv psi
Fc^
psi
Fc
psi
E
ksi
150*
395
990
1600
1500
Grading
Agency
Rules
Southern Pine
Dense Select Structural
1575
Select Struct.
No. 1 Dense
5” x 5” and
larger
No. 1
1350
900
150*
340
855
1395
945
150*
395
880
1600
1215
810
150*
340
745
1500
No. 2 Dense
880
585
150*
395
565
1300
No. 2
765
495
150*
340
475
1200
Dense Select Structural
2335
1485
135
400
1620
1710
Select Struct.
2180
1440
135
340
1510
1620
No. 1 Dense
1530
990
135
400
1440
1620
1415
945
135
340
1330
1530
1300
790
135
400
1330
1530
1150
745
135
340
1190
1440
2” to 4” thick
and
2” to 4” wide
No. 1
No. 2 Dense
No. 2
Nol 3 & stud
765
430
135
340
700
1260
Dense Select Structural
2065
1350
135
400
1550
1710
Select Struct.
1950
1260
135
340
1440
1620
No. 1 Dense
2” to 4” thick
and
5” to 6” wide
No. 1
No. 2 Dense
1340
855
135
400
1370
1620
1260
810
135
340
1260
1530
1110
700
135
400
1260
1530
No. 2
955
655
135
340
1150
1440
Nol 3 & stud
675
385
135
340
665
1260
Dense Select Structural
1875
1215
135
400
1475
1710
Select Struct.
1760
1170
135
340
1370
1620
1260
790
135
400
1295
1620
1150
745
135
340
1190
1530
1070
610
135
400
1225
1530
No. 1 Dense
2” to 4” thick
and
8” wide
No. 1
No. 2 Dense
No. 2
920
585
135
340
1115
1440
Nol 3 & stud
630
360
135
340
630
1260
Dense Select Structural
1645
1080
135
400
1440
1710
1620
Select Struct.
1570
990
135
340
1330
No. 1 Dense
1110
700
135
400
1260
1620
995
655
135
340
1150
1530
2” to 4” thick
and
10” wide
No. 1
No. 2 Dense
No. 2
920
565
135
400
1190
1530
945
520
135
340
1080
1440
Nol 3 & stud
540
295
135
340
610
1260
Dense Select Structural
1570
990
135
400
1405
1710
Select Struct.
1455
945
135
340
1295
1620
No. 1 Dense
1035
655
135
400
1225
1620
955
610
135
340
1150
1530
1035
520
135
400
1150
1530
No. 2
880
495
135
340
1045
1440
Nol 3 & stud
520
295
135
340
745**
1260
No. 1
No. 2 Dense
1
1080
2” to 4” thick
and
12” wide
SPIB
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-24
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)1
(Continued)
Railroad values wet conditions (over 19% MC)
Grade
Size
Classification
Fb
psi
Ft
psi
Fv psi
Fc^
psi
Fc
psi
E
ksi
1100
Grading
Agency
Rules
Mixed Maple
Select Str.
No. 1
Select Str.
No. 1
Beams and
Stringers
Posts and
Timbers
Select Str.
No. 1
No. 2
No. 3
Construction
Standard
2” to 4” thick by
2” and wider (use
dimension
lumber
adjustment
factors)
Stud
890
590
145
375
615
710
485
145
375
530
1100
890
590
145
375
615
1100
710
485
145
375
530
1100
765
540
170
540
630
1170
555
385
170
540
630**
1080
535
385
170
540
495**
990
305
225
170
540
295**
900
610
430
170
540
655**
990
345
250
170
540
520**
900
420
295
170
540
315**
900
NELMA
Red Oak
Select Str.
No. 1
Select Str.
No. 1
Beams and
Stringers
Posts and
Timbers
Select Str.
No. 1
No. 2
No. 3
Construction
Standard
2” to 4” thick by
2” and wider (use
dimension
lumber
adjustment
factors)
Stud
1215
720
140
495
675
1200
1035
495
140
495
575
1200
1125
765
140
495
715
1200
900
610
140
495
635
1200
880
610
150
495
720
1260
630
450
150
495
745**
1170
610
430
150
495
565**
1080
365
250
150
495
340**
990
710
495
150
495
610**
1080
400
270
150
495
585**
990
480
340
150
495
360**
990
1
NELMA
3
4
1
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-25
Timber Structures
Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad
Loading (Visual Grading)11 (Continued)
* : 150 psi value was derived from AAR beam fatigue tests
Note 1:
Abbreviations used in this table are as follows:
NELMA – Northeastern Lumber Manufacturers Association, Inc.
NLGA - National Lumber Grades Authority
SPIB – Southern Pine Inspection Bureau
WCLIB – West Coast Lumber Inspection Bureau
WWPA – Western Wood Products Association
Fb – Unit Stress in Extreme Fiber in Bending
Ft – Unit Stress in Tension Parallel to the Grain
Fv – Unit Stress in Horizontal Shear
Fc^ – Unit Stress in Compression Perpendicular to the Grain
Fc – Unit Stress in Compression Parallel to the Grain
E – Modulus of Elasticity
Str. – Structural
MC – Moisture Content
Note 2:
Conditions of use where the moisture content will not exceed 19%, the tabulated values above may be
multiplied by the following factors:
Dry use Factor: Cm
for 5” and Thicker Lumber
Fb
Ft
Fv
Fc^
Fc
E
1.00 1.00 1.00 1.49 1.10 1.00
for Nominal 2” to 4” Thick Lumber
Fb
Ft
Fv
Fc^
Fc
E
1.18 1.00 1.03 1.49 1.25
1.11
do not adjust values with ** next to them
Note 3:
For Beams & Stringers, Posts & Timbers, and Southern Pine sections 5” and wider, when the depth of
the member exceeds 12” the tabulated bending design stresses, Fb, shall be multiplied by the following
size factor: Cr = (12/d)1/9
Note 4:
Douglas-Fir South, Inland Douglas Fir and Douglas Fir-Larch are not deemed appropriate for outdoor
Railway use.
1 See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-26
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading
(Visual Grading)11 (Continued)
Note 5:
For all species except Southern Pine, the tabulated bending, tension, and compression parallel to grain
design values for dimension lumber 2” to 4” thick shall be multiplied by the following size factors:
Size Factors: Cf
Fb
Ft
Fc
Thickness
Grade
Select Structural
No. 1 & Btr.
No. 1, No. 2
No. 3
Stud
Width
2” & 3”
4”
2”, 3” & 4”
1.5
1.5
1.5
1.15
5”
1.4
1.4
1.4
1.1
6”
1.3
1.3
1.3
1.1
8”
1.2
1.3
1.2
1.05
10”
1.1
1.2
1.1
1.0
12”
1.0
1.1
1.0
1.0
14” and up
0.9
1.0
0.9
0.90
2”, 3” & 4”
1.1
1.1
1.1
1.05
5” & 6”
1.0
1.0
1.0
1.0
8” and up
Construction, Standard
Use No. 3 Grade design values and Cf
2”, 3” & 4”
1.0
1.0
1.0
1.0
1
Note 6:
The design values for dimension lumber 2” to 4” thick are based on edge-wise use. When such lumber is
used flat-wise, the design values for extreme fiber in bending for all species may be multiplied by the
following factors:
Width
2” & 3”
4 inch
2” & 3”
1.0
~
4”
1.1
1.0
5”
1.1
1.05
6”
1.15
1.05
8”
1.15
1.05
10” & up
1.2
1.1
Note 7:
1
Thickness
3
4
The design values for beams and stringers are based on edge-wise use. When such lumber is used flatwise, the design values for extreme fiber bending and modulus of elasticity for all species except
Southern Pine shall be multiplied by the following factors:
Grade
Fb
E
Select
Structural
0.86
1.00
No. 1
0.74
0.90
Note 8:
Grading restrictions for beams and stringers shall apply over the entire length of each piece. This will
make each piece suitable for use in simple spans as well as over 2 or more continuous spans or under
concentrated loads without the necessity of making special shear or other special stress requirements.
Note 9:
For normal conditions other than railroad loading, allowable unit stresses may be multiplied by 1.11 for
Fb , Ft , Fv, Fc^, and Fc. E shall remain unchanged.
See Part 6 Commentary.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-27
Short
Column
Stress
1300
1200
AREMA Manual for Railway Engineering
© 2011, American Railway Engineering and Maintenance-of-Way Association
1100
1000
900
800
Stress at Ratio of Length to Least Dimension (L/d)
Modulus of
Elasticity
K
1,300,000
11
12
14
16
18
20
25
30
35
40
45
50
20.3
1300
1247
1203
1132
1032
892
570
396
291
223
176
142
1,600,000
22.5
1300
1265
1235
1190
1123
1030
701
487
358
274
216
175
1,200,000
20.3
1200
1151
1110
1045
953
823
526
365
268
206
162
132
1,300,000
21.1
1200
1158
1122
1068
989
827
570
396
291
223
176
142
1,500,000
22.7
1200
1169
1142
1102
1042
959
658
457
336
257
203
164
1,600,000
23.4
1200
1172
1148
1112
1060
986
701
487
358
274
216
175
1,200,000
21.2
1100
1063
1031
981
910
810
526
365
268
206
162
132
1,300,000
22.1
1100
1068
1041
999
938
854
570
396
291
223
176
142
1,500,000
23.7
1100
1076
1055
1024
978
914
658
457
336
257
203
164
1,600,000
24.4
1100
1078
1060
1032
991
935
701
487
358
274
216
175
1,200,000
22.2
1000
972
947
910
856
780
526
365
268
206
162
132
1,300,000
23.1
1000
976
955
923
877
813
570
396
291
223
176
142
1,500,000
24.8
1000
982
966
942
908
859
658
457
336
257
203
164
1,600,000
25.6
1000
984
970
948
918
876
697
487
358
274
216
175
1,000,000
21.4
900
870
845
806
750
674
438
304
224
171
135
110
1,200,000
23.4
900
879
861
834
795
740
526
365
268
206
162
132
1,600,000
27.0
900
888
878
863
841
810
680
487
358
274
216
175
1,000,000
22.7
800
779
762
734
694
639
438
304
224
171
135
110
Timber Structures
7-2-28
Table 7-2-10. Unit Compression (Column) Stresses for Standard Stress Grades
Design of Wood Railway Bridges and Trestles for Railway Loading
2.5.7 BEARING AT ANGLE TO GRAIN (1988)
a.
Allowed bearing stresses on surfaces at an angle to the direction of the grain, may be taken from the
following formula:
PQ
N = -----------------------------------------------P sin 2 q + Q cos 2 q
where:
N = Unit compressive stress in a direction at inclination with the direction of the grain
P = Unit stress in compression parallel to the grain – Table 7-2-7
Q = Unit stress in compression perpendicular to the grain – Table 7-2-9
q = Angle between the grain and the normal to the inclined surface
b. The chart shown in Appendix 1 - Contemporary Designs and Design Aids, Figure 7-A1-3 gives a
graphical solution.
2.5.8 COMBINED AXIAL AND BENDING LOADS (1988)
a.
The general formulas for safe eccentric or combined bending and end loadings of square or rectangular
wood columns are:
P 6e
zP P
---- æ ------ö + M
----- + ------- ---è
ø
A
A d
S
A + --------------------------------------------- = 1
f
C
P 15e
zP P
---- æ ---------ö + M
----- + ------- ---è
ø
A
A 2d
S
A- -----------------------------------------------+ - = 1
c
P
f – ---A
1
L
for columns with ---- of 11 or less, and
d
3
L
for columns with ---- of 20 or more
d
where:
4
P
---- = average compressive stress induced by axial load.
A
M
----- = flexural stress induced by side loads.
S
z = ratio of flexural to average compressive stress when both result from the same loading, so that
the ratio remains constant while the load varies.
e = eccentricity of axial load.
d = width of column, measured in the direction of side loads and eccentricity. This is the depth to
use in computing the flexural stress.
f = allowable working unit stress for extreme fiber in bending.
c = allowable unit stress for the member if used as a centrally loaded column.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-29
Timber Structures
L
b. Stresses for columns with ---- between 11 and 20 are determined by straight-line interpolation between
d
L
L
the formula for a ---- of 11 and the formula for a ---- of 20.
d
d
c.
Where side loads are such that maximum deflection and flexural stress do not occur at mid-length of the
M
column, it is generally satisfactory to consider ----- as the maximum flexural stress due to the load or
S
loads, regardless of its position in the length of the column.
d. A more detailed discussion may be found in U.S. Forest Products Laboratory Report No. R 1782,
Formulas for Columns with Side Loads and Eccentricity.
2.5.9 HORIZONTAL SHEAR (2006)
a.
The following procedure shall be used for horizontal shear at the neutral plane:
3V
S = ----------2bh
where:
S = Maximum unit shear stress in pounds per square inch
V = Maxiumum shear in pounds
b = Breadth of beam in inches
h = Height of beam in inches
b. The results obtained must not exceed the allowable unit shear stress.
c.
In calculating the maximum shear, V, use the following rules:
(1) V shall be calculated at a distance away from the face of support equal to the height of the beam.
(2) Neglect all loads within the height of the beam from the face of the support.
(3) Moving loads shall be placed such that they will produce the maximum value for V.
(4) When a beam spans continuously over one or more supports, continuity shall be considered when
calculating V.
(5) Take into account any relief to the beam under consideration resulting from the loading being
distributed to adjacent parallel beams by flooring or other members of the construction.
2.5.10 NOTCHES (1988)
Notches with square corners should be avoided where possible because there will be a strong tendency for a
check or split to result. If a square-cornered notch is used near the end of a piece, the effective depth in
computing shear should be taken as
2
c
----d
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-30
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
where:
c = the net depth at the notch
d = total depth of the piece
2.5.11 SHEARING STRESS (1988)
The allowable shearing stress for joint details shall be taken at 50 percent greater than the values for
horizontal shear in Table 7-2-9.
2.5.12 BEARING ON BOLTS (1988)
a.
Working unit stresses for timber bearing on bolts may be taken as the product of the following factors:
• Basic unit stress for bearing, Table 7-2-11.
• Factor based on L/d ratio of bolt, Table 7-2-12.
• For bearing perpendicular to the grain only, a factor as follows:
Diameter of bolt, inches
3/ 8 1 / 2 5 / 8 3 / 4 7 / 8
Diameter factor
1.95 1.68 1.52 1.41 1.33 1.27 1.19
1
1 ---1 /4 1 --- 1 / 2 1 --- 3 / 4
1.14
1 1. 0
2 2 --- 1/ 2 3
1.07 1.03
1
1
b. Bolts acting at an angle with the grain shall be allowed bearing values by the formula in Article 2.5.7,
where P and Q are allowed bearing values computed for the L/d ratio of the bolt. Table 7-2-13 shows
bearing values for bolts for the most common condition of exposure occasionally wet but quickly dried.
For locations continuously dry, use 4/3 the values in the table, and for locations damp or wet most of the
time, use 8/9 the values in the table.
3
Table 7-2-11. Basic Unit Stresses for Bearing on Bolts
Basic Unit Stress
Group
Species of Wood
Parallel with Perpendicular
Grain
to Grain
4
Softwoods (Conifers)
1
Hemlock, Eastern
800
150
2
Cedar, Port Orford and Western Red; Douglas Fir,
Inland
1000
200
3
Cypress, Southern; Douglas Fir, Coast; Pine,
Southern; Redwood
1300
275
Hardwoods (Broad Leaved)
1
Chestnut
925
175
2
Elm, soft; Gum, Black and Red; Tupelo
1200
250
3
Ash, white; Beech; Birch; Elm, Rock; Maple,
hard; Oak, red, white
1500
400
Note:
Above values are for continuously dry location.
For occasionally wet but quickly dried, use 3/4 of values in table.
For damp or wet most of the time, use 2/3 of values in table.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-31
Timber Structures
Table 7-2-12. Percentage of Basic Stress for Various L/d Values
Parallel with Grain
Length
---------------------------Diameter
L
--d
Ratio
Common Bolts
Perpendicular to Grain
High Strength Bolts
Common Bolts
Conifers
High
HardConifers Group 3
woods Strength
Group Group Group Group Group Group Group
HardGroup
Group Bolts All
1
2
3
1
2
3
1
woods
2
Groups
3
Group 2
1 to 2
100
100
100
100
100
100
100
100
100
100
100
3
100
100
99.0
100
100
100
100
100
100
100
100
4
99.5
97.4
92.5
100
100
99.0
100
100
100
100
100
5
95.4
88.3
80.0
100
99.8
96.0
100
100
100
100
100
6
85.6
75.8
67.2
100
95.4
89.5
100
100
100
96.3
100
7
73.4
65.0
57.6
95.8
88.8
81.0
100
100
97.3
86.9
100
8
64.2
56.9
50.4
39.3
81.2
73.0
100
96.1
88.1
75.0
100
9
57.1
50.6
44.8
82.5
74.2
66.4
94.6
86.3
76.7
64.6
97.7
10
51.4
45 5
40.3
75.8
68.0
60.2
85.0
76.2
67.2
55.4
90.0
11
46.7
41.4
36.6
69.7
61.9
54.8
76.1
67.6
59.3
48.4
81.5
12
42.8
37.9
33.6
64.0
56.7
50.2
68.6
61.0
52.0
42.5
73.6
13
39.5
35.0
31.0
59.1
52.4
46.3
62.2
55.3
45.9
37.5
66.9
Note:
The above values are for joints with metal plates. (View a) Where wood
splice plates are used, each one-half of thickness of main timber, (View b)
use 80 percent of tabular value for bearing parallel with grain; no reduction
for bearing perpendicular to grain.
Common bolts: yield point about 45,000 pounds per square inch.
High strength bolts: yield point about 125,000 pounds per square inch.
L = length of bolt in main timber in inches.
d = diameter of bolt in inches.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-32
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
3
Perpendicular to
Grain, Q
2-5/8
Projected Area of Bolt, square inches
2
Hardwoods (Broad Leaved)
L/D
1-5/8
Softwoods (Conifers)
Diameter of Bolt, inches
Length of Bolt in Main Member L, inches
Table 7-2-13. Bearing Value for Bolts
Allowable Load per Bolt for Timber Bearing on Common Bolts with Wood Side Plates
(For timber occasionally wet but quickly dried.)
1 /2
3.3
0.813
150
390
200
480
280
620
180
450
260
580
410
710
5 /8
2.6
1.016
170
490
230
610
320
790
200
560
290
730
460
910
3 /4
2.2
1.219
190
590
260
730
350
950
230
680
320
880
520 1090
7 /8
1.9
1.422
210
680
280
850
390 1110
250
790
350 1020
570 1280
1
1.6
1.625
230
780
310
970
430 1270
270
900
390 1170
620 1460
1 /2
4.0
1.000
190
480
250
580
350
720
220
550
310
700
500
5 /8
3.2
1.250
210
600
280
750
390
950
250
690
360
900
570 1100
3 /4
2.7
1.500
240
720
320
900
440 1160
280
830
400 1080
630 1340
7 /8
2.3
1.750
260
840
350 1050
480 1360
310
970
440 1260
700 1570
1
2.0
2.000
290
960
380 1200
520 1560
330 1110
480 1440
760 1800
1 /2
5.3
1.313
250
580
330
670
450
780
290
670
410
650
5 /8
4.2
1.641
280
780
370
940
510 1150
330
900
470 1130
750 1320
3 /4
3.5
1.969
310
940
420 1170
570 1470
360 1090
520 1400
830 1700
7 /8
3.0
2.297
340 1100
460 1380
630 1770
400 1270
570 1650
920 2050
1
2.6
2.625
380 1260
500 1570
690 2040
440 1460
630 1890 1000 2350
1 /2
6.0
1.500
280
610
380
520
330
470
5 /8
4.8
1.875
320
870
430 1010
590 1210
370 1000
530 1220
860 1390
3 /4
4.0
2.250
360 1070
480 1310
650 1620
420 1240
590 1580
950 1870
7 /8
3.4
2.625
390 1260
520 1560
720 1970
460 1450
650 1870 1050 2280
1
3.0
3.000
430 1440
570 1800
790 2320
500 1660
710 2160 1140 2670
Group 1
Hemlock,
Eastern
Group 2
Group 3
Cedar, Port Cypress,
Orford and Southern;
Western Douglas Fir,
Red;
Coast; Pine,
Douglas Fir, Southern;
Inland
Redwood
Group 1
Chestnut
Group 3
Ash, White;
Group 2
Beech,
Elm, Soft;
Birch, Elm,
Gum, Black
Rock;
and Red;
Maple,
Tupelo
Hard; Oak,
Red, White
680
790
710
800
820
730
830
3
900
910
See Table 7-2-13 footnotes on Page 7-2-78
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
1
7-2-33
4
Timber Structures
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
4-1/2
Projected Area of Bolt, square inches
4
Hardwoods (Broad Leaved)
L/D
3-5/8
Softwoods (Conifers)
Diameter of Bolt, inches
Length of Bolt in Main Member L, inches
Table 7-2-13. Bearing Value for Bolts (Continued)
Allowable Load per Bolt for Timber Bearing on Common Bolts with Wood Side Plates
(For timber occasionally wet but quickly dried.)
1/ 2
7.3
1.813
340
610
450
680
590
790
400
710
540
820
760
910
5/ 8
5.8
2.266
390
950
520 1060
710 1230
450 1100
650 1280 1000 1420
3/ 4
4.8
2.719
430 1260
580 1470
790 1750
500 1450
720 1760 1150 2020
7/ 8
4.1
3.172
470 1510
630 1840
870 2260
550 1740
790 2200 1270 2610
1
3.6
3.625
520 1730
690 2140
950 2690
600 2010
860 2570 1380 3100
1/ 2
8.0
2.000
380
610
480
610
440
550
5/ 8
6.4
2.500
430
960
570 1070
780 1260
500 1120
700 1290 1060 1420
3/ 4
5.3
3.000
480 1330
630 1520
870 1770
560 1540
790 1830 1250 2060
7/ 8
4.6
3.500
520 1630
700 1930
960 2320
610 1890
870 2320 1400 2680
1
4.0
4.000
570 1910
760 2340 1050 2890
670 2210
950 2810 1520 3330
1/ 2
9.0
2.250
400
610
490
470
540
5/ 8
7.2
2.813
480
960
640 1070
840 1230
560 1120
770 1290 1080 1420
3/ 4
6.0
3.375
540 1390
710 1530
980 1770
620 1600
890 1840 1370 2060
7/ 8
5.1
3.938
590 1780
790 2060 1080 2440
690 2060
980 2470 1570 2790
1
4.5
4.500
640 2100
860 2510 1180 3040
750 2430 1070 3010 1710 3490
1-1/8
4.0
5.063
700 2420
930 2960 1280 3650
820 2800 1170 3550 1860 4220
Group 1
Hemlock,
Eastern
Group 3
Group 2
Cedar, Port Cypress,
Orford and Southern;
Western Douglas Fir,
Coast; Pine,
Red;
Douglas Fir, Southern;
Redwood
Inland
Group 1
Chestnut
Group 3
Ash, White;
Group 2
Beech,
Elm, Soft;
Birch, Elm,
Gum, Black
Rock;
and Red;
Maple,
Tupelo
Hard; Oak,
Red, White
680
680
600
790
790
710
710
820
820
760
730
910
910
See Table 7-2-13 footnotes on Page 7-2-78
5
1/ 2
10.0
2.500
400
610
480
5/ 8
8.0
3.125
530
960
670 1070
3/ 4
6.7
3.750
7/ 8
5.7
1
1-1/8
680
580
790
470
710
530
820
700
910
860 1230
620 1120
780 1290 1070 1420
590 1390
790 1540 1070 1770
690 1600
970 1840 1420 2060
4.375
650 1860
870 2090 1200 2400
760 2150 1090 2510 1700 2790
5.0
5.000
710 2290
950 2650 1310 3120
830 2650 1190 3180 1910 3600
4.4
5.625
780 2640 1040 3160 1430 3840
910 3060 1300 3800 2080 4430
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7-2-34
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
3.438
560
960
3 /4
7.3
4.125
650 1390
860 1540 1130 1770
760 1600 1030 1840 1450 2060
7 /8
6.3
4.813
720 1880
960 2090 1310 2400
840 2190 1190 2510 1800 2790
1
5.5
5.500
790 2390 1050 2710 1440 3150
920 2760 1310 3250 2060 3640
1-1/8
4.9
6.188
860 2850 1140 3310 1570 3920 1000 3290 1430 3980 2280 4520
5 /8
9.6
3.750
570
3 /4
8.0
4.500
710 1390
910 1540 1150 1770
830 1600 1050 1840 1430 2060
7 /8
6.9
5.250
790 1880 1050 2090 1410 2400
920 2190 1280 2510 1840 2790
1
6.0
6.000
860 2470 1140 2730 1570 3150 1000 2860 1430 3270 2200 3640
1-1/8
5.3
6.750
930 3000 1250 3420 1710 3980 1090 3460 1560 4110 2460 4630
5 /8
10.4
4.063
570
3 /4
8.7
4.875
740 1390
920 1540 1140 1770
860 1600 1030 1840 1400 2060
7 /8
7.4
5.688
850 1880 1120 2090 1460 2400
990 2190 1330 2510 1860 2790
1
6.5
6.500
930 2470 1240 2730 1680 3150 1080 2860 1530 3270 2270 3640
1-1/8
5.8
7.313 1010 3070 1350 3440 1860 3980 1180 3550 1690 4120 2620 4630
960
960
690 1070
690 1070
670 1070
850 1230
830 1230
820 1230
650 1120
660 1120
660 1120
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Parallel to
Grain, P
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
8.8
Group 1
Chestnut
Group 3
Ash, White;
Group 2
Beech,
Elm, Soft;
Birch, Elm,
Gum, Black
Rock;
and Red;
Maple,
Tupelo
Hard; Oak,
Red, White
Perpendicular to
Grain, Q
Parallel to
Grain, P
5 /8
Group 1
Hemlock,
Eastern
Group 3
Group 2
Cedar, Port Cypress,
Orford and Southern;
Western Douglas Fir,
Coast; Pine,
Red;
Douglas Fir, Southern;
Redwood
Inland
Perpendicular to
Grain, Q
Perpendicular to
Grain, Q
6-1/2
Projected Area of Bolt, square inches
6
Hardwoods (Broad Leaved)
L/D
5-1/2
Softwoods (Conifers)
Diameter of Bolt, inches
Length of Bolt in Main Member L, inches
Table 7-2-13. Bearing Value for Bolts (Continued)
Allowable Load per Bolt for Timber Bearing on Common Bolts with Wood Side Plates
(For timber occasionally wet but quickly dried.)
770 1290 1050 1420
760 1290 1010 1420
740 1290
7
5 /8
11.2
4.375
560
3 /4
9.3
5.250
760 1390
7 /8
8.0
6.125
920 1880 1170 2090 1480 2400 1070 2190 1350 2510 1830 2790
1
7.0
7.000 1000 2470 1330 2730 1780 3150 1170 2860 1620 3270 2320 3640
1-1/8
6.2
7.875 1090 3120 1450 3460 1990 3980 1270 3630 1810 4180 2740 4630
660 1070
790 1230
920 1540 1130 1770
650 1120
720 1290
940 1420
890 1600 1020 1840 1370 2060
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
3
970 1420
See Table 7-2-13 footnotes on Page 7-2-78
960
1
7-2-35
4
Timber Structures
4.688
550
960
3 /4
10.0
5.625
760 1390
7 /8
8.6
6.563
950 1880 1180 2090 1460 2400 1110 2190 1330 2510 1800 2790
1
7.5
7.500 1070 2470 1400 2730 1820 3150 1250 2860 1660 3270 2310 3640
1-1/8
6.7
8.438 1170 3120 1560 3460 2100 3980 1360 3630 1910 4180 2790 4630
5 /8
12.8
5.000
540
3 /4
10.7
6.000
750 1390
7 /8
9.1
7.000
980 1880 1190 2090 1450 2400 1140 2190 1320 2510 1780 2790
1
8.0
8.000 1140 2470 1460 2730 1850 3150 1330 2860 1680 3270 2290 3640
1-1/8
7.1
9.000 1250 3120 1650 3460 2200 3980 1450 3630 2000 4180 2850 4630
1-1/4
6.4 10.000 1340 3850 1780 4270 2430 4920 1560 4480 2210 5130 3300 5700
3 /4
12.7
7.125
720 1390
7 /8
10.9
8.313
960 1880 1140 2090 1370 2400 1120 2190 1250 2510 1630 2790
1
9.5
9.500 1220 2470 1470 2730 1790 3150 1420 2860 1630 3270 2170 3640
960
650 1070
760 1230
910 1540 1100 1770
640 1070
640 1120
690 1290
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Parallel to
Grain, P
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Perpendicular to
Grain, Q
12.0
Group 1
Chestnut
Group 3
Ash, White;
Group 2
Beech,
Elm, Soft;
Birch, Elm,
Gum, Black
Rock;
and Red;
Maple,
Tupelo
Hard; Oak,
Red, White
Perpendicular to
Grain, Q
Parallel to
Grain, P
5 /8
Group 1
Hemlock,
Eastern
Group 3
Group 2
Cedar, Port Cypress,
Orford and Southern;
Western Douglas Fir,
Coast; Pine,
Red;
Douglas Fir, Southern;
Redwood
Inland
Perpendicular to
Grain, Q
Perpendicular to
Grain, Q
9-1/2
Projected Area of Bolt, square inches
8
Hardwoods (Broad Leaved)
L/D
7-1/2
Softwoods (Conifers)
Diameter of Bolt, inches
Length of Bolt in Main Member L, inches
Table 7-2-13. Bearing Value for Bolts (Continued)
Allowable Load per Bolt for Timber Bearing on Common Bolts with Wood Side Plates
(For timber occasionally wet but quickly dried.)
910 1420
880 1600 1000 1840 1320 2060
740 1230
630 1120
670 1290
890 1540 1080 1770
870 1600
980 1840 1280 2060
860 1540
990 1770
850 1600
880 1420
900 1840 1180 2060
1-1/8
8.4 10.688 1450 3120 1820 3460 2270 3980 1690 3630 2060 4180 2790 4630
1-1/4
7.6 11.875 1590 3850 2070 4270 2670 4920 1850 4480 2430 5130 3380 5700
See Table 7-2-13 footnotes on Page 7-2-78
10
7 /8
1
11.4
8.750
960 1880 1130 2090 1350 2400 1120 2190 1230 2510 1610 2790
1-1/8
8.9 11.250 1480 3120 1810 3460 2220 3980 1720 3630 2020 4180 2720 4630
1-1/4
8.0 12.500 1670 3850 2140 4270 2700 4920 1950 4480 2460 5130 3350 5700
1
11 5 11.500 1190 2470 1410 2730 1680 3150 1390 2860 1520 3270 1990 3640
10.0 10.000 1210 2470 1450 2730 1760 3150 1410 2860 1600 3270 2110 3640
11-1/2 1-1/8 10.2 12.938 1490 3120 1780 3460 2150 3980 1740 3630 1960 4180 2580 4630
1-1/4
9.2 14.375 1780 3850 2160 4270 2640 4920 2080 4480 2400 5130 3220 5700
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-36
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
12
Group 1
Hemlock,
Eastern
Group 2
Group 3
Cedar, Port Cypress,
Orford and Southern;
Western Douglas Fir,
Red;
Coast; Pine,
Douglas Fir, Southern;
Inland
Redwood
Group 1
Chestnut
Group 3
Ash, White;
Group 2
Beech,
Elm, Soft;
Birch, Elm,
Gum, Black
Rock;
and Red;
Maple,
Tupelo
Hard; Oak,
Red, White
Perpendicular to
Grain, Q
Perpendicular to
Grain, Q
Perpendicular to
Grain, Q
Perpendicular to
Grain, Q
Hardwoods (Broad Leaved)
Parallel to
Grain, P
Perpendicular to
Grain, Q
Parallel to
Grain, P
Parallel to
Grain, P
Parallel to
Grain, P
Perpendicular to
Grain, Q
12.0 12.000 1180 2470 1390 2730 1630 3150 1370 2860 1490 3270 1940 3650
Parallel to
Grain, P
1
Parallel to
Grain, P
L/D
Projected Area of Bolt, square inches
Softwoods (Conifers)
Diameter of Bolt, inches
Length of Bolt in Main Member L, inches
Table 7-2-13. Bearing Value for Bolts (Continued)
Allowable Load per Bolt for Timber Bearing on Common Bolts with Wood Side Plates
(For timber occasionally wet but quickly dried.)
1-1/8 10.7 13.500 1470 3120 1750 3460 2110 3980 1710 3630 1920 4180 2520 4630
1-1/4
9.6 15.000 1780 3850 2150 4270 2610 4920 2080 4480 2380 5130 3160 5700
1
References, Vol. 51, 1950, p. 433; Vol. 52, 1951, pp. 428, 847.
Table 7-2-13 tabulated values are for joints when two wood side plates are used, each side plate one-half the
thickness of the main member:
a. If either side plate is thicker than one-half the thickness of the main member, no increase in the tabulated
value is permissible.
b. When one or both side plates are thinner than one-half the thickness of the main member, use tabulated
value indicated for a main member twice as thick as the thinnest side plate.
c. When a joint consists of two members only (bolt in single shear) of equal thickness, use one-half the
tabulated value for a main member twice the thickness of one of the members.
d. When a joint consists of two members only of unequal thickness, use one-half the tabulated value for a
main member twice as thick as the thinnest member.
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-37
Timber Structures
2.5.13 CONNECTORS (1988)
Where metal connectors are used, working values may be taken as those recommended in the National Design
Specification.
2.5.14 ROUND SECTIONS (1988)
a.
The strength, stiffness, and horizontal shearing value in bending of round timbers of any species may be
assumed to be identical with that of square timbers of the same grade and cross-sectional area. Tapered
timbers should be assumed as of uniform diameter, the point of measurement being one-third the span
from the small end, but the diameter should not be assumed to be more than 1-1/2 times the small end
diameter.
b. The strength of round columns may be considered the same as that of square columns of the same crosssectional area. In long tapered columns the strength may be assumed as identical with that of a square
column of the same length, and of cross-sectional area equal to that of the round timber measured at a
point one-third its length from the small end. The stress at the small end must not exceed the allowable
stress for short columns.
SECTION 2.6 DETAILS OF DESIGN
2.6.1 GENERAL (1988)
All members shall be framed, anchored, tied and braced to develop the strength and rigidity necessary for the
purposes intended.
2.6.2 NET SECTION (1988)
All stress computations shall be based on actual size of timbers. Where members are dapped or otherwise
framed to materially reduce the effective size, the net section of the piece shall be used.
2.6.3 BOLTED CONNECTIONS (1988)
a.
The center to center distance along the grain between bolts acting parallel with the grain shall be not
less than four times the bolt diameter.
b. The tension area remaining at the critical section should be at least 80 percent of the total area in
bearing under all bolts for coniferous woods; 100 percent for hardwoods.
c.
In a tension joint, the distance from the end of the timber to the center of nearest bolt shall be not less
than seven times the bolt diameter for coniferous woods; five times for hardwoods. For compression
stress, this end distance need be only four times the bolt diameter.
d. For loads acting perpendicular to the grain, the distance between the edge toward which the bolt
pressure is acting, and the center of the bolt nearest this edge, should be not less than four times the bolt
diameter.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-38
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
2.6.4 NOTCHED BEAMS (1988)
The allowable end reaction for beams with square-cornered notches at the ends shall be computed by the
following formula:
2
2 bc q
V = --- ------------d
3
where:
b = Width
c = Depth above the notch
d = Total depth of beam
q = Working unit stress in horizontal shear
V = Allowable end reaction
SECTION 2.7 RECOMMENDED PRACTICE FOR DESIGN OF WOOD CULVERTS1 (1962)
1
(Reapproved with revisions 1962)
2.7.1 WOOD CULVERTS (1988)
For the recommended practice for design of wood culverts refer to Figure 7-A3-79 and Table 7-A3-10 (See
Appendix 3 - Legacy Designs).
3
2.7.2 GENERAL NOTES (1988)
a.
Timber culverts should be constructed of pressure-treated timber conforming to AREMA specifications
for structural timber.
b. Timbers with appreciable warp, particularly wall timbers should not be used.
c.
4
Timbers should be cut to length and bored before treatment.
d. Surfaces of treated timber unavoidably cut or damaged in construction should be field treated with two
coats of hot creosote oil and one coat of hot sealing compound or equal. Holes unavoidably bored in the
field in treated timber should be thoroughly saturated with hot creosote oil and the fastener immediately
placed.
1
e.
Protective coatings or galvanizing of metal fastenings should conform to recommendations for “use of
protective coatings for iron and steel fastenings for wood bridges,” miscellaneous part, this chapter.
Spikes or fasteners should be dipped in a preservative before driving.
f.
Lock nut or spring washer should be used on all bolts, and nuts tightened securely.
References, Vol. 52, 1951, pp. 436, 849; Vol. 53, 1952, pp. 635, 1023; Vol. 61, 1960, pp. 587, 1095; Vol. 63, 1962, pp. 455, 684; Vol. 89, 1988,
p. 106.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-39
Timber Structures
g.
Backfilling of culverts should be built up uniformly on both sides, and embankment constructed in
layers, well compacted in accordance with best practice.
2.7.3 DESIGN DATA (TANGENT TRACK) (1988)
a.
Live Load. Cooper E72 Loading, Axle loads distributed uniformly over a distance of 5¢ -0² parallel to
track, and uniformly over a distance equal to length of tie plus depth of fill under ties perpendicular to
track.
b. Dead Load. Assumed weight of materials follows:
c.
Track rails and fastenings:
200 lb per linear foot of track
Earth fill and ballast:
120 lb per cubic foot
Timber:
60 lb per cubic foot
Lateral Earth Pressure. Active earth pressure equal to:
0.286w (h + h¢ )
where:
w = 120 lb per cubic foot
h = depth below base of rail
h¢ = live load surcharge
d. Timber Sections. Full nominal dimensions without reduction for bolt holes.
e.
Unit Working Stresses. For allowable unit working stresses for timber see specifications for design this
Chapter.
SECTION 2.8 RECOMMENDED PRACTICE FOR
SIMPLE STRESS LAMINATED DECK PANELS
2.8.1 MATERIAL (2000)
2.8.1.1 Wood Laminates
a.
Shall be Douglas Fir, Southern Pine or Red Oak No. 2 or better as per AREMA Manual for Railway
Engineering, Chapter 7, Timber Structures.
b. Shall be 5” thick or less, rough sawn to full size and surfaced on one side (S1S) to ensure uniform
thickness throughout its length.
c.
Laminate width shall equal the deck thickness, T in accordance with Table 7-A1-4 having selected the
design Cooper’s E loading and the span length based on the allowable stresses for the material to be
used.
d. Shall be predrilled for prestressing bars and trimmed prior to treatment.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-40
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
e.
Hole spacing (SP) shall be in accordance with the ranges shown on Table 7-2-14 having selected a deck
thickness (T). Bar spacing should also consider conflicts with other structural components such as
walkway support brackets.
Table 7-2-14. Spacing of Prestressing Bar, SP (Inches)
1” DIA BAR
(As=0.85 SQ.IN.)
THICKNESS OF
PANEL, T
1-1/4” DIA BAR
(As=1.25 SQ.IN.)
MAX.
MIN.
MAX.
MIN.
12”
74
44
--
--
14”
64
38
94
56
16”
56
33
82
49
Max. based on Ni=100psi
SP = (As x 0.70 x Fpu)/(Ni x T)
(1)
Min. based on max. wood/steel ratio of 0.0016
SP = As/(T x 0.0016)
(2)
f.
Predrilled hole diameter shall be twice the diameter of the prestressing bar to be used, but shall not
exceed 20% of the width of the laminates.
g.
Trimming shall be done in a way which would ensure maximum full face contact between laminate
members.
h. Shall be treated with 100% creosote in a clean treatment process as per AREMA Manual for Railway
Engineering, Chapter 30, Ties.
i.
Additional material shall be procured to allow for rejection of unsuitable pieces (up to 5% of total).
j.
All field holes and cuts in treated wood must be treated with preservative.
2.8.1.2 Prestressing Bars
a.
3
4
Shall be galvanized grade 150 ksi dywidag bars or approved equal in accordance with the latest issue
ASTM A-722.
b. Shall be sized in accordance with Table 7-2-14 having selected the deck thickness, T and bar spacing, SP
then checked for tensile strength. However, the steel-wood area ratio must not exceed 0.0016 (as per the
Ontario Highway Bridge Design Code).
c.
1
The required tensile load, P is determined by dividing the cross-sectional area of the bar, As into the
required prestressing force Fps (i.e. P = Fps/As). Fps is the product of the initial lamination stress, Ni
(from Table 7-A1-4) in psi and the bar spacing, SP and deck thickness, T both in inches
(i.e. Fps – Ni x SP x T).
d. The required tensile load, P must not exceed 89,250 lbs and 131,250 lbs for 1” dia. And 1 ¼” dia. Bars
respectively. If the required tensile load, P is greater than that permitted, a larger bar size or closer bar
spacing must be used.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-41
Timber Structures
e.
If bar ends are cut, they shall be coated with two coats of zinc rich paint or an approved equal.
f.
Do not weld on or near prestressing bars or use them as ground connections.
g.
Use nylon or rope slings for handling and transport of prestressing bars.
h. Do not use prestressing bars to lift or move the deck panel.
i.
Bars damaged during shipment shall be rejected and replaced with new bars.
2.8.1.3 Anchorage System
a.
Structural steel shall conform to the current ASTM A36 specifications.
b. Decks up to 16” in depth shall have a bulkhead channel or bearing plate anchorage configuration. Decks
over 16” in depth shall have only a bearing plate anchorage configuration.
c.
Channel sizes are to be in accordance with Table 7-2-15.
Table 7-2-15. Bulkhead Channel Sizes
THICKNESS OF
PANEL, T
RECOMMENDED
DEPTH OF
(IMPERIAL)
CHANNEL, Dc
Tw, WEB
THICKNESS
11”
C10 X 25
10”
0.53”
12” – 14”
C12 X 30
12”
0.51”
15” – 16“
C15 X 40
15”
0.52”
d. Anchor plate sizes for bulkhead channel anchorage configurations shall be in accordance with
Table 7-2-16.
Table 7-2-16. Bearing Plates Sizes For Channel Bulkhead Anchorage Configuration
THICKNESS OF
PANEL, T
WIDTH
Wp
LENGTH
Lp
THICKNESS
Tp
12”
9”
9” – 18”
Lp/12
14”
9”
9” – 18”
Lp/12
16”
12”
12” – 24”
Lp/12
Select a plate length, then check that effective bearing area is sufficient to prevent crushing of
the laminates (i.e. fc+ < F¢ c+ where F¢ c+ = 375 psi and + indicates perpendicular to the
grain of the material). For Douglas Fir fc+ can be determined as follows:
fc+ = (Ni x SP x T)/Dc(Lp+2Tw)(3)
Where Ni, SP, T, Dc and Tw are all known from prior design steps.
e.
Bearing plates sizes for bearing plate anchorage configurations shall be in accordance with Table 7-2-17.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-42
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
Table 7-2-17. Bearing Plates Sizes For Bearing Plate Anchorage Configuration
THICKNESS OF
PANEL, T
WIDTH
Wp
LENGTH
Lp
THICKNESS
Tp
12”
10”
10” – 20”
SEE BELOW
14”
12”
12” – 24”
“
“
16”
14”
14” – 28”
“
“
Select a plate length, then check that plate bearing area is sufficient to prevent crushing of the
laminates (i.e. fc+ < F¢ c+ where F¢ c+ = 375 psi and + indicates perpendicular to the grain of
the material). For Douglas Fir fc+ can be determined as follows
fc+ = (Ni x SP x T)/(Lp x Wp)(4)
Where Ni, SP and T are all known from prior design steps.
Actual plate thickness, Tp is based on the use of a 6” x 6” x 1” anchorage plate and can be
determined as follows:
Tp = square root of [(3 x (Tn x SP x T) x k x k)/Fb](5)
Where Ni, SP and T are all known from prior design steps, Fb – 24,200 psi for 44W steel and k
is the greater of (Wp-6)/2 or (Lp-6)/2
1
f.
Channel bulkhead anchorage, bearing plates, high strength steel nuts and other fasteners to be hot dip
galvanized to latest issue of ASTM 123 after fabrication.
3
2.8.1.4 Waterproofing
a.
Waterproofing shall cover the entire top surface of each panel
b. Consideration shall be given to facilitate drainage to the curb sides.
c.
4
The membrane shall be placed only after the second prestressing has occurred.
d. Coat all anchorage nuts to protect against corrosion.
e.
Each panel shall be supplied with drain holes through its curb on each side at span one-third points.
2.8.2 FABRICATION (2000)
2.8.2.1 Panel Assembly
a.
Panels may be assembled in a shop or on site in a staging area. In place assembly on active lines will not
be permitted as a panel cannot be placed into service until after the second prestressing.
b. A temporary support shall be constructed from timber and blocking to provide a level plane on which the
panel may be assembled.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-43
Timber Structures
c.
Laminates shall be oriented with their crown up, bottoms even at the bearing ends and the predrilled
holes aligned. Alternate laminates shall be flipped and turned end for end to allow for the inaccuracy of
milling. An 18” steel dowel, with a diameter larger than the selected prestressing bar diameter, can be
used to align the holes. Laminates may be nailed together temporarily to hold their position prior to
prestressing.
d. Prestressing bars shall be fed through the holes as assembly of laminates progresses thus ensuring
passage of the bars through the laminates.
e.
Once all laminates and bars are in place, bulkhead channels (when used), bearing anchor plates and nuts
are applied at the ends of each bar.
f.
Stressing of the panel shall be from one side only. Bars are adjusted to project 5” on the anchored side
and 12” or more on the stressing side to permit connection of the hydraulic jack(s).
g.
Tighten all anchorage nuts with a pipe wrench prior to prestressing.
h. Do not stress bars until all bars within a span have been installed complete with the selected anchorage
system and tightened with hand tools.
i.
Stressing operations must be supervised by a qualified individual.
2.8.2.2 Stressing Equipment
a.
60 ton hydraulic hollow core jacks (single or multiple jacks) may be used for prestressing.
b. Appropriate pull coupler suited to the selected prestressing bar size (one per jack).
c.
Prefabricated jack chair (one per jack) to allow tightening of the anchorage nut with an open end
wrench.
d. Jack chairs and wrench are not required if the jack is equipped with a built-in ratchet.
e.
Hydraulic pump with reservoir sufficient to supply all jacks that will be used simultaneously.
f.
Hoses and manifolds to connect all jacks to the hydraulic pumps.
2.8.2.3 Prestressing Procedures
a.
Stressing Sequence
(1) First stressing can be executed on completion of assembly. Stress the deck panel fully to 100% Ni,
the initial design in psi for the panel as per Table 7-A1-4. After the first stressing, bar projections
may be cut back using a cutoff saw to the minimum required to re-attach a jack but no shorter than
5”.
(2) Second stressing to be conducted one week after the initial stressing. Again stress fully to 100% Ni.
After second stressing and upon acceptance of the bars by the Engineer, apply corrosion protection
material, grease caps and galvanize lock nuts. Water proofing membrane and curb timbers may now
be applied.
(3) Final stressing to be conducted 4 to 6 weeks after the second stressing (5 to 7 weeks after assembly).
Again stress fully to 100% Ni. Do not stress while panel is under live load conditions.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-44
AREMA Manual for Railway Engineering
Design of Wood Railway Bridges and Trestles for Railway Loading
(4) Stress levels shall be periodically checked as part of an ongoing maintenance program. Bars shall be
re-stressed when stress levels approach N, the minimum stress in pounds required for the panel to
perform adequately per Table 7-A1-4.
b. Prestressing force required (Fps) is the stress that is applied to each of the bars in order to stress the
laminates fully to 100% Ni
Fps = Ni x SP x T(6)
Where SP is the selected spacing of bars, T is the selected deck thickness and Ni is the initial stress
required between laminations as per Table 7-A1-4.
c.
Stressing Methods
(1) Single Jack Method
• Attach the jack to the left most bar and stress the bar to the appropriate level using the pump.
• Tighten the nut using an open end wrench through the opening of the jack chair or by using the
built-in ratchet if so equipped.
• Release pressure, remove jack and attach it to the next bar to the right. Repeat this procedure
until all bars are stressed.
• Starting again at the left most bar repeat the entire procedure three additional times to achieve a
uniform stress throughout the panel.
1
(2) Multiple Jack Method 1 (number of jacks = number of bars in one panel)
• Connect all jacks to one pump.
• Attach one jack assembly to each bar and stress all bars to the appropriate level at the same time
using the pump.
3
• Tighten each nut using an open end wrench through the opening of the jack chair or by using the
built-in ratchet if so equipped.
4
• Release pressure, remove jacks, stressing is complete.
(3) Multiple Jack Method 2 (number of jacks < number of bars in one panel)
• Connect all jacks to one pump.
• Attach one jack assembly to a bar starting from the left most bar in the panel and stress these bars
to the appropriate level at the same time by using the pump.
• Tighten each nut using an open end wrench through the opening of the jack chair or by using the
built-in ratchet if so equipped.
• Release pressure, remove all but the right most jack and move them to the bars on the right side of
the jack remaining in place. Repeat the procedure until the entire span is stressed.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-2-45
Timber Structures
2.8.2.4 Stressing Record
a.
Record date of each stressing.
b. Record elongation of bars resulting from stressing.
2.8.2.5 Stressing Safety
a.
Pull couplers for stressing jack must be evenly and fully engaged to the bar projection prior to the
application of stress.
b. When stressing above grade, a safety rope must be used to secure jack and pull rod to the structure.
c.
A warning sign must be posted in the area affected by stressing.
d. Never stand behind a jack while stressing or while removing the jack from a stressed bar. Do not stand
on hoses while stressing.
e.
Pump must be connected to a proper power source with approved connection. Prior to stressing bars
cycle jacks(s) several times to check for leaks and to eliminate air from the system.
2.8.2.6 Handling Panels
a.
Handle the panels with extreme care to avoid damage to laminates and other components. Do not use
steel chains or cables if possible.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-2-46
AREMA Manual for Railway Engineering
7
Part 3
Rating Existing Wood Bridges and Trestles
— 2010 —
TABLE OF CONTENTS
Section/Article
Description
3.1 Rules for Rating Existing Wood Bridges and Trestles . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.1 Classification (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.2 General (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.3 Carrying Capacity (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.4 Inspection (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.5 Computation of Stresses (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.6 Loads and Forces (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.7 Dead Load (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.8 Live Load (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.9 Impact (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.10 Centrifugal Force (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.11 Other Lateral Forces (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.12 Longitudinal Force (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.13 Combined Stresses (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.14 Unit Stresses (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.15 Chord Deflection (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.16 Composite Trusses (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.17 Action to be Taken (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Page
7-3-2
7-3-2
7-3-2
7-3-2
7-3-2
7-3-3
7-3-3
7-3-3
7-3-3
7-3-3
7-3-4
7-3-4
7-3-4
7-3-4
7-3-4
7-3-5
7-3-5
7-3-6
LIST OF TABLES
Figure
Description
Page
7-3-1
Unit Stresses for Rating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-3-5
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-3-1
1
3
Timber Structures
SECTION 3.1 RULES FOR RATING EXISTING WOOD BRIDGES AND TRESTLES1
3.1.1 CLASSIFICATION (1988)
Wood railway bridges and trestles shall be classified according to their rated carrying capacity as determined by
the rules specified herein. The work of classifying bridges shall be as described in Chapter 15, Steel Structures,
Part 7, Existing Bridges.
3.1.2 GENERAL (1988)
Except as otherwise provided in these rules, the recommendations in this part shall govern.
3.1.3 CARRYING CAPACITY (1988)
The carrying capacity of a bridge shall be determined by the computation of stresses based on authentic records
of the design, details, species and grade of wood, materials, workmanship, and physical condition, including
data obtained by inspection. If deemed advisable, field determination of stresses shall be made and the results
given due consideration in the final assignment of the carrying capacity. For a specific service the location and
behavior under load shall be taken into account.
3.1.4 INSPECTION (2010)
An inspection of the bridge shall be made to determine:
a.
Whether the actual sections and details conform to the drawings. Where actual sections and details do
not conform to the drawings the differences shall be noted in detail; of special importance are the
number and spacing of piles, size of cap, height of bents, length of panels, size and number of stringers,
positioning of stringer joints on caps, whether stringers are continuous over bents, size and spacing of
ties, and size and location of sway and longitudinal bracing on bents, if any.
b. Any additions to the dead load not shown on the plan, such as heavier deck or rail, walks, pipelines,
conduits, signal devices, and wire supports.
c.
The position of the track with respect to the center line of the bridge.
d. Any loss of wood due to decay and wear. This determination should be made by increment borings.
e.
The physical condition, noting such conditions as loose bolts and excessive checks or splits.
f.
The condition of all points of bearing.
g.
The condition of bents, especially at the ground line and cap connection.
h. An inspection of the bridge shall be made to determine evidence of excessive deflection (c.f.
Article 3.1.15), lateral movement, or longitudinal movement that may necessitate immediate closure of
the structure to traffic. Stability of the structure as a whole as well as its parts must be assured under
live load.
1
References, Vol. 63, 1962, pp. 456, 687; Vol. 89, 1988, p. 106.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-3-2
AREMA Manual for Railway Engineering
Rating Existing Wood Bridges and Trestles
3.1.5 COMPUTATION OF STRESSES (1988)
The computation of stresses shall be made for the details as well as for the main members, giving particular
attention to:
a.
The increased load carried by a stringer, cap, floor member, or truss due to eccentricity of the load. This
applies to bridges on tangent where the tracks are off center as well as to bridges on curves.
b. Spacing of bents.
c.
Continuity occurring in stringers. Where the support under a rail consists of three or more stringers
assembled as a chord, or otherwise acting in unison, and extending over two spans with staggered joints,
a partially continuous beam action may be assumed to exist, and the computations may be made for
stringers based on the average stress as determined from single beam analysis and that for a fully
continuous condition.
3.1.6 LOADS AND FORCES (1988)
Stresses shall be computed for the following loads and forces:
a.
Dead Load.
b. Live Load.
1
c.
Impact.
d. Centrifugal force.
e.
Other lateral forces.
f.
Longitudinal force.
3
3.1.7 DEAD LOAD (1988)
The dead load shall be the weight of the bridge including the deck and track, together with any other fixed
loads.
4
3.1.8 LIVE LOAD (1988)
a.
The live load shall be one of the Cooper E series, other standard loading, or a load consisting of a specific
locomotive or other equipment, depending on the purpose for which the rating is desired.
b. If the live load is to be a specific locomotive and cars (or other equipment), complete data shall be
obtained, including the spacing of axles and the static load on each axle. This data shall be used to
convert the specific locomotive and cars (or other equipment) to equivalent standard loading for the
various span lengths of the bridges being rated.
3.1.9 IMPACT (1988)
The dynamic increment of load due to the effects of speed, roll and track irregularities is not well established
for timber structures. Its total effect is estimated to be less than the increased strength of timber for the short
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-3-3
Timber Structures
cumulative duration of loading to which railroad bridges are subjected in service, and is taken into
consideration in the derivation of allowable working stresses for design.
3.1.10 CENTRIFUGAL FORCE (1988)
Centrifugal force shall be determined as specified in Article 2.3.4.
3.1.11 OTHER LATERAL FORCES (1988)
Other lateral forces shall be determined as specified in Article 2.3.5, except that the wind force shall be taken as
not exceeding two-thirds of the forces shown and the nosing load shall be taken as 1/16 the weight of one
locomotive without tender, both applied as stated. Due to their limited duration, wind forces may be ignored in
the rating of pile or frame trestles where the bridge is geographically located in an area not normally exposed to
winds of exceptional magnitude.
3.1.12 LONGITUDINAL FORCE (1988)
Longitudinal force shall be determined as specified in Article 2.3.5.4.
3.1.13 COMBINED STRESSES (1988)
For stresses produced by longitudinal or other lateral forces, or by a combination of these forces with dead and
live loads and centrifugal force, the allowable rating stresses may be twice the working unit stress shown in
Table 7-2-9, provided the stress resulting from dead and live loads and centrifugal force only does not exceed
the rating unit stress established in Article 3.1.14.
3.1.14 UNIT STRESSES (2010)
a.
Loading beyond Design Load without careful regular inspection is not recommended. Frequent loading
beyond the Design Load shortens the useful life considerably. Recommendations in this Article assume
the structural connections are tight and structure geometry is correct.
b. The permissible unit stresses for rating resulting from dead and live loads and centrifugal force for
structures inspected in accordance with Article 3.1.4 are shown in Table 7-3-1, to be used without
allowance for impact due to live load.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-3-4
AREMA Manual for Railway Engineering
Rating Existing Wood Bridges and Trestles
Table 7-3-1. Unit Stresses for Rating
Description
f=
unit stress in extreme fiber in bending, in pounds per
square inch
All other unit stresses
E=
modulus of elasticity, in thousands of pounds per square
inch.
where:
k=
Fh =
Equipment or
Regularly Assigned
Locomotives Not
Equipment or
Regularly Assigned
Locomotives
1.3 kFh
1.1 kFh
1.3 k
1.1 k
As shown in Table 7-2-9
Unit Stress for Structural Lumber Subject to Railway Loading, Section 2.5, Allowable Unit Stresses
for Stress-Graded Lumber.
depth factor.
2
=
H + 143
0.81 -----------------------2
H + 88
where:
c.
H is the depth of the beam. For H of 16 inches or less, Fh = 1 may be used.
For structures inspected with a full tactile inspection by qualified timber inspectors, the permissible
stress for regularly assigned equipment or locomotives may be increased from 1.1 to 1.2 kFh for bending
and 1.2k for all other stresses.
This does not apply to caps or similar non-load sharing members, and does not apply to members with
end splits.
1
d. If the actual section modulus or cross-section area is less than 75% of that for which the Rating was
calculated, a new Rating using the revised properties must be made.
3
e.
For unit stress in compression parallel to grain for columns with L/d ratio greater than 11, see
Article 2.3.2.
f.
Where the grade of timber actually in use in any structure is not definitely known, k shall be assumed as
1.0 times the minimum grade shown in Table 7-2-9 for the species used, for timbers usually used in
stress grades.
g.
If a structure fails to qualify under the foregoing permissible stresses for equipment or locomotives not
regularly assigned, then speed may be restricted to not to exceed 10 mph and the members recomputed
with the k coefficient increased 15 percent.
4
3.1.15 CHORD DEFLECTION (2009)
Measured net chord deflection (inches) under live load should not exceed L/250, where L is the span length in
inches.
3.1.16 COMPOSITE TRUSSES (1988)
For trusses composed of both wood and steel or iron members, the metal portions shall be rated using stresses
as specified in the Rules for Rating Existing Steel Bridges, Chapter 15, Steel Structures; Part 7, Existing
Bridges.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-3-5
Timber Structures
3.1.17 ACTION TO BE TAKEN (1988)
If the stresses exceed those permissible under these rules, the loading shall be restricted so that the permissible
stresses will not be exceeded until the indicated remedial work has been done. The remedial work in general
will consist of replacing defective parts, adding posts or piles to bents where required, or placing additional
stringers. When the permissible stresses are closely approached, or when the physical condition of the main
members or the details are not good, the bridge shall be kept under frequent inspection as long as it is
continued in service.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-3-6
AREMA Manual for Railway Engineering
7
Part 4
Construction and Maintenance of
Timber Structures
— 2011 —
TABLE OF CONTENTS
Section/Article
Description
Page
4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1.1 Upgrading and Rehabilitating Timber Structures (1995). . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-2
7-4-2
4.2 Handling of Material (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-3
4.3 Storage of Material (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-3
4.4 Workmanship for Construction of Pile and Framed Trestles . . . . . . . . . . . . . . . . . . . .
7-4-3
4.5 Framing of Timber (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-4
4.6 Substructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6.1 Pile Posting, or Replacing Defective Portions of Piles (1995) . . . . . . . . . . . . . . . . . . . . . .
4.6.2 Driving Timber Piles (1984) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-5
7-4-5
7-4-6
4.7 Superstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-14
4.8 Support, Repair, Preserve, or Replace Damaged Portions of the Structure (2010) . .
4.8.1 Control Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.8.2 Field Application of Preservative Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-14
7-4-18
7-4-18
4.9 Methods of Fireproofing Wood Bridges and Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.9.1 Foreword (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.9.2 Metal Protection (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.9.3 Coatings (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.9.4 Impregnation (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.9.5 Fire Alarm Systems (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.9.6 Housekeeping (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.9.7 Fire Barriers (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-18
7-4-18
7-4-18
7-4-19
7-4-19
7-4-19
7-4-19
7-4-19
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7-4-1
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3
Timber Structures
TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
4.10 Use of Guard Rails and Guard Timbers (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.10.1 Field Side Guard or Spacer Timbers (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.10.2 Metal Gage Side Guard Rails (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.10.3 Combined Use of Guard Timbers and Guard Rails (1988). . . . . . . . . . . . . . . . . . . . . . . . .
7-4-20
7-4-20
7-4-20
7-4-21
4.11 Typical Plans for Timber Railway Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.11.1 Plans (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.11.2 General Notes (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-21
7-4-21
7-4-21
LIST OF FIGURES
Figure
7-4-1
7-4-2
7-4-3
7-4-4
7-4-5
7-4-6
7-4-7
7-4-8
7-4-9
Description
Page
Schematic Diagram of Pile Posting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sample Pile Record Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Splicing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Scabbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pile Restoration Using Cast in Place Reinforced Concrete Jacket. . . . . . . . . . . . . . . . . . . . . . .
Filling Voids with Grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Clamping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stitching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Earth Fill Break in a Long Trestle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-6
7-4-13
7-4-14
7-4-14
7-4-15
7-4-16
7-4-17
7-4-17
7-4-20
LIST OF TABLES
Table
7-4-1
Description
Page
Recommended Practice Plans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-4-23
SECTION 4.1 GENERAL
4.1.1 UPGRADING AND REHABILITATING TIMBER STRUCTURES (1995)
Replacement in kind must be adequate for current and anticipated traffic.
a.
Existing timber members may be replaced with timber of increased section or strength. Additional
timber members may be placed to increase capacity.
b. Timber Open Decks may be replaced by Timber Ballast Decks, in accordance with Part 2, Design of Wood
Railway Bridges and Trestles for Railway Loading.
c.
Timber bridges may be upgraded or rehabilitated by replacing caps, stringers or decking with concrete or
steel in accordance with Chapter 8, Concrete Structures and Foundations or Chapter 15, Steel
Structures respectively of this Manual while leaving existing timber piling in place for structure support.
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AREMA Manual for Railway Engineering
Construction and Maintenance of Timber Structures
SECTION 4.2 HANDLING OF MATERIAL (1995)
a.
All material should be handled to avoid structural damage or unnecessary disfiguring.
b. Piling or timber that has been treated with preservatives should be handled with extreme care in
unloading and assembling to avoid damage to the timber which would expose untreated wood. These
materials shall be preferably handled with rope slings. Sharp-pointed bars, peavies, hooks, tongs or
similar tools shall not be used, except as approved by the Engineer.
SECTION 4.3 STORAGE OF MATERIAL (1995)
a.
Materials should be stored at the site in a neat manner at proper clearance to operated tracks.
b. Care should be exercised to prevent fires in material held in storage. The ground underneath and in the
vicinity of piling and lumber should be scalped and cleared of all weeds, rubbish and combustible
material.
c.
Treated lumber should be close-stacked in a manner that will prevent long timbers or preframed
material from sagging or becoming crooked.
d. Untreated lumber should be open-stacked on suitable skids at least 1 foot above the ground and above
possible high water; it should be piled in a manner to shed water and to prevent warping. When
required, it shall be protected from the weather by suitable covering.
e.
Piling should be stacked in a manner to prevent excessive bending.
f.
Hardware received at the job site should be protected from corrosion by storing under cover or by a
protective coating.
3
SECTION 4.4 WORKMANSHIP FOR CONSTRUCTION OF PILE
AND FRAMED TRESTLES1
4
This section covers workmanship for the construction of pile or framed trestles carrying railway traffic.
a.
Trestles constructed under this recommended practice should be built complete, ready for the laying of
track rails, in a workmanlike manner, in strict accordance with the plans and the intent of this
recommended practice.
b. It is presumed that the design of structures to which this recommended practice attaches is in
accordance with prevailing practice, and, more specifically, in general accordance with, Part 2, Design of
Wood Railway Bridges and Trestles for Railway Loading.
c.
1
1
Nothing contained herein shall be construed as superseding details or notations shown on design
drawings. Where this recommended practice conflicts with the drawings, the drawings will govern.
References, Vol. 8, 1907, pp. 397, 442; Vol. 35, 1934, pp. 998, 1176; Vol. 36, 1935, pp. 781, 1009; Vol. 54, 1953, pp. 942, 1329; Vol. 61, 1960,
pp. 587, 1095; Vol. 89, 1988, p. 106.
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Timber Structures
d. Workmanship should be of the best quality in each class of work. Competent bridge carpenters shall be
employed and all framing shall be true and exact. No blocking or shimming will be permitted, except as
otherwise provided herein.
e.
On completion of the work, all surplus material or material salvaged from an existing structure should
be removed from the premises as directed. Material not salvageable and other refuse should be properly
disposed of. Premises shall be left in a clean, neat and orderly condition.
SECTION 4.5 FRAMING OF TIMBER (1988)
a.
All cutting, framing, and boring of timbers to be treated, shall be done before treatment unless otherwise
shown on the plans or specifically permitted by the Chief Engineer.
b. All cuts or abrasions made in or suffered by treated lumber shall be carefully trimmed and then field
treated by the application of two saturating coats of hot creosote oil. All holes bored in treated material
shall be field treated with hot creosote oil under pressure, using an approved type of bolt hole treater, in
such a manner that the entire surface of the hole receives thorough penetration. All countersunk
recesses for bolts which would form pockets to retain water shall be treated as for cuts and then filled
with a suitable mastic after the bolt is placed.
c.
Sills shall have a true and even bearing on foundation piles, timber grillages, mats or pedestals. All earth
shall be removed from around sills so that there will be free air circulation around them.
d. Posts in framed bents shall be sawed to proper length (vertical or batter) and shall have an even bearing
on caps and sills.
e.
Caps shall be sized to a uniform depth and placed to a uniform and even bearing on piles or posts.
f.
Sash and sway bracing, tower bracing and girts shall bear firmly against the piles or timber to which
secured. When necessary, filler shall be placed to avoid bending the bracing more than 1 inch out of line
when the bracing bolts or other fastenings are drawn up tight. Built-up fillers will not be permitted and
each filler shall be a single piece of creosoted lumber of like kind to that in the brace with a width of not
less than 6 inches and a length of not less than 12 inches.
g.
Stringers shall be sized to provide a uniform depth and even bearing at supports. They shall be
assembled in the structure according to plans.
h. Ties shall be sized and spaced in accordance with the plans.
i.
Guard timbers shall be framed in accordance with the plans and laid to line and uniform top surface.
j.
Deck plank and ballast retainers on ballasted deck trestles shall be placed in accordance with the plans.
Drainage shall be provided for in the manner specified.
k. Bulkheads at the ends of trestles shall be of sufficient height and width to retain properly the shoulders
of embankments and to provide a berm sufficient to prevent loss of embankment from beneath the
bulkhead. When necessary, special anchorage, such as bulkhead piles or dead-men buried in the
embankment, shall be provided to support the bulkhead.
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AREMA Manual for Railway Engineering
Construction and Maintenance of Timber Structures
l.
Refuse platforms, water barrels platforms, footwalks, motor car set-off or other special platforms shall be
in accordance with the plans.
m. All fastenings, including bolts, dowels, lag screws, timber connectors and other type fastenings shall be
placed in accordance with the plans, drawn up securely, and on completion of the structure shall be
retightened. Unless otherwise shown on the plans, holes for dowels and drift bolts shall be bored 1/16
inch smaller than the nominal diameter of the dowel or bolt used; holes shall not be bored deeper than
the length of the dowel or bolt. Holes for machine bolts and rods other than dowels and drift bolts shall
be bored the same size as the nominal diameter of the bolt or rod used. Holes for lag screws shall be
bored with a bit not larger than the body of the screw at the base of the thread.
n. Screw-type fastenings shall be screwed into place for the entire length of the fastening. Driving with a
maul or other tool will not be permitted.
o.
Timber connectors shall be of the types specified on the plans. Split-ring and shear-plate connectors shall
be installed in pre-cut grooves of the dimensions shown on the plans or as recommended by the
manufacturer. Toothed-ring and spike-grid connectors, and clamping plates, shall be forced into the
contact surfaces of the timbers joined by means of proper pressure tools; all connectors of these types at
any joint shall be embedded simultaneously and uniformly.
SECTION 4.6 SUBSTRUCTURE
1
4.6.1 PILE POSTING, OR REPLACING DEFECTIVE PORTIONS OF PILES (1995)
Pile Posting, or replacing defective portions of piles should be performed as follows:
a.
Posting of the outside piles should not be permitted on bridges on curves where bents exceed 12 feet in
height or on tangents where bents are over 23 feet in height.
3
b. Posting of 1 pile in a 4 pile bent, 2 piles in a 5 pile bent or 3 piles in a six or seven pile bent should be
permitted.
c.
No more than two posted piles should be adjacent to each other.
d. Bents should be framed or replaced in their entirety with suitable longitudinal and lateral bracing if
more than the allowable number of piles or more than two consecutive piles need posting.
e.
Posting may be accomplished per Figure 7-4-1.
f.
Where piles are decayed at the top, they may be cut off and double capped; a single pile may be corbeled.
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Timber Structures
Figure 7-4-1. Schematic Diagram of Pile Posting
4.6.2 DRIVING TIMBER PILES1 (1984)
4.6.2.1 Scope (1990)
This specification covers the driving of wood piles in trestles, foundations, and for protection work.2
4.6.2.2 Tests (1990)
In the absence of other reliable information to determine pile lengths, a thorough exploration shall be made at
the site by borings, driving test piles, or by pile loading tests, prior to the selection of the length of piles for the
work, and to determine characteristics incident to pile resistance and penetration.
4.6.2.3 Materials (1990)
The kinds of wood, physical requirements, dimensions, and manufacture are specified in Part 1, Material
Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties
1
References, Vol. 12, 1911, part 1, pp. 279, 307; Vol. 16, 1915, pp. 894, 1181; Vol. 41, 1940, pp. 326, 864; Vol. 54, 1953, pp. 943, 1329; Vol.
62, 1961, pp. 513, 848; Vol. 89, 1988, p. 106; Vol. 91, 1990, p. 57.
2 For the driving of concrete piles and steel piles, and for information on loading tests, see Chapter 8, Concrete Structures and
Foundations.
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Construction and Maintenance of Timber Structures
and Recommendations for Fire-Retardant Coating for Creosoted Wood, under the subject title Specifications for
Timber Piles.
4.6.2.4 Handling of Material (1990)
a.
Treated piles shall be handled with rope slings, taking care to avoid dropping, bruising or breaking of
outer fibers, or penetrating the surface with tools. Sharp pointed tools shall not be used in handling
treated piles or turning them in the leads.
b. The surface of treated piles below cut-off elevation shall not be disturbed by boring holes or driving nails
or spikes into them to support temporary material or staging. Staging may be supported in rope slings
carried over the tops of piles or attached to pile clamps of an approved design.
4.6.2.5 Selection and Preparation of Piles (1990)
4.6.2.5.1 Size
a.
The piles in each bent of a pile trestle shall be selected for uniformity of size to facilitate placing of the
brace timbers.
b. It is presumed that piles will be furnished in approximately the lengths required to secure the desired
penetration and bearing. In the event piles are found to be much in excess of the required lengths, they
shall be shortened at the small end before driving, as may be directed by the engineer, in order to
preserve the desired diameter of pile at the cut-off.
1
4.6.2.5.2 Pointing
Under ordinary conditions points of piles shall be cut perpendicular to the axis of the pile; where necessary or
desirable, points may be trimmed to form a truncated pyramid 4 inches to 6 inches square at the end and with
length of trimming not to exceed twice the tip diameter of the pile.
3
4.6.2.5.3 Pile Shoes
a.
Where the driving of a test pile or former experience at the site indicates that difficult driving will be
encountered, metal shoes of an approved design may be attached to the tips of the piles.
b. Each pile point shall be carefully trimmed to fit the shoe and obtain full and uniform bearing, and to
avoid displacement of the shoe or damage to the pile or shoe.
4.6.2.5.4 Collars
Where the heads of piles tend to split when being driven, the heads shall be tightly wrapped with No. 12 gage
annealed iron wire to form a band not less than 2 inches in width, held in place with staples, or shall be
protected with strap-iron bands applied with a banding tool, or other effective means shall be used to prevent
splitting.
4.6.2.5.5 Driving Cap
The heads of piles shall be protected while being driven with a driving cap (bonnet) of approved design. The cap
shall be shaped to fit over the head of the pile to provide lateral support, and to uniformly distribute the
hammer blow. Pile heads shall be trimmed to fit snugly into the cap.
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AREMA Manual for Railway Engineering
7-4-7
4
Timber Structures
4.6.2.6 Types of Hammers (1988)
a.
Pile driving shall not be started on any project until approval is secured from the engineer as to the type
and weight of the hammer to be used.
b. Piles shall be driven with the heaviest hammer that, in the judgement of the engineer, can be used to
secure maximum penetration without appreciable damage to the pile.1
c.
Where a drop hammer is used, the striking ram shall weigh not less than 3000 lbs. The fall shall be so
regulated as to avoid injury to the pile.
d. Special care shall be used in choice of hammer where the shock to surrounding material may cause
damage to an adjacent structure.
4.6.2.7 Driving (1988)
4.6.2.7.1 Leads
Pile driver leads shall be constructed in such a manner as to afford freedom of movement of the hammer, and
they shall be held in position by guys or stiff braces to insure support for the pile during driving. Inclined leads
shall be used to drive batter piles.
4.6.2.7.2 Followers
The use of followers shall be avoided if practicable and shall be used only with the written permission of the
engineer.
4.6.2.7.3 Line
Piles shall be driven as accurately as possible in the correct location, true to line both laterally and
longitudinally, and to the vertical or batter lines as indicated on the plans. On sloping ground or under difficult
conditions of driving, the pile shall be started in a hole or guiding template or other necessary means provided
to insure driving in the proper location. In case a pile works out of line in driving, it shall be properly aligned
before it is cut off or braced, and the distance that it may be pulled shall be determined by the engineer.
4.6.2.7.4 Jetting
Jetting shall not be done unless specifically permitted by the engineer. When waterjets are used, the number of
jets and the volume and pressure of water shall be sufficient to freely erode the material adjacent to the pile.
The plant shall have sufficient capacity to deliver at least 100 psi pressure at two 3/4 inch nozzles. Before the
desired penetration is reached, the jets shall be removed and the pile finally set under normal driving by at
least 50 blows from a gravity or single-acting hammer or 200 blows from a double acting hammer.
4.6.2.7.5 Drilling
a.
When it has been satisfactorily demonstrated to the engineer that piling cannot be driven in the regular
manner or by jetting, holes may be drilled to facilitate the driving.
b. Where drilling is permitted, the holes drilled shall have a diameter not more than 1 inch larger than the
tip diameter of the pile and the drilling will continue only through the strata of hard material
obstructing the driving. Where the hard material extends below the desired penetration, the drilling
1
For a discussion of the proper relationship of weight of ram to weight of pile, and net effective energy of blow, in selecting pile driving
hammers, reference is made to Vol. 37, 1936, AREMA Proceedings.
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AREMA Manual for Railway Engineering
Construction and Maintenance of Timber Structures
shall be stopped above that penetration level and the pile finally set under normal driving in accordance
to the bearing required. At least 50 blows from a gravity or single-acting hammer or 200 blows from a
double-acting hammer shall be used if possible to do so without damaging the pile.
4.6.2.7.6 Drilling and Shooting
Where it is impossible to drive, jet, or drill and drive the piles, the engineer will determine whether shooting the
holes with explosives or redesign of the structure is necessary. Shooting will not be permitted except by written
permission of the engineer.
4.6.2.7.7 Penetration
It is expected that piles shall be driven, jetted or drilled and driven to the full penetration shown on the plans or
as otherwise required. This shall not be construed to mean that driving may stop when such penetration as
shown on the plans has been secured, but on the contrary, driving shall continue in every case until the total
penetration obtained is satisfactory to the engineer, regardless of the fact that sufficient bearing capacity as
determined by formula may be obtained at a lesser depth.
4.6.2.7.8 Bearing Capacity
a.
Where possible, test piles shall be driven and loading tests made before construction is started, as
referred to under Article 4.6.2.2. In the absence of such data, the following “Engineering News”
formulas may be used to estimate the approximate safe bearing capacity of piles in most soils:
1
For drop hammers:
P = FWh
-------------S+1
For double-acting steam hammers:
3
Fh ( W + ap )
P = -------------------------------S + 0.1
For single-acting hammers:
4
FWh
P = ----------------S + 0.1
where:
P = safe load in pounds
W = weight of hammer or ram in pounds
h = fall of hammer or stroke of piston in feet
S = average penetration in inches per blow, for the last 5 blows of a drop hammer or 20 blows of a
single or double-acting hammer
a = effective area of piston in square inches
p = mean effective steam pressure in pounds per square inch
F = 2 for piles driven to practical refusal in any material
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Timber Structures
b. These formulas are applicable only when the hammer has a free fall, the head of the pile is not broomed
or crushed, the penetration is reasonably uniform, and there is no appreciable bounce of the hammer.
The character of the soil penetrated; conditions of driving; spacing, size and length of piles; and
experience under similar conditions; shall be given due consideration in determining the value of piles by
formula.
c.
The formulas should not be applied to friction piles driving into such soils as silt, muck, peat, or plastic
clays, nor to piles which act as end-bearing piles.
d. For jetted piles the same formulas will apply and the test shall be made when driving is resumed after
removal of the jets. For piles driven in drilled holes, the tests shall be made after the tip of the pile has
passed the bottom of the hole.
4.6.2.7.9 Delay
When driving is interrupted before final preparation is reached, record for bearing capacity shall not be taken
until at least 12 inches penetration or refusal has been obtained after driving has been resumed.
4.6.2.7.10 Overdriving
When the point of refusal is reached, care shall be taken to avoid damaging the pile by overdriving. This
condition is indicated when the hammer begins to bounce or when the energy of the blow is dissipated in the
bending or kicking of the pile.
4.6.2.7.11 Replacing
Any pile driving too far out of line, driven below cut-off elevation, or so injured in driving or straightening as to
impair its structural value as a pile under the conditions of use, shall be pulled and replaced by a new pile.
4.6.2.8 Framing (1988)
4.6.2.8.1 Cut-Off
The tops of piles shall be pulled into line if necessary, fixed in position, cut off to a true plane as shown on the
plans, and at the elevation established by the engineer. Piles shall show a solid head at the plane of the cut off.
4.6.2.8.2 Treatment
After the cut-off has been made, the tops of treated piles shall be saturated with hot preservative, followed by
two coats of hot sealing compound. The sealing compound shall be a mixture of creosote coal-tar pitch, mixed to
about the consistency of Vaseline, and brushed thoroughly into the wood.
4.6.2.8.3 Pile Covering
a.
The treated pile cut-off may be covered with plastic cement used with or without a fabric layer and
topped with a 1/4 inch neoprene pad if desired.
b. The use of roofing material or sheet metal to cover the cut-off has been found to retain moisture or
increase wetting and is not recommended.
4.6.2.8.4 Placing Caps
Caps shall be placed while the piles are held in correct position. Where drift bolts are used for making the
connection, the caps and tops of piles shall be bored the same diameter as the drift bolt and to a depth of 3
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Construction and Maintenance of Timber Structures
inches less than its length. Where the connection is made with straps and bolts, see Article 4.6.2.8.6 for boring
and treatment of holes.
4.6.2.8.5 Bracing
Piling shall not be trimmed or cut to facilitate the framing of sway or longitudinal bracing. Where necessary,
filler blocks shall be used between the pile and brace to establish the bracing in a true plane.
4.6.2.8.6 Holes for Bolts
a.
Holes shall be bored the same diameter as the bolt and 1/8 inch less than the nominal diameter of drive
spikes.
b. When holes are bored in treated piles, caps or bracing in the field, the entire hole shall be pressure
treated or swabbed with hot preservative and sealing compound just before the bolt is placed. Bolts shall
be cleaned of rust and scale, and dipped in hot sealing compound before placing. All unused holes shall be
plugged at each end with tight fitting treated wooden plugs.
4.6.2.8.7 General Field Treatment
Where it is necessary to disturb the surface of treated piles or timber, or where the surface has been damaged in
handling, such surfaces shall be treated with a liberal quantity of hot preservative followed by two applications
of hot sealing compound.
1
4.6.2.9 Foundation Piles (1990)
a.
For the design of pile foundations, exploration at the site, and test pile loading, see Chapter 8, Concrete
Structures and Foundations; Part 4, Pile Foundations.
b. The general specifications above shall apply to the driving of wood foundation piles.
c.
3
Pile driving shall not be started until foundation excavation has been carried to plan depth.
d. After all of the piles are driven, tests shall be made to determine if any of the piles have raised due to
driving of adjacent piles. Any piles that have raised shall be driven down again.
e.
After driving is completed, the piles shall be cut off as shown on the plans and at the elevation
established by the engineer. All loose and displaced materials down to the level of original excavation
shall be removed from the foundation pit, leaving a clean solid surface on the piles, and bottom and walls
of the pit.
4.6.2.10 Protection Work (1990)
a.
The general specifications above shall apply to the driving of wood piles for protection work.
b. It is essential that protection work be constructed as securely as possible, accurately located as shown on
the plans, and the piles driven to a fixed penetration or to refusal as may be determined by the engineer.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-4-11
4
Timber Structures
4.6.2.11 Pile Record (1988)1
a.
An accurate record shall be kept of all piles, as each is driven, to show the location in the structure, size
of pile, penetration, resistance to driving and other essential data. See suggested form for reporting this
information, Figure 7-4-2. Size can be 8-1/2² ´ 11² or 8² ´ 10-1/2².
b. The size and arrangement of pile driving record forms may be varied to adapt them to the convenience of
user, method of filing, and use to be made of the data. The form found in Figure 7-4-2 embodies the
minimum of information for a satisfactory record. Among additional items which may be desirable are:
• reference to piles other than wood;
• steam hammer blows per minute;
• data on batter;
• reference to jetting;
• computed bearing value; and
• other arrangement of data on length between butt, cut-off, ground and point of pile.
1
References, Vol. 12, 1911, part 1, pp. 278, 307; Vol. 52, 1951, pp. 426, 846; Vol. 62, 1961, pp. 514, 848; Vol. 89, 1988, p. 106.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-4-12
AREMA Manual for Railway Engineering
Construction and Maintenance of Timber Structures
North and South Railroad
Pile Record of Bridge:
Location:
Weight and Kind of Hammer:
Date:
Avg. Last Blows
(Note 3)
Size of Pile
Date
Bent
No. of
Kind of
Base-rail
Total
No.
Pile
Cutoff
Wood
to
Ground
Penetration
(Note 1) (Note 2) Tip Butt Length
End End
Drop
of
Penetration
Hammer
Kind of
Remarks
Soil
1
3
4
Note 1: Bents numbered in direction in which mile posts increase.
Note 2: Piles numbered from left to right.
Note 3: Five blows for drop hammers and 20 blows for single or double-acting hammers.
Figure 7-4-2. Sample Pile Record Form
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-4-13
Timber Structures
SECTION 4.7 SUPERSTRUCTURE
Under Development
SECTION 4.8 SUPPORT, REPAIR, PRESERVE, OR REPLACE DAMAGED PORTIONS OF
THE STRUCTURE (2010)
a.
Splicing provides additional material to support small structurally deficient areas. Sufficient connections
must be provided for adequate load transfer. A structural analysis should be performed to verify stress
distribution and adequacy. See Figure 7-4-3.
Figure 7-4-3. Splicing
b. Scabbing provides additional material to support large structurally deficient areas. Sufficient
connections must be provided for adequate load transfer and support. Scabbing may also be used to
increase capacity of a member and may be composed of timber or steel. A structural analyses should be
performed to verify stress distribution and adequacy. See Figure 7-4-4.
Figure 7-4-4. Scabbing
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-4-14
AREMA Manual for Railway Engineering
Construction and Maintenance of Timber Structures
c.
Deteriorated pile may be restored by using a cast in place reinforced concrete jacket. The jacket must
extend above and below the defective area to adequately support the loads. See Figure 7-4-5.
1
3
Figure 7-4-5. Pile Restoration Using Cast in Place Reinforced Concrete Jacket
4
d. Voids in pile may be filled with an epoxy or other suitable grout. See Figure 7-4-6.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-4-15
Timber Structures
Figure 7-4-6. Filling Voids with Grout
e.
Splits or checks may be arrested by clamping, using steel assemblies to compress the member, or
stitching, using through bolts to hold the member together. Configuration, number and size of fasteners
should be determined on a case by case basis. Stitch bolt spacing should be determined by Part 2, Design
of Wood Railway Bridges and Trestles for Railway Loading; Section 2.6, Details of Design, Article 2.6.3.
Holes for stitch bolts should be sized in accordance with Article 4.5.m. Stitch bolts should only be
tightened to the point where they begin to take tension. Splits or checks should not be closed as this may
extend the defect to the other side of the clamp or stitched area. See Figure 7-4-7 and Figure 7-4-8.
f.
When individual caps, sills, braces or struts have become weakened beyond their ability to perform their
intended function, replacing these members with similar sized members may be performed.
g.
Shimming of stringers to provide proper surface and cross level should be performed using a single hard
wood shim under each chord or stringer. Shimming with stacked or multiple shims is to be avoided.
h. All bolts should be retightened during normal servicing of the structure.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-4-16
AREMA Manual for Railway Engineering
Construction and Maintenance of Timber Structures
Figure 7-4-7. Clamping
1
3
Figure 7-4-8. Stitching
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-4-17
Timber Structures
4.8.1 CONTROL MOISTURE
The hazard of decay is reduced by controlling the amount of moisture present in timber bridges. Once visible
wetting or high moisture contact areas are located, the following action is recommended:
a.
Remove dirt and debris.
b. Provide adequate drainage from deck.
c.
Ensure adequate support surface for tie plates.
d. Provide water proofing systems for ballast decks.
e.
Ensure hardware is tight, sealing holes preventing moisture entrance.
f.
Plug any unused holes with treated wood plugs.
4.8.2 FIELD APPLICATION OF PRESERVATIVE CHEMICALS
Timber decay can be arrested by field application of preservative chemicals which should be applied in
accordance with manufacturer’s specifications. It is recommended they be used by qualified personnel with
experience in treating structural timber.
a.
Liquids are brushed, squirted or sprayed on the surface and may be injected into timber.
b. Semi-solids, greases or pastes are spread on the affected area. They are mostly used in ground line
applications or treating fresh cuts.
c.
Fumigants are normally injected into the wood. They originally are liquid and volatilize, creating a gas
which permeates wood cells inhibiting decay.
d. Plugs or pastes containing salts, which, when combined with moisture release an active ingredient which
permeates wood cells inhibiting decay.
SECTION 4.9 METHODS OF FIREPROOFING WOOD BRIDGES AND TRESTLES1
4.9.1 FOREWORD (1988)
The following methods are used in providing fire protection for open-deck bridges and trestles:
4.9.2 METAL PROTECTION (1988)
This method consists of covering the deck partially or completely with sheets of No. 24 gage galvanized iron
fastened with 12d heavy galvanized barbed car nails with flat heads and diamond points.
1
References, Vol. 42, 1941, pp. 291, 868; Vol. 54, 1953, pp. 962, 1331; Vol. 62, 1961, pp. 514, 848; Vol. 63, 1962, pp. 453, 684; Vol. 89, 1988,
p. 106.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-4-18
AREMA Manual for Railway Engineering
Construction and Maintenance of Timber Structures
4.9.3 COATINGS (1988)
Coatings of bituminous and non-bituminous materials with clean gravel embedded in them are showing
promise of being fire resistant when applied on horizontal surfaces. Vertical surfaces require special treatment.
4.9.4 IMPREGNATION (1988)
This method includes the use of various salt solutions applied at treating plants. The treated wood, in addition
to being made fire resistant, is also given protection against decay and termite attack.
4.9.5 FIRE ALARM SYSTEMS (1988)
a.
Under this method fusible-link detector systems are so connected with the signal and communication
systems that in case of fire the block signals will show warning indications, and the nearest telegraph
operator will receive notification so that maintenance of way forces may be assembled to combat the fire.
b. Special fire-fighting apparatus and watchmen are employed in unusual cases where conditions warrant.
4.9.6 HOUSEKEEPING (1988)
NOTE:
a.
The following practices, applicable to both open- and ballasted-deck bridges and trestles,
are being employed where conditions warrant.
Decks are kept clear of all combustible material, and decayed spots in exposed ties or timbers kept
trimmed.
b. Brush and weeds are kept down for a distance of at least 25 feet from the bridge, both underneath and on
the embankment at the ends of the bridge or trestle. Also, all sod is removed from under timber bridges
and for a distance of 3 feet outside the timbers. This is accomplished by scalping or by the use of a soil
sterilant.
c.
NOTE:
4
Applicable to both open and ballasted-deck bridge and trestles.
Under this method long bridges and trestles are protected by introducing fire barriers at intervals of about 400
feet. This reduces the hazard by preventing loss of the entire structure in case of fire. Such barriers may be
grouped by types of construction, as follows:
Earth fill (see Figure 7-4-9).
b. Reinforced concrete piers or concrete pile bents (see Figure 7-A3-58).
c.
3
Water barrels with buckets are installed on timber bridges, 1 barrel each for structures up to 50 feet long
and 1 additional barrel for each additional 150 feet or fraction thereof. For creosoted structures, sand
boxes with water-tight covers for keeping the sand dry are used, dry sand being more effective than
water in extinguishing small fires on creosoted structures.
4.9.7 FIRE BARRIERS (2011)
a.
1
Facing bents with fire-resisting materials (see Figure 7-A3-59).
d. Application of mastic materials to open-deck structures (see Figure 7-A3-60).
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-4-19
Timber Structures
Figure 7-4-9. Earth Fill Break in a Long Trestle
SECTION 4.10 USE OF GUARD RAILS AND GUARD TIMBERS1 (2004)
4.10.1 FIELD SIDE GUARD OR SPACER TIMBERS (1988)
On all open-floor railway bridges, the ties should be held securely in their proper spacing; guard or spacer
timbers fastened to every tie near its end are effective. If such continuous timbers are not placed, blocks or
other suitable fastenings should be used for spacer timber attachment; on track where speed or other
circumstances so indicate it may be advisable also to embed clamping plates or timber connectors between the
timbers and ties. Such metal fastenings are more effective than dapping of the spacer timbers, because of the
tendency of the wood to split off between daps.
4.10.2 METAL GAGE SIDE GUARD RAILS (2004)
a.
Consideration should be given to the use of metal inner guard rails taking into account the alignment,
train speed, deck type, density and type of traffic, as well as height and length of bridge.
b. It is recommended that the inner guard rails, when used, be steel track rails not higher than the running
rails. If 5 inches or more in height they should not be more than 2 inches lower than the running rails. If
less than 5 inches in height they should not be more than 1 inch lower than the running rails. Normally,
they will consist of two rails, spaced about 10 inches inside the running rails (measured between near
sides of head) spiked to every tie and spliced with joint bars, fully bolted. The inner guard rails may be tie
plated when deemed advisable. They must not contact tie plates of tracks carrying electric signal circuits.
Where they protect against a hazard on one side only, a single line of rails may be used, adjacent to the
running rail further from the hazard.
1
References, Vol. 14, 1913, pp. 652, 1136; Vol. 15, 1914, pp. 402, 1036; Vol. 21, 1920, pp. 1285, 1434; Vol. 52, 1951, pp. 426, 847; Vol. 62,
1961, pp. 514, 848; Vol. 63, 1962, pp. 454, 684; Vol. 89, 1988, p. 106.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-4-20
AREMA Manual for Railway Engineering
Construction and Maintenance of Timber Structures
c.
It is further recommended that where inner guard rails are used, they extend at least 50 feet beyond the
end of the bridge or other structure. This distance may be increased where train speed, curves or other
factors warrant the increase, and may be decreased on the leaving end where traffic is in one direction.
The ends should run to the center of the track and be beveled, bent down or otherwise protected against
direct impact. A filler block or plate should be provided at the meeting of the converging rails.
4.10.3 COMBINED USE OF GUARD TIMBERS AND GUARD RAILS (1988)
Where both guard timbers and inner guard rails are used they should be so spaced that a derailed truck will
strike the inner guard rail and not the timber.
1
SECTION 4.11 TYPICAL PLANS FOR TIMBER RAILWAY BRIDGES
4.11.1 PLANS (1988)
For aligning of plans for open-deck pile and framed trestles, multiple-story trestles, and ballasted deck pile and
framed trestles refer to Table 7-4-1.
4.11.2 GENERAL NOTES (1988)
a.
For various combinations of loading, panel lengths, number and size of stringers, number of piles and
permissible working stresses, see Part 2, Design of Wood Railway Bridges and Trestles for Railway
Loading.
1
b. All lumber and piles should be pressure treated in accordance with AREMA Chapter 30, Ties. All lumber
should be framed and bored before treatment wherever possible.
c.
Holes should be bored the same diameter as the bolt and 1/8 inch less than the nominal diameter of drive
spikes.
3
d. Lumber cut after treatment should be painted with three coats of hot creosote oil.
e.
Holes bored after treating should be treated with hot creosote oil applied with a pressure bolt hole
treater.
f.
Each bolt should have a square head, suitable type lock nut and 2 “OG” washers, with a double-coil
spring when shown on the plans.
g.
Trestles on curves should be built to follow the curve. Bents should be placed on radial lines and spaced
to maintain standard panel lengths under the outside stringer.
h. Crushed-rock ballast should be hard, durable stone and should conform to size No. 4 of the National
Bureau of Standards.
1
i.
For use of protective coating for hardware see Part 1, Material Specifications for Lumber, Timber,
Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for
Fire-Retardant Coating for Creosoted Wood, Section 1.6, Specifications of Fasteners for Timber Trestles.
j.
For use of inner guard rails see Section 4.10, Use of Guard Rails and Guard Timbers (2004).
References, Vol. 23, 1922, pp. 709, 1148; Vol. 24, 1923, pp. 773, 1196; Vol. 37, 1936, pp. 667, 704, 1036, 1038; Vol. 38, 1937, pp. 183, 624;
Vol. 45, 1944, pp. 203, 596; Vol. 49, 1948, pp. 272, 672; Vol. 60, 1959, pp. 556, 1081; Vol. 63, 1962, pp. 455, 684; Vol. 89, 1988, p. 106.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-4-21
4
Timber Structures
Table 7-4-1. Recommended Practice Plans
Figure No.
Plan Name
Page No.
7-A3-61
Floor Plan for Open-Deck Trestles
7-A3-65
7-A3-62
Floor Plan for Ballasted-Deck Trestles
7-A3-48
7-A3-63
Bulkheads and Miscellaneous Details
7-A3-49
7-A3-64
Cap Stringer Fastening and Pile Top Protection
7-A3-50
7-A3-65
Bent Details for Open-Deck Pile Trestles
7-A3-51
7-A3-66
Bent Details for Ballasted-Deck Pile Trestles
7-A3-52
7-A3-67
Longitudinal Bracing
7-A3-53
7-A3-68
Details of Footings for Framed Bents
7-A3-54
7-A3-69
Multiple-Story Trestle Bents (6 Post Bent)
7-A3-55
7-A3-70
Multiple-Story Trestle Bents (5 Post Bent)
7-A3-56
7-A3-71
Walk and Handrail - Open-Deck Trestles (to be used where required)
7-A3-57
7-A3-72
Water Barrel and Refuge Platform - Open-Deck Trestles (to be used
where required)
7-A3-58
7-A3-73
Track Car Platforms - Open-Deck Trestles (to be used where
required)
7-A3-59
7-A3-74
Walk and Handrail - Ballasted-Deck Trestles (to be used where
required)
7-A3-60
7-A3-75
Water Barrel and Refuge Platform - Ballasted-Deck Trestles (to be
used where required)
7-A3-61
7-A3-76
Track Car Platform - Ballasted-Deck Trestles (to be used where
required)
7-A3-62
7-A3-77
Recommended Practice for Creosoted Timber Pile Piers for Long
Spans, E60 Loading-Pier for 150-foot and 80-foot Spans
7-A3-63
7-A3-78
Recommended Practice for Creosoted Timber Pile Piers for Long
Spans, E60 Loading-Pier for 150-foot Span and Trestle Approach
7-A3-66
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-4-22
AREMA Manual for Railway Engineering
7
Part 5
Inspection of Timber Structures
— 2010 —
TABLE OF CONTENTS
Section/Article
Description
Page
5.1 General (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-5-1
5.2 Details of Inspection (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.1 Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.2 Waterway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.3 Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.4 Superstructure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.5 Substructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.6 Fire Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.7 Earthquakes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-5-2
7-5-2
7-5-2
7-5-3
7-5-3
7-5-3
7-5-4
7-5-4
3
FOREWORD
It is the purpose of these instructions to describe the manner of inspecting a timber bridge; no attempt is made
to set up the organization nor to fix the responsibility or the functioning of the various members of the
organization.
SECTION 5.1 GENERAL (1988)
The method of inspecting timber, regardless of its location in the structure, follows:
a.
Make a careful surface inspection of each timber for cross grain, tension or horizontal shear failures that
may have developed from uneven bearing, original defects, overstress or other causes. Note whether
timber and piling are treated or untreated.
b. Test each timber and pile for soundness, especially at points of contact with other timbers, ground, or at
low water line, and where end grain bears on a sill or cap.
(1) For treated timber, test shall be made by sounding with the knob end of an inspection bar or lightweight hammer, using care to avoid injuring or disfiguring the fiber. If hollow or dead sound results,
© 2011, American Railway Engineering and Maintenance-of-Way Association
1
7-5-1
Timber Structures
determine nature and extent of the defect by boring, preferably with an increment borer. Bore holes,
where possible, so water can drain, and carefully plug with treated wood.
(2) For untreated timber, test may be made by sounding with the knob end of an inspection bar or lightweight hammer, also by probing with pointed end of inspection bar, using care to avoid any
unnecessary injury or disfiguring of the wood. Note the feel and sound when struck by the bar, the
appearance of the fiber, and of all decayed or otherwise unsound wood, which should be trimmed
away to sound timber.
c.
Make a careful surface inspection of the timber and adjacent ground surface for evidence of termites,
carpenter ants, marine borers or other destructive insects.
d. Make inspection on new work, where timber is treated, of all field cuts for exposed untreated wood.
e.
Make an outline of repairs based on information from Part 4 and Part 5. The inspector should determine
the cause of the deterioriation of the structural component and suggest maintenance or repair measures
that would correct existing deficiences and prevent their reoccurance.
SECTION 5.2 DETAILS OF INSPECTION (2002)
The bridge inspector’s notes for each bridge shall be written while at the structure after a careful examination
has been made covering the following points:
5.2.1 IDENTIFICATION
a.
Division or subdivision. Name of inspector and members of inspection party. Date of inspection.
b. Bridge Number. Name of nearest station and mile-post location. Age and type of structure. Total length,
height and number of panels.
c.
Number of bents, towers, spans or panels in each bridge in the direction in which the mile post numbers
increase, starting with the dump bent as No. 1. Number the piles in each bent or tower and the stringers
in each panel from left to right, when facing in the direction in which the mile post numbers increase.
5.2.2 WATERWAY
a.
Observe if the opening appears adequate for drainage area and if free of obstructions, such as drift,
vegetation, displaced revetment stone, or old pile stubs. Note whether the channel is stable, filling,
deepening or subject to scour, and if public improvements have altered the general condition in any way.
Measure and record the distance from base of rail to ground line at each bent. Measure and record high
water mark if obtainable. If heavy or accumulated drift is troublesome during high water, ascertain the
type, such as logs, trees, ice, etc., and observe whether of such intensity as to force the bridge out of line
and/or break piling.
b. Note if protection work is required or whether cleaning and straightening of the channel are necessary.
Note whether bent alignment obstructs or deflects normal flow and if revetment or deflection dikes are
needed.
c.
Note evidence that would indicate the presence of any buried cable, conduit, tile or pipe lines crossing
under the bridge, giving the panel location, together with size and use.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-5-2
AREMA Manual for Railway Engineering
Inspection of Timber Structures
5.2.3 TRACK
a.
State whether track is level or on a grade, and if alignment is tangent or curved. If on a curve, note how
superelevation is provided, whether by cutoff in the bents, taper in the caps or in the ballast section.
Note location of track with reference to the chords for uniformity of loading.
b. Observe condition of embankment at the bridge ends for fullness of crown, steepness of slopes and depth
of bulkheads. Note whether track ties are fully ballasted and well bedded.
c.
Record the weight and condition of the track rails and inside guard rails; also the condition of the rail
joints and fastenings. Note the size and condition of the tie plates.
d. Where track is out of line or surface, the location, amount and probable cause should be determined.
5.2.4 SUPERSTRUCTURE
a.
Ascertain size, spacing and uniformity of bearing of the ties. Note condition as to soundness, mechanical
wear, spike killing and other defects.
b. Determine the size, condition, and security of anchorage of the guard timber.
c.
Inspect all walks, railings, and refuge bays, noting the condition as to soundness and security of
fastening devices.
1
d. Note all members to determine if any are broken or have moved out of proper position and whether all
fastening devices are functioning properly. On ballasted-deck trestles, note whether ballast is clean and
in full section.
e.
f.
Examine all stringers for soundness and surface defects. Note size and kind, and the number used in
each panel. Note if bearing is sound and uniform, if all stringers are properly chorded and securely
anchored, and if all shims and blocking are properly installed. Note whether packers or separators are
used and the condition of all chord bolts.
Note and report presence of any wires, cables, pipe lines or other attachments which are foreign to the
bridge structure.
5.2.5 SUBSTRUCTURE
a.
4
Make careful examination of all piles and posts for soundness, noting particularly the condition at points
of contact with the caps, girts, bracing, sills, and at the ground or water line.
b. Examine all bents and towers for plumbness, settlement, sliding and churning, and give an accurate
description of the nature and extent of any irregularities. Note particularly whether caps and sills have
full and uniform bearing on the supports.
c.
Record number and kind of piles or posts in the bents or towers. Note uniformity of spacing and the
location of any stubbed or spliced members, especially if the bridge is on a curve or the bent is more than
15 feet in height.
d. Ascertain whether all bents and towers are properly sway, sash and tower braced, and if girts and struts
are applied as needed.
e.
3
Examine all fastening devices for physical condition and tightness.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-5-3
Timber Structures
f.
Observe action of bridge under movement of trains, where practicable, in order to evaluate better the
riding condition and soundness of the structure.
5.2.6 FIRE PROTECTION
a.
Note whether surface of the ground around and beneath the structure is kept clean of grass, weeds, drift
or other combustible material.
b. Where rust-resisting sheet metal is used as a fire protection covering for deck members, note condition of
metal and fastenings.
c.
Note if any other method of fire protection has been used, such as fire retardant salts, external or surface
protective coatings, or fire walls. Record such apparent observations as are pertinent to the physical
condition and effectiveness of such protective applications.
d. Where water barrels are provided, note the number, condition, if filled, and if buckets for bailing are on
hand. If sand is used, note whether bins are full and in condition to keep the sand dry.
e.
Note if timber, particularly top surfaces of ties and stringers in open deck bridges, is free from frayed
fiber, punk wood, or numerous checks.
5.2.7 EARTHQUAKES
In the occurrence of a seismic event refer to Chapter 9 of this manual.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-5-4
AREMA Manual for Railway Engineering
7
Part 6
Commentary
— 2010 —
TABLE OF CONTENTS
Section/Article
Description
Page
6.1 Materials Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.1 Structural Grades of Lumber and Timber and Method of Their Derivation (2010) . . . . .
6.1.3 Specifications for Engineered Wood Products (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.4 Examples for Inquiry or Purchase Order (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-6-2
7-6-2
7-6-2
7-6-5
6.2 Design Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2.2 General Features of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2.4 Designing for Engineered Wood Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2.5 Notes on the Use of Stress-Graded Lumber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-6-5
7-6-5
7-6-6
7-6-6
7-6-7
6.3 Rating Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-6-13
6.4 Construction and Maintenance Commentary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-6-13
6.5 Inspection Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-6-13
LIST OF FIGURES
Figure
Description
Page
7-6-1
Chart Showing Relation of Design Stress to Duration of Load . . . . . . . . . . . . . . . . . . . . . . . . . .
7-6-11
LIST OF TABLES
Table
Description
Page
7-6-1
Derivation of listed values, using combination 16F-1.5E DF as an example . . . . . . . . . . . . . . .
7-6-12
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-6-1
1
3
Timber Structures
SECTION 6.1 MATERIALS COMMENTARY
6.1.1 STRUCTURAL GRADES OF LUMBER AND TIMBER AND METHOD OF THEIR
DERIVATION (2010)
a.
Lumber, including structural lumber, is the product of the saw and planing mill not further
manufactured than by sawing, resawing, passing lengthwise through a standard planing machine, cross
cutting to length and working. After the lumber is produced, it is necessary to inspect each piece
individually to determine its grade. Lumber which is so graded that working stresses can be assigned is
called stress-graded or structural lumber.
b. Traditional design values for wood are based on testing of small clear samples; results summarized in
ASTM D2555, and are developed in accordance with ASTM D245 with reductions applied to account for
various wood defects. For a detailed explanation of the intial concepts see AREA Proceedings Vol. 30,
1929, pages 1206 to 1224. Starting in the 1980s, the coordinated Canadian and U.S. in-grade testing
program started to develop properties based on full-sized structural tests of members (Madsen) using
proof loading concepts. At present there is a large database for dimension lumber sizes in Douglas FirLarch, Hem-Fir and Spruce-Pine-Fir. As in-grade testing is expanded to timber sizes and other species,
the values from this program will replace the results of tests done on small clear samples adjusted for
defects.
LUMBER INDUSTRY ABBREVIATIONS (2007)
a.
The same as American Softwood Lumber Abbreviations, as approved by the American Lumber
Standards Committee.
b. These standard lumber abbreviations are commonly used for softwood lumber, although all of them are
not necessarily applicable to all species. When used in the preparation or writing of contracts and other
documents arising in transactions of purchase and sale of American Softwood Standard Lumber, these
abbreviations shall be construed as provided therein.
NOMENCLATURE OF COMMERCIAL DOMESTIC HARDWOODS AND SOFTWOODS
(2007)
The standard commercial names for lumber cut from species or species groups of domestic hardwoods or
softwoods are the same as those used in the current standard grading rules for the species
6.1.3 SPECIFICATIONS FOR ENGINEERED WOOD PRODUCTS (2006)
6.1.3.1 Structural Glued Laminated Timber - Glulam
Glued laminated timbers (glulam) are manufactured by end jointing individual pieces of stress-graded lumber
together with rigid structural adhesives to create long lamination lengths. The laminations are then face
bonded to create the desired member depth in accordance with layup specifications. The manufacturing
standard for the glulam industry is America National Standard - ANSI A190.1.
Chapter 7 Sections 1.3.1 and 2.4 are to be used in conjunction with railroad design practices and design
methodology provided in other sections of the chapter, and in conjunction with basic structural engineering
equations. Glulam material properties to be used for design are available primarily from industry technical
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AREMA Manual for Railway Engineering
Commentary
trade associations. The values listed in Tables 7-2-7 and 7-2-8 are traceable to association sources and the
glulam section of the National Design Specification (NDS).
The glulam content in Chapter 7 has been heavily edited from building design and construction reference
documents (such as the NDS), to serve the needs of railroad bridge designers. Content in Sections 1.3.1 and 2.4
has been arranged to simplify use of the material for design engineers that may not be familiar with glulam
properties and recommended practices as they apply to the use of glulam in railroad bridge applications. The
primary need for editing glulam design reference tables and design literature excerpts was to reduce the
information by removing adjustment factors and design considerations commonly used in building
construction, but not applicable to railroad bridge design. Decisions on options for this simplification process
were guided primarily by committee members knowledgeable in railroad timber bridge design practices, input
from glulam industry members on Committee 7, and through contact with the glulam industry technical trade
associations.
A number of modifications to basic glulam industry practice were included in this section to tailor the material
for railroad bridge structure applications. For this reason, direct comparisons with common glulam industry
standards and specifications will show differences.
6.1.3.1.1 Appearance Classifications
b. Industry recommendations for finished appearance of glued laminated timber typically identify four
classifications: Premium, Architectural, Industrial and Framing. Framing and Industrial appearance
classifications are shown. Premium and Architectural appearance classifications are not applicable to
railroad bridge applications.
1
It should be noted that appearance classifications are cosmetic in nature and do not affect the structural
properties of glulam members.
The glulam manufacturer should be contacted for details on Framing appearance classification.
6.1.3.1.2 Layup Combinations
3
Layup combinations listed in the reference design property tables (Tables 7-2-7 and 7-2-8) have been limited to
bending "Stress Groups" that are most likely to be used for railroad bridge applications. Both Balanced and
Unbalanced combinations are available in the respective stress groups. Only Balanced combinations are listed
in Table 7-2-7 for the two major species (Douglas fir and Southern pine) used for railroad structures in North
America.
4
A comprehensive list of all available layup combinations (for a variety of lumber species) is available from
agencies, such as APA - The Engineered Wood Association (http://www.apawood.org) or American Institute of
Timber Construction (AITC, http://www.aitc-glulam.org) certifyng glulam manufacturers.
Glulam members may also be supplied with all laminations of a single grade, from the desired species.
Combinations for this option are intended primarily for axial loading, such as columns. Combinations listed in
Table 7-2-8 are for all one grade of given species. All one-grade combinations are identified by number
designations that identify specific lumber grade categories within species groups.
Grade Requirements
Layup grade requirements may be achieved with the use of both visual and mechanically graded lumber
sources in a variety of species. Glulam manufacturers have the option to use alternate sources of lumber as
long as species criteria are maintained in layup grade requirements. Douglas fir and Southern pine species are
generally available in the United States, with Spruces more common in Canada.
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Timber Structures
Manufacturing specifications for layup combinations are generally not needed by the designer. Glulam
industry manufacturing specifications are referenced in ANSI A190.1. Customized layup options are possible
to meet specialized design requirements within the scope of industry standards for glulam manufacture.
Bending Members
Bending members are typically specified on the basis of the maximum allowable bending stress and modulus of
elasticity of the member. For example, a 24F-1.8E designation indicates a member with an allowable bending
stress of 2400 psi and a MOE of 1,800,000 psi. This “stress class” may be produced in a variety of different
species, each with the same properties listed for the 24F-1.8E stress class. Table 7-2-7 is a simlified version of a
stress class table listing only DF and SP balanced combinations.
Glulam layup combinations are specified to provide the highest lumber grades int he zones of the member
depth where bending stresses are highest. Layup stress group combinations for members stresses primarily in
bending are listed in Table 7-2-7. Layup combinations may be provided based on selective grade zones through
the member depth however only properties for balanced combinations are shown in Table 7-2-7.
6.1.3.1.3 Balanced Beams
Balanced beams must be used in applications such as continuous stringer applications, where the top and
bottom of the member is stressed in tension.
6.1.3.1.6 Finished Sizes
Finished sizes are provided for typical bridge stringers, deck panels and pile caps only. Other sizes are
available.
Glulam can be manufactured in widths greater than 12-inch nominal widths through the use of laminations
made up of multiple-pieces of lumber. Specifications for special order members of this type should be
negotiated directly with the glulam manufacturer.
Multiple-piece laminations may be used to develop glulam members in widths greater than nominal lumber
widths. Where multiple-piece laminations are used, the allowable gap between laminations shall be limited to a
maximum of 1/16 inch if a gap-filling structural adhesive is specified. Otherwise, multiple-piece laminations to
be used for pile cap applications shall be edge-glued.
Typical Net Finished Glulam Deck Panels:
Depths (Thickness):
2-1/2 to 12-1/4-in. (hit & miss surfaces)
Widths:
45 to 52 in.
Lengths:
24 to 24 ft.
Other sizes may be supplied for specific applications as required.
Typical Net Finished Glulam Pile Caps:
Depth:
Width:
Length:
14 in., 16 in. or deeper as required
12 in. (hit & miss), 11-3/4 in. finished
Multiple-piece lams for 14 in., 16 in. or wider
Stock lengths up to 60 ft.
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AREMA Manual for Railway Engineering
Commentary
6.1.3.1.7 Preservative Treatments
In general, pressure preservative treatment processes commonly used for glulam do not affect the strength
properties of glued laminated timbers. Information on the possible effects of specific treatment is available
through the AWPA or the treatment provider.
Waterborne Treatments
Waterborne treatments are typically applied to lumber prior to the laminating process. Waterborne treatments
applied to glulam after the laminating process can cause dimensional changes such as warping, and twisting, in
addition to excessive checking as the result of the necessary re-drying process.
6.1.3.1.9 Certification, Wrapping and Shipping
Glulam members may be supplied in virtually any length, limited only by treating facilities, shipping routes
and jobsite handling capabilities. Glulam members to be pressure-treated with preservatives after
manufacture may be supplied without cover depending on conditions, or load wrapped as needed. If wrapping is
to be specified for environmental protection or for other reasons, members may be supplied either load
wrapped, bundle wrapped or individually wrapped.
6.1.3.1.10 Storage and Handling
Seasoning checks in glulam members may be excessive if members are stored flat and placed unprotected in an
environment where changes in the relative moisture content of members is forced to change rapidly.
1
6.1.4 EXAMPLES FOR INQUIRY OR PURCHASE ORDER (2010)
Example 1: 30,000 fbm 2 x 8 x 12 feet, S4S, Select Structural joist and plank, Bald Cypress, Grading for
structural Cypress, Southern Pine Inspection Bureau (SPIB).
Example 2: 120 pieces 3 x 12 x 20 feet, S4S, selected structural joists and planks, Douglas-fir, coast region, in
accordance with Paragraph 123(a) Standard No. 17, Grading Rules for West Coast Lumber issued by West
Coast Lumber Inspection Bureau, except to have 90% heartwood.
3
Example 3: 48 pieces 2 x 12 x 12 feet, rough, dense select structural, Southern Yellow Pine, in accordance
with Paragraph 401.1 of Southern Pine Inspection Bureau’s Grading Rules, except to be free of wane.
4
SECTION 6.2 DESIGN COMMENTARY
6.2.2 GENERAL FEATURES OF DESIGN
6.2.2.3 Stringers (2009)
An approximate analysis to determine the division of rail load to several stringers is given in the chart, Figure
7-A1-1, in Appendix 1 - Contemporary Designs and Design Aids.
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Timber Structures
6.2.3 LOADS, FORCES AND STRESSES
6.2.3.5 Other Lateral Forces (2009)
6.2.3.5.4 Longitudinal Force
d. Since longitudinal bracing in timber trestles is essentially there to provide L/d stability and geometrical
constraint, the longitudinal forces are transferred through the stringer and deck system with some help
from the rails in proportion to their axial stiffness. Where stringers are discontinuous, the load is likely
transferred through the dowels to the cap and back to the next set of stringers. This load path needs to
be adequate to do this.
Traditionally this has been accomplished by the use of earth fill or similar fire barriers at 400-foot
intervals but with the addition of Articles 2.3.5.4.b, c and d it is necessary to include this limitation, as
some of these fire details would not transmit any appreciable force.
6.2.4 DESIGNING FOR ENGINEERED WOOD PRODUCTS
6.2.4.1 Design Values for Glued Laminated Timber (Glulam) (2006)
Methods used to establish glulam design properties take into account basic lumber properties. Lumber
properties published by the grading agencies for Douglas fir and Southern pine are derived from standard
practices provided in ASTM D245 in conjunction with clear wood properties published in ASTM D2555. Basic
lumber grade characteristics are adapted to a glulam beam design modeling method described in ASTM D3737
to establish glulam beam properties for the various layup "combinations" listed in Tables 7-2-7 and 7-2-8.
Railroad bridge design applications require the use of basic structural engineering principles and design
equations in conjunction with published glulam allowable stresses.
6.2.4.1.1 Allowable Stresses
The National Design Specification (NDS) provides an "equation format" that may be used with the specialized
equations and loading requirements specified in the AREMA Manual for Railway Engineering for design of
bridge structures. Design methodology for connections is also included in the NDS. The allowable stresses
included in Tables 7-2-7 and 7-2-8 may be used directly for glulam bridge design. Appropriate stress adjustment
factors for typical railroad bridge applications described in the NDS and glulam industry design publications
have been applied to these table values to simplify use of the values in basic engineering equations.
Glulam beams are "engineered" to optimize grade characteristics of the lumber used to make the product. The
highest lamination grades are used in the outer zones of the beam depth. The X-X, Y-Y and Axial orientations
are defined here to explain the use of these terms as they are used in glulam product design.
Fasteners: The design methodology provided in Section 2.4 is applicable to glulam products. In addition, the
information provided in the NDS for fasteners in solid sawn members is applicable for glulam design. Fastener
capacities for withdrawal, single shear, double shear, and fastener group patterns in glulam members are
controlled by wood species and the specific gravity within species groups. Specific gravity values to be used with
the stress groups listed in Tables 7-2-7 and 7-2-8 are provided.
6.2.4.1.2 Tabular Design Values
See Appendix 1 - Contemporary Designs and Design Aids.
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AREMA Manual for Railway Engineering
Commentary
6.2.4.1.3 Adjustment Factors
Adjustment factors for wet-use, cyclic loading and the RR Use as defined in this section have been applied to
the appropriate values in Tables 7-2-7 and 7-2-8. Other factors that may be considered have been included in
Table 7-2-3. In cases where factors are not applicable, "none" is entered in the table. If adjustment for a given
condition may be considered, but has been judged to be not necessary for glulam applications, a value of 1.0 is
noted in the table. For example the Beam Stability factor CL is 1.0 when the compression side of a bending
member is supported throughout its length, and the ends at points of bearing have lateral support to prevent
rotation.
Temperature effects (CT) are reversible for normal day/night cycles even in climates where daytime
temperatures may be extreme. The US Forest Service Handbook No. 72 indicates that potential temporary
strength reductions due to temperatures above 120oF will be offset by low member moisture content common
to arid climates. The depth of heat penetration in given members must also be recognized when considering the
possible effect of temporary (daily) exposure to high temperatures on beam properties. The Railroad Use Factor
as defined for use in Chapter 7 is a duration of load adjustment not applicable to the glulam shear stress values
listed in Tables 7-2-7 and 7-2-8 since a compensating adjustment to account for cyclic loading has already been
applied by glulam industry standard recommendations. A factor of 0.72 has been applied to the listed values to
account for possible cyclic loading effects. The base value for glulam shear (prior to adjustment) is derived from
full-scale beam test results using static loading. Base shear values used in Tables 7-2-7 and 7-2-8, prior to
application of the wet use factor, are 265 psi for Douglas fir and 300 psi for southern pine. This base value is
higher than values originally derived from small sample blocks shear tests and ASTM D245 adjustment factors.
Design shear stresses may also require adjustment to account for seasoning checks when they are expected to
exceed 15% of the member width in high shear zones --center half of the depth, in the end fourths of the
member length, and mid depth over intermediate supports. Technical Notes on the evaluation of checking in
glued laminated timbers are available from industry trade associations.
The KcE factor to be used in the column stability equation (shown as 0.418 for glulam), is related to stiffness
COV (Coefficient of Variation), and varies between products. The COV for glulam Modulus of Elasticity is
assumed to be 10% for members with 6 or more laminations.
1
3
6.2.4.2 Design Equations (2006)
In addition to basic structural design principles, the use of specialized design procedures and assumptions to
account for loading conditions unique to railroad bridge structures, as presented in Section 2.5, may be applied
for glulam design in conjunction with stresses listed in Tables 7-2-7 and 7-2-8.
4
Tables 7-2-7 and 7-2-8: To simplify use of these tables, basic adjustment factors that are to be applied generally
for railroad bridge applications have been applied to the respective values listed in the tables. An explanation
of the methodology used to derive the table values is provided below.
6.2.5 NOTES ON THE USE OF STRESS-GRADED LUMBER
6.2.5.1 Working Unit Stresses (1988)
Introduction
To make the most effective and efficient use of any material the designer should be familiar with the
characteristics of that material. In the following, the important characteristics which affect the strength of
lumber are discussed briefly. Other characteristics, such as durability, resistance to splitting, resistance to wear,
hardness, holding power of nails, finishing characteristics, etc., are not discussed, although they may be
important and must not be overlooked.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-6-7
Timber Structures
Basic Stress
The term “basic stress” is used to denote the allowable working stress for lumber which is unchecked, straight
grained, and clear, and which will be subject to maximum load for a long time and will be saturated all of the
time. The basic stress is not a working stress for any commercial grade. It must be modified for the grade of the
lumber and for actual loading and moisture conditions to obtain working unit stresses. For basic stresses and
for the quantitative effect of lumber characteristics on strength, see the Wood Handbook. The stresses given in
Table 7-2-9 take into account the characteristics permitted in the grading rules.
Knots and Holes
The distortion of the grain around a knot causes stresses across the grain which limit the allowable stress in
tension and compression parallel to grain for fully intergrown knots the same as for loose knots and knot holes.
The effect of knots and knot holes on compression perpendicular to the grain and on shear stress may
ordinarily be disregarded. Holes from other causes, such as bored holes, have approximately the same effect as
knots. If there are many holes or large holes or grooves made in the lumber during fabrication and erection,
their effect on stress should not be disregarded.
Slope of Grain
Lumber is much stronger in both tension and compression along the grain than in any other direction, and
since in a straight beam or post there will be a component of stress across the grain whenever the grain is not
parallel to the axis of the beam or post, it is necessary to limit slope of grain. Ordinarily, grading rules limit the
slope of grain throughout the length of posts, but only in the middle half of beams and joists, on the assumption
that the slope of grain near the ends will not be much greater than the slope in the central part. If a beam or
joist is to be used for continuous spans or a tension member, the slope of grain should be further limited (see
Note 8, Table 7-2-9). Since the allowable slope of grain for posts is somewhat greater than for beams and joists,
it is not considered necessary to limit specifically the slope of grain near the ends of beams or joists which are to
be used as posts.
Pitch and Gum Pockets, Seams and Streaks
The effect of pitch or gum on the strength of wood may be disregarded, although it is sometimes associated with
pockets or seams where the absence of wood may affect the strength.
Wane
Wane is permitted in most structural grades. Its effect on the strength of the piece in bending or compression
parallel to grain is not great. Wane at a point of bearing perpendicular to grain has a proportional effect on
bearing stress and, in addition, may cause eccentricity of load or support. Where bearing stresses are high or
eccentricity is objectionable, the structure can be designed so that the wane will be removed in framing or the
lumber can be ordered “to be free of wane.”
Density
Density has a large effect on the strength of lumber. For a few species a visual inspection method has been
developed which will separate the lumber into two density classifications, but there is considerable overlap of
actual densities in the two classifications. If a more accurate method of density segregation, economically
applicable to commercial production, could be devised, a large increase in allowable stress could be made for
most lumber.
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AREMA Manual for Railway Engineering
Commentary
Warp, Cup, Bow
Warp, cup and bow may cause eccentricity of loading and torsional stresses and difficulties in framing. For
ordinary construction the stresses produced can be disregarded if the member is straight enough for easy
framing.
Checks, Splits, Shakes
Some grading rules limit checks, splits and shakes throughout the length of structural lumber because of their
effect on hazard of decay, appearance, etc., and these considerations are the primary ones in post grades. In
beams and joists the checks, splits and shakes within the middle half of the height of the piece within a distance
from each end equal to three times the height of the piece are limited because of their effect on shear stresses.
Outside of these limits checks, splits or shakes large enough to cause a shear failure are unlikely.
Mismanufacture
Mismanufacture affects framing primarily. If the strength of the pieces is based on the smallest size permitted,
mismanufacture may be disregarded.
Moisture Content
a.
The strength of lumber in tension, compression and shear is a function of the moisture content at the
time and is practically independent of its previous condition. However, changes in moisture content
produce checks, and enlarge checks and splits already present. The amount of checking will increase
with an increase in the size of the piece and will vary with the method of seasoning and exposure to
weather. In Table 7-2-9, assume the lumber has not become more severely checked, because of improper
seasoning or severe exposure to weather, than contemplated by the grading rules.
b. Under most conditions lumber which has been installed when green or saturated will dry out in service,
and prolonged exposure to moisture will be required to raise the moisture content very much. Lumber of
joist and plank sizes and larger which is not submerged or framed to retain moisture will not acquire
much moisture content in exposure to usual weather most places in the United States. Some contact
surfaces, such as the bearing between stringers and caps of railway trestles, are conducive to the
retention of moisture, and at such surfaces it is recommended that the stresses be limited to those
applicable to green or saturated lumber.
c.
1
3
Good timber preservatives do not affect the strength-moisture content relations.
Decay
4
Decay weakens wood. The decrease in strength may be very marked when the decay is barely perceptible, and
since decay may spread rapidly, infected structural members should be inspected frequently until replaced. It is
common practice to reduce the allowable stresses for untreated lumber subject to decay hazard to offset loss of
strength due to undetected decay. Such reductions should not be relied on to compensate for loss of strength
due to known decay. Good preservatives can protect wood against decay for many years, and if applied by
modern treating processes, properly conducted, the damage to the wood by the treating process may be
disregarded.
Duration of Load
The allowable load varies with the length of time the load is applied. Figure 7-6-1 shows graphically the
approximate relation of allowable stress to time. If the load is removed before failure is reached, there will be
some recovery, but so little is known about the amount of recovery that it should be disregarded, and the
duration of load should be figured as the sum of all the lengths of time that the load is applied. If lumber is
subjected to several different loads with different durations, each combination should be investigated, and if
each alone is safe the lumber may be considered safe.
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AREMA Manual for Railway Engineering
7-6-9
Timber Structures
Temperature, Heat
The stresses recommended in Table 7-2-9, and the provisions in these notes on the use of stress-graded lumber
assume the lumber is to be used under ordinary conditions of temperature. If abnormal temperatures are
anticipated, the designer should refer to the U.S. Forest Laboratory Report No. R 471, Effect of Heat on the
Properties and Serviceability of Wood.
6.2.5.6 Allowable Unit Stresses for Stress-Graded Lumber (2010)
6.2.5.6.1 Working Stresses
Table 7-6-1, Note 4: Inland Douglas Fir and Douglas Fir-Larch are deemed to be refractory and hence very
difficult to treat. Douglas Fir South is not produced in sufficient quantities and is somewhat weaker; its
suitability for Timber Railroad Bridges is questionable.
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7-6-10
AREMA Manual for Railway Engineering
Commentary
1
3
4
Figure 7-6-1. Chart Showing Relation of Design Stress to Duration of Load
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-6-11
Timber Structures
Table 7-6-1. Derivation of listed values, using combination 16F-1.5E DF as an example
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AREMA Manual for Railway Engineering
Commentary
SECTION 6.3 RATING COMMENTARY
6.3.1.3 Factor of Safety, Variability (1988)
There are many factors affecting the strength of lumber for which no satisfactory, commercially applicable
methods of evaluating the effects have been found. These factors produce a variability among pieces which
otherwise seem to be alike. Since the allowable stresses of Table 7-2-9 are based on the strength of the weakest
pieces that may occur in the grade and assume that each piece must carry its load, it follows that if a load is
carried by several members, not independent of each other, the designer could reasonably allow somewhat
higher stresses. Conversely, if the failure of a single member would cause unusually great damage, the
allowable stress on that member should be reduced. An overload of 50 percent will cause failure in only rare
cases, but if the load is doubled, failures will be frequent.
SECTION 6.4 CONSTRUCTION AND MAINTENANCE COMMENTARY
SECTION 6.5 INSPECTION COMMENTARY
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7
Chapter 7 Glossary1
1. LUMBER INDUSTRY ABBREVIATIONS2
a.
The same as American Softwood Lumber Standard as developed by the National Bureau of Standards.
b. These standard lumber abbreviations are commonly used for softwood lumber although all of them are
not necessarily applicable to all species when used in the construction of contracts and other documents
arising in transactions of purchase and sale of American Softwood Standard Lumber, these abbreviations
shall be construed as provided therein.
c.
There are additional abbreviations applicable to a particular region or species which may be included in
approved grading rules.
d. Abbreviations are commonly used in the forms indicated, but variations, such as the use of periods and
other forms of punctuation, are optional.
2. NOMENCLATURE OF COMMERCIAL DOMESTIC HARDWOODS AND SOFTWOODS3
1
The standard commercial names for lumber cut from species or species groups of domestic hardwoods and
softwoods are the same as those listed in the current standard grading rules for the species.
3. TERMS
3
The following terms are used in Chapter 7, Timber Structures, and are placed here in alphabetical order for
your convenience.
Air Dried
Seasoned by exposure to the atmosphere, in the open or under cover, without artificial heat.
All-heart
Of heartwood throughout; that is, free of sapwood.
American Standard Lumber
See American Softwood Lumber Standards.
Annual Ring
Growth layer put on in a single growth year.
1
References, Vol. 42, 1941, pp. 253, 868; Vol. 54, 1953, pp. 960, 1330; Vol. 61, 1960, pp. 587, 1095; Vol. 89, 1988, p. 106.
References, Vol. 28, 1927, pp. 333, 1425; Vol. 42, 1941, pp. 261, 868; Vol. 54, 1953, pp. 961, 1330; Vol. 61, 1960, pp. 587, 1095; Vol. 89,
1988, p. 106.
3 References, Vol. 22, 1921, pp. 494, 1062; Vol. 27, 1926, pp. 833, 1406; Vol. 28, 1927, pp. 323, 1425; Vol. 30, 1929, pp. 1147, 1456; Vol. 34,
1933, pp. 66, 760; Vol. 37, 1936, pp. 671, 1037; Vol. 42, 1941, pp. 253, 868; Vol. 54, 1953, pp. 960, 1330; Vol. 61, 1960, pp. 587, 1095; Vol.
89, 1988, p. 106.
2
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-G-1
Timber Structures
Bark Pocket
Patch of bark partially or wholly enclosed in the wood; classified as are pitch pockets.
Board
See American Softwood Lumber Standards.
Bow
See Warp.
Boxed Pith
When the pith is between the four faces on an end of a piece.
Bright (sapwood)
Unstained.
Characteristics
Distinguishing features which by their extent and number determine the quality of a piece of lumber.
Check
Lengthwise grain separation, usually occurring through the growth rings as a result of seasoning.
• Surface Check.
• Small Surface Check. Perceptible opening not over 4 inches long and 1/32 inch wide.
• Medium Surface Check. Not over 1/32 inch wide and over 4 inches, but not over 10 inches long.
• Large Surface Check. Over 1/32 inch wide or over 10 inches long.
• End Check. Occurs on an end of a piece.
• Through Check. Extends from one surface through the piece to the opposite surface or to an adjoining
surface.
Chipped Grain
Area where the surface is chipped or broken out in very short particles below the line of cut. Not classed as
torn grain and, as usually found, is not considered unless in excess of 25 percent of the surface involved.
Clear
Free, or practically free, of all blemishes, characteristics or defects.
Compression Wood
Abnormal wood that forms on the underside of leaning and coniferous tress. It is characterized aside from its
distinguishing color by being hard and brittle and by its relatively lifeless appearance.
Corner
The intersection of two adjacent faces.
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AREMA Manual for Railway Engineering
Glossary
Crook
See Warp.
Cross Break
Separation of the wood across the width, such as may be due to tension resulting from unequal shrinkage or
mechanical stress.
Cup
See Warp.
Cutting
Resulting pieces after crosscutting and/or ripping.
Decay
Disintegration of wood substance due to action of wood-destroying fungi. Also known as dote and rot.
• Advanced or Typical Decay. Older stage of decay in which disintegration is readily recognized because the
wood has become punky, soft, and spongy, stringy, shaky, pitted, or crumbly. Decided discoloration or
bleaching of the rotted wood is often apparent.
• Incipient Decay. Early stage of decay in which disintegration has not proceeded far enough to soften or
otherwise change the hardness of the wood perceptibly. Usually accompanied by a slight discoloration or
bleaching of the wood.
1
• Pocket Rot. Typical decay which appears in the form of a hole, pocket, or area of soft rot, usually
surrounded by apparently sound wood.
• Water Soak or Stain. Water-soaked area in heartwood, usually interpreted as the incipient stage of certain
wood rots.
3
De-grades
Pieces which on reinspection prove of lower quality than the grade in which they were shipped.
Discoloration
4
See Stain.
Double End Trimmed
Trimmed reasonably square by saw on both ends.
Dry
Seasoned, not green (for the purpose of this standard, dry lumber is defined as lumber which has been
seasoned to a maximum moisture content of 19 percent or less).
Edge
The narrow face of rectangular shaped lumber.
Edge Grain (Vertical Grain)
Annual rings (so-called grain) which form an angle of 45 degrees or more with the surface of the piece.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-G-3
Timber Structures
Firm Red Heart
A stage of incipient decay characterized by a reddish color in the heartwood, which does not unfit the wood
for the majority of yard purposes, not to be confused with the natural red heart of some species.
Flat Grain (Splash Grain)
Annual rings (so-called grain) which form an angle of less than 45 degrees with the surface of the piece.
Free of Heart Centers (FOHC)
Free of heart centers (f.o.h.c.). when the pitch is not enclosed within the four sides of the piece.
Green
Not fully seasoned (for the purpose of this standard, green lumber is defined as lumber having a moisture
content in excess of 19 percent).
Gum Pocket
Openings between growth rings which usually contains or has contained resin or bark or both.
Gum Seam
Check or shake filled with gum.
Gum Spot
Accumulation of gumlike substance occurring as a small patch. May occur in conjunction with a bird-peck or
other injury to the growing wood.
Gum Streak
Well-defined accumulation of gum in more or less regular streak. Classified as are pitch streaks.
Heart Face
Face side free of sapwood.
Heart Shake
See Shake-pitch Shake.
Heartwood
Inner core of the tree trunk comprising the annual rings containing nonliving elements; usually darker in
color than sapwood.
Hit and Miss
Series of surfaced areas with skips not over 1/16 inch deep between them.
Hit or Miss
To skip or surface a piece for a part or the whole of its length, provided it is nowhere more tha 1/16 inch
scant.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-G-4
AREMA Manual for Railway Engineering
Glossary
Holes
Holes may extend partially or entirely through a piece and be from any cause. To determine the size of a
hole, average the maximum and minimum diameters, unless otherwise specified.
• Pin Hole. Not over 1/16 inch in diameter.
• Medium Hole. Ove 1/16 inch but not over 1/4 inch in diameter.
• Large Hole. Over 1/4 inch in diameter.
Honeycomb
Honeycomb is indicated by large pits in the wood.
Kiln Dried
Seasoned in a chamber by means of artificial heat.
Knot
Branch or limb, embedded in the tree and cut through in the process of lumber manufacture; classified
according to size, quality, and occurrence. To determine the size of a knot, average the maximum length and
maximum width, unless otherwise specified.
Knot Quality
1
• Decayed Knot. Softer than the surrounding wood, and containing advanced decay.
• Encased Knot. Its rings of annual growth are not intergrown with those of the surrounding wood.
• Hollow Knot. Apparently sound, except that it contains a hole over 1/4 inch in diameter.
• Intergrown Knot. Its rings of annual growth are completely intergrown with those of the surrounding
wood.
3
• Loose Knot. Not held tightly in place by growth or position, and cannot be relied upon to remain in place.
• Fixed Knot. Will hold its place in a dry piece under ordinary conditions; can be moved under pressure,
though not easily pushed out.
• Pith Knot. Sound knot except that it contains pith hole not over 1/4 inch in diameter.
• Sound Knot. Solid across its face, as hard as the surrounding wood, shows no indication of decay and may
vary in color from the natural color of the wood to reddish brown or black.
• Star-checked Knot. Having radial checks.
• Tight Knot. So fixed by growth or position as to retain its place.
• Firm Knot. Solid across its face, but containing incipient decay.
• Water-tight Knot. Its rings of annual growth are completely intergrown with those of the surrounding
wood on one surface of the piece, and it is sound on that surface.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-G-5
4
Timber Structures
Knot Occurrence
• Branch Knots. Two or more divergent knots sawed lengthwise and tapering toward the pith at a common
point.
• Corner Knot. Located at the intersection of adjacent faces.
• Knot Cluster. Two or more knots grouped together, the fibers of the wood being deflected around the
entire unit. A group of single knots is not a knot cluster.
• Single Knot. Occurs by itself, the fibers of the wood being deflected around it.
• Spike Knot. A knot sawed in a lengthwise direction.
Loosened Grain
Small portion of the wood loosened but not displaced.
Machine Burn
Darkening or charring due to overheating by machine knives.
Machine Gouge
Groove due to the machine cutting below the desired line cut.
Mismanufacture
Includes all defects or blemished produced in manufacturing. See Chipped Grain, Hit and Miss, Hit or Miss,
Loosened Grain, Machine Burn, Machine Gouge, Mismatched Lumber, Raised Grain, Skip, Torn Grain, and
Variation in Sawing.
Mismatched Lumber
Worked lumber that does not fit tightly at all points of contact between adjoining pieces, or in which the
surfaces of adjoining pieces are not in the same plane.
• Slight Mismatch. Surface variation not over 1/64 inch.
• Medium Mismatch. Surface variation over 1/64 inch, but not over 1/32 inch.
• Heavy Mismatch. Surface variation over 1/32 inch.
Mixed Grain
Any combination of edge grain and flat grain.
Moisture Content
Weight of the water in wood expressed in percentage of the weight of oven-dry wood.
Peck
Channeled or pitted areas or pockets as sometimes found in cedar and cypress.
Pecky
Characterized by Peck.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-G-6
AREMA Manual for Railway Engineering
Glossary
Pitch
Accumulation of resin in the wood cells in a more or less irregular patch.
• Light Pitch. Lightly evident presence of pitch.
• Medium Pitch. Trace of pitch slightly more evident than light pitch.
• Heavy Pitch. Very evident presence of pitch showing by its color and consistency.
• Massed Pitch. Clearly defined accumulation of solid pitch in a body by itself.
Pitch Pocket
Well-defined opening between growth rings which usually contain or has contained resin or bark or both.
Bark also may be present in the pocket.
• Very Small Pitch Pocket. Not over 1/8 inch in width and not over 2 inches in length.
• Small Pitch Pocket. Not over 1/8 inch in width and not over 4 inches in length; or not over 1/4 inch in
width and not over 2 inches in length.
• Medium Pitch Pocket. Not over 1/8 inch in width and not over 8 inches in length; or not over 3/8 inch, in
width and not over 4 inches in length.
1
• Large Pitch Pocket. Width or length exceeds the maximum permissible for a medium pitch pocket.
• Closed Pitch Pocket. Does not show an opening on both sides of the piece.
• Open (through) Pitch Pocket. Is cut across on both sides of the piece.
Pitch Seam
3
Shake or check filled with pitch.
Pitch Streak
Well-defined accumulation of pitch in a more or less regular streak.
• Small Pitch Streak. Not over one-twelfth the width by one-sixth the length of the surface on which it
occurs.
• Medium Pitch Streak. Over one-twelfth, but not over one-sixth the width by over one-sixth but not over
one-third the length of the surface on which it occurs.
• Large Pitch Streak. Over one-sixth the width by one-third the length of the surface on which it occurs.
Pith
Small soft core in the structural center of a log.
• Boxed Pith. When the pith is within the four faces on an end of a piece.
Pith Fleck
Narrow streak resembling pith on the surface of a piece, usually brownish, up to several inches in length,
resulting from burrowing of larvae in the growing tissue of the tree.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-G-7
4
Timber Structures
Quarter Sawed
See, Edge Grain.
Radial
Coincident with a radius from the axis (pith) of the tree to the circumference.
Raised Grain
Roughened condition of the surface of dressed lumber in which the hard summerwood is raised above the
softer springwood, but not torn loose from it.
Sapwood
Outer layers of growth in a tree, exclusive of bark, which contain living elements; usually lighter in color
than heartwood.
• Bright Sapwood. Unstained.
Saw Butted
Trimmed by a saw on both ends.
Seasoning
Evaporation or extraction of moisture from green or partially dried wood.
Shake
A lengthwise separation between or through the growth rings and may be further classified as ring shake or
pith shake.
• Fine Shake. A barely perceptible opening.
• Slight Shake. More than a perceptible opening, but not over 1/32 inch wide.
• Medium Shake. Over 1/32, but not over 1/8 inch wide.
• Open Shake. Over 1/8 inch wide.
• Cup Shake. Does not completely encircle the pith.
• Round Shake. Completely encircles the pith.
• Shell Shake. When both ends of a shake which has been cut across occur on the face or edge of a piece.
• Through Shake. Extending from one surface through the piece to the opposite surface or to an adjoining
surface.
• Pith Shake (Heart Check). Extends across the rings of annual growth in one or more directions from the
pith toward, but not to the surface of a piece. Distinguished from season check by having its greatest width
nearest the pith, whereas the greatest width of a season check is ordinarily at the surface of a piece, and
when a piece has boxed pith the greatest width of a season check is farthest from the pith.
Side Cut
When the pith is not enclosed within the four sides of the piece.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-G-8
AREMA Manual for Railway Engineering
Glossary
Skip
Area on a piece that failed to surface, classified as follows:
• Slight Skip. Area not over six times the width of the piece that the planer knife failed to surface smoothly.
• Shallow Skip (Small). Area not over six times the width of the piece that the planer knife failed to touch by
not over 1/32 inch.
• Deep (Heavy) Skip. Area not over twelve times the width of the piece that the planer knife failed to touch
by not over 1/16 inch.
Smoke Dried
Seasoned in the open, exposed to the heat and smoke of a fire maintained beneath and within stacks of
lumber.
Softwood
One of the group of trees which have needle-like or scale-like leaves. The term has no reference to the
softness of the wood.
Sound
Free of decay.
1
Spiral Grain
Fibers which extend spirally about, instead of vertically along, the hole of a tree.
Split
Lengthwise separation of the wood extending from one surface through the piece to the opposite surface or
to an adjoining surface.
3
• Short Split. Length does not exceed either the width of a piece or one-sixth its length.
• Medium Split. Length exceeds the width of a piece, but does not exceed one-sixth its length.
• Long Split. Length exceeds one-sixth the length of a piece.
4
Springwood
More or less open and porous tissue marking the inner part of each annual ring, formed early in the period of
growth.
Stain
Discoloration on or in lumber, of any color other than its natural color of the piece on which it appears;
classified as follows:
• Light Stain. Slight difference in color which will not materially impair the appearance of the piece if given
a natural finish.
• Medium Stain. Pronounced difference in color which, although it does not obscure the grain of the wood, is
customarily objectionable in a natural but not a painted finish.
• Heavy Stain. Difference in color so pronounced as practically to obscure the grain of the wood.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-G-9
Timber Structures
Summerwood
Denser fibrous outer portion of each annual ring, usually without conspicuous pores, formed late in the
growing period, not necessarily in summer.
Torn Grain
Part of the wood torn out in dressing; classified as follows;
• Slight Torn Grain. Not over 1/32 inch in depth.
• Medium Torn Grain. Over 1/32 inch, but not over 1/16 inch deep.
• Heavy Torn Grain. Over 1/16 inch, but not over 1/8 inch deep.
• Deep Torn Grain. Over 1/8 inch deep.
Unsound
Decayed.
Variation in Sawing
A deviation from the line of cut. Slight variation is not over 1/16 inch in 1 inch lumber, 1/8 inch in 2 inches,
3/16 inch in 3 to 7 inches, and 1/4 inch in 8 inches and larger.
Wane
This is bark or the lack of wood from any cause, on the corner of a piece.
• Slight Wane. Not over 1/4 inch wide on the surface on which it appears, for one-sixth the length and onefourth the thickness of the piece.
• Medium Wane. Over 1/4 inch, but not over 1/2 inch wide on the surface on which it appears, for one-sixth
the length and one-fourth the thickness of the piece.
• Large Wane. Over 1/2 inch wide on the surface on which it appears, or over one-sixth the length and onefourth the thickness of the piece, or both.
Warp
Any variation from a true or plane surface; includes bow, crook, cup, or any combination thereof.
• Bow. Deviation flatwise from a straight line from end to end of a piece; measured at the point of greatest
distance from the straight line.
• Crook. Deviation edgewise from a straight line from end to end of a piece; measured at the point of
greatest distance from the straight line, and classified as slight, small, medium, and large. Based on a piece
4 inches wide and 16 feet long, the distance from each degree of crook shall be: slight crook, 1 inch; small
crook, 1-1/2 inches; medium crook, 3 inches; and large crook, over 3 inches. For wider pieces it shall be 1/8
inch less for each additional 2 inches of width. Shorter or longer pieces may have the same curvature.
• Cup. Curve in a piece across the grain or width of a piece; measured at the point of greatest deviation from
a straight line from edge to edge and classified as slight, medium, and deep. Based on a piece 12 inches
wide, the distance for each degree of cup shall be; slight cup, 1/4 inch, medium cup, 3/8 inch, and deep cup,
1/2 inch Narrower or wider pieces may have the same curvature.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-G-10
AREMA Manual for Railway Engineering
7
References
The following list of references used in Chapter 7, Timber Structures is placed here in alphabetical order for
your convenience.
1. American Institute of Timber Construction. Standard Specifications for Hardwood Glued Laminated
Timber. AITC 119-76.
2. American Institute of Timber Construction. Standard Specifications for Structural Glued Laminated
Timber of Douglas Fir, Western Larch, Southern Pine, and California Redwood, AITC 117-76.
3. American Institute of Timber Construction. Standard Specifications for Structural Glued Laminated
Timber Using Visually Graded Lumber of Douglas-Fir, Southern Pine, Hem-Fir, and Lodgepole Pine. AITC
120-76.
4. American Institute of Timber Construction. Timber Construction Standards AITC 100-72.
5. American Society for Testing and Materials. Standard Method for Establishing Stresses for Structural
Glued Laminated Timber (Glulam) Manufactured From Visually Graded Lumber. ASTM D3737-78.
1
6. American Wood-Preservers Association. Standards C20 and C28.
7. AWPA. 2007. Book of Standards. Birmingham, AL: American Wood Preservers Association.
3
8. Current National Design Specification for Stress-Grade Lumber and Its Fastenings, National Forest
Products Association.
9. Fry, G., “Rail-Stringer Interaction.” Presentation to AREMA Committee No. 7, 12 August 2008.
10. Madsen, Borg, “Structural Behaviour of Timber” Timber Engineering Ltd., 1992.
11. Timber Construction Manual, by American Institute of Timber Construction, John Wiley and Sons, Inc.,
1973.
12. U.S. Department of Agriculture Technical Bulletin 1069, Fabrication and Design of Glued Laminated Wood
Structural Members, by A.D. Freas and M.L. Selbo, Forest Products Laboratory. Available from American
Institute of Timber Construction.
13. U.S. Department of Commerce, Voluntary Product Standard PS 56-73, Structural Glued Laminated Timber
(available from Superintendent of Documents, U.S. Government Printing Office).
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-R-1
THIS PAGE INTENTIONALLY LEFT BLANK.
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30
Appendix 1 - Contemporary Designs and Design Aids
— 2011 —
TABLE OF CONTENTS
Section/Article
Description
Page
A1.1 Introduction . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-2
A1.2 Stringers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-3
A1.3 Pile Design Aids . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-4
A1.4 Hankinson Formula . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-6
1
A1.5 Comparison of Unit Stresses in Timbers in Open and Ballasted-Deck Trestles (2009) 7-A1-6
A1.5.1 For Open-Deck Trestles, E-80 Loading (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-6
A1.5.2 For Ballasted-Deck Trestles, E-80 Loading (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-10
A1.6 Stress Laminated Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-19
A1.6.1 Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing
Required for Various Span Lengths and Panel Thicknesses . . . . . . . . . . . . . . . . . . . . . .
7-A1-19
A1.6.2 Calculation of Deck Loads for Stress Laminated Decks . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-28
A1.6.3 Allowable Unit Stresses for Stress Graded Lumber - Railroad Loading (Visual Grading) 7-A1-28
A1.6.4 Typical Design Example for a Simple Stress Laminated Lumber Deck Panel . . . . . . . . . 7-A1-29
A1.6.5 Tables for Simple Stress Laminated Lumber Deck Panel Design . . . . . . . . . . . . . . . . . . . 7-A1-31
LIST OF FIGURES
Figure
Description
Page
7-A1-1
7-A1-2
7-A1-3
7-A1-4
Distribution of Load to Stringers of Timber Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Distribution of Load to Piles of Timber Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Graphical Solution of Hankinson Formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Typical Design Example for a Simple Stress Laminated Lumber Deck Panel. . . . . . . . . . . .
7-A1-3
7-A1-4
7-A1-6
7-A1-30
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-1
3
Timber Structures
LIST OF TABLES
Table
Description
Page
7-A1-1 Comparison of Unit Stresses in Open Deck Trestles, Cooper E 80 Loading, No Impact . . . . .
7-A1-7
7-A1-2 Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact . .
7-A1-11
7-A1-3 Comparison of Unit Stresses in Open Deck Trestles, E - 80 Cooper Loadings, No Impact . . .
7-A1-17
7-A1-4 Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required
for Various Span Lengths & Panel Thicknesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-20
7-A1-5 Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing
Required for Various Span Lengths & Panel Thicknesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-22
7-A1-6 Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing
Required for Various Span Lengths & Panel Thicknesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-24
7-A1-7 Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required
for Various Span Lengths & Panel Thicknesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-26
7-A1-8 Tabulation of Deck Loads for Stress Laminated Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A1-28
7-A1-9 Allowable Unit Stresses for Stress Graded Lumber - Railroad Loading (Visual Grading) . . . .
7-A1-29
7-A1-10Tables for Simple Stress Laminated Lumber Deck Panel Design . . . . . . . . . . . . . . . . . . . . . . .
7-A1-32
A1.1 INTRODUCTION
This Appendix contains information useful in the design of Recommended Contemporary Structures.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-2
AREMA Manual for Railway Engineering
Appendix 1 - Contemporary Designs and Design Aids
A1.2
STRINGERS
1
3
4
Figure 7-A1-1. Distribution of Load to Stringers of Timber Trestles
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A1-3
Timber Structures
A1.3 PILE DESIGN AIDS
Figure 7-A1-2. Distribution of Load to Piles of Timber Trestles
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-4
AREMA Manual for Railway Engineering
Appendix 1 - Contemporary Designs and Design Aids
1
3
4
Figure 7-A1-2. Distribution of Load to Piles of Timber Trestles (Continued)
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A1-5
Timber Structures
A1.4 HANKINSON FORMULA
Figure 7-A1-3. Graphical Solution of Hankinson Formula
A1.5 COMPARISON OF UNIT STRESSES IN TIMBERS IN OPEN AND BALLASTED-DECK
TRESTLES (2009)
A1.5.1 FOR OPEN-DECK TRESTLES, E-80 LOADING (2010)
For Open-Deck Trestles, E-80 Loading refer to Table 7-A1-1.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-6
AREMA Manual for Railway Engineering
Appendix 1 - Contemporary Designs and Design Aids
Table 7-A1-1. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 80 Loading, No Impact
12’, 13’ and 14’ Spans
All loads in pounds per track. All moments in foot-pounds per track.
Panel length C to C of bents
12’
13’
13’
14’
14’
Number and size of stringers
8-10” x 16”
8-9” x 18”
8-10” x 18”
8-10” x 18”
6-10” x 20”
Above stringers
500
500
500
500
500
Stringers-nominal size
535
540
600
600
500
Total dead load
1035
1040
1100
1100
1000
Dead load per foot of track
Reaction on bent in pounds
Dead load
12420
13520
14300
15400
14000
Live load
186740
197030
197030
208690
208690
Total
199160
210550
Pile
Pile
6
6
14D
12x14
Frame
Pile
6
6
14D
12x14
6
6
14D
12x14
222690
Number of piles or posts
Size of piles or posts
Total area of piles or posts-sq. in.
924
1008
924
1008
924
1008
924
1008
924
1008
Unit bearing stress on piles and posts-psi 216
198
228
209
229
210
243
222
241
221
16.6
Frame
224090
Pile
Average load in tons per pile or post
Frame
211330
Kind of bent
Frame
Pile
Frame
6
6
6
6
14D
12x14
14D
12x14
17.5
17.6
18.7
18.6
1
Bearing-Stringers on caps for continuous butt type deck.
Area sq.in.-14” cap
1120
1008
1120
1120
840
Bearing stress-psi- 14” cap
178
209
189
200
265
Area sq.in.-16” cap
1280
1152
1280
1280
960
Bearing stress-psi- 16” cap
156
183
165
175
232
16608
19764
20904
24432
22211
Bending in stringers
Dead load moment-foot pounds per track
Live load moment-foot pounds per track
280000
327000
327000
387000
387000
Total load moment-foot pounds per track
297000
347000
348000
412000
410000
Section modulus-nominal size
3413
3888
4320
4320
4000
Bending stress-psi-nominal size
1044
1071
967
1144
1230
Section modulus-dressed size
3225
3676
4096
4096
3803
Bending stress-psi-dressed size
1105
1133
1020
1207
1294
18
20
Longitudinal shear-Standard formula- First driver at height of the beam from the support.
Depth nominal
16
18
18
c to c
12
13
13
14
14
L = (c to c) + 0.5 - 14/12
11.33
12.33
12.33
13.33
13.33
L’ ignore within d of face
8.17
8.83
8.83
9.83
9.50
a
10
10.83
10.83
11.83
11.67
b
5
5.83
5.83
c, if > d
W
Dead load = WL/2
6.83
6.67
1.83
1.67
10.5
1040
1100
1100
1000
4226
4593
4858
5408
4750
Live Load
102353
104865
104865
109000
107000
Total load
106579
109458
108723
114408
111750
Cross section-sq. in.-nominal size
1280
1296
1440
1440
1200
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A1-7
3
4
Timber Structures
Table 7-A1-1. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 80 Loading, No Impact
12’, 13’ and 14’ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track.
Panel length C to C of bents
12’
13’
13’
14’
14’
Number and size of stringers
8-10” x 16”
8-9” x 18”
8-10” x 18”
8-10” x 18”
6-10” x 20”
Unit shear- psi- = 3R/2bh
125
127
114
119
140
Cross section-sq. in.-dressed size
1240
1260
1400
1400
1170
Unit shear- psi- = 3R/2bh
129
130
118
123
143
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for stringer bending and shear.
(Assume 14² Cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 80000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-8
AREMA Manual for Railway Engineering
Appendix 1 - Contemporary Designs and Design Aids
Table 7-A1-1. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 80 Loading, No Impact
15’ and 16’ Spans
All loads in pounds per track. All moments in foot-pounds per track.
Panel length C to C of bents
15’
15’
16’
16’
Number and size of stringers
8-10” x 18”
8-10” x 20”
8-10” x 20”
8-12” x 20”
Above stringers
500
500
500
500
Stringers-nominal size
600
667
667
800
Total dead load
1100
1167
1167
1300
Dead load
16500
17505
18672
20800
Live load
218740
218740
227430
227430
Total
235240
236245
246102
248230
Dead load per foot of track
Reaction on bent in pounds
Kind of bent
Pile
Frame
Pile
Frame
Pile
Frame
Pile
Frame
Number of piles or posts
6
6
6
6
6
6
6
6
Size of piles or posts
14D
12x14
14D
12x14
14D
12x14
14D
12x14
Total area of piles or posts-sq. in.
924
1008
924
1008
924
1008
924
1008
Unit bearing stress on piles and postspsi
255
233
256
234
266
244
269
246
Average load in tons per pile or post
19.6
19.7
20.5
20.7
Area sq.in.-14”cap
1120
1120
1120
1344
Bearing stress-psi- 14” cap
210
211
220
185
Area sq.in.-16” cap
1280
1280
1280
1536
Bearing stress-psi- 16” cap
184
185
192
162
Dead load moment-foot pounds per track
28235
29955
34282
38189
Live load moment-foot pounds per track
447000
447000
506000
506000
Total load moment-foot pounds per track
476000
477000
541000
545000
Section modulus-nominal size
4320
5333
5333
6400
Bending stress-psi-nominal size
1322
1073
1217
1022
Section modulus-dressed size
4096
5071
5071
6111
Bending stress-psi-dressed size
1395
1129
1280
1070
1
Bearing-Stringers on caps for continuous butt type deck.
3
Bending in stringers
Longitudinal shear-Standard formula- First driver at height of the beam from the support.
Depth nominal
18
20
20
20
c to c
15
15
16
16
L = (c to c) + 0.5 - 14/12
14.33
14.33
15.33
15.33
L’ ignore within d of face
10.83
10.50
11.50
11.50
a
13.08
13.08
14.00
14.00
b
8.08
8.08
9.00
9.00
c, if > d
3.08
3.08
4.00
4.00
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A1-9
4
Timber Structures
Table 7-A1-1. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 80 Loading, No Impact
15’ and 16’ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track.
Panel length C to C of bents
15’
15’
16’
16’
Number and size of stringers
8-10” x 18”
8-10” x 20”
8-10” x 20”
8-12” x 20”
1100
1167
1167
1300
Dead load = WL/2
W
5958
6127
6710
7475
Live Load
126977
124313
131739
131739
Total load
132935
130313
138449
139214
Cross section-sq. in.-nominal size
1440
1600
1600
1920
Unit shear- psi- = 3R/2bh
138
122
130
109
Cross section-sq. in.-dressed size
1400
1560
1560
1872
Unit shear- psi- = 3R/2bh
142
125
133
112
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for stringer bending and shear.
(Assume 14² Cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 80000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
A1.5.2 FOR BALLASTED-DECK TRESTLES, E-80 LOADING (2010)
For Ballasted-Deck Trestles, E-80 Loading refer to Table 7-A1-2.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-10
AREMA Manual for Railway Engineering
Appendix 1 - Contemporary Designs and Design Aids
Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact
11.5’, 12’, and 12.5’ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel length C to C of bents
11.5’
12’
12’
12.5’
Number and size of stringers
10-8” x 16”
8-9” x 18”
10-9” x 16”
12-8” x 16”
Above stringers
2310
2310
2310
2310
Stringers-nominal size
530
540
600
640
Total dead load
2840
2850
2910
2950
Dead load per foot of track
Reaction on bent in pounds
Dead load
32660
34200
34920
36875
Live load
180690
186740
186740
191890
Total
213350
220940
221660
228765
Kind of bent
Pile
Frame
Pile
Number of piles or posts
Size of piles or posts
6
6
14D
12x14
Total area of piles or posts-sq. in.
924
Unit bearing stress on piles and posts-psi
231
Average load in tons per pile or post
Frame
Pile
6
6
6
6
6
6
14D
12x14
14D
12x14
14D
12x14
1008
924
1008
924
1008
924
1008
212
239
219
240
220
248
227
17.8
Frame
Pile
Frame
18.4
18.5
19.1
1
Bearing-Stringers on caps for continuous butt type deck.
Area sq.in.-14” cap
896
756
1008
1120
Bearing stress-psi- 14” cap
238
292
220
204
Area sq.in.-16” cap
1024
864
1152
1280
Bearing stress-psi- 16” cap
208
256
192
179
41000
46000
47000
52000
3
Bending in stringers
Dead load moment-foot pounds per track
Live load moment-foot pounds per track
257000
280000
280000
310000
Total load moment-foot pounds per track
299000
327000
328000
363000
Section modulus-nominal size
2731
2916
3072
3413
Bending stress-psi-nominal size
1314
1346
1281
1276
Section modulus-dressed size
2563
2756
2883
3203
Bending stress-psi-dressed size
1400
1424
1365
1360
16
16
4
Longitudinal shear-Standard formula- First driver at height of the beam from the support.
Depth nominal
16
18
c to c
11.5
12
12
12.5
L = (c to c) + 0.5 - 14/12
10.83
11.33
11.33
11.83
L’ ignore within d of face
7.67
7.83
8.17
8.67
a
9.5
9.83
10.00
10.50
b
4.5
4.83
5.00
5.50
2840
2850
2910
2950
c, if > d
W
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A1-11
Timber Structures
Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact
11.5’, 12’, and 12.5’ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel length C to C of bents
11.5’
12’
12’
12.5’
Number and size of stringers
10-8” x 16”
8-9” x 18”
10-9” x 16”
12-8” x 16”
Dead load = WL/2
10887
11163
11883
12783
Live Load
99692
100000
102353
104789
Total load
110579
111163
114235
117572
Cross section-sq. in.-nominal size
1280
1296
1440
1536
Unit shear- psi- = 3R/2bh
130
129
119
115
Cross section-sq. in.-dressed size
1240
1260
1395
1488
Unit shear- psi- = 3R/2bh
134
132
123
119
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for stringer
bending and shear. (Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 80000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
In calculating bearing, bending, and shear stresses
outer stringers are considered as carrying no
load.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-12
AREMA Manual for Railway Engineering
Appendix 1 - Contemporary Designs and Design Aids
Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact
13’ and 14’ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel length C to C of bents
13’
13’
13’
14’
14’
Number and size of stringers
10-10” x 16”
10-9” x 18”
12-9” x 16”
10-10” x 18”
8-10” x 20”
Above stringers
2310
2310
2310
2310
2310
Stringers-nominal size
670
680
720
750
670
Total dead load
2980
2990
3030
3060
2980
Dead load
38740
38870
39390
42840
41720
Live load
197030
197030
197030
208690
208690
Total
235770
235900
236420
251530
250410
Dead load per foot of track
Reaction on bent in pounds
Kind of bent
Pile
Frame
Pile
Frame
Pile
Frame
Pile
Frame
Pile
Frame
Number of piles or posts
6
6
6
6
6
6
6
6
6
6
Size of piles or posts
14D
12x14
14D
12x14
14D
12x14
14D
12x14
14D
12x14
Total area of piles or posts-sq. in.
924
1008
924
1008
924
1008
924
1008
924
1008
Unit bearing stress on piles and posts-psi 255
234
255
234
256
235
272
250
271
248
Average load in tons per pile or post
19.6
19.7
19.7
21.0
20.9
1
Bearing-Stringers on caps for continuous butt type deck.
Area sq.in.-14” cap
1120
1008
1260
1120
840
Bearing stress-psi- 14” cap
211
234
188
225
298
Area sq.in.-16” cap
1280
1152
1440
1280
960
Bearing stress-psi- 16” cap
184
205
164
197
261
Dead load moment-foot pounds per track
57000
57000
58000
68000
66000
Live load moment-foot pounds per track
340000
340000
340000
400000
400000
Total load moment-foot pounds per
track
398000
398000
399000
469000
467000
Section modulus-nominal size
3413
3888
3840
4320
4000
Bending stress-psi-nominal size
1399
1228
1247
1303
1401
Section modulus-dressed size
3203
3675
3604
4083
3803
Bending stress-psi-dressed size
1491
1300
1329
1378
1474
3
Bending in stringers
Longitudinal shear-Standard formula- First driver at height of the beam from the support.
Depth nominal
16
18
16
18
20
c to c
13
13
13
14
14
L = (c to c) + 0.5 - 14/12
12.33
12.33
12.33
13.33
13.33
L’ ignore within d of face
9.17
8.83
9.17
9.83
9.50
a
11.00
10.83
11.00
11.83
11.67
b
6.00
5.83
6.00
6.83
6.67
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A1-13
4
Timber Structures
Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact
13’ and 14’ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel length C to C of bents
13’
13’
13’
14’
14’
Number and size of stringers
10-10” x 16”
10-9” x 18”
12-9” x 16”
10-10” x 18”
8-10” x 20”
1.83
1.67
c, if > d
W
2890
2990
3030
3060
2980
Dead load = WL/2
13246
13206
13888
15045
14155
Live Load
107027
104865
107027
109000
107000
Total load
120273
118071
120915
124045
121155
Cross section-sq. in.-nominal size
1600
1620
1728
1800
1600
Unit shear- psi- = 3R/2bh
113
109
105
103
114
Cross section-sq. in.-dressed size
1550
1575
1674
1750
1560
Unit shear- psi- = 3R/2bh
116
112
108
106
116
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for stringer bending and shear.
(Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 80000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
In calculating bearing, bending, and shear stresses
outer stringers are considered as carrying no
load.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-14
AREMA Manual for Railway Engineering
Appendix 1 - Contemporary Designs and Design Aids
Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact
15’ and 16’ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel length C to C of bents
15’
15’
15’
16’
16’
Number and size of stringers
12-9” x 18”
10-10” x 18”
12-10” x 18”
10-10” x 20”
10-12” x 20”
Above stringers
2310
2310
2310
2310
2310
Stringers-nominal size
810
750
900
830
1000
Total dead load
3120
3060
3210
3140
3310
Dead load
46800
45900
48150
50240
52960
Live load
218740
218740
218740
227430
227430
Total
265540
264640
266890
277670
280390
Dead load per foot of track
Reaction on bent in pounds
Kind of bent
Pile
Frame
Pile
Frame
Pile
Frame
Pile
Frame
Pile
Frame
Number of piles or posts
6
6
6
6
6
6
6
6
6
6
Size of piles or posts
14D
12x14
14D
12x14
14D
12x14
14D
12x14
14D
12x14
Total area of piles or posts-sq. in.
924
1008
924
1008
924
1008
924
1008
924
1008
Unit bearing stress on piles and posts-psi 287
263
292
263
289
265
241
221
303
278
Average load in tons per pile or post
22.1
22.1
22.2
23.1
23.4
1
Bearing-Stringers on caps for continuous butt type deck.
Area sq.in.-14” cap
1260
1120
1400
1120
1344
Bearing stress-psi- 14” cap
211
236
191
248
209
Area sq.in.-16” cap
1440
1280
1600
1280
1536
Bearing stress-psi- 16” cap
184
207
167
217
183
Dead load moment-foot pounds per track
80000
79000
82000
92000
97000
Live load moment-foot pounds per track
460000
460000
460000
520000
520000
Total load moment-foot pounds per
track
541000
540000
543000
613000
618000
Section modulus-nominal size
4860
4320
5400
5333
6400
Bending stress-psi-nominal size
1336
1500
1207
1379
1159
Section modulus-dressed size
4594
4083
5104
5070
6084
Bending stress-psi-dressed size
1413
1587
1277
1451
1219
3
Bending in stringers
Longitudinal shear-Standard formula- First driver at height of the beam from the support.
Depth nominal
18
18
18
20
20
c to c
15
15
15
16
16
L = (c to c) + 0.5 - 14/12
14.33
14.33
14.33
15.33
15.33
L’ ignore within d of face
10.83
10.83
10.83
11.50
11.50
a
13.08
13.08
13.08
14.00
14.00
b
8.08
8.08
8.08
9.00
9.00
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A1-15
4
Timber Structures
Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact
15’ and 16’ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel length C to C of bents
15’
15’
15’
16’
16’
Number and size of stringers
12-9” x 18”
10-10” x 18”
12-10” x 18”
10-10” x 20”
10-12” x 20”
c, if > d
3.08
3.08
3.08
4.00
4.00
W
3120
3060
3210
3140
3310
Dead load = WL/2
16900
16575
17388
18055
19033
Live Load
126977
126977
126977
131739
131739
Total load
143877
143552
144364
149794
150772
Cross section-sq. in.-nominal size
1944
1800
2160
2000
2400
Unit shear- psi- = 3R/2bh
111
120
100
112
94
Cross section-sq. in.-dressed size
1890
1750
2100
1950
2340
Unit shear- psi- = 3R/2bh
114
123
103
115
97
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for stringer bending and shear.
(Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 80000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
In calculating bearing, bending, and shear stresses
outer stringers are considered as carrying no
load.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-16
AREMA Manual for Railway Engineering
Glued Laminated Sections
Assume 24F-1.8E DF or SP
Cooper Design Load
80
80
80
80
15' 0
10-6.75 x18
14' 0
10-6.75 x16.5
12' 6"
8- 6.75 × 16.5
500
506
1006
500
464
964
500
371
871
15094
218666
233760
Pile
Frame
6
6
14" D 12 x 14
924
1008
13497
208571
222068
Pile
Frame
6
6
14" D 12 x 14
924
1008
10891
192000
202891
Pile
Frame
6
6
14" D 12 x 14
924
1008
240
19
220
17
80
Panel Length C to C of Bents
12' 6"
14' 0
8- 6.75 × 16
8-6.75x 18
Number and size of Stringers
Dead Load per foot of track
500
500
Above Stringers
360
405
Stringers -nominal size
860
905
Total Dead Load
Reaction on bent, pounds
10750
12670
Dead Load
192000
208571
Live Load
202750
221241
Total
Pile
Frame
Pile
Frame
Kind of Bent
Number of piles of posts
6
6
6
6
Size of piles or posts
14" D 12 x 14 14" D 12 x 14
Total Area of piles of posts, sq.-in.
924
1008
924
1008
Unit bearing stress on piles or posts, lb. per sq.
219
201
239
219
in.
Average load in Tons per pile or post
17
17
18
18
Bearing-Stringers on caps for contineous Butt type Deck
756
756
Area sq. in. - 14" cap
268
293
Bearing stress - lb. Per sq. in. - 14" cap
864
864
Average sq. in. 16" cap
235
256
Bearing stress - lb. Per sq. in. - 16" cap
Bending in Stringers
15053
20111
Dead Load Moment - foot pounds per track
310000
400000
Live Load Moments - foot pounds per track
325053
420111
Total Load Moment - foot pounds per track
2304
2916
Section Modulus-nominal size
1693
1729
Bending stress-lb per sq. in - nominal size
Longitudinal shear-Standard formula - - First driver at height of the beam from the support
16
18
depth nominal
253
232
19
19
220
19
201
17
945
247
1080
216
945
235
1080
206
756
268
864
235
25841
460000
485841
3645
1599
21424
400000
421424
3063
1651
15250
310000
325250
2304
1694
18
16.5
16.5
7-A1-17
Appendix 1 - Contemporary Designs and Design Aids
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
Table 7-A1-3. Comparison of Unit Stresses in Open Deck Trestles, E - 80 Cooper Loadings, No Impact
All loads in pounds per track. All moments in foot-pounds per track.
AREMA Manual for Railway Engineering
© 2011, American Railway Engineering and Maintenance-of-Way Association
c, if > d
810
W
3308
Dead load = WL'/2
71135
Live load
74443
Total load
768
Cross section - sq. in.-nominal size
145
Unit shear-lb per sq. in. = 3R/2bh
744
Cross section - sq. in.-dressed size
150
Unit shear-lb per sq. in. = 3R/2bh
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for stringer
bending and shear. (Assume 14 cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R = Total Reaction
900
3675
89303
92978
960
145
930
150
905
3997
90446
94443
972
146
945
150
927
3552
95705
99257
1024
145
992
150
905
3545
91000
94545
972
146
945
150
950
3958
100997
104956
1080
146
1050
150
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 72000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2 in depth
In calculating bearing, bending, and shear stresses,
outer stringers are considered as carrying no load.
950
4196
100801
104997
1080
146
1050
150
2.42
1000
5250
111767
117017
1200
146
1170
150
Timber Structures
7-A1-18
Table 7-A1-3. Comparison of Unit Stresses in Open Deck Trestles, E - 80 Cooper Loadings, No Impact (Continued)
All loads in pounds per track. All moments in foot-pounds per track.
Appendix 1 - Contemporary Designs and Design Aids
A1.6 STRESS LAMINATED DECKS
A1.6.1 STRESS LAMINATED PANEL DESIGN STRESSES, LL DEFLECTION AND
MINIMUM TRANSVERSE STRESSING REQUIRED FOR VARIOUS SPAN LENGTHS AND
PANEL THICKNESSES
Ensure that the allowable stresses for the material you have selected are not exceeded by any of the design
stresses tabulated for the particular span and panel thickness chosen.
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A1-19
Species: Douglas Fir
Grade: No. 1
Allowable
Stresses (psi)
Fb 1150 x Cls
1.5
Fv 80
1.33
Wet
Condition
Fc+ 375
(> 19% M.C.)
E
x Cv
1750000
Fb’ 1725 Dead Load (includes: track, ballast, curb,
Fv’ 106 protective cover, stressing system)
4128 lb/ft
Variable Dead Load due to various panels’
thicknesses (per inch of panel thickness)
70 lb/ft
Timber Structures
7-A1-20
Table 7-A1-4. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span
Lengths & Panel Thicknesses
AREMA Manual for Railway Engineering
© 2011, American Railway Engineering and Maintenance-of-Way Association
Species: Douglas Fir - Larch
Grade: No. 1
Allowable
Stresses (psi)
Fb 1150 x Cls
1.5
Fv 80
1.33
Wet
Condition
Fc+ 375
(> 19% M.C.)
E
x Cv
1750000
Fb’ 1725 Dead Load (includes: track, ballast, curb,
Fv’ 106 protective cover, stressing system)
4128 lb/ft
Variable Dead Load due to various panels’
thicknesses (per inch of panel thickness)
70 lb/ft
7-A1-21
Appendix 1 - Contemporary Designs and Design Aids
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
Table 7-A1-4. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span
Lengths & Panel Thicknesses (Continued)
Species: Southern Pine
Grade: No. 1
Allowable
Stresses (psi)
Fb 1075 x Cls
1.5
Fv 75
1
Wet
Condition
Fc+ 340
(> 19% M.C.)
E
x Cv
1500000
Fb’ 1613 Dead Load (includes: track, ballast, curb,
protective cover, stressing system)
Fv’ 75
4128 lb/ft
Variable Dead Load due to various panels’
thicknesses (per inch of panel thickness)
70 lb/ft
Timber Structures
7-A1-22
Table 7-A1-5. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span
Lengths & Panel Thicknesses
AREMA Manual for Railway Engineering
© 2011, American Railway Engineering and Maintenance-of-Way Association
Species: Southern Pine
Grade: No. 1
Allowable
Stresses (psi)
Fb 1075 x Cls
1.5
Fv 75
1
Wet
Condition
Fc+ 340
(> 19% M.C.)
E
x Cv
1500000
Fb’ 1613 Dead Load (includes: track, ballast, curb,
protective cover, stressing system)
Fv’ 75
4128 lb/ft
Variable Dead Load due to various panels’
thicknesses (per inch of panel thickness)
70 lb/ft
7-A1-23
Appendix 1 - Contemporary Designs and Design Aids
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
Table 7-A1-5. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span
Lengths & Panel Thicknesses (Continued)
Species: Red Oak
Grade: No. 1
Allowable
Stresses (psi)
Fb 1000 x Cls
1.5
Fv 75
1.33
Wet
Condition
Fc+ 495
(> 19% M.C.)
E
x Cv
1350000
Fb’ 1500 Dead Load (includes: track, ballast, curb,
Fv’ 99.8 protective cover, stressing system)
4128 lb/ft
Variable Dead Load due to various panels’
thicknesses (per inch of panel thickness)
70 lb/ft
Timber Structures
7-A1-24
Table 7-A1-6. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span
Lengths & Panel Thicknesses
AREMA Manual for Railway Engineering
© 2011, American Railway Engineering and Maintenance-of-Way Association
Species: Red Oak
Grade: No. 1
Allowable
Stresses (psi)
Fb 1000 x Cls
1.5
Fv 75
1.33
Wet
Condition
Fc+ 495
(> 19% M.C.)
E
x Cv
1350000
Fb’ 1500 Dead Load (includes: track, ballast, curb,
Fv’ 99.8 protective cover, stressing system)
4128 lb/ft
Variable Dead Load due to various panels’
thicknesses (per inch of panel thickness)
70 lb/ft
7-A1-25
Appendix 1 - Contemporary Designs and Design Aids
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
Table 7-A1-6. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span
Lengths & Panel Thicknesses (Continued)
Ensure that the allowable stresses for the material you have Dead Load (includes: track, ballast, curb, protective cover,
stressing system):
selected are not exceeded by any of the design stresses
tabulated for the particular span and panel thickness chosen.
4128 lb/ft
AREMA Manual for Railway Engineering
© 2011, American Railway Engineering and Maintenance-of-Way Association
NOTE: i, ii, and iii are the governing case for max.
longitudinal shear (AREMA); i = 1st driver @ qtr. point; ii =
shear formula with 1st driver @ 3x height of beam; iii =
revised shear formula with 1st driver @ 3x height of beam.
See Table 7-A1- for details.
Variable Dead Load due to various panels’ thicknesses (per
inch of panel thickness):
70 lb/ft
Timber Structures
7-A1-26
Table 7-A1-7. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span
Lengths & Panel Thicknesses
Ensure that the allowable stresses for the material you have Dead Load (includes: track, ballast, curb, protective cover,
selected are not exceeded by any of the design stresses
stressing system):
tabulated for the particular span and panel thickness chosen.
4128 lb/ft
NOTE: i, ii, and iii are the governing case for max.
longitudinal shear (AREMA); i = 1st driver @ qtr. point; ii =
shear formula with 1st driver @ 3x height of beam; iii =
revised shear formula with 1st driver @ 3x height of beam.
See Table 7-A1- for details.
Variable Dead Load due to various panels’ thicknesses (per
inch of panel thickness):
70 lb/ft
7-A1-27
Appendix 1 - Contemporary Designs and Design Aids
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
Table 7-A1-7. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span
Lengths & Panel Thicknesses (Continued)
Timber Structures
A1.6.2 CALCULATION OF DECK LOADS FOR STRESS LAMINATED DECKS
Table 7-A1-8. Tabulation of Deck Loads for Stress Laminated Decks
ASSUMPTIONS:
width of timber portion of laminated deck =
width of curb timber =
maximum ballast depth below track ties =
additional depth of ballast between track ties =
weight per volume of treated timber =
weight per volume of ballast =
weight per volume of waterproofing =
prestressing rods 2’ spacing, 1” dia. rod with nut & cap each end =
bearing/anchorage = C15X40 each side with 20 lb anchor plates =
walkway 0 lb/ft or 110 lb/ft =
track tie length =
14 ft.
9 in.
24 in.
5 in.
60 lb/cu.ft.
120 lb/cu.ft.
0.2 lb/sq.ft.
20 lb/ft.
100 lb/ft.
0 lb/ft.
8.5 ft.
ITEMS (excluding laminate members):
Track c/w rails, inside guard rails and fastenings
200 lb/ft
Ballast including track ties
3625 lb/ft
Curb timbers on both sides
180 lb/ft
Protective cover (Geotextile)
3 lb/ft
Walkway
0 lb/ft
Prestressing rods
20 lb/ft
Bearing/Anchorage
100 lb/ft
TOTAL
4128 lb/ft
DECK LAMINAE:
Per inch thickness of deck
70 lb/ft
(i.e. 14” thick deck panel, 14 x 70 = 980 lb/ft)
A1.6.3 ALLOWABLE UNIT STRESSES FOR STRESS GRADED LUMBER - RAILROAD
LOADING (VISUAL GRADING)
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-28
AREMA Manual for Railway Engineering
Cls - load sharing factor applied to Fb, 1.3 for select structural and 1.5 for No. 1 or No. 2
Cv - Shear stress factor applied to Fv, provided length for split on wide face is limited to 1 x wide face
(not applicable for Southern Pine as per AREMA Manual)
A1.6.4 TYPICAL DESIGN EXAMPLE FOR A SIMPLE STRESS LAMINATED LUMBER DECK PANEL
7-A1-29
Appendix 1 - Contemporary Designs and Design Aids
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
Table 7-A1-9. Allowable Unit Stresses for Stress Graded Lumber - Railroad Loading (Visual Grading)
Timber Structures
Figure 7-A1-4. Typical Design Example for a Simple Stress Laminated Lumber Deck Panel
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-30
AREMA Manual for Railway Engineering
Appendix 1 - Contemporary Designs and Design Aids
1
3
4
Figure 7-A1-4. Typical Design Example for a Simple Stress Laminated Lumber Deck Panel (Continued)
A1.6.5 TABLES FOR SIMPLE STRESS LAMINATED LUMBER DECK PANEL DESIGN
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A1-31
Timber Structures
Table 7-A1-10. Tables for Simple Stress Laminated Lumber Deck Panel Design
The following table has been
developed for Cooper’s E 80 loading
and is used as a base for all other E
loadings. Multiply the table value by
the design E-rating and divide by 80.
The following tables are based on an HS 20-44 vehicle
with maximum wheel load of 16,000 lbs. vt & mt must be
multiplied by the design axle load in kips (or E-rating)
and divided by 32 kips (2 x 16,000 lbs wheel load) to
obtain the appropriate Mt & Vt.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A1-32
AREMA Manual for Railway Engineering
30
Appendix 2 - Temporary Structures
— 2010 —
TABLE OF CONTENTS
Section/Article
Description
Page
A2.1 General Considerations (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A2-1
A2.2 Criteria for Use of Increased Allowable Stresses (2003) . . . . . . . . . . . . . . . . . . . . . . .
7-A2-1
A2.3 Increases to Allowable Stresses to Temporary Structures (2003) . . . . . . . . . . .. . . . .
7-A2-2
A2.4 Load for the Design of Temporary Structures (2003) . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A2-2
1
A2.1 GENERAL CONSIDERATIONS (2003)
In general, temporary timber structures, temporary blocking, falsework and similar constructions supporting
railroad loading should be designed in accordance with the requirements of Section 2.1 through Section 2.4.
Under certain conditions it may be permissible to increase the allowable design stresses because of the limited
duration of use and the controlled conditions. The use of allowable stresses greater than those indicated in
Section 2.2 will only be allowed when the design engineer has carefully reviewed the specific application to
verify its appropriateness and has received approval from the Chief Engineer of the operating railroad.
A2.2
CRITERIA FOR USE OF INCREASED ALLOWABLE STRESSES (2003)
Before using increased allowable stresses in the design of temporary structures, the designer shall ensure the
following requirements are met.
a.
The design engineer has reviewed the specific application verifying that the use of increased allowable
design stresses is appropriate, has clearly defined the duration of the temporary structure’s service life,
and has obtained authorization from the Chief Engineer of the operating railroad.
b. New material should be properly seasoned.
c.
No increase in allowable stresses shall be permitted when reused or second-hand material is used unless
authorized by the railroad’s Chief Engineer.
d. If green lumber is used in temporary construction, considerations should be made for this in the
allowable stresses used and also provisions should be made to ensure that connections will be
continuously checked and tightened as required.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A2-1
3
Timber Structures
e.
If untreated material is used, the designer shall ensure that the conditions of use and the duration of use
are such that decay will not become a factor.
f.
The structure shall be inspected at intervals as determined by the Chief Engineer of the operating
railroad.
A2.3 INCREASES TO ALLOWABLE STRESSES TO TEMPORARY STRUCTURES (2003)
If the conditions of Paragraph 2.4.1 are satisfied, the allowable stresses listed in Table 7-2-7 may be multiplied
by a factor of 1.1. The modulus of elasticity, E, shall remain unchanged.
A2.4 LOAD FOR THE DESIGN OF TEMPORARY STRUCTURES (2003)
The live load used for the design of temporary structures shall be Cooper E-80, unless otherwise directed by the
Chief Engineer of the operating railroad. Refer to Chapter 8 Concrete Structures and Foundations or Chapter
15 Steel Structures for the axle load and axle spacing configuration for Cooper E-80 loading.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A2-2
AREMA Manual for Railway Engineering
30
Appendix 3 - Legacy Designs
— 2011 —
TABLE OF CONTENTS
Section/Article
Description
Page
A3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A3.1.1 Fire Tests (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . .
7-A3-3
7-A3-4
A3.2 Pile Design Aids. . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-8
A3.3 Legacy Timber Trestle Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-43
A3.4 Legacy Culvert Designs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-92
1
LIST OF FIGURES
Figure
Description
7-A3-1 Fire Test Cabinet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-2 Fire Test Cabinet Door. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-3 Fire Test Cabinet Burner. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-4 Fire Test Cabinet with Door and Burner in Place . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-5 4-Pile Bent 12” x 14” Timber Cap a=23” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-6 4-Pile Bent 12” x 14” Timber Cap a=29”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-7 4-Pile Bent 12” x 14” Timber Cap a=31”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-8 4-Pile Bent 14” x 14” Timber Cap a=23” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-9 4-Pile Bent 14” x 14” Timber Cap a=29”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-10 4-Pile Bent 14” x 14” Timber Cap a=31”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-11 4-Pile Bent 15” x 15” Concrete Cap a=23” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-12 4-Pile Bent 15” x 15” Concrete Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-13 4-Pile Bent 15” x 15” Concrete Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-14 5-Pile Bent 12” x 14” Timber Cap a=29”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-15 5-Pile Bent 12” x 14” Timber Cap a=31”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-16 5-Pile Bent 12” x 14” Timber Cap a=39”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-17 5-Pile Bent 12” x 14” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-18 5-Pile Bent 14” x 14” Timber Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-19 5-Pile Bent 14” x 14” Timber Cap a=31”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-20 5-Pile Bent 14” x 14” Timber Cap a=39”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
© 2011, American Railway Engineering and Maintenance-of-Way Association
Page
7-A3-4
7-A3-5
7-A3-6
7-A3-7
7-A3-9
7-A3-9
7-A3-10
7-A3-10
7-A3-11
7-A3-11
7-A3-12
7-A3-12
7-A3-13
7-A3-15
7-A3-15
7-A3-16
7-A3-16
7-A3-17
7-A3-17
7-A3-18
7-A3-1
3
Timber Structures
LIST OF FIGURES (CONT)
Figure
Description
Page
7-A3-21 5-Pile Bent 14” x 14” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-22 5-Pile Bent 16” x 16” Timber Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-23 5-Pile Bent 16” x 16” Timber Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-24 5-Pile Bent 16” x 16” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-25 5-Pile Bent 16” x 16” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-26 5-Pile Bent 15” x 15” Concrete Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-27 5-Pile Bent 15” x 15” Concrete Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-28 5-Pile Bent 15” x 15” Concrete Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-29 5-Pile Bent 15” x 15” Concrete Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-30 6-Pile Bent 12” x 14” Timber Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-31 6-Pile Bent 12” x 14” Timber Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-32 6-Pile Bent 12” x 14” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-33 6-Pile Bent 12” x 14” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-34 6-Pile Bent 14” x 14” Timber Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-35 6-Pile Bent 14” x 14” Timber Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-36 6-Pile Bent 14” x 14” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-37 6-Pile Bent 14” x 14” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-38 6-Pile Bent 16” x 16” Timber Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-39 6-Pile Bent 16” x 16” Timber Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-40 6-Pile Bent 16” x 16” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-41 6-Pile Bent 16” x 16” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-42 6-Pile Bent 15” x 15” Concrete Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-43 6-Pile Bent 15” x 15” Concrete Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-44 6-Pile Bent 15” x 15” Concrete Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-45 6-Pile Bent 15” x 15” Concrete Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-46 6-Pile Bent 15” x 18” Concrete Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-47 6-Pile Bent 15” x 18” Concrete Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-48 6-Pile Bent 15” x 18” Concrete Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-49 6-Pile Bent 15” x 18” Concrete Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-50 7-Pile Bent 14” x 14” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-51 7-Pile Bent 14” x 14” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-52 7-Pile Bent 16” x 16” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-53 7-Pile Bent 16” x 16” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-54 7-Pile Bent 15” x 15” Concrete Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-55 7-Pile Bent 15” x 15” Concrete Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-56 7-Pile Bent 15” x 18” Concrete Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-57 7-Pile Bent 15” x 18” Concrete Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-58 Reinforced Concrete Piers and Bents as Fire Stops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-59 Wood Bents Faced with Fire Resisting Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-60 Application of Mastic Material in Open-Deck Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-61 Floor Plan for Open-Deck Trestles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-62 Floor Plan for Ballasted-Deck Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-63 Bulkheads and Miscellaneous Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-64 Cap Stringer Fastening and Pile Top Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-65 Bent Details for Open-Deck Pile Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-66 Bent Details for Ballasted-Deck Pile Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-67 Longitudinal Bracing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-68 Details of Footings for Framed Bents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-69 Multiple-Story Trestle Bents (6 Post Bent) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-18
7-A3-19
7-A3-19
7-A3-20
7-A3-20
7-A3-21
7-A3-21
7-A3-22
7-A3-22
7-A3-24
7-A3-24
7-A3-25
7-A3-25
7-A3-26
7-A3-26
7-A3-27
7-A3-27
7-A3-28
7-A3-28
7-A3-29
7-A3-29
7-A3-30
7-A3-30
7-A3-31
7-A3-31
7-A3-32
7-A3-32
7-A3-33
7-A3-33
7-A3-35
7-A3-36
7-A3-37
7-A3-38
7-A3-39
7-A3-40
7-A3-41
7-A3-42
7-A3-43
7-A3-44
7-A3-45
7-A3-46
7-A3-47
7-A3-48
7-A3-49
7-A3-50
7-A3-51
7-A3-52
7-A3-53
7-A3-54
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-2
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
LIST OF FIGURES (CONT)
Figure
Description
Page
7-A3-70 Multiple-Story Trestle Bents (5 Post Bent) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-55
7-A3-71 Walk and Handrail - Open-Deck Trestles (to be used where required) . . . . . . . . . . . . . . . . . . 7-A3-56
7-A3-72 Water Barrel and Refuge Platform - Open-Deck Trestles (to be used where required). . . . . . 7-A3-57
7-A3-73 Track Car Platforms - Open-Deck Trestles (to be used where required) . . . . . . . . . . . . . . . . . 7-A3-58
7-A3-74 Walk and Handrail - Ballasted-Deck Trestles (to be used where required) . . . . . . . . . . . . . . . 7-A3-59
7-A3-75 Water Barrel and Refuge Platform - Ballasted-Deck Trestles (to be used where required) . . 7-A3-60
7-A3-76 Track Car Platform - Ballasted-Deck Trestles (to be used where required). . . . . . . . . . . . . . . 7-A3-61
7-A3-77 Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 Loading-Pier for 150-foot
and 80-foot Spans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-62
7-A3-78 Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 Loading-Pier for 150-foot
Span and Trestle Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-64
7-A3-79 Recommended Practice for Design of Wood Culverts, E 72 Loading, for Heights up to
15 Foot Base of Rail to Flow Line area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-92
LIST OF TABLES
Table
Description
7-A3-1 4-Pile Bents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-2 5-Pile Bents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-3 6-Pile Bents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-4 7-Pile Bents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7-A3-5 Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact. . . . . .
7-A3-6 Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact. . . . . .
7-A3-7 Comparison of Unit Stresses in Open Deck Trestles, Various Cooper Loadings, No Impact . .
7-A3-8 Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact . .
7-A3-9 Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact . .
7-A3-10Typical Size Boxes and Unit Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Page
7-A3-8
7-A3-14
7-A3-23
7-A3-34
7-A3-66
7-A3-72
7-A3-78
7-A3-80
7-A3-86
7-A3-93
A3.1 INTRODUCTION
3
4
This Appendix contains information useful for Rating purposes of existing structures of many existing legacy
designs.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
1
7-A3-3
Timber Structures
A3.1.1 FIRE TESTS (2011)
Figure 7-A3-1. Fire Test Cabinet
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-4
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-2. Fire Test Cabinet Door
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-5
Timber Structures
Figure 7-A3-3. Fire Test Cabinet Burner
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-6
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
Figure 7-A3-4. Fire Test Cabinet with Door and Burner in Place
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-7
Timber Structures
A3.2 PILE DESIGN AIDS
Table 7-A3-1. 4-Pile Bents
b=80, 90, 100, 110, 120, 130, 132, 140 & 144 inches
Pile Cap
Eff. Pile Length
a
C1
Figure No.
12” x 14” Timber
10’
23
12, 18, 24
Figure 7-A3-5
29
12, 18, 24
Figure 7-A3-6
31
12, 18, 24
Figure 7-A3-7
23
12, 18, 24
Figure 7-A3-5
29
12, 18, 24
Figure 7-A3-6
31
12, 18, 24
Figure 7-A3-7
23
12, 18, 24
Figure 7-A3-8
29
12, 18, 24
Figure 7-A3-9
31
12, 18, 24
Figure 7-A3-10
23
12, 18, 24
Figure 7-A3-8
29
12, 18, 24
Figure 7-A3-9
31
12, 18, 24
Figure 7-A3-10
23
12, 18, 24
Figure 7-A3-11
29
12, 18, 24
Figure 7-A3-12
31
12, 18, 24
Figure 7-A3-13
23
12, 18, 24
Figure 7-A3-11
29
12, 18, 24
Figure 7-A3-12
31
12, 18, 24
Figure 7-A3-13
30’
14” x 14” Timber
10’
30’
15” x 15” Concrete
10’
30’
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-8
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-5. 4-Pile Bent 12” x 14” Timber Cap a=23” Figure 7-A3-6. 4-Pile Bent 12” x 14” Timber Cap a=29”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-9
Timber Structures
Figure 7-A3-7. 4-Pile Bent 12” x 14” Timber Cap
a=31”
Figure 7-A3-8. 4-Pile Bent 14” x 14” Timber Cap a=23”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-10
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
7Figure 7-A3-9. 4-Pile Bent 14” x 14” Timber Cap a=29” Figure 7-A3-10. 4-Pile Bent 14” x 14” Timber Cap a=31”
Part 2
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-11
Timber Structures
Figure 7-A3-11. 4-Pile Bent 15” x 15” Concrete Cap
a=23”
Figure 7-A3-12. 4-Pile Bent 15” x 15” Concrete Cap
a=29”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-12
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-13. 4-Pile Bent 15” x 15” Concrete Cap a=31”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-13
Timber Structures
Table 7-A3-2. 5-Pile Bents
b= 90, 100, 110, 120, 130, 132, 140, 144 & 150 inches
Pile Cap
Eff. Pile
Length
a
C2
Figure No.
12” x 14” Timber
10’
29
24, 30, 36, 42
Figure 7-A3-14
31
24, 30, 36, 42
Figure 7-A3-15
39
24, 30, 36, 42
Figure 7-A3-16
60
24, 30, 36, 42
Figure 7-A3-17
29
24, 30, 36, 42
Figure 7-A3-14
31
24, 30, 36, 42
Figure 7-A3-15
39
24, 30, 36, 42
Figure 7-A3-16
60
24, 30, 36, 42
Figure 7-A3-17
29
24, 30, 36, 42
Figure 7-A3-18
31
24, 30, 36, 42
Figure 7-A3-19
39
24, 30, 36, 42
Figure 7-A3-20
60
24, 30, 36, 42
Figure 7-A3-21
29
24, 30, 36, 42
Figure 7-A3-18
31
24, 30, 36, 42
Figure 7-A3-19
39
24, 30, 36, 42
Figure 7-A3-20
60
24, 30, 36, 42
Figure 7-A3-21
29
24, 30, 36, 42
Figure 7-A3-22
31
24, 30, 36, 42
Figure 7-A3-23
39
24, 30, 36, 42
Figure 7-A3-24
60
24, 30, 36, 42
Figure 7-A3-25
29
24, 30, 36, 42
Figure 7-A3-22
31
24, 30, 36, 42
Figure 7-A3-23
39
24, 30, 36, 42
Figure 7-A3-24
60
24, 30, 36, 42
Figure 7-A3-25
29
24, 30, 36, 42
Figure 7-A3-26
31
24, 30, 36, 42
Figure 7-A3-27
39
24, 30, 36, 42
Figure 7-A3-28
60
24, 30, 36, 42
Figure 7-A3-29
29
24, 30, 36, 42
Figure 7-A3-26
31
24, 30, 36, 42
Figure 7-A3-27
39
24, 30, 36, 42
Figure 7-A3-28
60
24, 30, 36, 42
Figure 7-A3-29
30’
14” x 14” Timber
10’
30’
16” x 16” Timber
10’
30’
15” x 15” Concrete
10’
30’
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-14
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
7 Figure 7-A3-14. 5-Pile Bent 12” x 14” Timber Cap
a=29”
Part 2
Figure 7-A3-15. 5-Pile Bent 12” x 14” Timber Cap
a=31”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-15
Timber Structures
Figure 7-A3-16. 5-Pile Bent 12” x 14” Timber Cap a=39” Figure 7-A3-17. 5-Pile Bent 12” x 14” Timber Cap a=60”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-16
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-18. 5-Pile Bent 14” x 14” Timber Cap
a=29”
Example:
Given:
Note:
Figure 7-A3-19. 5-Pile Bent 14” x 14” Timber Cap
a=31”
The 5 pile-bent of a trestle which carries a chord of bunched stringers
under each rail, has a 14" x 14" timber cap. The spacing of the piles is
36" and the effective length of piles (i.e. the exposed length plus onehalf of the penetration) is 30 feet. Each chord possesses four 8" x 16"
stringers. Using graphs or tables, find out the distribution of the
wheel load (assumed as one or axle assumed as two) on the piles.
a = 31", c2 = 36", b = 144" and L = 30 feet
Intermediate pile (2)=0.562
Outside pile (3)=0.133
Centre pile (1)=2x (1-(0.562+0.133)) = 0.610
Answer:Pile #12345
Load0.1330.5620.6100.5620.133
The middle pile takes the maximum load,
then the intermediate piles and the load carried
by the outside piles is the smallest.
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-17
Timber Structures
Figure 7-A3-20. 5-Pile Bent 14” x 14” Timber Cap
a=39”
Example:
Given:
Note:
Figure 7-A3-21. 5-Pile Bent 14” x 14” Timber Cap
a=60”
Data same as in the previous Example in Figure 7-A3-19, except
that the chords now consist of five 8" x 16" stringers. Find out the
distribution of wheel load on piles of the bent.
a = 39" and the rest of the data is same as in the Example in Figure
7-A3-19.
Intermediate pile (2)=0.550
Outside pile (3)=0.143
Centre pile (1)=2x(1-0.550+0.143)) = 0.614
Answer:Pile #12345
Load0.1430.5500.6140.5500.143
Increase in the value of "a" has resulted in decrease
of load on the intermediate piles and a corresponding
increase of load on the outside and the centre pile.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-18
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-22. 5-Pile Bent 16” x 16” Timber Cap
a=29”
Figure 7-A3-23. 5-Pile Bent 16” x 16” Timber Cap a=31”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-19
Timber Structures
7 Figure 7-A3-24. 5-Pile Bent 16” x 16” Timber Cap
a=39”
Part 2
Figure 7-A3-25. 5-Pile Bent 16” x 16” Timber Cap
a=60”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-20
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-26. 5-Pile Bent 15” x 15” Concrete Cap a=29”
Figure 7-A3-27. 5-Pile Bent 15” x 15” Concrete Cap a=31”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-21
Timber Structures
7
Part
2 x 15” Concrete Cap a=39” Figure 7-A3-29. 5-Pile Bent 15” x 15” Concrete Cap a=60”
Figure 7-A3-28. 5-Pile Bent
15”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-22
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-3. 6-Pile Bents
b= 100, 110, 120, 130, 132, 140, 144 & 150 inches
Pile Cap
Eff. Pile
Length
12” x 14” Timber
10’
30’
14” x 14” Timber
10’
30’
16” x 16” Timber
10’
30’
15” x 15” Concrete
10’
30’
15” x 18” Concrete
10’
30’
a
29
31
39
60
29
31
39
60
29
31
39
60
29
31
39
60
29
31
39
60
29
31
39
60
29
31
39
60
29
31
39
60
29
31
39
60
29
31
39
60
C1
C2
Figure No.
12, 15, 15 36, 39, 45 Figure 7-A3-30
12, 15, 15 36, 39, 45 Figure 7-A3-31
12, 15, 15 36, 39, 45 Figure 7-A3-32
12, 15, 15 36, 39, 45 Figure 7-A3-33
12, 15, 15 36, 39, 45 Figure 7-A3-30
12, 15, 15 36, 39, 45 Figure 7-A3-31
12, 15, 15 36, 39, 45 Figure 7-A3-32
12, 15, 15 36, 39, 45 Figure 7-A3-33
12, 15, 15 36, 39, 45 Figure 7-A3-34
12, 15, 15 36, 39, 45 Figure 7-A3-35
12, 15, 15 36, 39, 45 Figure 7-A3-38
12, 15, 15 36, 39, 45 Figure 7-A3-37
12, 15, 15 36, 39, 45 Figure 7-A3-34
12, 15, 15 36, 39, 45 Figure 7-A3-35
12, 15, 15 36, 39, 45 Figure 7-A3-36
12, 15, 15 36, 39, 45 Figure 7-A3-37
12, 15, 15 36, 39, 45 Figure 7-A3-38
12, 15, 15 36, 39, 45 Figure 7-A3-39
12, 15, 15 36, 39, 45 Figure 7-A3-40
12, 15, 15 36, 39, 45 Figure 7-A3-41
12, 15, 15 36, 39, 45 Figure 7-A3-38
12, 15, 15 36, 39, 45 Figure 7-A3-39
12, 15, 15 36, 39, 45 Figure 7-A3-40
12, 15, 15 36, 39, 45 Figure 7-A3-41
12, 15, 15 36, 39, 45 Figure 7-A3-42
12, 15, 15 36, 39, 45 Figure 7-A3-43
12, 15, 15 36, 39, 45 Figure 7-A3-44
12, 15, 15 36, 39, 45 Figure 7-A3-45
12, 15, 15 36, 39, 45 Figure 7-A3-42
12, 15, 15 36, 39, 45 Figure 7-A3-43
12, 15, 15 36, 39, 45 Figure 7-A3-44
12, 15, 15 36, 39, 45 Figure 7-A3-45
12, 15, 15 36, 39, 45 Figure 7-A3-46
12, 15, 15 36, 39, 45 Figure 7-A3-47
12, 15, 15 36, 39, 45 Figure 7-A3-48
12, 15, 15 36, 39, 45 Figure 7-A3-49
12, 15, 15 36, 39, 45 Figure 7-A3-46
12, 15, 15 36, 39, 45 Figure 7-A3-47
12, 15, 15 36, 39, 45 Figure 7-A3-48
12, 15, 15 36, 39, 45 Figure 7-A3-49
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-23
Timber Structures
Figure 7-A3-30. 6-Pile Bent 12” x 14” Timber Cap
a=29”
Figure 7-A3-31. 6-Pile Bent 12” x 14” Timber Cap
a=31”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-24
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
7 Figure 7-A3-32. 6-Pile Bent 12” x 14” Timber Cap
a=39”
Part 2
Figure 7-A3-33. 6-Pile Bent 12” x 14” Timber Cap a=60”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-25
Timber Structures
Figure 7-A3-34. 6-Pile Bent 14” x 14” Timber Cap a=29” Figure 7-A3-35. 6-Pile Bent 14” x 14” Timber Cap a=31”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-26
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
7 Figure 7-A3-36. 6-Pile Bent 14” x 14” Timber Cap
a=39”
Part 2
Example:
Given:
Answer:
Note:
Figure 7-A3-37. 6-Pile Bent 14” x 14” Timber Cap
a=60”
The 6 pile-bent of a trestle which carries a ballast deck
and has a 14" x 14" timber cap. The spacing of the piles
is 30" and the effective length of piles (i.e. the exposed
length plus one-half of the penetration) is 30 feet. The
deck possesses ten 8" x 16" stringers. Using graphs or
tables, find out the distribution of the wheel load
(assumed as one) on piles of the bent.
A = 60", c1 = 15", c2 = 45", b = 150" and L = 30 feet.
Intermediate pile (2) =0.380
Outside pile(3)=0.114
Middle pile (1)= 1-(0.380+0.114) = 0.506
Pile #123456
Load0.1140.3800.5060.5060.3800.114
The outside piles are carrying a smaller amount of
wheel
load even when compared to a 5 - pile bent of the
Example in Figure 7-A3-31 and Figure 7-A3-22 (See
Appendix 3 - Legacy Designs).
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-27
Timber Structures
7 Figure 7-A3-38. 6-Pile Bent 16” x 16” Timber Cap
a=29”
Part 2
Figure 7-A3-39. 6-Pile Bent 16” x 16” Timber Cap
a=31”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-28
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-40. 6-Pile Bent 16” x 16” Timber Cap
a=39”
Figure 7-A3-41. 6-Pile Bent 16” x 16” Timber Cap a=60”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-29
Timber Structures
Figure 7-A3-42. 6-Pile Bent 15” x 15” Concrete Cap a=29”
Figure 7-A3-43. 6-Pile Bent 15” x 15” Concrete Cap a=31”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-30
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-44. 6-Pile Bent 15” x 15” Concrete Cap a=39”
Figure 7-A3-45. 6-Pile Bent 15” x 15” Concrete Cap
a=60”
Example:
Given:
Note:
Same as the Example in Figure 7-A3-37, except that the
timber cap is now substituted with a 15" x 15" concrete
cap.
Other data remains the same as for the Example in
Figure 7-A3-37.
Intermediate pile (2) =0.363
Outside pile (3)=0.159
Middle pile (1)= 1-(0.363+0.159) = 0.478
The 15" x 15" concrete cap being stiffer than the 14" x
14" timber cap of the Example No. 6 provides a better
distribution of wheel load on piles.
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-31
Timber Structures
Figure 7-A3-46. 6-Pile Bent 15” x 18” Concrete Cap a=29”
Figure 7-A3-47. 6-Pile Bent 15” x 18” Concrete Cap a=31”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-32
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-48. 6-Pile Bent 15” x 18” Concrete Cap a=39”
Figure 7-A3-49. 6-Pile Bent 15” x 18” Concrete Cap a=60”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-33
Timber Structures
Table 7-A3-4. 7-Pile Bents
b= 120, 130, 132, 140, 144, 150, 156, 160 & 168 inches
Pile Cap
Eff. Pile
Length
a
C2
C3
Figure No.
14” x 14” Timber
10’
39
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-50
60
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-51
39
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-50
60
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-51
39
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-52
60
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-53
39
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-52
60
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-53
39
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-54
60
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-55
39
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-54
60
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-55
39
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-56
60
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-57
39
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-56
60
24, 27, 27,
30, 30
48, 51, 57,
54, 60
Figure 7-A3-57
30’
16” x 16” Timber
10’
30’
15” x 15” Concrete
10’
30’
15” x 18” Concrete
10’
30’
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-34
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-50. 7-Pile Bent 14” x 14” Timber Cap a=39”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-35
Timber Structures
Figure 7-A3-51. 7-Pile Bent 14” x 14” Timber Cap a=60”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-36
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-52. 7-Pile Bent 16” x 16” Timber Cap a=39”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-37
Timber Structures
7
Part 2
Figure 7-A3-53. 7-Pile Bent 16” x 16” Timber Cap a=60”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-38
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-54. 7-Pile Bent 15” x 15” Concrete Cap a=39”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-39
Timber Structures
Part 2
Figure 7-A3-55. 7-Pile Bent 15” x 15” Concrete Cap a=60”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-40
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
Figure 7-A3-56. 7-Pile Bent 15” x 18” Concrete Cap a=39”
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-41
Timber Structures
Figure 7-A3-57. 7-Pile Bent 15” x 18” Concrete Cap a=60”
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-42
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
A3.3 LEGACY TIMBER TRESTLE DESIGNS
1
3
4
Figure 7-A3-58. Reinforced Concrete Piers and Bents as Fire Stops
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-43
Timber Structures
Figure 7-A3-59. Wood Bents Faced with Fire Resisting Material
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-44
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
Figure 7-A3-60. Application of Mastic Material in Open-Deck Structures
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-45
Timber Structures
10’-0 TIES
4x8 SPACER TIMBER
NOTE:
3’-0
FOR ALTERNATE CAP-
CLASS OF LOADING
FOR PILE TOP
STRINGER FASTENING,
AND SPECIES OF
PROTECTION SEE
SEE FIGURE 7-4-16
LUMBER USED
FIGURE 7-4-16
WILL GOVERN
SIZE OF TIES.
END SPAN
INTERMEDIATE SPAN
ELEVATION
34 DIA. PACKING BOLTS
34 DIA. DRIFT BOLTS
34 DIA. x 10 WASHER
PENETRATION 8 IN.
HEAD DRIVE SPIKE,
INTO CAP
SINGLE GRIP
C
L RAIL
C
L RAIL
34 DIA. WASHER HEAD DRIVE
34 DIA.
SPIKE, SINGLE GRIP, 5 IN.
BOLTS
PENETRATION INTO
AT ENDS
STRINGERS
C
L STRINGERS
C
L BENT
C
L BENT
C
L BENT
PLAN (4 PLY CHORD)
34 DIA. PACKING BOLTS
C
L RAIL
SCHEMATIC DIAGRAM
CONTINUOUS LAP-TYPE
DECK - 4 PLY CHORD
C
L STRINGERS
C
L BENT
C
L BENT
C
L BENT
C
L RAIL
PLAN (3 PLY CHORD)
SCHEMATIC DIAGRAM
CONTINUOUS LAP-TYPE
DECK - 3 PLY CHORD
Figure 7-A3-61. Floor Plan for Open-Deck Trestles
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-46
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-62. Floor Plan for Ballasted-Deck Trestles
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-47
Timber Structures
Figure 7-A3-63. Bulkheads and Miscellaneous Details
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-48
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-64. Cap Stringer Fastening and Pile Top Protection
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-49
Timber Structures
Figure 7-A3-65. Bent Details for Open-Deck Pile Trestles
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-50
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-66. Bent Details for Ballasted-Deck Pile Trestles
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-51
Timber Structures
Figure 7-A3-67. Longitudinal Bracing
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-52
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-68. Details of Footings for Framed Bents
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-53
Timber Structures
Figure 7-A3-69. Multiple-Story Trestle Bents (6 Post Bent)
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-54
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-70. Multiple-Story Trestle Bents (5 Post Bent)
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-55
Timber Structures
Figure 7-A3-71. Walk and Handrail - Open-Deck Trestles (to be used where required)
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-56
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-72. Water Barrel and Refuge Platform - Open-Deck Trestles (to be used where required)
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-57
Timber Structures
Figure 7-A3-73. Track Car Platforms - Open-Deck Trestles (to be used where required)
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-58
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-74. Walk and Handrail - Ballasted-Deck Trestles (to be used where required)
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-59
Timber Structures
Figure 7-A3-75. Water Barrel and Refuge Platform - Ballasted-Deck Trestles (to be used where required)
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-60
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-76. Track Car Platform - Ballasted-Deck Trestles (to be used where required)
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-61
Timber Structures
Figure 7-A3-77. Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 LoadingPier for 150-foot and 80-foot Spans
Sheet 1 of 2
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-62
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-77. Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 LoadingPier for 150-foot and 80-foot Spans
Sheet 2 of 2
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-63
Timber Structures
Figure 7-A3-78. Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 LoadingPier for 150-foot Span and Trestle Approach
Sheet 1 of 2
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-64
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
1
3
4
Figure 7-A3-78. Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 LoadingPier for 150-foot Span and Trestle Approach
Sheet 2 of 2
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-65
Timber Structures
Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact
12 ¢ and 13 ¢ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
12¢
13¢
13¢
13¢
Number and Size of Stringers
8-7² ´ 16²
8-8² ´ 16²
8-9² ´ 16²
6-10² ´ 16²
490
Dead load per foot of track
Above stringers
490
490
490
Stringers-nominal size
375
430
480
400
865
920
970
890
Total dead load
Reaction on bent in pounds
Dead load
10380
11960
12610
11570
Live load
139980
147660
147660
147660
Total
150360
159620
160270
159230
Kind of bent
Pile
Frame
Pile
Frame
Pile
Frame
Pile
Number of piles or posts
5
5
5
5
5
5
5
Frame
5
Size of piles or posts
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Total area of piles or posts-sq. in.
770
840
770
840
770
840
770
840
Unit bearing stress on piles or
posts-lb per sq. in.
195
179
207
190
208
191
207
190
Average load in tons per pile or post
15.0
150
16.0
16.0
16.0
16.0
15.9
15.9
Bearing-Stringers on caps for continuous butt type deck
Area sq. in.-14² cap
784
896
1008
Bearing stress-lb per sq. in.-14² cap
192
178
159
840
190
Area sq. in.-16² cap
896
1024
1152
960
Bearing stress-lb per sq. in.-16² cap
168
156
189
166
Dead load moment-foot pounds per
track
13888
17493
18443
16917
Live load moment-foot pounds per
track
210000
255000
255000
255000
Total load moment-foot pounds per
track
223888
272493
273443
271917
Section modulus-nominal size
2389
2730
3072
2560
Bending stress-lb per sq. in.-nominal
size
1124
1198
1068
1275
Section modulus-dressed size
2242
2563
2883
2402
Bending stress-lb per sq. in.-dressed
size
1196
1276
1138
1358
Bending in stringers
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 ft for stringer
bending and shear. (Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per
linear foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 60000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-66
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact
12 ¢ and 13 ¢ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
12¢
13¢
13¢
13¢
Number and Size of Stringers
8-7² ´ 16²
8-8² ´ 16²
8-9² ´ 16²
6-10² ´ 16²
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
16
16
16
16
c to c
12
13
13
13
L = (c to c) + 0.5 - 14/12
11.33
12.33
12.33
12.33
L’ ignore with d of face
8.17
9.17
9.17
9.17
a
10
11
11
11
b
5
6
6
6
W
865
920
970
890
WL
Dead load = --------2
3532
4217
4446
4079
c, if > d
Live load
76765
80270
80270
80270
Total load
80297
84487
84716
84349
Cross section-sq. in.-nominal size
896
1024
1152
960
3 R
Unit shear-lb per sq. in. = --- -----2 bh
134
124
110
132
Cross section-sq. in.-dressed size
868
992
1116
930
3 R
Unit shear-lb per sq. in. = --- -----2 bh
139
128
114
136
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-67
Timber Structures
Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact
14 ¢ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
14¢
14¢
14¢
14¢
14¢
Number and Size of Stringers
8-8² ´ 16²
8-9² ´ 16²
8-10² ´ 16²
6-9² ´ 18²
6-10² ´ 18²
Above stringers
490
490
490
490
490
Stringers-nominal size
430
480
535
405
450
920
970
1025
895
940
Dead load per foot of track
Total dead load
Reaction on bent in pounds
Dead load
12880
13580
14350
12540
13160
Live load
156360
156360
156360
156360
156360
Total
169240
169940
170710
168900
169520
Kind of bent
Pile
Frame
Pile
Frame
Pile
Frame
Pile
Frame
Pile
5
5
5
5
5
5
5
5
5
5
Size of piles or posts
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Total area of piles or posts-sq. in.
770
840
770
840
770
840
770
840
770
840
Unit bearing stress on piles or posts-lb
per sq. in.
220
201
221
202
222
203
220
201
220
202
Average load in tons per pile or post
16.9
16.9
17.0
17.0
17.1
17.1
16.9
16.9
17.0
17.0
Number of piles or posts
Frame
Bearing-Stringers on caps for continuous butt type deck
Area sq. in.-14² cap
896
1008
1120
756
840
Bearing stress-lb per sq. in.-14² cap
189
169
152
224
202
Area sq. in.-16² cap
1024
1152
1280
864
960
Bearing stress-lb per sq. in.-16² cap
165
148
133
196
176
Dead load moment-foot pounds per
track
20440
21555
22778
19870
20888
Live load moment-foot pounds per
track
300000
300000
300000
300000
300000
Total load moment-foot pounds per
track
320440
321555
322778
319870
320888
Section modulus-nominal size
2730
3072
3413
2916
3240
Bending stress-lb per sq. in.-nominal
size
1409
1256
1135
1317
1190
Section modulus-dressed size
2563
2883
3203
2756
3062
Bending stress-lb per sq. in.-dressed
size
1500
1340
1209
1392
1257
Bending in stringers
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for
stringer bending and shear. (Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per
linear foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 60000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-68
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact
14 ¢ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
14¢
14¢
14¢
14¢
14¢
Number and Size of Stringers
8-8² ´ 16²
8-9² ´ 16²
8-10² ´ 16²
6-9² ´ 18²
6-10² ´ 18²
18
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
16
16
16
18
c to c
14
14
14
14
14
L = (c to c) + 0.5 - 14/12
13.33
13.33
13.33
13.33
13.33
L’ ignore within d of face
10.17
10.17
10.17
9.83
9.83
a
12
12
12
11.83
11.83
b
7
7
7
6.83
6.83
c, if > d
2
2
2
1.83
1.83
W
920
970
1025
895
940
WL
Dead load = --------2
4677
4931
5210
4400
4622
Live load
91125
91125
91125
88875
88875
Total load
95802
96056
96335
93275
93497
Cross section-sq. in.-nominal size
1024
1152
1280
972
1080
3 R
Unit shear-lb per sq. in. = --- -----2 bh
140
125
113
144
130
Cross section-sq. in.-dressed size
992
1116
1240
945
1050
R--- ----Unit shear-lb per sq. in. = 3
2 bh
145
129
117
149
134
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-69
Timber Structures
Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact
15 ¢ and 16 ¢ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
15¢
15¢
16¢
16¢
16¢
Number and Size of Stringers
8-10² ´ 16²
8-9² ´ 18²
8-9² ´ 18²
8-10² ´ 18²
6-10² ´ 20²
Above stringers
490
490
490
490
490
Stringers-nominal size
535
540
540
600
500
1025
1030
1030
1090
990
Dead load per foot of track
Total dead load
Reaction on bent in pounds
Dead load
15375
15450
16480
17440
15840
Live load
163920
163920
170580
170580
170580
Total
179295
179370
187060
188020
186420
Kind of bent
Pile
Frame
Pile
Frame
Pile
Frame
Pile
Frame
Pile
5
5
5
5
6
6
6
6
6
6
Size of piles or posts
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Total area of piles or posts-sq. in.
770
840
770
840
924
1008
924
1008
924
1008
Unit bearing stress on piles or posts-lb
per sq. in.
233
214
233
214
202
185
204
187
202
185
Average load in tons per pile or post
17.9
17.9
17.9
17.9
15.6
15.6
15.7
15.7
15.6
15.6
Number of piles or posts
Frame
Bearing-Stringers on caps for continuous butt type deck
Area sq. in.-14² cap
1120
1008
1008
1120
Bearing stress-lb per sq. in.-14² cap
176
180
185
168
840
222
Area sq. in.-16² cap
1280
1152
1152
1280
960
Bearing stress-lb per sq. in.-16² cap
155
140
162
147
194
Dead load moment-foot pounds per
track
26323
26450
30270
32003
29100
Live load moment-foot pounds per
track
345000
345000
390000
390000
390000
Total load moment-foot pounds per
track
371323
371450
420270
422003
419100
Section modulus-nominal size
3413
3888
3888
4320
4000
Bending stress-lb per sq. in.-nominal
size
1304
1145
1297
1172
1259
Section modulus-dressed size
3203
3675
3675
4083
3802
Bending stress-lb per sq. in.-dressed
size
1390
1212
1372
1240
1323
Bending in stringers
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for
stringer bending and shear. (Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per
linear foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 60000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-70
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact
15 ¢ and 16 ¢ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
15¢
15¢
16¢
16¢
16¢
Number and Size of Stringers
8-10² ´ 16²
8-9² ´ 18²
8-9² ´ 18²
8-10² ´ 18²
6-10² ´ 20²
20
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
16
18
18
18
c to c
15
15
16
16
16
L = (c to c) + 0.5 - 14/12
14.33
14.33
15.33
15.33
15.33
L’ ignore within d of face
11.17
10.83
11.83
11.83
11.50
a
13
12.83
13.83
13.83
13.67
b
8
7.83
8.83
8.83
8.67
c, if > d
3
2.83
3.83
3.83
3.67
W
1025
1030
1030
1090
990
WL
Dead load = --------2
5723
5579
6094
6449
5693
Live load
97326
95233
100761
100761
98804
Total load
403048
100812
106855
107210
104497
Cross section-sq. in.-nominal size
1280
1296
1296
1440
1200
3 R
Unit shear-lb per sq. in. = --- -----2 bh
121
117
12498
11288
131
Cross section-sq. in.-dressed size
1240
1260
1260
1400
1170
R--- ----Unit shear-lb per sq. in. = 3
2 bh
125
120
127
115
134
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-71
Timber Structures
Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact
12 ¢ and 12 ¢ 6 ² Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
12¢
12¢
12¢ 6²
Number and Size of Stringers
8-8² ´ 16²
6-9² ´ 18²
8-8² ´ 16²
Dead load per foot of track
Above stringers
500
500
500
Stringers-nominal size
427
405
427
927
905
927
Total dead load
Reaction on bent in pounds
Dead load
11100
10900
11600
Live load
168000
168000
173000
Total
179100
178900
184600
Kind of bent
Pile
Frame
Pile
Frame
Pile
Number of piles or posts
5
5
5
5
6
6
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Size of piles or posts
Frame
Total area of piles or posts-sq. in.
770
840
770
840
924
1008
Unit bearing stress on piles or posts-lb
per sq. in.
233
213
232
213
200
183
Average load in tons per pile or post
17.9
17.9
17.9
17.9
15.4
15.4
Bearing-Stringers on caps for continuous butt type deck
Area sq. in.-14² cap
896
756
Bearing stress-lb per sq. in.-14² cap
200
237
896
206
Area sq. in.-16² cap
1024
864
1024
Bearing stress-lb per sq. in.-16² cap
176
207
180
Bending in stringers
Dead load moment-foot pounds per track
14900
14500
16200
Live load moment-foot pounds per track
255000
255000
279000
Total load moment-foot pounds per track
269900
269500
295200
Section modulus-nominal size
2730
2916
2730
Bending stress-lb per sq. in.-nominal size
1190
1110
1300
Section modulus-dressed size
2560
2756
2560
Bending stress-lb per sq. in.-dressed size
1270
1170
1380
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
16
18
16
c to c
12
12
12.5
L = (c to c) + 0.5 - 14/12
11.33
11.33
11.83
L’ ignore within d of face
8.17
7.83
8.67
a
10
9.83
10.5
b
5
4.83
5.5
W
927
905
927
WL
Dead load = --------2
3785
3545
4017
Live load
92118
90000
94310
Total load
95903
93545
98327
c, if > d
Assumptions:
L=
Distance C to C bents for bearing on caps in feet
=
Distance face to face of caps plus 0.5 foot for stringer
bending and shear. (Assume 14² Cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot
R=
Total Reaction
h=
Height of stringer in feet
b=
Breadth of stringers in feet
P=
Weight on one driving axle = 72000 pounds
a=
Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-72
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact
12 ¢ and 12 ¢ 6 ² Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
12¢
12¢
12¢ 6²
Number and Size of Stringers
8-8² ´ 16²
6-9² ´ 18²
8-8² ´ 16²
Cross section-sq. in.-nominal size
1024
1024
1152
RUnit shear-lb per sq. in. = 3
--- ----2 bh
140
137
128
Cross section-sq. in.-dressed size
992
992
1116
3 R
Unit shear-lb per sq. in. = --- -----2 bh
145
141
132
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-73
Timber Structures
Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact
13 ¢ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
13¢
13¢
Number and Size of Stringers
8-10² ´ 16²
6-10² ´ 18²
Dead load per foot of track
Above stringers
500
500
Stringers-nominal size
533
450
1033
950
Total dead load
Reaction on bent in pounds
Dead load
13400
12400
Live load
177000
177000
Total
194400
189400
Kind of bent
Pile
Frame
Pile
Number of piles or posts
6
6
6
6
14² D
12´ 14
14² D
12´ 14
Size of piles or posts
Frame
Total area of piles or posts-sq. in.
924
1008
924
1008
Unit bearing stress on piles or posts-lb per
sq. in.
206
189
205
188
Average load in tons per pile or post
15.9
15.9
15.8
15.8
Bearing-Stringers on caps for
continuous butt type deck
Area sq. in.-14² cap
1120
840
Bearing stress-lb per sq. in.-14² cap
170
225
Area sq. in.-16² cap
1280
960
Bearing stress-lb per sq. in.-16² cap
149
197
Bending in stringers
Dead load moment-foot pounds per track
19600
18100
Live load moment-foot pounds per track
30600
306000
Total load moment-foot pounds per track
325600
324100
Section modulus-nominal size
3413
3240
Bending stress-lb per sq. in.-nominal size
1150
1200
Section modulus-dressed size
3200
3060
Bending stress-lb per sq. in.-dressed size
1220
1270
Longitudinal shear-Standard formula-First driver at height of the beam from the support
Depth nominal
16
c to c
13
18
13
L = (c to c) + 0.5 - 14/12
12.33
12.33
L’ ignore within d of face
9.17
8.83
a
11
10.83
b
6
5.83
W
1033
950
WL
Dead load = --------2
4735
4196
Live load
96324
94378
Total load
101059
98574
c, if > d
Assumptions:
L=
Distance C to C bents for bearing on caps in feet
h =Height of stringer in feet
=
Distance face to face of caps plus 0.5 foot for stringer
b =Breadth of stringers in feet
bending and shear. (Assume 14² Cap)
P =Weight on one driving axle = 72000
W = Total Dead Load per linear foot of track:
pounds
Rail and fastenings = 200 pounds per linear foot
a =Distance from load P to support, in feet
Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot Dressed size = Nominal size less 1/2² in
R=
Total Reaction
depth
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-74
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact
13 ¢ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
13¢
13¢
Number and Size of Stringers
8-10² ´ 16²
6-10² ´ 18²
Cross section-sq. in.-nominal size
1280
1080
RUnit shear-lb per sq. in. = 3--- ----2 bh
118
137
Cross section-sq. in.-dressed size
1240
1050
3 R
Unit shear-lb per sq. in. = --- -----2 bh
122
141
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-75
Timber Structures
Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact
14 ¢ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
14¢
14¢
14¢
14¢
Number and Size of Stringers
8-10² ´ 16²
8-9² ´ 18²
6-10² ´ 18²
6-10² ´ 20²
Dead load per foot of track
Above stringers
500
500
500
500
Stringers-nominal size
533
540
450
500
1033
1040
950
1000
Total dead load
Reaction on bent in pounds
Dead load
14500
14600
13300
14000
Live load
188000
188000
188000
188000
Total
202500
Kind of bent
202600
201300
202000
Pile
Frame
Pile
Frame
Pile
Frame
Pile
6
6
6
6
6
6
6
6
Size of piles or posts
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Total area of piles or posts-sq. in.
924
Number of piles or posts
Frame
1008
924
1008
924
1008
924
1008
Unit bearing stress on piles or posts-lb 219
per sq. in.
200
219
201
216
199
219
200
Average load in tons per pile or post
16.9
16.9
16.9
16.8
16.8
16.8
16.8
16.9
Bearing-Stringers on caps for continuous butt type deck
Area sq. in.-14² cap
1120
1008
840
840
Bearing stress-lb per sq. in.-14² cap
181
201
240
240
Area sq. in.-16² cap
1280
1152
960
960
Bearing stress-lb per sq. in.-16² cap
158
176
210
210
Bending in stringers
Dead load moment-foot pounds per track
23000
23100
21100
22200
Live load moment-foot pounds per track
360000
360000
360000
360000
Total load moment-foot pounds per track
383000
383100
381100
382200
Section modulus-nominal size
3413
3888
3240
4000
Bending stress-lb per sq. in.-nominal size
1350
1180
1410
1150
Section modulus-dressed size
3200
3680
3060
3802
Bending stress-lb per sq. in.-dressed size
1140
1250
1490
1210
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
16
18
18
c to c
14
14
14
20
14
L = (c to c) + 0.5 - 14/12
13.33
13.33
13.33
13.33
L’ ignore within d of face
10.17
9.83
9.83
9.50
a
12
11.83
11.83
11.67
b
7
6.83
6.83
6.67
c, if > d
2
W
1033
1040
950
1000
WL
Dead load = --------2
5251
5113
4671
4750
Live load
109350
98100
98100
96300
Total load
114601
103213
102771
101050
Assumptions:
L=
Distance C to C bents for bearing on caps in feet
=
Distance face to face of caps plus 0.5 foot for stringer
bending and shear. (Assume 14² Cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot
R=
Total Reaction
h=
Height of stringer in feet
b=
Breadth of stringers in feet
P=
Weight on one driving axle = 72000 pounds
a=
Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-76
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact
14 ¢ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
14¢
14¢
14¢
14¢
Number and Size of Stringers
8-10² ´ 16²
8-9² ´ 18²
6-10² ´ 18²
6-10² ´ 20²
Cross section-sq. in.-nominal size
1280
1296
1080
1200
RUnit shear-lb per sq. in. = 3
--- ----2 bh
134
119
143
126
Cross section-sq. in.-dressed size
1240
1260
1050
1170
3 R
Unit shear-lb per sq. in. = --- -----2 bh
139
123
147
130
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-77
p
AREMA Manual for Railway Engineering
© 2011, American Railway Engineering and Maintenance-of-Way Association
Cooper Design Load
55.6
69.8
Panel Length C to C of Bents
12
12
Number and size of Stringers
6- 8 × 16
6- 10 × 16
Dead Load per foot of track
Above Stringers
490
500
Stringers -nominal size
320
400
Total Dead Load
810
900
Reaction on bent, pounds
Dead Load
10800
9720
Live Load
129733
162864
Total
139453
173664
Kind of Bent
Pile
Frame
Pile
Frame
Number of piles or posts
5
5
5
5
Size of piles or posts
14" D
12 x 14
14" D
12 x 14
Total Area of piles of posts, sq.-in.
770
840
770
840
Unit bearing stress on piles or posts, lb. per sq.
181
166
226
207
in.
Average load in Tons per pile or post
14
14
17
17
Bearing-Stringers on caps for continuous Butt type Deck
Area sq. in. - 14" cap
672
840
Bearing Stress - lb. Per sq. in. - 14" cap
208
207
Average sq. in. 16" cap
960
768
Bearing stress - lb. Per sq. in. - 16" cap
181
182
Bending in Stringers
Dead Load Moment - ft. pounds per track
13005
14450
Live Load Moments - ft. pounds per track
194600
244300
Total Load Moment - ft. pounds per track
207605
258750
Section Modulus-nominal size
2048
2560
Bending stress-lb per sq. in. -nominal size
1216
1213
Section modulus- dressed size
1922
2403
Bending stress-lb per sq. in. - dressed size
1296
1292
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
depth nominal
16
16
c to c
12
12
L = (c to c) +0.5-14/12
11.33
11.33
L' ignore within d of face
8.17
8.17
a
9.75
9.75
b
4.75
4.75
p
p
p
69.0
13'
6- 9 × 18
76.8
11'-6"
8- 8 × 16
72.8
12'
6- 9 × 18
78.8
12' 6"
6- 10 × 18
76.9
13'
6- 10 × 18
72.0
15'
6- 10 × 20
500
405
905
500
427
927
500
405
905
500
450
950
500
450
950
500
500
1000
11765
169846
181611
Pile
Frame
6
6
14" D
12 x 14
924
1008
10657
173635
184291
Pile
Frame
6
6
14" D
12 x 14
924
1008
10860
169866
180726
Pile
Frame
6
6
14" D
12 x 14
924
1008
11875
189120
200995
Pile
Frame
6
6
14" D
12 x 14
924
1008
12350
191599
203949
Pile
Frame
6
6
14" D
12 x 14
924
1008
15000
196800
211800
Pile
Frame
6
6
14" D
12 x 14
924
1008
197
180
199
183
196
179
218
199
221
202
229
210
15
15
15
15
15.1
15.1
16.7
16.7
17.0
17.0
17.6
17.6
756
240
864
210
896
206
1024
180
756
239
864
209
840
239
960
209
840
243
960
212
840
252
960
221
17207
293250
310457
2916
1278
2756
1352
13594
246154
259748
2731
1141
2563
1216
14530
254800
269330
2916
1108
2756
1173
16628
305350
321978
3240
1193
3063
1262
18063
326825
344888
3240
1277
3063
1351
25680
414000
439680
4000
1319
3803
1388
18
13
12.33
8.83
10.58
5.58
16
11.5
10.83
7.67
9.25
4.25
18
12
11.33
7.83
9.58
4.58
18
12.5
11.83
8.33
10.08
5.08
18
13
12.33
8.83
10.58
5.58
20
15
14.33
10.50
12.42
7.42
Timber Structures
7-A3-78
Table 7-A3-7. Comparison of Unit Stresses in Open Deck Trestles, Various Cooper Loadings, No Impact
All loads in pounds per track. All moments in foot-pounds per track.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
Table 7-A3-7. Comparison of Unit Stresses in Open Deck Trestles, Various Cooper Loadings, No Impact
All loads in pounds per track. All moments in foot-pounds per track. (Continued)
c, if > d
W
810
Dead load = WL'/2
3308
Live load
71135
Total load
74443
Cross section - sq. in.-nominal size
768
Unit shear-lb per sq. in. = 3R/2bh
145
Cross section - sq. in.-dressed size
744
Unit shear-lb per sq. in. = 3R/2bh
150
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for stringer
bending and shear. (Assume 14 cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R = Total Reaction
900
3675
89303
92978
960
145
930
150
905
3997
90446
94443
972
146
945
150
927
3552
95705
99257
1024
145
992
150
905
3545
91000
94545
972
146
945
150
950
3958
100997
104956
1080
146
1050
150
950
4196
100801
104997
1080
146
1050
150
2.42
1000
5250
111767
117017
1200
146
1170
150
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 72000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2 in depth
In calculating bearing, bending, and shear stresses,
outer stringers are considered as carrying no load.
Outer stringers are considered as carrying no load.
Based on appropriate grades of Douglas Fir and Southern Yellow Pine from Table Table 30-A-2-13
Appendix 3 - Legacy Designs
7-A3-79
Timber Structures
Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact
12 ¢ and 12 ¢ 6 ² Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
12¢
12¢
12¢ 6²
Number and Size of Stringers
12-7² ´ 14²
10-7² ´ 16²
10-8² ´ 16²
Above stringers
2310
2310
2310
Stringers-nominal size
490
470
535
2800
2780
2845
Dead load per foot of track
Total dead load
Reaction on bent in pounds
Dead load
33600
33400
35600
Live load
140000
140000
144000
Total
173600
Kind of bent
Pile
Number of piles or posts
Size of piles or posts
Frame
173400
Pile
Frame
179600
Pile
Frame
6
6
6
6
6
6
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Total area of piles or posts-sq. in.
924
1008
924
1008
924
1008
Unit bearing stress on piles or posts-lb per
sq. in.
188
172
188
172
194
178
Average load in tons per pile or post
14.5
14.5
14.5
14.5
15.0
15.0
Bearing-Stringers on caps for continuous butt type deck
Area sq. in.-14² cap
980
784
Bearing stress-lb per sq. in.-14² cap
177
221
896
200
Area sq. in.-16² cap
1120
896
1024
Bearing stress-lb per sq. in.-16² cap
155
194
175
Dead load moment-foot pounds per
track
45000
44500
49800
Live load moment-foot pounds per
track
210000
210000
252500
Total load moment-foot pounds per
track
255000
254500
282300
Section modulus-nominal size
2285
2380
2728
Bending stress-lb per sq. in.-nominal
size
1340
1280
1240
Section modulus-dressed size
2125
2240
2560
Bending stress-lb per sq. in.-dressed
size
1440
1360
1320
Bending in stringers
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
14
16
16
c to c
12
12
12.5
L = (c to c) + 0.5 - 14/12
11.33
11.33
11.83
L’ ignore within d of face
8.50
8.17
8.67
a
10.17
10.00
10.50
b
5.17
5.00
5.50
W
2800
2780
2845
WL
Dead load = --------2
11900
11352
12328
c, if > d
Live load
78529
76765
78592
Total load
90429
88116
90920
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-80
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact
12 ¢ and 12 ¢ 6 ² Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
12¢
12¢
12¢ 6²
Number and Size of Stringers
12-7² ´ 14²
10-7² ´ 16²
10-8² ´ 16²
Cross section-sq. in.-nominal size
1176
1120
1280
3 R
Unit shear-lb per sq. in. = --- -----2 bh
115
118
107
Cross section-sq. in.-dressed size
1134
1085
1240
3 R
Unit shear-lb per sq. in. = --- -----2 bh
120
122
110
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for stringer bending
and shear. (Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 60000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
In calculating bearing, bending, and shear stresses
outer stringers are considered as carrying no load.
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-81
Timber Structures
Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact
13 ¢ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
13¢
13¢
13¢
13¢
Number and Size of Stringers
12-7² ´ 16²
10-8² ´ 16²
9-10² ´ 16²
8-9² ´ 18²
Above stringers
2310
2310
2310
2310
Stringers-nominal size
560
535
600
540
2870
2845
2910
2850
Dead load per foot of track
Total dead load
Reaction on bent in pounds
Dead load
37400
37000
37800
37100
Live load
147800
147800
147800
147800
Total
185200
Kind of bent
Pile
Number of piles or posts
Frame
184800
Pile
Frame
185600
Pile
Frame
184900
Pile
Frame
6
6
6
6
6
6
6
6
Size of piles or posts
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Total area of piles or posts-sq. in.
924
1008
924
1008
924
1008
924
1008
Unit bearing stress on piles or posts-lb 200
per sq. in.
184
200
184
202
184
200
183
Average load in tons per pile or post
15.4
15.4
15.4
15.4
15.4
15.4
15.4
15.4
Bearing-Stringers on caps for
continuous butt type deck
Area sq. in.-14² cap
980
896
980
756
Bearing stress-lb per sq. in.-14² cap
189
206
189
244
Area sq. in.-16² cap
1120
1024
1120
865
Bearing stress-lb per sq. in.-16² cap
165
180
166
214
Dead load moment-foot pounds per
track
54600
54100
55500
54200
Live load moment-foot pounds per
track
255000
255000
255000
255000
Total load moment-foot pounds per
track
309600
309100
310500
309200
Section modulus-nominal size
2980
2728
2990
2920
Bending stress-lb per sq. in.-nominal
size
1250
1360
1245
1270
Section modulus-dressed size
2800
2560
2800
2750
Bending stress-lb per sq. in.-dressed
size
1320
1450
1330
1350
Bending in stringers
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for stringer
bending and shear. (Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 60000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
In calculating bearing, bending, and shear stresses
outer stringers are considered as carrying no
load.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-82
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact
13 ¢ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
13¢
13¢
13¢
13¢
Number and Size of Stringers
12-7² ´ 16²
10-8² ´ 16²
9-10² ´ 16²
8-9² ´ 18²
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
16
16
16
c to c
13
13
13
18
13
L = (c to c) + 0.5 - 14/12
12.33
12.33
12.33
12.33
L’ ignore within d of face
9.17
9.17
9.17
8.83
a
11.00
11.00
11.00
10.83
b
6.00
6.00
6.00
5.83
W
2870
2845
2910
2850
WL
Dead load = --------2
13154
13040
13338
12588
Live load
80270
80270
80270
78649
Total load
93424
93310
93608
91236
Cross section-sq. in.-nominal size
1344
1280
1440
1296
3 R
Unit shear-lb per sq. in. = --- -----2 bh
104
109
98
106
Cross section-sq. in.-dressed size
1302
1240
1395
1260
3 R
Unit shear-lb per sq. in. = --- -----2 bh
108
113
101
109
c, if > d
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-83
Timber Structures
Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact
15 ¢ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
15¢
15¢
15¢
15¢
Number and Size of Stringers
13-8² ´ 16²
11-10² ´ 16²
10-9² ´ 18²
9-10² ´ 18²
Above stringers
2310
2310
2310
2310
Stringers-nominal size
690
740
680
680
3000
3050
2990
2990
Dead load per foot of track
Total dead load
Reaction on bent in pounds
Dead load
45000
48700
44900
44900
Live load
164200
164200
164200
164200
Total
209200
Kind of bent
Pile
Number of piles or posts
Frame
209900
Pile
Frame
209100
Pile
Frame
209100
Pile
Frame
6
6
6
6
6
6
6
6
Size of piles or posts
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Total area of piles or posts-sq. in.
924
1008
924
1008
924
1008
924
1008
Unit bearing stress on piles or posts-lb 226
per sq. in.
206
227
208
226
207
226
207
Average load in tons per pile or post
17.4
17.5
17.5
17.4
17.4
17.4
17.4
17.4
Bearing-Stringers on caps for continuous butt type deck
Area sq. in.-14² cap
1252
1260
1008
980
Bearing stress-lb per sq. in.-14² cap
170
167
208
214
Area sq. in.-16² cap
1408
1440
1152
1120
Bearing stress-lb per sq. in.-16² cap
148
146
182
187
Dead load moment-foot pounds per
track
77000
78500
76700
76700
Live load moment-foot pounds per
track
346000
346000
346000
346000
Total load moment-foot pounds per
track
423000
424500
422700
422700
Section modulus-nominal size
3750
3840
3890
3780
Bending stress-lb per sq. in.-nominal
size
1260
1320
1300
1340
Section modulus-dressed size
3520
3600
3660
3570
Bending stress-lb per sq. in.-dressed
size
1440
1410
1380
1420
Bending in stringers
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 fooot for
stringer bending and shear. (Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R = Total Reaction
h = Height of stringer in feet
b = Breadth of stringers in feet
P = Weight on one driving axle = 60000 pounds
a = Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
In calculating bearing, bending, and shear stresses
outer stringers are considered as carrying no
load.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-84
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact
15 ¢ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
15¢
15¢
15¢
15¢
Number and Size of Stringers
13-8² ´ 16²
11-10² ´ 16²
10-9² ´ 18²
9-10² ´ 18²
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
16
16
18
c to c
15
15
15
18
15
L = (c to c) + 0.5 - 14/12
14.33
14.33
14.33
14.33
L’ ignore within d of face
11.17
11.17
10.83
10.83
a
13.08
13.08
13.08
13.08
b
8.08
8.08
8.08
8.08
c, if > d
3.08
3.08
3.08
3.08
W
3000
3050
2990
2990
WL
Dead load = --------2
16750
17029
16196
16196
Live load
97326
97326
95233
95233
Total load
114076
114355
111428
111428
Cross section-sq. in.-nominal size
1664
1760
1620
1620
3 R
Unit shear-lb per sq. in. = --- -----2 bh
103
97
103
103
Cross section-sq. in.-dressed size
1612
1705
1575
1575
3 R
Unit shear-lb per sq. in. = --- -----2 bh
106
101
106
106
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-85
Timber Structures
Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact
12 ¢ and 12 ¢ 6 ² Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
12¢
12¢
12¢ 6²
Number and Size of Stringers
14-7² ´ 14²
12-7² ´ 16²
12-8² ´ 16²
Above stringers
2310
2310
2310
Stringers-nominal size
570
560
640
2880
2870
2950
Dead load per foot of track
Total dead load
Reaction on bent in pounds
Dead load
34600
34500
36900
Live load
168000
168000
173000
Total
202000
Kind of bent
202500
209900
Pile
Frame
Pile
Frame
Pile
6
6
6
6
6
6
Size of piles or posts
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Total area of piles or posts-sq. in.
Number of piles or posts
Frame
924
1008
924
1008
924
1008
Unit bearing stress on piles or posts-lb 219
per sq. in.
201
219
201
227
208
Average load in tons per pile or post
16.9
16.9
16.9
17.5
17.5
16.9
Bearing-Stringers on caps for
continuous butt type deck
Area sq. in.-14² cap
1176
980
Bearing stress-lb per sq. in.-14² cap
173
207
1120
187
Area sq. in.-16² cap
1344
1120
1280
Bearing stress-lb per sq. in.-16² cap
151
181
164
Dead load moment-foot pounds per
track
46200
46100
51600
Live load moment-foot pounds per
track
252000
252000
279000
Total load moment-foot pounds per
track
298200
298100
330600
Section modulus-nominal size
2740
2990
3410
Bending stress-lb per sq. in.-nominal
size
1310
1200
1170
Section modulus-dressed size
2550
2800
3200
Bending stress-lb per sq. in.-dressed
size
1400
1280
1240
Bending in stringers
Assumptions:
L = Distance C to C bents for bearing on caps in feet
= Distance face to face of caps plus 0.5 foot for stringer
bending and shear. (Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R = Total Reaction
h=
b=
P=
Height of stringer in feet
Breadth of stringers in feet
Weight on one driving axle =
60000 pounds
a = Distance from load P to
support, in feet
Dressed size = Nominal size less
1/2 in depth
In calculating bearing, bending,
and shear stresses outer
stringers are considered as
carrying no load.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-86
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact
12 ¢ and 12 ¢ 6 ² Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
12¢
12¢
12¢ 6²
Number and Size of Stringers
14-7² ´ 14²
12-7² ´ 16²
12-8² ´ 16²
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
14
16
16
c to c
12
12
12.5
L = (c to c) + 0.5 - 14/12
11.33
11.33
11.83
L’ ignore within d of face
8.50
8.17
8.67
a
10.17
10.00
10.5
b
5.17
5.00
5.5
W
2880
2870
2950
--------Dead load = WL
2
12240
11719
12783
c, if > d
Live load
94235
92118
94310
Total load
106475
103837
107093
Cross section-sq. in.-nominal size
1372
1344
1536
3 R
Unit shear-lb per sq. in. = --- -----2 bh
116
116
105
Cross section-sq. in.-dressed size
1323
1302
1488
3 R
Unit shear-lb per sq. in. = --- -----2 bh
121
120
108
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-87
Timber Structures
Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact
13 ¢ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
13¢
13¢
13¢
13¢
Number and Size of Stringers
14-7² ´ 16²
12-8² ´ 16²
10-10² ´ 16²
10-9² ´ 18²
Above stringers
2310
2310
2310
2310
Stringers-nominal size
650
640
670
675
2960
2950
2980
2985
Dead load per foot of track
Total dead load
Reaction on bent in pounds
Dead load
38500
38400
38800
38800
Live load
177200
177200
177200
177200
Total
215700
Kind of bent
Number of piles or posts
Size of piles or posts
215600
216000
216000
Pile
Frame
Pile
Frame
Pile
Frame
Pile
7
6
7
6
7
6
7
Frame
6
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Total area of piles or posts-sq. in.
1077
1008
1077
1008
1077
1008
1077
1008
Unit bearing stress on piles or posts-lb per
sq. in.
200
214
200
214
201
214
201
214
Average load in tons per pile or post
15.4
18.0
15.4
18.0
15.4
18.0
15.4
18.0
Bearing-Stringers on caps for continuous butt type deck
Area sq. in.-14² cap
1176
1120
1120
Bearing stress-lb per sq. in.-14² cap
183
192
193
1008
214
Area sq. in.-16² cap
1344
1280
1280
1152
Bearing stress-lb per sq. in.-16² cap
160
168
169
187
56700
Bending in stringers
Dead load moment-foot pounds per track
56200
56000
56600
Live load moment-foot pounds per track
306000
306000
306000
Total load moment-foot pounds per track
362200
362000
362600
306000
Section modulus-nominal size
3580
3410
3410
3890
Bending stress-lb per sq. in.-nominal size
1220
1280
1280
1120
Section modulus-dressed size
3360
3200
3200
3670
Bending stress-lb. per sq. in.-dressed size
1300
1360
1360
1190
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
16
16
16
c to c
13
13
13
18
13
L = (c to c) + 0.5 - 14/12
12.33
12.33
12.33
12.33
L’ ignore within d of face
9.17
9.17
9.17
8.83
a
11.00
11.00
11.00
10.83
b
6.00
6.00
6.00
5.83
W
2960
2950
2980
2985
WL
Dead load = --------2
13567
13521
13658
13184
c, if > d
Live load
96324
96324
96324
94378
Total load
109891
109845
109983
107562
Assumptions:
L=
Distance C to C bents for bearing on caps in feet
=
Distance face to face of caps plus 0.5 foot for stringer
bending and shear. (Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R=
Total Reaction
h=
Height of stringer in feet
b=
Breadth of stringers in feet
P=
Weight on one driving axle = 72000 pounds
a=
Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
In calculating bearing, bending, and shear stresses outer
stringers are considered as carrying no load.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-88
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact
13 ¢ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
13¢
13¢
13¢
13¢
Number and Size of Stringers
14-7² ´ 16²
12-8² ´ 16²
10-10² ´ 16²
10-9² ´ 18²
Cross section-sq. in.-nominal size
1568
1536
1600
1620
RUnit shear-lb per sq. in. = 3
--- ----2 bh
105
107
103
100
Cross section-sq. in.-dressed size
1519
1488
1550
1575
3 R
Unit shear-lb per sq. in. = --- -----2 bh
109
111
106
102
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-89
Timber Structures
Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact
15 ¢ Spans
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
15¢
15¢
15¢
15¢
Number and Size of Stringers
14-8² ´ 16²
12-10² ´ 16²
12-9² ´ 18²
10-10² ´ 18²
Above stringers
2310
2310
2310
2310
Stringers-nominal size
750
800
810
750
3050
3110
3120
3060
Dead load per foot of track
Total dead load
Reaction on bent in pounds
Dead load
46000
46600
46800
46000
Live load
197000
197000
197000
197000
Total
243000
Kind of bent
Number of piles or posts
Size of piles or posts
243600
243800
243000
Pile
Frame
Pile
Frame
Pile
Frame
Pile
7
6
7
6
7
6
7
Frame
6
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
14² D
12´ 14
Total area of piles or posts-sq. in.
1077
1008
1077
1008
1077
1008
1077
1008
Unit bearing stress on piles or posts-lb per
sq. in.
226
241
226
242
226
242
226
241
Average load in tons per pile or post
17.4
20.2
17.4
20.3
17.4
20.3
17.4
20.2
Bearing-Stringers on caps for continuous butt type deck
Area sq. in.-14² cap
1344
1400
1260
Bearing stress-lb per sq. in.-14² cap
181
174
193
1120
217
Area sq. in.-16² cap
1536
1600
1440
1280
Bearing stress-lb per sq. in.-16² cap
158
152
169
190
Bending in stringers
Dead load moment-foot pounds per track
78500
79800
80100
78500
Live load moment-foot pounds per track
415000
415000
415000
415000
Total load moment-foot pounds per track
493500
494800
495100
493500
Section modulus-nominal size
4100
4270
4860
4320
Bending stress-lb per sq. in.-nominal size
1450
1390
1220
1370
Section modulus-dressed size
3840
4000
4600
4080
Bending stress-lb per sq. in.-dressed size
1540
1490
1290
1450
Longitudinal shear-Standard formula-First driver at height of the beam from the support.
Depth nominal
16
16
18
c to c
15
15
15
18
15
L = (c to c) + 0.5 - 14/12
14.33
14.33
14.33
14.33
L’ ignore within d of face
11.17
11.17
10.83
10.83
a
13.00
13.00
12.83
12.83
b
8.00
8.00
7.83
7.83
c, if > d
3.00
3.00
2.83
2.83
W
3050
3110
3120
3060
WL
Dead load = --------2
17029
17364
16900
16575
Live load
116791
116791
114279
114279
Total load
133820
134155
131179
130854
Assumptions:
L=
Distance C to C bents for bearing on caps in feet
=
Distance face to face of caps plus 0.5 foot for stringer
bending and shear. (Assume 14² cap)
W = Total Dead Load per linear foot of track:
Rail and fastenings = 200 pounds per linear foot
Ballast = 120 pounds per cubic foot
R=
Total Reaction
h=
Height of stringer in feet
b=
Breadth of stringers in feet
P=
Weight on one driving axle = 72000 pounds
a=
Distance from load P to support, in feet
Dressed size = Nominal size less 1/2² in depth
In calculating bearing, bending, and shear stresses outer
stringers are considered as carrying no load.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-90
AREMA Manual for Railway Engineering
Appendix 3 - Legacy Designs
Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact
15 ¢ Spans (Continued)
All loads in pounds per track. All moments in foot-pounds per track
Panel Length C to C of Bents
15¢
15¢
15¢
15¢
Number and Size of Stringers
14-8² ´ 16²
12-10² ´ 16²
12-9² ´ 18²
10-10² ´ 18²
Cross section-sq. in.-nominal size
1792
1920
1944
1800
RUnit shear-lb per sq. in. = 3
--- ----2 bh
112
105
101
109
Cross section-sq. in.-dressed size
1736
1860
1890
1750
3 R
Unit shear-lb per sq. in. = --- -----2 bh
116
108
104
112
1
3
4
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
7-A3-91
Timber Structures
A3.4 LEGACY CULVERT DESIGNS
Figure 7-A3-79. Recommended Practice for Design of Wood Culverts, E 72 Loading,
for Heights up to 15 Foot Base of Rail to Flow Line area
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-92
AREMA Manual for Railway Engineering
Size of Boxes and Requirements
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
Table 7-A3-10. Typical Size Boxes and Unit Stresses
Maximum Stress in Timber in lb per square inch
Top and
Bottom
Bending
Holdbacks
Width
W
in
Ft-In.
Height Top and Sides
H
Bottom
B
in
in
in
Ft-In. Inches Inches
2¢ -0²
1¢ -0²
3
3
NONE
2¢ -0²
1¢ -6²
3
4
4´ 4
5
2¢ -0²
2¢ -0²
3
4
4´ 6
2¢ -6²
2¢ -6²
3
4
3¢ -0²
2¢ -0²
4
3¢ -0²
3¢ -0²
3¢ -6²
Size in
Inches
Max
Spacing
Feet
Side Walls
Bearing
Center Wall
Bearing
Holdbacks
Bending
Max Tension in
Bolts lb per Bolt
Number Min
Max
Min
Max
Min
Max
Min
Max
Min
of Bolts Depth Depth Depth Depth Depth Depth Depth Depth Depth
Max
Depth
730
990
60
83
135
183
2
785
1040
48
64
105
139
1033
1450
1800
2540
6
2
785
1020
48
63
105
136
905
1270
2860
4000
4´ 6
5
2
1156
1480
57
73
127
163
1128
1565
2930
4130
4
4´ 6
6
2
901
1170
66
86
151
195
975
1370
2860
4020
4
6
6´ 6
5
3
1000
1240
48
61
105
132
1153
1520
2390
3270
3¢ -6²
6
6
6´ 8
6
3
582
702
55
66
121
145
1078
1440
3360
4550
4¢ -0²
3¢ -0²
6
6
6´ 6
5
3
736
910
61
75
136
169
1217
1650
2390
3240
4¢ -0²
4¢ -0²
6
6
6´ 8
5
3
736
880
61
72
136
163
1140
1525
3200
4300
4¢ -0²
6¢ -0²
6
6
8 ´ 10
5
4
736
816
61
67
136
154
1165
1470
3670
4650
4¢ -6²
4¢ -6²
6
8
8´ 8
6
4
970
1135
53
62
118
138
1273
1680
3260
4320
5¢ -0²
5¢ -0²
6
8
8´ 8
5
4
1170
1345
58
66
129
148
1291
1675
3040
3950
6¢ -0²
6¢ -0²
8
8
8 ´ 10
5
4
912
1010
67
74
152
168
1230
1545
3700
4650
Appendix 3 - Legacy Designs
7-A3-93
Timber Structures
THIS PAGE INTENTIONALLY LEFT BLANK.
© 2011, American Railway Engineering and Maintenance-of-Way Association
7-A3-94
AREMA Manual for Railway Engineering
8
CHAPTER 8
CONCRETE STRUCTURES AND
FOUNDATIONS1
FOREWORD
The material in this chapter is written with regard to typical North American Railroad Concrete Structures and
Foundations and other structures mentioned herein with
• Standard Gage Track,
1
• Normal North American passenger and freight equipment, and
• Speeds of freight trains up to 80 mph and passenger trains up to 90 mph.
Additional special provisions for speeds higher than those listed above may be added by the Engineer as necessary.
This chapter is presented as a consensus document by a committee composed of railroad industry professionals
having substantial and broad-based experience designing, evaluating, and investigating Concrete Structures and
Foundations used by railroads. The recommendations contained herein are based upon past successful usage,
advances in the state of knowledge, and current design and maintenance practices. These recommendations are
intended for routine use and might not provide sufficient criteria for infrequently encountered conditions.
Professional judgement must be exercised when applying the recommendations of this chapter as part of an overall
solution to any particular issue.
This chapter is published annually, incorporating revisions made in the previous year. The latest published edition of
the chapter should be used, regardless of the age of an existing structure. For purposes of determining historical
recommendations under which an existing structure may have been built and maintained, it can prove useful to
examine previous editions of the chapter. However, when historical recommendations differ from the
recommendations contained in the latest published edition of the chapter, the recommendations of the latest
published edition of the chapter should be used.
Part 8, Rigid Frame Concrete Bridges was deleted from the manual in 1975. Part 9, Reinforced Concrete Trestles was
deleted from the manual in 1971. Part 15 is reserved for future use. Part 18, Elastomeric Bridge Bearings was moved
to Chapter 15 in 2001.
1
The material in this and other chapters in the AREMA Manual for Railway Engineering is published as recommended practice to railroads
and others concerned with the engineering, design and construction of railroad fixed properties (except signals and communications), and
allied services and facilities. For the purpose of this Manual, RECOMMENDED PRACTICE is defined as a material, device, design, plan,
specification, principle or practice recommended to the railways for use as required, either exactly as presented or with such modifications as
may be necessary or desirable to meet the needs of individual railways, but in either event, with a view to promoting efficiency and economy in
the location, construction, operation or maintenance of railways. It is not intended to imply that other practices may not be equally acceptable.
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-i
3
TABLE OF CONTENTS
Part/Section
Description
Page
1
Materials, Tests and Construction Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2
Cement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3
Other Cementitious Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4
Aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5
Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6
Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7
Concrete Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.8
Storage of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.9
Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.10 Details of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.11 Concrete Jointing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.12 Proportioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.13 Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14 Depositing Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15 Depositing Concrete Under Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.16 Concrete in Sea Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.17 Concrete in Alkali Soils or Alkali Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.18 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.19 Formed Surface Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.20 Unformed Surface Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.21 Decorative Finishes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.22 Penetrating Water Repellent T reatment of Concrete Surfaces . . . . . . . . . . . . . . . . . . . . . . .
1.23 Repairs and Anchorage Using Reactive Resins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.24 High Strength Concrete (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.25 Specialty Concretes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-1
8-1-6
8-1-8
8-1-9
8-1-11
8-1-16
8-1-16
8-1-19
8-1-19
8-1-21
8-1-24
8-1-27
8-1-31
8-1-38
8-1-39
8-1-44
8-1-47
8-1-48
8-1-49
8-1-52
8-1-53
8-1-54
8-1-54
8-1-56
8-1-57
8-1-58
8-1-60
2
Reinforced Concrete Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2
Notations, Definitions and Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3
Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4
Hooks and Bends. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5
Spacing of Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6
Concrete Protection for Reinforcement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.7
Minimum Reinforcement of Flexural Members (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.8
Distribution of Reinforcement in Flexural Members (2005) . . . . . . . . . . . . . . . . . . . . . . . . .
2.9
Lateral Reinforcement of Flexural Members (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.10 Shear Reinforcement – General Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.11 Limits for Reinforcement of Compression Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.12 Shrinkage and Temperature Reinforcement (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-1
8-2-5
8-2-8
8-2-20
8-2-21
8-2-22
8-2-22
8-2-23
8-2-23
8-2-24
8-2-25
8-2-26
8-2-27
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-ii
AREMA Manual for Railway Engineering
TABLE OF CONTENTS (CONT)
Part/Section
3
4
Description
Page
2.13 Development Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.14 Development Length of Deformed Bars and Deformed Wire in Tension (2005) . . . . . . . . . .
2.15 Development Length of Deformed Bars in Compression (2005). . . . . . . . . . . . . . . . . . . . . . .
2.16 Development Length of Bundled Bars (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.17 Development of Standard Hooks in Tension (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.18 Combination Development Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.19 Development of Welded Wire Fabric in Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.20 Mechanical Anchorage (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.21 Anchorage of Shear Reinforcement (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.22 Splices of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23 Analysis Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.24 Design Methods (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.25 General Requirements (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.26 Allowable Service Load Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.27 Flexure (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.28 Compression Members with or without Flexure (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.29 Shear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.30 Strength Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.31 Design Assumptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.32 Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.33 Compression Members with or without Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.34 Slenderness Effects in Compression Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.35 Shear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.36 Permissible Bearing Stress (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.37 Serviceability Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.38 Fatigue Stress Limit for Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.39 Distribution of Flexural Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.40 Control of Deflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-28
8-2-29
8-2-31
8-2-31
8-2-31
8-2-33
8-2-33
8-2-34
8-2-34
8-2-35
8-2-38
8-2-43
8-2-43
8-2-43
8-2-45
8-2-45
8-2-45
8-2-53
8-2-54
8-2-55
8-2-57
8-2-60
8-2-62
8-2-70
8-2-70
8-2-70
8-2-71
8-2-71
8-2-72
Spread Footing Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2
Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3
Depth of Base of Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4
Sizing of Footings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5
Footings with Eccentric Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6
Footing Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7
Field Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8
Combined Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-3-1
8-3-2
8-3-4
8-3-7
8-3-7
8-3-12
8-3-14
8-3-14
8-3-15
Pile Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2
Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3
Allowable Load on Piles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4
Pile T ypes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5
Installation of Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6
Inspection of Pile Driving (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4-1
8-4-2
8-4-2
8-4-5
8-4-9
8-4-14
8-4-16
8-4-16
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-iii
1
3
4
TABLE OF CONTENTS (CONT)
Part/Section
Description
Page
5
Retaining Walls, Abutments and Piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2
Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3
Computation of Applied Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4
Stability Computation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5
Design of Backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.6
Designing Bridges to Resist Scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.7
Details of Design and Construction for Abutments and Retaining Walls . . . . . . . . . . . . . . .
5.8
Details of Design and Construction for Bridge Piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-1
8-5-2
8-5-4
8-5-5
8-5-7
8-5-8
8-5-9
8-5-11
8-5-12
6
Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2
Design of Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3
Requirements for Reinforced Concrete Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4
Requirements for Metal Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5
Requirements for Timber Crib Walls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-6-1
8-6-2
8-6-2
8-6-3
8-6-5
8-6-6
7
Mechanically Stabilized Embankment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.2
Design of Mechanically Stabilized Embankments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.3
Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-7-1
8-7-2
8-7-2
8-7-3
10 Reinforced Concrete Culvert Pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.4 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-10-1
8-10-2
8-10-3
8-10-4
8-10-12
11 Lining Railway Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.3 Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11.4 Concrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-11-1
8-11-2
8-11-2
8-11-7
8-11-8
12 Cantilever Poles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.3 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-12-1
8-12-2
8-12-2
8-12-2
8-12-3
14 Repair and Rehabilitation of Concrete Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.1 Scope (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2 Determination of the Causes of Concrete Deterioration (2006). . . . . . . . . . . . . . . . . . . . . . .
14.3 Evaluation of the Effects of Deterioration and Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4 Principal Materials Used in the Repair of Concrete Structures . . . . . . . . . . . . . . . . . . . . . .
14.5 Repair Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.6 Repair Methods for Prestressed Members. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-14-1
8-14-3
8-14-3
8-14-4
8-14-5
8-14-7
8-14-22
8-14-25
© 2011, American Railway Engineering and Maintenance-of-Way Association
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TABLE OF CONTENTS (CONT)
Part/Section
Description
Page
16 Design and Construction of Reinforced Concrete Box Culverts . . . . . . . . . . . . . . . . . . .
16.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3 Design Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.4 Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.5 Details of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.6 Manufacture of Precast Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.7 Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-16-1
8-16-2
8-16-4
8-16-6
8-16-7
8-16-13
8-16-16
8-16-17
17 Prestressed Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.1 General Requirements and Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2 Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3 Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.4 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.5 Details of Prestressing Tendons and Ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.6 General Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.7 Expansion and Contraction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.8 Span Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.9 Frames and Continuous Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.10 Effective Flange Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.11 Flange and Web Thickness-Box Girders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.12 Diaphragms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.13 Deflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.14 General Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.15 Load Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.16 Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.17 Loss of Prestress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.18 Flexural Strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.19 Ductility Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.20 Non-Prestressed Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.21 Shear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.22 Post-Tensioned Anchorage Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.23 Pretensioned Anchorage Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.24 Concrete Strength at Stress Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.25 General Detailing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.26 General Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.27 Mortar and Grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.28 Application of Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.29 Materials - Reinforcing Steel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.30 Prestressed Concrete Cap and/or Sill for Timber Pile Trestle (2003) . . . . . . . . . . . . . . . . . .
Commentary (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-17-1
8-17-4
8-17-5
8-17-7
8-17-10
8-17-11
8-17-13
8-17-13
8-17-13
8-17-14
8-17-15
8-17-16
8-17-16
8-17-16
8-17-17
8-17-18
8-17-18
8-17-21
8-17-26
8-17-28
8-17-29
8-17-30
8-17-35
8-17-45
8-17-46
8-17-46
8-17-50
8-17-53
8-17-54
8-17-54
8-17-56
8-17-58
19 Rating of Existing Concrete Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2 Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3 Loads and Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.4 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.5 Load Combinations and Rating Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.6 Excessive Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-19-1
8-19-2
8-19-2
8-19-4
8-19-5
8-19-8
8-19-10
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Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-19-11
20 Flexible Sheet Pile Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20.2 Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20.3 Computation of Lateral Forces Acting on Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20.4 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20.5 Design of Anchored Bulkheads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20.6 Cantilever Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20.7 Notations (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-20-1
8-20-2
8-20-3
8-20-5
8-20-9
8-20-10
8-20-13
8-20-15
8-20-16
21 Inspection of Concrete and Masonry Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21.1 General (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21.2 Reporting of Defects (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21.3 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-21-1
8-21-1
8-21-2
8-21-2
8-21-20
22 Geotechnical Subsurface Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.1 General (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.2 Scope (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.3 Classification of Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.4 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.5 Exploration Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.6 Determination of Groundwater Level (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.7 Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.8 Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.9 Inspection (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.10 Geophysical Explorations (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.11 In-Situ Testing of Soil (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.12 Backfilling Bore Holes (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22.13 Cleaning Site (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-22-1
8-22-2
8-22-2
8-22-2
8-22-3
8-22-5
8-22-6
8-22-6
8-22-7
8-22-9
8-22-9
8-22-10
8-22-10
8-22-10
23 Pier Protection Systems at Spans Over Navigable Streams. . . . . . . . . . . . . . . . . . . . . . .
23.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.2 Special Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23.4 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Commentary (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-23-1
8-23-2
8-23-3
8-23-4
8-23-20
8-23-24
24 Drilled Shaft Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24.2 Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24.4 Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24.5 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24.6 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C - Commentary (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-24-1
8-24-2
8-24-5
8-24-5
8-24-9
8-24-9
8-24-12
8-24-13
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25 Slurry Wall Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25.3 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25.4 Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-25-1
8-25-2
8-25-3
8-25-7
8-25-10
26 Recommendations for the Design of Segmental Bridges . . . . . . . . . . . . . . . . . . . . . . . . .
26.1 General Requirements and Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.2 Methods of Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.3 Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.4 Load Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.5 Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.6 Prestress Losses (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.7 Flexural Strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.8 Shear and Torsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.9 Fatigue Stress Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.10 Design of Local and General Anchorage Zones, Anchorage Blisters and Deviation Saddles
26.11 Provisional Post-Tensioning Ducts and Anchorages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.12 Duct Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.13 Couplers (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.14 Connection of Secondary Beams (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.15 Concrete Cover and Reinforcement Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.16 Inspection Access (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26.17 Box Girder Cross Section Dimensions and Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-26-1
8-26-4
8-26-8
8-26-12
8-26-16
8-26-21
8-26-22
8-26-23
8-26-23
8-26-32
8-26-33
8-26-36
8-26-37
8-26-39
8-26-39
8-26-41
8-26-41
8-26-41
8-26-42
27 Concrete Slab Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27.1 Scope and Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27.2 Application and Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27.3 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27.4 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27.5 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27.6 Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27.7 Direct Fixation Fastening System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27.8 Special Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-27-1
8-27-3
8-27-3
8-27-6
8-27-7
8-27-8
8-27-10
8-27-15
8-27-18
8-27-26
28 Temporary Structures for Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28.2 Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28.3 Computation of Lateral Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28.4 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28.5 Design of Shoring Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
28.6 Design of Falsework Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-28-1
8-28-2
8-28-4
8-28-5
8-28-5
8-28-5
8-28-14
8-28-20
29 Waterproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.1 General Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.2 Waterproofing (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-29-1
8-29-4
8-29-4
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29.3 Dampproofing (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.4 Specific Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.5 Terms (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.6 Applicable ASTM Designations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.7 General Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.8 Primers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.9 Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.10 Membrane Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.11 Sealing Compounds for Joints and Edges of Membrane Protection (2001) . . . . . . . . . . . . .
29.12 Anti-Bonding Paper (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.13 Inspection and Tests (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.14 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.15 Introduction to Damproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.16 Materials for Damproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29.17 Application of Damproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C - Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-29-5
8-29-5
8-29-8
8-29-8
8-29-12
8-29-13
8-29-14
8-29-17
8-29-20
8-29-20
8-29-20
8-29-20
8-29-28
8-29-28
8-29-29
8-29-30
Chapter 8 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-G-1
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-R-1
INTRODUCTION
The Chapters of the AREMA Manual are divided into numbered Parts, each comprised of related documents
(specifications, recommended practices, plans, etc.). Individual Parts are divided into Sections by centered headings
set in capital letters and identified by a Section number. These Sections are subdivided into Articles designated by
numbered side headings.
Page Numbers – In the page numbering of the Manual (8-2-1, for example) the first numeral designates the Chapter
number, the second denotes the Part number in the Chapter, and the third numeral designates the page number in
the Part. Thus, 8-2-1 means Chapter 8, Part 2, page 1.
In the Glossary and References, the Part number is replaced by either a “G” for Glossary or “R” for References.
Document Dates – The bold type date (Document Date) at the beginning of each document (Part) applies to the
document as a whole and designates the year in which revisions were last made somewhere in the document, unless
an attached footnote indicates that the document was adopted, reapproved, or rewritten in that year.
Article Dates – Each Article shows the date (in parenthesis) of the last time that Article was modified.
Revision Marks – All current year revisions (changes and additions) which have been incorporated into the
document are identified by a vertical line along the outside margin of the page, directly beside the modified
information.
Proceedings Footnote – The Proceedings footnote on the first page of each document gives references to all
Association action with respect to the document.
Annual Updates – New manuals, as well as revision sets, will be printed and issued yearly.
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-viii
AREMA Manual for Railway Engineering
8
Part 1
Materials, Tests and Construction Requirements1
— 2011 —
TABLE OF CONTENTS
Section/Article
Description
Page
1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.1 Purpose (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.2 Scope (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.3 Terms (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.4 Acceptability (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.5 ASTM - International (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.6 Selection of Materials (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.7 Test of Materials (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.8 Defective Materials (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1.9 Equipment (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-6
8-1-6
8-1-6
8-1-6
8-1-7
8-1-7
8-1-7
8-1-7
8-1-7
8-1-7
1.2 Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2.1 General (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2.2 Specifications (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2.3 Quality, Sampling and Testing (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-8
8-1-8
8-1-8
8-1-9
1.3 Other Cementitious Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3.1 General (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3.2 Acceptability (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3.3 Specifications (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3.4 Materials Not Included in This Recommended Practice (2004) . . . . . . . . . . . . . . . . . . . . .
1.3.5 Documentation (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-9
8-1-9
8-1-9
8-1-10
8-1-10
8-1-10
1.4 Aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.1 General (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.2 Fine Aggregates (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.3 Normal Weight Coarse Aggregate (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-11
8-1-11
8-1-12
8-1-14
1
References, Vol. 3, 1902, p. 311; Vol. 4, 1903, pp. 336,397; Vol. 5, 1904, pp. 605,610; Vol. 6, 1905, pp. 704,726; Vol. 11, 1910, p. 956; Vol. 13,
1912, pp. 333, 1564; Vol. 24, 1923, pp. 478, 1324; Vol. 28, 1927, pp. 1056, 1436; Vol. 29, 1928, pp. 607, 1399; Vol. 30, 1929, pp. 783, 1461;
Vol. 31, 1930, pp. 1148, 1737; Vol. 32, 1931, pp. 330, 796; Vol. 33, 1932, pp. 622, 732; Vol. 34, 1933, pp. 578, 868; Vol. 35, 1934, pp. 953,
1130; Vol. 36, 1935, pp. 843, 1018; Vol. 37, 1936, pp. 632, 1040; Vol. 39, 1938, pp. 136, 332; Vol. 45, pp. 227, 642; Vol. 54, 1953, pp. 793,
1341; Vol. 56, 1955, pp. 436, 1084; Vol. 58, 1957, pp. 650, 1182; Vol. 59, 1958, pp. 637, 1970, p. 230; Vol. 72, 1971, p. 136; Vol. 74, 1973, p.
138; Vol. 75, 1974, p. 465; Vol. 78, 1977, p. 108; Vol. 83, 1982, p. 285; Vol. 92, 1991, p. 62; Vol. 93, 1992, p. 78; Vol. 96, p. 55; Vol. 97, p. 57.
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-1-1
1
3
Concrete Structures and Foundations
TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
Lightweight Coarse Aggregate for Structural Concrete (2004) . . . . . . . . . . . . . . . . . . . . .
8-1-15
1.5 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5.1 General (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-16
8-1-16
1.6 Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6.1 General (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6.2 Welding (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6.3 Specifications (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6.4 Bending and Straightening (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-16
8-1-16
8-1-16
8-1-16
8-1-18
1.7 Concrete Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.1 General (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7.2 Types of Admixtures and Standard Specifications (2004) . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-19
8-1-19
8-1-19
1.8 Storage of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.8.1 Cementitious Materials and Concrete Admixtures (2009). . . . . . . . . . . . . . . . . . . . . . . . .
1.8.2 Aggregates (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.8.3 Reinforcement (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-19
8-1-19
8-1-20
8-1-20
1.9 Forms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.9.1 General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.9.2 Safety (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.9.3 Design (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.9.4 Construction (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.9.5 Moldings (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.9.6 Form Coating and Release (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.9.7 Temporary Openings (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.9.8 Removal (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-21
8-1-21
8-1-21
8-1-21
8-1-22
8-1-22
8-1-22
8-1-23
8-1-23
1.10 Details of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.10.1 Surface Conditions of Reinforcement (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.10.2 Fabrication (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.10.3 Provisions for Seismic Loading (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.10.4 Placing of Reinforcement (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.10.5 Spacing of Reinforcement (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.10.6 Concrete Protection for Reinforcement (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.10.7 Future Bonding (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-24
8-1-24
8-1-24
8-1-24
8-1-24
8-1-26
8-1-26
8-1-27
1.11 Concrete Jointing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.11.1 Scope (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.11.2 Types of Jointing (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.11.3 Expansion Joints (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.11.4 Expansion Joints in Walls (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.11.5 Contraction Joints (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.11.6 Construction Joints (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.11.7 Watertight Construction Joints (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-27
8-1-27
8-1-27
8-1-27
8-1-28
8-1-28
8-1-29
8-1-29
1.12 Proportioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.12.1 General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-31
8-1-31
1.4.4
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-1-2
AREMA Manual for Railway Engineering
Materials, Tests and Construction Requirements
TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
1.12.2 Measurement of Materials (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-31
1.12.3 Water-Cementitious Materials Ratio (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-31
1.12.4 Air Content of Air-Entrained Concrete (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-32
1.12.5 Strength of Concrete Mixtures (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-33
1.12.6 Workability (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-35
1.12.7 Slump (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-35
1.12.8 Compression Tests (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-35
1.12.9 Field Tests (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-35
1.12.10 Special Provisions When Using Cementitious Materials Other Than Portland Cement
(2009 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1- 36
1.13 Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.13.1 General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.13.2 Site-Mixed Concrete (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.13.3 Ready-Mixed Concrete (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.13.4 Delivery (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.13.5 Requirements When Using Silica Fume in Concrete (2009). . . . . . . . . . . . . . . . . . . . . . . .
8-1-38
8-1-38
8-1-38
8-1-39
8-1-39
8-1-39
1.14 Depositing Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.1 General (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.2 Handling and Placing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.3 Chuting (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.4 Pneumatic Placing (Shotcreting) (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.5 Pumping Concrete (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.6 Compacting (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.7 Temperature (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.8 Continuous Depositing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.9 Bonding (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.10 Placing Cyclopean Concrete (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.11 Placing Rubble Concrete (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.12 Placing Concrete Containing Silica Fume (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.13 Placing Concrete Containing Fly Ash (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.14.14 Water Gain (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-39
8-1-39
8-1-40
8-1-40
8-1-40
8-1-41
8-1-41
8-1-42
8-1-42
8-1-42
8-1-43
8-1-43
8-1-43
8-1-43
8-1-43
1.15 Depositing Concrete Under Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.1 General (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.2 Capacity of Plant (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.3 Standard Specifications (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.4 Cement (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.5 Coarse Aggregates (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.6 Mixing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.7 Caissons, Cofferdams or Forms (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.8 Leveling and Cleaning the Bottom to Receive Concrete (1993) . . . . . . . . . . . . . . . . . . . . .
1.15.9 Continuous Work (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.10 Methods of Depositing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.11 Soundings (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.12 Removing Laitance (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.15.13 Concrete Seals (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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8-1-44
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8-1-44
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8-1-45
8-1-45
8-1-45
8-1-46
8-1-46
8-1-46
1.16 Concrete in Sea Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Section/Article
Description
Page
Concrete (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Depositing in Sea Water (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Construction Joints (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Minimum Cover (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Protecting Concrete in Sea Water (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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8-1-47
8-1-47
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1.17 Concrete in Alkali Soils or Alkali Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.17.1 Condition of Exposure (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.17.2 Concrete for Moderate Exposure (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.17.3 Concrete for Severe Exposure (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.17.4 Concrete for Very Severe Exposure (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.17.6 Construction Joints (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.17.7 Minimum Cover (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.17.8 Placement of Concrete (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1.18 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.18.1 General (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.18.2 Hot Weather Curing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.18.3 Wet Curing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.18.4 Membrane Curing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.18.5 Steam Curing (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.18.6 Curing Concrete Containing Silica Fume (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.18.7 Curing Concrete Containing Ground Granulated Blast-Furnace Slag (2004) . . . . . . . . .
1.18.8 Curing Concrete Containing Fly Ash (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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8-1-51
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1.19 Formed Surface Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.19.1 General (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.19.2 Rubbed Finish (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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8-1-53
1.20 Unformed Surface Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.20.1 General (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.20.2 Sidewalk Finish (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.20.3 Finishing Concrete Containing Silica Fume (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.20.4 Finishing Concrete Containing Ground Granulated Blast-Furnace Slag (2004) . . . . . . .
1.20.5 Finishing Concrete Containing Fly Ash (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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8-1-53
8-1-53
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1.21 Decorative Finishes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-54
1.22 Penetrating Water Repellent Treatment of Concrete Surfaces. . . . . . . . . . . . . . . . . . .
1.22.1 General (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.22.2 Surface Preparation (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.22.3 Environmental Requirements (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.22.4 Application (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.22.5 Materials (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.22.6 Quality Assurance (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.22.7 Delivery, Storage and Handling (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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8-1-54
8-1-54
8-1-54
8-1-55
8-1-55
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8-1-56
1.23 Repairs and Anchorage Using Reactive Resins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.23.1 General (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1.16.1
1.16.2
1.16.3
1.16.4
1.16.5
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TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
1.23.2 Surface Preparation (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.23.3 Application (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1.24 High Strength Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.24.1 General (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.24.2 Materials (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.24.3 Concrete Mixture Proportions (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1.25 Specialty Concretes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.25.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.25.2 Sulfur Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.25.3 Heavyweight Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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8-1-58
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8-1-59
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-60
LIST OF FIGURES
Figure
Description
Page
8-1-1
8-1-2
8-1-3
Full-Depth Expansion Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Two Methods for Making Contraction Joints for Slabs-on-Grade . . . . . . . . . . . . . . . . . . . . . . .
Keyed Construction Joint with Waterstop Inserted Perpendicular to the Plane of the Joint .
8-1-28
8-1-30
8-1-30
1
LIST OF TABLES
Table
Description
Page
8-1-1
8-1-2
8-1-3
8-1-4
8-1-5
8-1-6
8-1-7
8-1-8
8-1-9
Portland Cement ASTM C150 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Blended Hydraulic Cements ASTM C595. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sampling and Testing Methods in Addition to those of ASTM C33 . . . . . . . . . . . . . . . . . . . . . .
Aggregate Soundness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fine Aggregate Grading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Deleterious Substances in Fine Aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ASTM Specifications for Reinforcement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ASTM Specifications for Coated Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Maximum Permissible Water-Cementitious Materials Ratio (by Weight)
for Different Types of Structures and Degrees of Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air-Entrained Concrete Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Water-Cementitious Materials Ratio for Air Entrained Concrete . . . . . . . . . . . . . . . . . . . . . . .
Concrete Exposed to Deicing Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Concrete Temperature Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommendations For Concrete In Sulfate Exposures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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8-1-9
8-1-11
8-1-12
8-1-13
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8-1-17
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SECTION 1.1 GENERAL
1.1.1 PURPOSE (2004)
This recommended practice is for work carried out by the Company or by Contractors for the Company when so
requested by the Engineer.
1.1.2 SCOPE (2004)
This recommended practice describes the selection, sampling and testing of materials to be used, the
composition of concrete, and the mixing, transporting, placing, finishing and curing of concrete. This
recommended practice shall govern whenever it is in conflict with other cited references.
1.1.3 TERMS (2006)
Following is a list of terms associated with this Part. These terms are defined in the Glossary located at the end
of this Chapter.
AASHTO
Absorption
ACI International
Admixture
Admixture, Accelerating
Admixture, Air-Entraining
Admixture, Retarding
Admixture, Water Reducing
Admixture, Water Reducing (High Range)
Admixture, Water Reducing and Accelerating
Admixture, Water Reducing and Retarding
Agent, Bonding
Aggregate
Air, Entrained
Approved or Approval
ASTM - International
Blast-Furnace Slag
Blast-Furnace Slag, Ground Granulated
Bleeding
Cement, Blended
Cement, Hydraulic
Cement, Slag
Cementitious
Centering
Company
Compound, Curing
Concrete
Concrete, Cyclopean
Concrete, Polymer
Concrete, Polymer Cement
Concrete, Structural Lightweight
Contractor
Engineer
Falsework
FHWA
Fly Ash
Form / Formwork
Honeycomb
Joint, Expansion
Laitance
Modulus, Fineness
PCI
Plans
Plasticizer
Pozzolan
Reinforcement
Reinforcement, Deformed
Reinforcement, Plain
Resistance, Chemical
Shore / Shoring
Sieve
Sieve Analysis
Sieve Number
Silica Fume
Slump
Soundness
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Strength, Compressive
Superplasticizer
USDOT
Water Absorption
Water-Cementitious Material Ratio
1.1.4 ACCEPTABILITY (2004)
a.
Concrete shall be proportioned, mixed, transported, placed and cured by the methods herein
recommended.
b. All materials used in the work shall be subject to the approval of the Engineer who shall be the sole judge
of their quality, suitability, and acceptability as to type. The Engineer shall be notified in advance
whenever any phase of the work is to begin.
1.1.5 ASTM - INTERNATIONAL (2004)
Whenever reference is made to the ASTM - International (ASTM), the letter ‘M’ indicating a metric edition and
the number indicating the year of issue are omitted from the designation. The latest issue of the referenced
designation is to be used in each case.
1.1.6 SELECTION OF MATERIALS (2004)
The concrete materials shall be selected for strength, durability and chemical resistance, and ability to attain
specified properties as required, in accordance with this recommended practice and as approved by the
Engineer. They shall be combined in such a manner as to produce uniformity of color and texture in the surface
of any structure or group of structures in which they are to be used. No change shall be made in the brand,
type, source or characteristics of cementitious materials, the character and source of aggregate or water, or the
class of concrete and method of transporting, placing, finishing or curing without approval of the Engineer.
1
1.1.7 TEST OF MATERIALS (2004)
3
a.
The Engineer shall have the right to order testing of any materials used in concrete construction to
determine if they are of the quality specified.
b. Tests of materials and concrete shall be made in accordance with appropriate standards of the ASTM International as specified.
c.
Pre-construction tests shall be carried out on cementitious materials, other than portland cement, as
indicated in this recommended practice.
1.1.8 DEFECTIVE MATERIALS (2004)
All materials of any kind rejected by the Engineer shall be immediately removed from the site and any work
affected by the defective material shall be remedied by the Contractor at his own expense and to the
satisfaction of the Engineer.
1.1.9 EQUIPMENT (2004)
The Contractor shall provide all equipment required for the work, including all staging, scaffolding, apparatus,
tools, etc., as necessary. All equipment must be approved by the Engineer who may require the removal of any
piece of equipment. The Contractor shall substitute satisfactory equipment to replace rejected equipment
without delay. Upon request, the Contractor shall furnish for approval a statement of methods and equipment
proposed for use in all aspects of the work. Exercise of this approval by the Engineer shall not relieve the
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Contractor of his sole responsibility for the safe, adequate and lawful construction, maintenance and use of
such methods and equipment.
SECTION 1.2 CEMENT
1.2.1 GENERAL (2004)
Cement shall be furnished by the Contractor or the Company as provided for in the contract. Cement used in
the work shall be the same as that required by the mix design.
1.2.2 SPECIFICATIONS (2004)1
a.
Cement shall conform to one of the following Standard Specifications except as modified in this Chapter.
(1) ASTM C150 Standard Specification for Portland Cement as shown in Table 8-1-1
(2) ASTM C595 Standard Specification for Blended Hydraulic Cements as shown in Table 8-1-2
b. The use of slag cement Types ‘S’ and ‘S(A)’ as defined in ASTM C595 are not included in this
recommended practice.
c.
Refer also to Section 1.3 Other Cementitious Materials.
Table 8-1-1. Portland Cement ASTM C150
Type
1
Description
Type I
For use when the special properties specified for any other type are not required.
Type IA
Air-entraining cement for the same uses as Type I, where air-entrainment is desired.
Type II
For general use, especially when moderate sulfate resistance, or moderate heat of
hydration is desired.
Type IIA
Air-entraining cement for the same uses as Type II, where air-entrainment is desired.
Type III
For use when high early strength is desired.
Type IIIA
Air-entraining cement for the same use as Type III, where air-entrainment is desired.
Type IV
For use when a low heat of hydration is desired.
Type V
For use when high sulfate resistance is desired.
See C - Commentary
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Table 8-1-2. Blended Hydraulic Cements ASTM C595
Type
Description
Portland Blast-Furnace Slag Cement
Type IS
Portland blast-furnace slag cement for use in general concrete construction.
Type IS( )
Modified sulfate resistant (MS), air-entrainment (A), or moderate heat of hydration (MH),
or any combination may be specified by adding the appropriate suffixes.
Portland-Pozzolan Cement
Type IP
Portland-pozzolan cement for use in general concrete construction.
Type IP( )
Moderate sulfate resistance (MS), air-entrainment (A), or moderate heat of hydration
(MH), or any combination may be specified by adding the appropriate suffixes.
Type P
Portland-pozzolan cement for use in concrete construction where high early strengths are
not required.
Type P( )
Modified sulfate resistance (MS), air-entrainment (A), or low heat of hydration (LH), or
any combination may be specified by adding the appropriate suffixes.
Pozzolan-Modified Portland Cement
Type I(PM)
Pozzolan-modified portland cement for use in general concrete construction.
Type I(PM)( ) Modified sulfate resistance (MS), air-entrainment (A), or moderate heat of hydration (MH),
or any combination may be specified by adding the appropriate suffixes.
1
Slag-Modified Portland Cement
Type I(SM)
Cement for use in general concrete construction.
Type I(SM)( ) Modified sulfate resistance (MS), air-entrainment (A), or moderate heat of hydration (MH),
or any combination may be specified by adding the appropriate suffixes.
3
1.2.3 QUALITY, SAMPLING AND TESTING (2004)
The quality of the cement and the methods of sampling and testing shall meet the requirements of the
appropriate ASTM Standard Specification or Method of Test.
4
SECTION 1.3 OTHER CEMENTITIOUS MATERIALS
1.3.1 GENERAL (2004)
When using cementitious materials other than portland cement, reference should also be made to the
provisions of Section 1.12 Proportioning; Section 1.13 Mixing; Section 1.14 Depositing Concrete; Section 1.16
Concrete in Sea Water; Section 1.17 Concrete in Alkali Soils or Alkali Water; Section 1.18 Curing; and Section
1.20 Unformed Surface Finish.
1.3.2 ACCEPTABILITY (2004)
Cementitious materials other than portland cement will be permitted only if approved in writing by the
Engineer of the Railroad Company.
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1.3.3 SPECIFICATIONS (2004)1
The specifications listed in Articles 1.3.3.1 and 1.3.3.2 apply to the use of other cementitious materials, either
supplied in blended form with portland cement or added separately at the time of mixing.
1.3.3.1 ASTM C595 Standard Specification for Blended Hydraulic Cements; and ASTM C618 Standard
Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland
Cement Concrete, and the following:
a.
Silica Fume - ASTM C1240 Standard Specification for Silica Fume for Use in Hydraulic-Cement
Concrete, Mortar, and Grout, of the following types:
(1) As-produced silica fume -- in its original form of an extremely fine powder
(2) Slurried silica fume -- in a water base, containing 40 to 60% silica fume by mass
(3) Densified silica fume -- a compacted form of as-produced silica fume
b. Fly Ash - ASTM C618 Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for
Use as a Mineral Admixture in Concrete, of the following Classes:
(1) Class F -- Normally produced from high energy coals such as bituminous and anthracite coals, but
sometimes produced with sub-bituminous and lignite coals
(2) Class C -- Normally produced from sub-bituminous and lignite coals
(3) Class N – Natural materials such as highly reactive volcanic ash, metakaolin (and other calcined
clays), diatomaceous earths, calcined shales, and other reactive materials
1.3.3.2 Ground Granulated Blast-Furnace Slag - ASTM C989 Standard Specification for Ground Granulated
Iron Blast-Furnace Slag for Use in Concrete and Mortars.
1.3.4 MATERIALS NOT INCLUDED IN THIS RECOMMENDED PRACTICE (2004)
The following materials are not included in this recommended practice:
a.
Pelletized silica fume -- consisting of hard pellets, not presently being used as an additive for concrete.
b. Types of slag not produced in the iron making process.
c.
Types ‘S’ and ‘S(A)’ blended hydraulic cements containing ground granulated blast-furnace slag, as
defined in ASTM C595.
d. Blended cements containing ground granulated blast-furnace slag blended with hydrated lime.
1.3.5 DOCUMENTATION (2004)
a.
Each shipment of fly ash or silica fume or ground granulated blast-furnace slag used on a project shall
have a certificate of compliance which includes the following:
(1) Name of supplier
1
See C - Commentary
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(2) Consignee and destination of the shipment
(3) Vehicle identification number
(4) A unique unrepeated order number or other identification number for each shipment
(5) Source
b. Each shipment of fly ash shall also include a certificate of compliance indicating the Class (either Class C
or Class F), with certified test numbers demonstrating that the material meets ASTM C618.
c.
Each shipment of silica fume shall also include a certificate of compliance demonstrating that it meets
the requirements of ASTM C1240.
d. Each shipment of ground granulated blast-furnace slag shall also include a certificate of compliance
indicating its grade (either Grade 80, 100 or 120), with certified test numbers demonstrating that it
meets the requirements of ASTM C989.
SECTION 1.4 AGGREGATES
1.4.1 GENERAL (2004)
1
1.4.1.1 Specifications
Except as specified otherwise herein, all aggregates shall conform to the requirements of ASTM C33, Standard
Specification for Concrete Aggregates.
3
1.4.1.2 Sampling and Testing
a.
Representative samples shall be selected and sent to the testing laboratory at frequent intervals as
directed by the Engineer. Aggregates may not be used until the samples have been tested by the
laboratory and approved by the Engineer.
b. Sampling and testing shall be in accordance with ASTM C33 and the Standard Specifications and
Methods of Test of ASTM - International found in Table 8-1-3.
4
Table 8-1-3. Sampling and Testing Methods in Addition to those of ASTM C33
Type
c.
ASTM
Designation
Surface Moisture in Fine Aggregate
C70
Specific Gravity and Absorption of Coarse Aggregate
C127
Specific Gravity and Absorption of Fine Aggregate
C128
Standard Sand
C778
The required tests shall be made on test samples that comply with requirements of the designated test
methods and are representative of the grading that will be used in the concrete. The same test sample
may be used for sieve analysis and for determination of material finer than the No. 200 (75 mm) sieve.
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Separated sizes from the sieve analysis may be used in preparation of samples for soundness or abrasion
tests. For determination of all other tests and for evaluation of potential alkali reactivity where required,
independent test samples shall be used.
d. The fineness modulus of an aggregate is the sum of the percentages of a sample retained on each of a
specified series of sieves divided by 100, using the following standard sieve sizes: No. 100, No. 50, No. 30,
No. 16, No. 8, No. 4, 3/8 inch, 3/4 inch, 1-1/2 inches (150 mm, 300 mm, 600 mm, 1.18 mm, 2.36 mm, 4.75
mm, 9.5 mm, 19.0 mm, 37.5 mm) and larger, increasing in the ratio of 2 to 1. Sieving shall be done in
accordance with ASTM Method C136.
1.4.1.3 Soundness
a.
Except as provided in Paragraph 1.4.1.3(b), aggregate subjected to five cycles of ASTM C88 Soundness of
Aggregates by Use of Sodium Sulfate or Magnesium Sulfate shall show a loss weighed in accordance with
the grading procedures, not greater than the percentages found in Table 8-1-4.
Table 8-1-4. Aggregate Soundness
Aggregate
Sodium Sulfate
Magnesium Sulfate
Fine
10
15
Coarse
12
18
b. Aggregate failing to meet the requirements of Paragraph 1.4.1.3(a) may be accepted provided that
concrete of comparable properties, made with similar aggregate from the same source, has given
satisfactory service when exposed to weathering similar to that to be encountered.
1.4.2 FINE AGGREGATES (2004)
1.4.2.1 General1
Fine aggregate shall consist of natural sand or, subject to the approval of the Engineer, manufactured sand with
similar characteristics. Lightweight fine aggregate shall not be used.
1.4.2.2 Grading
a.
1
Sieve Analysis–Fine aggregate, except as provided in ASTM C33, shall be graded within the limits found
in Table 8-1-5.
See C - Commentary
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Table 8-1-5. Fine Aggregate Grading
Sieve Size
Total Passing
Percentage by
Weight
3/8 inch (9.5 mm)
100
No. 4 (4.75 mm)
95-100
No. 8 (2.36 mm)
80-100
No. 16 (1.18 mm)
50-85
No. 30 (600 mm)
25-60
No. 50 (300 mm)
10-30
No. 100 (150 mm)
2-10
No. 200 (75 mm)
zero
b. The minimum percentages shown above for material passing the No. 50 (300 mm) and No. 100 (150 mm)
sieves may be reduced to 5 and 0, respectively, if the aggregate is to be used in air-entrained concrete
containing more than 420 lb of cement per cubic yard (250 kg per cubic meter), or in non-air-entrained
concrete containing more than 520 lb of cement per cubic yard (310 kg per cubic meter). Air-entrained
concrete is here considered to be concrete containing air-entraining cement or an air-entraining
admixture and having an air content of more than 3%.
c.
The fine aggregate shall have not more than 45% retained between any two consecutive sieves of those
shown in Table 8-1-5 and its fineness modulus shall be not less than 2.3 nor more than 3.1.
d. For walls and other locations where smooth surfaces are desired, the fine aggregate shall be graded
within the limits shown in Table 8-1-5, except that not less than 15% shall pass the No. 50 (300 mm) sieve
and not less than 3% shall pass the No. 100 (150 mm) sieve.
e.
To provide the uniform grading of fine aggregate, a preliminary sample representative of the material to
be furnished shall be submitted at least 10 days prior to actual deliveries. Any shipment made during
progress of the work which varies by more than 0.2 from the fineness modulus of the preliminary sample
shall be rejected or, at the option of the Engineer, may be accepted provided that suitable adjustments
are made in concrete proportions to compensate for the difference in grading.
f.
The percentages listed above do not apply when using pozzolans or ground granulated blast-furnace slag.
Such percentages shall be determined by tests as outlined in this recommended practice.
1.4.2.3 Mortar Strength
Fine aggregate shall be of such quality that when made into a mortar and subjected to the mortar strength test
prescribed in ASTM C87, the mortar shall develop a compressive strength not less than that developed by a
mortar prepared in the same manner with the same cementitious materials and graded standard sand having a
fineness modulus of 2.40±0.10. The graded sand shall conform to the requirements of ASTM C778.
1.4.2.4 Deleterious Substances
a.
The amount of deleterious substances in fine aggregate shall not exceed the limits found in Table 8-16.
b. A fine aggregate failing the test for organic impurities may be used provided that, when tested for
mortar-making properties, the mortar develops a compressive strength at 7 and 28 days of not less than
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3
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Table 8-1-6. Deleterious Substances in Fine Aggregate
Item
Maximum Limit
Percentage by Weight
Clay Lumps
1.0
Coal and Lignite
0.5 (Note 1)
Material finer than No. 200 sieve (75 mm):
Concrete subject to abrasion
All other classes of concrete
3.0 (Note 2)
5.0 (Note 2)
Note 1: Does not apply to manufactured sand produced from blast-furnace slag.
Note 2: For manufactured sand, if the material finer than the No. 200 (75 mm) sieve
consists of the dust of fracture, essentially free from clay or shale, these limits do
not apply.
95% of that developed in a similar mortar made from another portion of the same sample which has been
washed in a 3% solution of sodium hydroxide followed by thorough rinsing in water. The treatment shall
be sufficient so that the test of the washed material made in accordance with ASTM C40 will have a color
lighter than the standard color solution.
c.
Fine aggregate for use in concrete that will be subject to wetting, extended exposure to humid
atmosphere, or contact with moist ground shall not contain any materials that are deleteriously reactive
with the alkalies in the cement in an amount sufficient to cause excessive expansion of mortar or
concrete, except that if such materials are present in injurious amounts, the fine aggregate may be used
with a cement containing less than 0.6% alkalies as measured by percentage of sodium oxide plus 0.658
times percentage of potassium oxide, or with the addition of a material that has been shown to prevent
harmful expansion due to the alkali-aggregate reaction.
1.4.3 NORMAL WEIGHT COARSE AGGREGATE (2004)
1.4.3.1 General
a.
Coarse aggregate shall consist of crushed stone, gravel, crushed slag, or a combination thereof or, subject
to the approval of the Engineer, other inert materials with similar characteristics, having hard, strong
durable pieces, free from adherent coatings, and shall conform to the requirements of ASTM C33 except
as required by this Part.
b. Crushed slag shall be rough cubical fragments of air-cooled blast-furnace slag, which when graded as it is
to be used in the concrete, shall have a compact weight of not less than 70 lb per cubic foot (1100 kg per
cubic meter). It shall be obtained only from sources approved by the Engineer.
1.4.3.2 Grading
a.
Coarse aggregate shall be graded between the limits specified by ASTM C33.
b. The maximum size of aggregate shall be not larger than one-fifth of the narrowest dimension between
forms of the member for which concrete is used, nor larger than one-half of the minimum clear space
between reinforcing bars, except as provided for precast concrete in Section 2.5.
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1.4.3.3 Deleterious Substances
a.
The amount of deleterious substances in coarse aggregate shall not exceed the limits found in
ASTM C33.
1.4.3.4 Abrasion Loss
Coarse aggregate to be used in concrete when subjected to test for resistance to abrasion (ASTM C535 or ASTM
C131) shall show a loss of weight not more than the following:
a.
For concrete subject to severe abrasion such as concrete in water, precast concrete piles, paving for
sidewalks, platforms or roadways, floor wearing surfaces, and concrete cross or bridge ties, the loss of
weight shall not exceed 40%.
b. For concrete subject to medium abrasion such as concrete exposed to the weather, the loss of weight shall
not exceed 50%.
c.
For concrete not subject to abrasion, the loss in weight shall not exceed 60%.
1.4.3.5 Rubble Aggregate
Rubble aggregate shall consist of clean, hard, durable stone retained on a 6-inch (150 mm) square opening and
with individual pieces weighing not more than 100 lb (45 kg).
1
1.4.3.6 Cyclopean Aggregate
Cyclopean aggregate shall consist of clean, hard, durable stone with individual pieces weighing more than 100
lb (45 kg).
1.4.4 LIGHTWEIGHT COARSE AGGREGATE FOR STRUCTURAL CONCRETE (2004)
3
1.4.4.1 Scope
a.
This recommended practice covers lightweight coarse aggregates intended for use in lightweight
concrete in which prime considerations are durability, compressive strength, and light weight. Structural
lightweight concrete shall only be used where shown on the plans or specified.
b. Aggregates for use in non-structural concrete such as fireproofing and fill, and for concrete construction
where capacity is based on load tests rather than conventional design procedures, are not included in
this recommended practice.
1.4.4.2 General Characteristics
The aggregates shall conform to the requirements of ASTM C330 Standard Specifications for Lightweight
Aggregates for Structural Concrete, except as otherwise specified herein.
1.4.4.3 Unit Weight (Mass Density)
a.
The dry weight (mass density) of lightweight aggregates shall not exceed 55 lb per cubic foot (880 kg per
cubic meter), measured loose by accepted ASTM practice.
b. Uniformity of weight (density). The unit weight (mass density) of successive shipments of lightweight
aggregate shall not differ by more than 6% from that of the sample submitted for acceptance tests.
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1.4.4.4 Concrete Making Properties
Concrete specimens containing lightweight coarse aggregate under test shall conform to ASTM C330 and shall
meet the following requirements. A magnesium sulfate soundness test shall be conducted for 10 cycles in
accordance with ASTM C88. Loss thus determined shall not exceed 15%. Loss of individual gradation size shall
not exceed 20% of that size.
SECTION 1.5 WATER
1.5.1 GENERAL (2010)
1.5.1.1 Specifications
Mixing water shall conform to the requirements of ASTM C 1602, Standard Specification for Mixing Water
Used in the Production of Hydraulic Cement Concrete.
SECTION 1.6 REINFORCEMENT
1.6.1 GENERAL (2003)
Reinforcement shall be deformed reinforcement, except that plain bars and plain wire shall be permitted for
spirals or tendons, or for dowels at expansion or contraction joints. Reinforcement consisting of structural
steel, steel pipe, or steel tubing shall be permitted for composite compression members.
1.6.2 WELDING (2003)
a.
Welding of reinforcing bars shall conform to “Structural Welding Code–Reinforcing Steel” (ANSI/AWS
D1.4) of the American Welding Society. Type and location of welded splices and other required welding of
reinforcing bars shall be indicated on the plans or in the project specifications. The ASTM specifications
for reinforcing bars, except for ASTM A706, shall be supplemented to require a report of material
properties necessary to conform to welding procedures specified in ANSI/AWS D1.4.
b. If welding of wire to wire, and of wire or welded wire fabric to reinforcing bars or structural steel is to be
required on a project, the Engineer shall specify procedures or performance criteria for the welding.
c.
Welders of reinforcing bars shall maintain certification by the American Welding Society.
1.6.3 SPECIFICATIONS (2003)
1.6.3.1 Reinforcement
Bars, wire, welded wire fabric, prestressing tendons, structural steel, steel pipe and tubing shall conform to one
of the ASTM specifications found in Table 8-1-7.
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Table 8-1-7. ASTM Specifications for Reinforcement
Type
Designation
Bars, Wire and Fabric
Deformed and Plain Billet-Steel Bars
A615
Deformed and Plain Low-Alloy Steel Bars
A706
Deformed Rail-Steel and Axle-Steel Bars
A996
Deformed and Plain Stainless Steel Bars
A955
Welded or Forged Headed Bars
A970
Steel Wire, Plain (wire shall not be smaller than size W4
A82
(0.226 inch (5.74 mm) dia.))
Steel Welded Wire Fabric, Plain
A185
Steel Wire, Deformed (wire shall not be smaller than size D4 (0.225 inch A496
(5.72 mm) dia.))
Steel Welded Wire Fabric, Deformed (welded intersections shall not be A497
spaced farther apart than 16 inches (400 mm) in direction of primary
flexural reinforcement)
1
Prestressing Tendons
Uncoated Seven-Wire Steel Strand
Uncoated Stress-Relieved Steel Wire
Uncoated High-Strength Steel Bar
A416
A421
A722
Structural Steel, Steel Pipe and Tubing
Structural-Steel
A36, A242, A529, A572, A588 or
A709 (Grade 36, 50 or 50W)
A53 (Grade B)
A500, A501 or A618
Steel Pipe
Steel Tubing
1.6.3.2 Coated Reinforcement
a.
3
4
Coated reinforcement, when specified or shown on the plans as a corrosion-protection system, shall
conform to one of the ASTM specifications found in Table 8-1-8.
Table 8-1-8. ASTM Specifications for Coated Reinforcement
Type
Specification
Epoxy-Coated Steel Reinforcing Bars
A775
Epoxy-Coated Prefabricated Steel Reinforcing Bars
A934
Epoxy-Coated Steel Wire and Welded Wire Fabric
A884
Epoxy-Coated Seven-Wire Prestressing Steel Strand
A882
Zinc-Coated (Galvanized) Steel Reinforcing Bars
A767
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b. Repair all damaged epoxy coating on reinforcing bars due to shipping, handling and placing with
patching material conforming to ASTM A775 or A934. Repair shall be done in accordance with the
material manufacturer’s recommendations.
c.
Repair all damaged epoxy coating on wire or welded wire fabric due to shipping, handling and placing
with patching material conforming to ASTM A884. Repair shall be done in accordance with the material
manufacturer’s recommendations.
d. Repair all damaged zinc coating on reinforcing bars due to shipping, handling, and placing in accordance
with ASTM A780. The maximum amount of damaged areas shall not exceed 2% of the total surface area
in each linear foot (300 mm) of the bar.
e.
Equipment for handling epoxy-coated reinforcing bars shall have protected contact areas. Bundles of
coated bars shall be lifted at multiple pickup points to prevent bar-to-bar abrasion from sags in the
bundles. Coated bars or bundles of coated bars shall not be dropped or dragged. Coated bars shall be
stored on protective cribbing. All damaged coating due to handling, shipping, and placing shall be
repaired. The maximum amount of damaged areas shall not exceed 2% of the surface area of each linear
foot (300 mm) of the bar. If the damaged areas exceed 2% of the total surface area in each linear foot (300
mm) of the bar, the bar shall be replaced.
f.
After installation of mechanical splices on epoxy-coated or zinc-coated (galvanized) reinforcing bars, any
damaged coating shall be repaired. All parts of mechanical splices used on coated bars, including steel
splice sleeves, bolts, and nuts shall be coated with the same material used for repair of damaged coating
on the spliced material. Remove coating for two inches (50 mm) back from the mechanical splice to
bright metal before repair.
g.
After completion of welding for welded splices on epoxy-coated or zinc-coated (galvanized) reinforcing
bars, coating damage shall be repaired. All welds, and steel splice members when used to splice bars,
shall be coated with the same material used for repair of damaged coating. Remove coating for six inches
(150 mm) back from the welded splice to bright metal before repair.
h. Plants applying fusion-bonded epoxy coatings to reinforcing bars shall maintain certification by the
Concrete Reinforcing Steel Institute.
1.6.4 BENDING AND STRAIGHTENING1 (2003)
a.
Reinforceing bars shall be fabricated in accordance with Article 1.10.2 and Part 2, Reinforced Concrete
Design, Article 2.4.2. Field bending and/or straightening of bars that are partially embedded in concrete
shall be done in accordance with the Plans or as permitted by the Engineer.
b. When epoxy-coated reinforcing bars or zinc-coated (galvanized) reinforcing bars are field bent and/or
straightened, damaged coating shall be repaired in accordance with Articles 1.6.3.2b and 1.6.3.2d,
respectively. Field bending and/or straightening of epoxy-coated reinforcing bars conforming to ASTM
A934 shall be prohibited.
1
See C - Commentary
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SECTION 1.7 CONCRETE ADMIXTURES
1.7.1 GENERAL (2004)
a.
The selection of admixtures to be used in concrete, if any, shall be subject to the prior written approval of
the Engineer of the Railroad Company.
b. An admixture shall be shown capable of maintaining essentially the same composition and performance
throughout the work as the product used in establishing concrete proportions in accordance with Section
1.12 Proportioning.
c.
Admixtures containing chloride ions shall not be used unless approved by the Engineer.
d. Special purpose admixtures may be used if approved in writing by the Engineer of the Railroad
Company. However, before an admixture can be approved for use, it must be shown that its use will not
adversely affect the placement, strength and/or durability of the concrete. Admixtures used in
combination may be incompatible and their performance should be verified by prior testing.
1.7.2 TYPES OF ADMIXTURES AND STANDARD SPECIFICATIONS (2004)
The specifications listed in Paragraphs 1.7.2(a) and 1.7.2(b) apply in the use of admixtures.
a.
Air Entraining Agent - ASTM C260 Air-Entraining Admixtures for Concrete.
1
b. ASTM C494 Standard Specification for Chemical Admixtures for Concrete:
(1) Accelerating Admixture
(2) Retarding Admixture
3
(3) Water-Reducing Admixture
(4) Water-Reducing Admixture, High-Range
(5) Water-Reducing and Accelerating Admixture
(6) Water-Reducing and Retarding Admixture
4
SECTION 1.8 STORAGE OF MATERIALS
1.8.1 CEMENTITIOUS MATERIALS AND CONCRETE ADMIXTURES (2009)
a.
Immediately upon delivery, all cement shall be stored in watertight ventilated structures to prevent
absorption of water.
b. Sacked cement shall be stacked on pallets or similar platforms to permit circulation of air and access for
inspection. The cement sacks shall not be stacked against outside walls.
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c.
Cement sacks shall not be stacked more than 14 layers high for periods of up to 60 days, nor more than 7
layers high for periods over 60 days. Older cement shall be used first.
d. Storage facilities for bulk cement shall include separate compartments for each type of cement used. The
bins shall be so constructed as to prevent dead storage in corners.
e.
All cement shall be subject at any time to retest. If under retest it fails to meet any of the requirements
of the specifications, it will be rejected and shall be promptly removed from the site of the work by the
Contractor.
f.
Where the Company furnishes the cement and the failure of the cement to pass the retest is due to
negligence on the part of the Contractor to store it properly, the cost of such cement shall be charged to
the Contractor.
g.
The above provisions also apply to other cementitious materials and blended cementitious materials,
except that fly ash shall be stored in a separate structure or bin without common walls to avoid leakage
of the fly ash into the other cementitious materials.
h. Liquid admixtures shall be protected from freezing. If freezing occurs then the material shall not be used
in concrete unless the manufacturer approves a method of ensuring the effectiveness of the thawed
material, such as agitation.
1.8.2 AGGREGATES (2009)
a.
The storage of coarse aggregates shall be minimized, as to avoid the natural tendency of such stockpiles
to segregate.
b. Fine and coarse aggregates shall be stored separately and in such a manner as to avoid the inclusion of
foreign materials in the concrete. Aggregates shall be unloaded and piled in such a manner as to
maintain the uniform grading of the sizes. Stockpiles of coarse aggregates shall be built in horizontal
layers, not by end dumping, to avoid segregation. Equipment such as dozers and loaders shall not be
operated on the stockpile, so as to avoid contamination, segregation and breakage.
c.
A hard base shall be provided to prevent contamination from underlying material. Overlap of the
different sizes shall be prevented by suitable walls or ample spacing between stockpiles. Stockpiles shall
not be contaminated by swinging aggregate-filled buckets or clams over the various stockpiled aggregate
sizes. Crushed slag shall be wetted down when necessary to ensure a minimum 3% moisture content.
d. Special measures shall be taken to maintain a uniform moisture content in the aggregates as batched.
Control and testing procedures shall be subject to the approval of the Engineer.
1.8.3 REINFORCEMENT (2009)
a.
Reinforcement shall be stored in such a manner as to avoid contact with the ground. If reinforcement
remains in storage at the site for more than 1 month, it shall be covered to protect it from the weather.
If reinforcement accumulates heavy rust, dirt, mud, loose scale, paint, oil, or any foreign substance
during storage, it shall be cleaned before being used. Deterioration may be a basis for rejection.
Reinforcement shall be handled in accordance with Section 1.6.
b. Epoxy-coated reinforcement shall be covered by an opaque polyethylene sheeting or other suitable
opaque protective material as approved by the Engineer. For stacked bundles, the protective covering
shall be draped around the perimeter of the stack. The covering shall be secured in a manner that allows
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for air circulation around the bars to minimize condensation under the covering. Epoxy-coated
reinforcement shall be handled and repaired in accordance with Section 1.6.
SECTION 1.9 FORMS
1.9.1 GENERAL (2009)
Forms shall be constructed of wood, steel, or other suitable material, and be of a type, size, shape, quality and
strength, which will produce true, smooth lines and surfaces conforming to the lines and dimensions shown on
the plans. Forms shall be substantial and designed to resist the pressures to which they are subjected. Lumber
in forms for exposed surfaces should be dressed to a uniform thickness. Undressed lumber may be used in
forms for unexposed surfaces. Forms shall be kept free of rust, grease and other foreign matter which will
discolor the concrete.
Forms may be omitted for foundation concrete if, in the opinion of the Engineer, the sides of the excavation are
sufficiently firm so that the concrete may be thoroughly vibrated without causing the adjacent earth to slough.
The actual dimensions of the excavation shall then be slightly greater than the plan dimensions of the
foundation so as to ensure design requirements.
1.9.2 SAFETY (2009)
The Contractor shall follow all local, state and federal codes, ordinances and regulations pertaining to forming
of concrete at all stages of construction, in addition to the requirements of this Section and the railroad
Company.
1
1.9.3 DESIGN (2009)
a.
The Contractor shall be responsible for the design of all forms required to complete the work.
b. Structural design of forms shall be performed in conformance with ACI 347R, Guide to Formwork for
Concrete, or other generally accepted standards, subject to the approval of the Engineer.
c.
Forms shall be designed by a licensed engineer.
d. Drawings and structural design calculations shall be provided to the Engineer for review and acceptance
prior to undertaking the work, unless excluded by the project Plans.
e.
Documentation demonstrating the adequacy of forms supports to safely resist the design loads shall be
provided for review and acceptance prior to undertaking the work, unless excluded by the project Plans.
f.
Shoring and falsework shall be in accordance with Part 28 except as provided herein.
g.
Special provision for load transfer and movements shall be taken into account in the design of forms for
prestressed concrete.
h. Special provision for forms supporting concrete that is required to act compositely with other materials
in the finished work shall be made.
i.
3
The review and acceptance of Contractor’s submittals shall not relieve the Contractor of responsibility
for the safe and functional design of the forms and their supports.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-1-21
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Concrete Structures and Foundations
1.9.4 CONSTRUCTION (2009)
a.
The supervisor responsible for construction of forms should be certified by the American Concrete
Institute Inspector Certification Program as a Concrete Transportation Construction Inspector. The
Contractor may appoint a similarly qualified and experienced individual with the approval of the
Engineer.
b. Forms shall be constructed mortar-tight, and shall be made sufficiently rigid by the use of ties and
bracing to prevent displacement or sagging and to withstand the pressure and vibration without
deflection and/or objectionable distortion from the prescribed lines during and after placement of the
concrete.
c.
Joints in forms shall be horizontal or vertical, and suitable devices shall be used to hold adjacent edges
together in accurate alignment.
d. All forms shall be constructed and maintained so as to prevent warping and the opening of joints.
e.
All forms shall be constructed so that they may be readily removed without damaging the concrete.
f.
Bolts and/or rods shall be used for internal form ties. They shall be so arranged that, when the forms are
removed, no corrodible metal shall be within 1-1/2 inches (38 mm) of any surface.
g.
When wire form ties are used, where permitted, spacer blocks shall be removed as the concrete is placed.
Wire form ties shall be cut back 1-1/2 inches (38 mm) from the face of the concrete upon removal of the
forms.
h. All fittings for ties shall be of such a design that upon their removal the remaining cavities will be the
smallest practicable size. The cavities shall be filled with cement mortar and the surfaces left in a sound
condition, even and uniform in color with respect to the original surface.
i.
All temporary fasteners in contact with concrete shall be countersunk.
j.
Any material once used in forms shall be thoroughly cleaned and form release agent shall be applied
before erection in a new location. All rough surfaces shall be smoothed and repairs made to the
satisfaction of the Engineer. Forms which have been used repeatedly and are not acceptable to the
Engineer for further use shall be removed from the site.
k. In the case of long spans where no intermediate supports are possible, deflection in the forms due to the
weight of the fresh concrete shall be compensated for by using camber strips, wedges or other devices so
that the finished members conform accurately to the desired line and grade.
l.
Foundations for falsework shall be provided in accordance with Part 28.
1.9.5 MOLDINGS (2009)
Unless otherwise specified or directed by the Engineer, suitable moldings or bevels shall be placed in the angles
of forms to round or bevel the edges of the concrete, including abutting edges of expansion joints.
1.9.6 FORM COATING AND RELEASE (2009)
Prior to placing reinforcement, the inside surfaces of forms shall be coated with a non-staining form release
agent. A thin film shall be applied to all surfaces that will be in contact with the fresh concrete.
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8-1-22
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Materials, Tests and Construction Requirements
1.9.7 TEMPORARY OPENINGS (2009)
Temporary openings shall be provided at the base of the column and wall forms, and at other locations where
necessary, to facilitate cleaning and inspection immediately before depositing concrete. Forms for walls or other
thin sections of considerable height shall be provided with openings or other devices which will permit the
concrete to be placed in a manner to avoid accumulation of hardened concrete on the forms or reinforcement.
1.9.8 REMOVAL (2009)
a.
Forms shall be removed in such a manner as to ensure the complete safety of the structure. Care shall be
taken to preserve formed surfaces and not to damage the corners or surfaces of the concrete. Hammering
on or prying between forms and concrete shall not be permitted.
b. Form and falsework shall not be removed until the following are achieved:
(1) The concrete has adequately cured and has acquired sufficient strength to support its weight and
any anticipated loads.
(2) The minimum time specified in the Plans has elapsed.
(3) The Contractor has submitted and the Engineer has accepted a procedure and schedule for removal
of form and falsework with calculations, if applicable, for loads transferred to the structure during
the process.
1
c.
The time of removal of forms will depend on the type of the concrete, the location of the form, and the
temperature and moisture conditions which affect the strength of the concrete.
d. The age-strength relationship of the concrete used in determining the time for form and falsework
removal shall be determined from tests conducted on representative samples of the same concrete as
used in the structure and cured under job conditions, in accordance with ASTM C 39.
e.
If not otherwise specified on the Plans or by the Engineer, formwork and supports shall not be released
until the concrete has attained sufficient strength to support its weight and any anticipated loads upon
it, but not less than 70% of its specified compressive strength. In continuous structures, support shall
not be released in any span until the first and second adjoining spans on each side have reached the
specified strength.
f.
Bulkheads at construction joints shall not be removed for a period of 15 hours after casting adjacent
concrete.
g.
Forms for ornamental work, railings, parapets, and vertical surfaces which require a surface finishing
operation shall be removed not less than 12 hours, nor more than 48 hours after casting the concrete,
depending upon weather conditions.
h. Support for pretensioned and post-tensioned concrete members shall not be removed until sufficient
prestress has been applied to enable the member to support its weight and anticipated loads.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-1-23
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SECTION 1.10 DETAILS OF REINFORCEMENT
1.10.1 SURFACE CONDITIONS OF REINFORCEMENT (2003)
a.
Reinforcement at the time concrete is placed shall be free from mud, oil, or other non-metallic coatings
that adversely affect bonding capacity. Epoxy coatings on bars, wire, and welded wire fabric conforming
to standards referenced in Table 8-1-8 is permitted.
b. Reinforcement, except prestressing tendons with rust, mill scale, or a combination of both, shall be
considered as satisfactory, provided the minimum dimensions, including height of deformations, and
weight of a hand wire-brushed test specimen are not less than the applicable ASTM designation
requirements.
c.
Prestressing tendons shall be clean and free of oil, excessive soaps, dirt, scale, pitting and excessive rust.
A light coating of rust without pitting shall be permitted.
1.10.2 FABRICATION (2003)
a.
Reinforcement shall be prefabricated to the dimensions shown on the plans. Reinforcement shall be bent
cold, and shall not be bent or straightened in a manner that will damage the material. Bars with kinks or
bends not shown on the plans shall be rejected. Hot bending of reinforcement will be permitted only
when approved by the Engineer.
b. Diameter of bends measured on the inside of the bar shall be as shown on the plans. When diameter of
bend is not shown, minimum bend diameter shall be in accordance with Part 2, Reinforced Concrete
Design.
c.
Unless otherwise specified by the Engineer, the tolerance in fabricated lengths of bars from that shown
on the placing drawings shall be ±1 inch (25 mm) for bar sizes #11 (36 mm) and under and 2 inches (51
mm) for bar sizes #14 and #18 (43 mm and 57 mm); the tolerance in out-to-out dimensions of hooks
shall be ±1/2 inch (13 mm); the tolerance in out-to-out dimensions of stirrups and ties shall be ±1 inch
(25 mm) and the maximum angular deviation on 90 degree hooks or bends shall be 0.5 inches per foot (1
in 24).
1.10.3 PROVISIONS FOR SEISMIC LOADING (2003)
For structures located in seismic risk areas as determined from Chapter 9, consideration shall be given to
reinforcement details that will provide adequate ductility and enable reinforcement to be strained beyond yield
to allow the structure to absorb the energy of an earthquake.
1.10.4 PLACING OF REINFORCEMENT (2003)
1.10.4.1 General
a.
Reinforcement, prestressing tendons and ducts shall be accurately placed and adequately supported
before concrete is placed, and shall be secured against displacement within permitted tolerances. Tie
wire shall be 16-1/2 gage (1.4 mm) or heavier, black-annealed. Welding of crossing bars shall not be
permitted for the assembly of reinforcement unless authorized by the Engineer.
b. Reinforcing bars shall not be cut in the field except when authorized by the Engineer. Flame-cutting of
epoxy-coated reinforcing bars shall not be permitted.
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Materials, Tests and Construction Requirements
c.
When epoxy-coated or zinc-coated (galvanized) reinforcing bars are cut in the field, the ends of the bars
shall be coated with the same material that is used for the repair of damaged coating and shall be
repaired in accordance with Articles 1.6.3.2b and 1.6.3.2d. The limit on the amount of repaired damaged
coating does not apply to cut ends that are coated with patching material.
d. The supervisor responsible for placing reinforcing bars, tendons, and ducts shall maintain certification
by the American Concrete Institute as a Concrete Transportation Construction Inspector.
1.10.4.2 Tolerances
Unless otherwise specified by the Engineer, reinforcement, prestressing tendons, and prestressing ducts shall
be placed in flexural members, walls and compression members within the following tolerances:
a.
Clear distance to formed or unformed concrete surfaces:
When member size is 12 inches (300 mm) or less . . . . . . . . . . . . . . . . . . . . . . .
±3/8 inch (10 mm)
When member size is over 12 inches (300 mm) but not over 2 feet (600 mm). . . ±1/2 inch (13 mm)
When member size is over 2 feet (600 mm) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
±1 inch (25 mm)
Reduction in concrete cover shall not exceed one-third specified concrete cover.
Reduction in concrete cover to formed soffits shall not exceed 1/4 inch (6 mm).
Tolerances shall not permit a reduction in concrete cover except as shown above, and shall not
permit reduction in concrete cover below values specified as minimums as defined in
Article 1.10.6.
1
b. Tolerance on minimum distance between bars shall be minus 1/4 inch (6 mm).
c.
Tolerance in uniform spacing of reinforcement from theoretical location shall be ±2 inches (50 mm).
d. Tolerance in uniform spacing of stirrups and ties from theoretical location shall be ±1 inch (25 mm).
e.
Tolerance for longitudinal location of bends and ends of bars shall be ±2 inches (50 mm), except at
discontinuous ends of members where the tolerance shall be ±1-1/2 inches (40 mm).
f.
Tolerance in length of bar laps shall be minus 1-1/2 inches (40 mm).
g.
Tolerance in embedded length shall be minus 1 inch (25 mm) for #3 to #11 bars (#10 to #36) and minus
2 inches (50 mm) for #14 and #18 bars (#43 and #57).
h. When it is necessary to move bars to avoid interference with other reinforcement, conduits, or embedded
items by an amount exceeding the specified placing tolerances, the resulting arrangement of bars shall
be approved by the Engineer.
i.
Tolerance in the vertical and horizontal location of prestressing strand shall be ±1/4 inches (6 mm)
except in precast slabs. The tolerance for vertical location in precast slabs shall be ±1/4 inches (6 mm).
The tolerance for horizontal location of prestressing strand in precast slabs shall be ±1 inch (25 mm) in
any 15 feet (4.5 m) of strand length.
j.
Tolerance in the vertical and horizontal location of unbonded post-tensioning tendons and ducts in
bonded post-tensioning shall be ±1/4 inches (6 mm) except in slabs. The tolerance for vertical location in
slabs shall be ±1/4 inches (6 mm). The tolerance for horizontal location of post-tensioning tendons and
ducts in bonded post-tensioning in slabs shall be ±1 inch (25 mm) in any 15 feet (4.5 m) of strand length.
k. In precast elements the bearing plates shall be concentric with the tendons and tolerance for the
perpendicularity with tendons in concrete shall be ±1 degree.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-1-25
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Concrete Structures and Foundations
1.10.4.3 Bar Supports and Side-Form Spacers
a.
Unless otherwise specified by the Engineer, reinforcement supported from the ground shall rest on
precast concrete blocks not less than 4 inches (100 mm) square, and having a compressive strength equal
to or greater than the specified compressive strength of the concrete being placed. Reinforcement
supported by formwork shall rest on bar supports and spacers made of concrete, metal, plastic, or other
materials approved by the Engineer.
b. Where noted on the plans and at all formed surfaces that will be exposed to the weather in the finished
structure, bar supports and side-form spacers spaced no further than four feet (1200 mm) on center shall
be provided. Bar supports and spacers and all other accessories within 1/2 inch (13 mm) of the concrete
surface shall be noncorrosive or protected against corrosion.
c.
Epoxy-coated reinforcing bars supported from formwork shall rest on coated wire bar supports, or on bar
supports made of dielectric material and other acceptable materials. Wire bar supports shall be coated
with dielectric material for a minimum distance of 2 inches (50 mm) from the point of contact with the
epoxy-coated reinforcing bars. Reinforcing bars used as support bars shall be epoxy-coated. In walls
having epoxy-coated reinforcing bars, spreader bars where specified shall be epoxy-coated. Proprietary
combination bar clips and spreaders used in walls with epoxy-coated reinforcing bars shall be made of
corrosion-resistant material or coated with dielectric material.
d. Zinc-coated (galvanized) reinforcing bars supported from formwork shall rest on galvanized wire bar
supports coated with dielectric material, or on bar supports made of dielectric material or other
acceptable materials. All other reinforcement and embedded steel items in contact with galvanized
reinforcing bars, or within a minimum clear distance of 2 inches (50 mm) from galvanized reinforcing
bars unless otherwise required or permitted, shall be galvanized.
e.
Epoxy-coated reinforcing bars shall be fastened (tied) with plastic-coated or epoxy-coated tie wire; or
other materials authorized by the Engineer.
f.
Zinc-coated (galvanized) reinforcing bars shall be fastened (tied) with zinc-coated tie wire, or
nonmetallic-coated tie wire, or other materials authorized by the Engineer.
1.10.4.4 Draped Welded Wire Fabric
When welded wire fabric with wire size not greater than W5 or D5 is used for slab reinforcement in slabs not
exceeding 10 feet (3000 mm) in span, the reinforcement may be curved from a point near the top of the slab
over the support to a point near the bottom of the slab at mid-span, provided such reinforcement is either
continuous over, or securely anchored, at the support.
1.10.5 SPACING OF REINFORCEMENT (2003)
Spacing of reinforcement shall be as shown on the plans. When spacing of reinforcement is not shown, spacing
shall be in accordance with Part 2, Reinforced Concrete Design for reinforcing bars, and Part 17, Prestressed
Concrete, Section 17.5 Details of Prestressing Tendons and Ducts.
1.10.6 CONCRETE PROTECTION FOR REINFORCEMENT (2003)
Concrete cover for reinforcement shall be as shown on the plans. When concrete cover is not shown, minimum
concrete cover shall be provided in accordance with Part 2, Reinforced Concrete Design, Details of
Reinforcement, Section 2.6 for bars and wire, and Part 17, Prestressed Concrete, Article 17.5.2 for prestressing
tendons and ducts.
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Materials, Tests and Construction Requirements
1.10.7 FUTURE BONDING (2003)
Exposed reinforcement intended for bonding with future extensions shall be protected from corrosion in an
approved manner.
SECTION 1.11 CONCRETE JOINTING
1.11.1 SCOPE (2009)
This recommended practice is applicable to the design of concrete slabs and walls in concrete structures such
as bridges, buildings and flat work, finger joints and other mechanical joint systems are not included in these
recommended practices.
1.11.2 TYPES OF JOINTING (2009)
a.
Expansion joints are filled separations between adjoining parts of the concrete structure which are
provided to allow for relative movement such as those caused by thermal changes.
b. Contraction joints are sawed, tooled, or constructed in a concrete surface to create a weakened plane to
control the location of cracking resulting from dimensional changes caused by shrinkage.
c.
1
Construction joints occur where two successive placements of concrete meet, across which it is desired to
maintain bond between two concrete placements, and through which any reinforcement which may be
present is not interrupted.
1.11.3 EXPANSION JOINTS (2009)
a.
Expansion joints allow for differential movement of the concrete mass on either side of the joint. These
may also be referred to as isolation joints.
3
b. The Engineer may require that the joint be designed to resist movements in other directions, such as
those resulting from shear.
c.
Expansion joints shall be installed as shown on the Plans or as specified by the Engineer. Waterstops
may also be required.
d. Jointing materials shall be in accordance with ASTM D994 or ASTM D1751. There shall be no
connection across the joint except as shown on the Plans or as required by the Engineer.
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AREMA Manual for Railway Engineering
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Concrete Structures and Foundations
Figure 8-1-1. Full-Depth Expansion Joint
1.11.4 EXPANSION JOINTS IN WALLS (2009)
Expansion joints between the finished surface and the waterstop shall be filled with a material such as a 1/2
inch (13 mm) thick strip of Preformed Expansion Joint meeting ASTM D994, ASTM D1751 or ASTM D1752.
1.11.5 CONTRACTION JOINTS (2009)
a.
These recommended practices do not include full contraction joints, where all reinforcement is
terminated at the joint and where joint details may include waterstops, bond breakers, joint sealant or
shear connectors.
b. Contraction joints allow for differential movement across the joint only in one direction, usually in the
plane of the finished surface. They are provided to allow for dimensional changes such as those caused by
drying shrinkage of the concrete.
c.
Contraction joints in slabs-on-grade shall be located and detailed as shown on the plans. Unless
otherwise shown or noted, joints shall be placed at 15 to 25 foot (5 – 8 m) intervals in each direction.
d. Contraction joints for slabs-on-grade shall be made by one of the methods shown in Figure 8-1-2 or as
shown on the plans.
e.
Sawing of contraction joints shall be done as soon as the concrete has hardened sufficiently to prevent
aggregates being dislocated by the saw and shall be completed within twelve hours after placement
unless otherwise approved by the Engineer. Sawing shall not be done when the concrete temperature is
falling, unless approved by the Engineer.
f.
Contraction joints may also be constructed by means or methods specifically designed to create a plane of
weakness in freshly placed concrete. This may include a reduction in the amount of reinforcement
passing through the joint if approved by the Engineer.
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Materials, Tests and Construction Requirements
g.
Contraction joints may also be made by other methods if approved by the Engineer. Sawed or tooled
contraction joints shall be cleaned and filled with polymeric sealant conforming to ASTM D1190 or
ASTM D3405 or as specified by the Engineer.
h. Prior to the application of a polymeric sealing material, a heat resistant backer rod shall be inserted to a
minimum depth of 1/2 inch (13 mm) below the slab surface. The remaining reservoir shall then be filled
flush with the slab surface (see Figure 8-1-2).
1.11.6 CONSTRUCTION JOINTS (2009)
a.
Construction joints allow for no differential movement across the plane of the joint. They are provided
only at locations where casting is temporarily suspended or interrupted.
b. The procedures specified in Article 1.14.9 for bonding fresh concrete to hardened concrete shall be
followed in the formation of all construction joints.
c.
Reinforcement shall continue through the joint. Additional reinforcement such as dowels and other
features such as keys and waterstops may also be included. Special measures such as attention to
vibration shall be taken in the casting of concrete to either side of the joint in the vicinity of keys.
d. Structures or portions of the structures shall be continuously cast except as specified herein. When
necessary to provide construction joints not indicated or specified by the Plans, such construction joints
shall be located as approved by the Engineer and formed so as not to impair the strength, appearance, or
durability of the structure.
1
1.11.7 WATERTIGHT CONSTRUCTION JOINTS (2009)
a.
Contraction joints shall not be used in watertight construction unless shown on the plans approved by
the Engineer. See Figure 8-1-1.
b. Where a construction joint is used in watertight construction, special care shall be taken in finishing the
concrete to which the succeeding concrete is to be bonded. The consistency of the concrete shall be
carefully controlled and the surface shall be protected from loss of moisture as described in Article
1.18.4.
c.
Where construction joints are required to be watertight, a continuous keyway shall be constructed in the
interface of the first section of the concrete placed with an approved waterstop embedded in this first
placement. One half of the waterstop shall be embedded in the first placement and the remaining
material shall be embedded in the adjacent placement. See Figure 8-1-3 for details. The concrete shall be
thoroughly vibrated to ensure uniform contact over the entire surface of the waterstop and the key on
either side of the construction joint. The waterstop shall be in accordance with Corps of Engineers
Specification CRD C 572 (PVC) or CRD C 513 (Rubber).
d. Keyed joints shall not be used in slabs less than 6 inches (150 mm) thick.
© 2011, American Railway Engineering and Maintenance-of-Way Association
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Figure 8-1-2. Two Methods for Making Contraction Joints for Slabs-on-Grade
t
Figure 8-1-3. Keyed Construction Joint with Waterstop Inserted Perpendicular to the Plane of the Joint
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Materials, Tests and Construction Requirements
SECTION 1.12 PROPORTIONING
1.12.1 GENERAL (2009)
Mix proportions shall be proposed by the Contractor for the various parts of the work subject to the approval of
the Engineer. Revised mix proportions may be submitted by the Contractor for approval by the Engineer
during the work to reflect concrete test results. Proportions of materials for making concrete shall be selected
to provide the strength, workability, durability and other qualities specified on the Plans and required by the
Engineer.
1.12.2 MEASUREMENT OF MATERIALS (2009)
a.
In the measurement of cement, 94 lb, 1 bag, 1/4 barrel or 1#cubic foot all are assumed equivalent (1.5 Kg
of cement shall be assumed as one liter). Materials shall be measured by weighing, except as otherwise
specified or where other methods are specifically authorized by the Engineer. The apparatus provided for
weighing the aggregates and cement shall be suitably designed and constructed for this purpose. The
aggregates and cement shall be weighed separately. The accuracy of all weighing devices shall be such
that successive quantities can be measured to within 1% of the desired amount. Cement in standard
packages (bags) need not be weighed, but bulk cement and fractional packages shall be weighed. The
mixing water shall be measured by volume or by weight. The water-measuring device shall be accurate
to within 1/2%. All measuring devices shall be subject to approval of the Engineer.
b. Where volumetric measurements are authorized by the Engineer, the weight proportions shall be
converted to equivalent volumetric proportions. In making this conversion, suitable allowance shall be
made for variations in the moisture condition of the aggregates, including the bulking effect in the fine
aggregate.
1
1.12.3 WATER-CEMENTITIOUS MATERIALS RATIO (2009)
a.
The proportioning of materials shall be based on the requirements for a plastic and workable mix suited
to the conditions of placement containing not more than the specified amount of water, including the free
water contained in the aggregates. The maximum specified amount of water shall not exceed the
quantities shown in Table 8-1-9 for the type of structure and the condition of exposure to which it will be
subjected. Moisture in the aggregates shall be measured by methods satisfactory to the Engineer.
b. Free water content of aggregates included in the quantities specified must be deducted from the amounts
given in the Table to determine the amount to be added at the mixer. Allowance may be made for
absorption when aggregates are not saturated.
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Table 8-1-9. Maximum Permissible Water-Cementitious Materials Ratio (by Weight)
for Different Types of Structures and Degrees of Exposure
Exposure Conditions (Note 1)
Severe wider range in
temperature or
frequent alternations of
freezing and thawing
(air-entrained conc. only)
Mild temperature rarely
below freezing,
or rainy, or arid
At the water line or
within the range of
fluctuating water
level or spray
Description
In Air
In Sea
Water or In
In Fresh Contact
With
Water
Sulfates
(Note 2)
At the water line or
within the range of
fluctuating water
level or spray
In Air
In Sea
Water or In
In
Contact
Fresh
With
Water
Sulfates
(Note 2)
Thin sections, such as railings, curbs, sills,
ledges, ornamental or architectural
concrete, reinforced piles, and pipe
0.49
0.44
0.40
(Note 3)
0.53
0.49
0.40
(Note 3)
Moderate sections, such as retaining walls,
abutments, piers, girders, beams
0.53
0.49
0.44
(Note 3)
(Note 4)
0.53
0.44
(Note 3)
Exterior portions of heavy (mass) sections
0.58
0.49
0.44
(Note 3)
(Note 4)
0.53
0.44
(Note 3)
Concrete deposited by tremie underwater
–
0.44
0.44
–
0.44
0.44
0.53
–
–
(Note 4)
–
–
Concrete protected from weather, interiors
of buildings, concrete below ground
(Note 4)
–
–
(Note 4)
–
–
Concrete which will later be protected by
enclosure of backfill but which may be
exposed to freezing and thawing for several
years before such protection is offered
0.53
–
–
(Note 4)
–
–
Concrete slabs laid on the ground
Note 1: Air-entrained concrete shall be used under all conditions involving severe exposure and may be used
under mild exposure conditions to improve workability of the mixture.
Note 2: Soil or ground water containing sulfate concentrations of more than 0.2%.
Note 3: When sulfate resisting cement is used, maximum water-cementitious material ratio may be increased
by 0.05.
Note 4: Water-cementitious material ratio should be selected on basis of strength requirements.
Note 5: The water-cementitious materials ratio may require adjustment as outlined in Article 1.12.10.
1.12.4 AIR CONTENT OF AIR-ENTRAINED CONCRETE (2009)
a.
The volume of entrained air in concrete shall be within the limits shown in Table 8-1-10.
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Materials, Tests and Construction Requirements
Table 8-1-10. Air-Entrained Concrete Volume
Maximum Size Coarse
Aggregate Inches (mm)
Air Content %
by Volume
1-1/2, 2, or 2-1/2 (38, 50, 63)
5
±1
3/4, 1 (19, 25)
6
±1
7-1/2
±1
3 / 8 , 1 / 2 (10 ,13 )
b. The air content shall be determined by one of the following methods:
(1) The gravimetric method, ASTM C138.
(2) The volumetric method, ASTM C173.
(3) The pressure method, ASTM C231.
1.12.5 STRENGTH OF CONCRETE MIXTURES (2011)
a.
The provisions of this Section are not applicable when using cementitious materials other than Portland
cement.
b. When preliminary tests of the materials to be used are not available, the required water-cementitious
materials ratio shall be determined in accordance with Method 1 (Article 1.12.5.1). When strengths in
excess of 4000 psi (28 MPa) are required, or where lightweight aggregates or admixtures (other than
those exclusively for the purpose of entraining air) are to be used, the required water-cementitious
materials ratio shall be determined in accordance with Method 2 (Article 1.12.5.2). Method 3
(Article 1.12.5.3) may be used if statistical data conforming to Article 1.12.5.3 are available.
1
3
1.12.5.1 Method 1 – Without Preliminary Tests
a.
Concrete proportions may be determined in accordance with this method if approved by the Engineer.
Concrete proportions shall then be based on the water-cementitious materials ratio limits found in
Table 8-1-11. These limits are only for concrete that is made with cements meeting Types I, IA, II, IIA,
III, IIIA, or V of ASTM C150, or Types IS, IS-(A), IS(MS), IS-(A)(MS), IP or IP-(A), of ASTM C595.
Volume of entrained air shall be within limits of Article 1.12.4. Air Content of Air-Entrained Concrete
(2009) ratio shall not be greater than that required by Article 1.12.3.
Table 8-1-11. Water-Cementitious Materials Ratio for Air Entrained Concrete
Specified 28 Day Compressive Strength
of Concrete, f¢ c psi (MPa)
Absolute Water-Cementitious Materials
Ratio by Weight (Mass)(Note)
2,500 (17)
0.66
3,000 (21)
0.58
3,500 (24)
0.51
4,000 (28)
0.46
5,000 (34)
0.40
Note:
Not applicable for concrete containing lightweight aggregates or admixtures other than
for entraining air.
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b. The values in Table 8-1-11 are based on the use of cement and aggregates meeting the requirements of
this Section and the concrete being sufficiently protected from loss of moisture and from low
temperatures to ensure that proper curing will take place. When Type III Portland cement is used in lieu
of Type I or Type II Portland cement, it may be assumed that the specified compressive strength will be
obtained at the age of 7 days.
c.
The strength of cylinders made with Types I, IA, II or IIA Portland cement and tested at the age of 7
days shall not fall below 65% of the assumed compressive strength at the age of 28 days. The strength of
cylinders made with Types III or IIIA Portland cement and tested at the age of 3 days shall not fall below
65% of the assumed minimum compressive strength at the age of 28 days shown for Types I, IA, II and
IIA Portland cement. The strength of cylinders tested at the age of 28 days shall be at least 1200 psi (8.3
MPa) greater than the strength specified on the plans when using this method.
1.12.5.2 Method 2 – With Preliminary Tests
The strength of concrete shall be determined by tests made with representative samples of the materials to be
used in the work. The results of the tests shall be submitted to the Engineer in advance of construction. These
tests shall be made using the consistencies suitable for the work. These samples shall be proportioned to
produce a slump of within 3/4 inch (19 mm) of the maximum permitted slump and with an entrained air
content of within 0.5 percent of the maximum air content required. Tests shall be conducted in accordance with
ASTM C192 Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory and with
ASTM C39 Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens. At least three
tests shall be conducted for each of three water-cementitious material ratios that will encompass the required
concrete strength. A curve representing the relation between the water content and the average 28 day
compressive strength or earlier strength at which the concrete is to receive its full working load shall be
established for this range of values. The maximum permissible water-cementitious material ratio for the
concrete to be used shall be shown by the curve to produce a strength 15% greater than specified on the Plans
or specifications. If any changes are to be made in the materials, new curves shall be established by tests as
described above.
1.12.5.3 Method 3 – On Basis of Field Experience
a.
Where a concrete production facility has a record based upon at least 30 consecutive strength tests that
represent similar materials and conditions to those expected, required average compressive strength
used as the basis for selecting concrete proportions shall exceed required f’c at designated test ages by at
least:
(1) 1.34 standard deviations, where the standard deviation is less than or equal to 500 psi (3.45 MPa).
(2) 2.33 standard deviations less 500 psi (3.45 MPa), where the standard deviation is greater than 500
psi (3.45 MPa).
b. Strength test data for determining standard deviation shall be considered to comply with the above if
data represents either a group of at least 30 consecutive tests or a statistical average for two groups
totaling 30 or more tests.
c.
Strength tests used to establish standard deviation shall represent concrete produced to meet a specified
strength within ±1000 psi (±6.90 MPa) of that specified for the proposed work.
d. Changes in materials and proportions within the population of background tests used to establish
standard deviation shall not have been more closely restricted than for the proposed work.
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Materials, Tests and Construction Requirements
1.12.6 WORKABILITY (2009)
The concrete shall be of such consistency and composition that it can be worked readily into the corners and
angles of the forms and around the reinforcement without segregation of materials or the collection of free
water on the surface. Subject to the limiting requirements of Article 1.12.3, the contractor shall, if the Engineer
requires, submit a new mix design to adjust the proportions of cement and aggregates so as to produce a
mixture which will be easily placeable at all times, due consideration being given to the methods of placing and
compacting used on the work and subject to the approval of the Engineer.
1.12.7 SLUMP (2009)
The slump test may be used as a control measure to maintain the consistency suitable for the work. When
mechanical vibrators are used to compact the concrete, the consistency suitable to that method shall be used.
The slump test shall be made in accordance with the ASTM Method of Test C143 Standard Test Method for
Slump of Hydraulic Cement Concrete.
1.12.8 COMPRESSION TESTS (2009)
Specimens for compression tests shall be made and stored in accordance with ASTM C31 Standard Practice for
Making and Curing Concrete Test Specimens in the Field. These specimens shall be tested in accordance with
ASTM C39.
1.12.9 FIELD TESTS (2009)
a.
1
During the progress of construction, the Engineer will have tests made to determine whether the
concrete produced compares to the quality specified by the Plans. The Contractor shall cooperate in the
making of such tests and allow free access to the work for selection of samples and storage of specimens
and in affording protection to the specimens against injury or loss through construction operations.
b. Four cylinders will generally be made for each class of concrete used in any one day’s operation. In
special cases, this normal number of control specimens may be exceeded when in the opinion of the
Engineer such additional tests are required. The Contractor, however, shall not be required to furnish for
such additional tests more than 2 cubic feet (75 liters) of concrete for each 100 cubic yard (76 cubic
meter) of concrete being placed (75 liters for each 100 cu. m).
c.
Samples of concrete for test specimens shall be taken at the mixer, or in the case of ready-mix concrete,
from the transportation vehicle during discharge. When, in the opinion of the Engineer, it is desirable to
take samples elsewhere, they shall be taken as directed. Specimens shall be made and stored in
accordance with Article 1.12.8.
d. The air content of freshly mixed air-entrained concrete shall be checked at least twice daily for each class
of concrete, or each time cylinders are cast. Changes in air content above or below the amount specified
shall be corrected by adjustment in the mix design or quantities of air-entraining material being used.
e.
If the strengths shown by the test specimens fall below the values given in Article 1.12.5 or as specified
by the Plans, then the Engineer shall have the right to require changes in proportions to apply on the
remainder of the work.
f.
Technicians performing field tests of concrete materials shall maintain Level I certification by the
American Concrete Institute as a Concrete Field Testing Technician. The person in responsible charge of
field test operations shall maintain Level 3 certification by the National Ready Mix Concrete Association
as a Concrete Technologist.
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1.12.10 SPECIAL PROVISIONS WHEN USING CEMENTITIOUS MATERIALS OTHER THAN
PORTLAND CEMENT (2009)
1.12.10.1 Maximum Cementitious Materials
Concrete exposed to deicing chemicals shall contain total weights (masses) of cementitious materials no greater
than those specified in Table 8-1-12.
Table 8-1-12. Concrete Exposed to Deicing Chemicals
Cementitious Material
Maximum Percentage of Total
Cementitious Materials by Weight
(mass)
Fly ash or other pozzolans conforming to
ASTM C618
25
Ground granulated blast-furnace slag
conforming to ASTM C989
50
Silica fume conforming to ASTM C1240
10
Total fly ash or other pozzolans, ground
granulated blast-furnace slag and silica
fume
50
Total fly ash or other pozzolans, and
silica fume
35
Notes: Total cementitious material also includes ASTM C150, ASTM C595, ASTM
C845 and ASTM C1157 cements (ASTM C845 is the Standard Specification
for Expansive Hydraulic Cement and is not included in this recommended
practice).
The maximum percentages include:
a. Fly ash and other pozzolans and ground granulated blast-furnace slag
included in Types IP or I(PM) or IS or I(SM) blended cements, ASTM
C595
b. Silica fume, ASTM C1240, present in blended cements
1.12.10.2 Requirements When Using Silica Fume in Concrete
1.12.10.2.1 General
The ability of the concrete mixture to exhibit special properties should be determined by tests for each source of
silica fume.
1.12.10.2.2 High-Range Water Reducing Admixtures
High-range water reducing admixtures should be used in concrete containing silica fume in order to achieve the
desired workability.
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Materials, Tests and Construction Requirements
1.12.10.2.3 Entrained Air
The amount of admixture required to entrain the desired amount of air should be determined by tests as part of
the design of the concrete mixture.
1.12.10.3 Requirements When Using Fly Ash in Concrete
1.12.10.3.1 General
Mix proportions, including the proportions of fly ash, shall be determined by tests.
1.12.10.3.2 Water-Reducing Admixtures and High Range Water-Reducing Admixtures
Water reducing admixtures and high-range water reducing admixtures may be used in concrete containing fly
ash.
1.12.10.3.3 Testing to Verify Mix Design
The mixture shall be designed and proportioned to provide the properties for which the fly ash was used, and to
avoid other possible undesirable properties. Tests shall include slump/workability, requirements for airentraining admixtures, the rate of bleeding of fresh concrete, the time of setting, the rate of early strength gain
and any need to use an accelerating admixture or a water-reducing admixture, the heat of hydration (if
required), reactivity with sulphates or expansion due to alkali-silica reactions (if required), and the 28-day or
later strength as required by the design parameters.
1
1.12.10.3.4 Water to Cementitious Materials Ratio
The water to cementitious material ratio will normally be reduced in concrete containing fly ash.
1.12.10.3.5 Air Entrainment
Concrete containing fly ash should be air entrained if it is to be subjected to freezing and thawing conditions.
Concrete should also attain the desired design strength before being subjected to chlorides.
3
1.12.10.4 Requirements When Using Ground Granulated Blast-Furnace Slag in Concrete
1.12.10.4.1 General
4
Mix proportions, including the proportion of ground granulated blast-furnace slag, shall be determined by tests.
1.12.10.4.2 Water-Reducing Admixtures
Water-reducing admixtures may be used in concrete containing ground granulated blast-furnace slag, in order
to increase the rate of strength gain.
1.12.10.4.3 Accelerators
An accelerating admixture may be used when using ground granulated blast-furnace slag in a concrete mix.
1.12.10.4.4 Proportioning of Aggregates
Concrete containing ground granulated blast-furnace slag will normally be proportioned for a larger quantity of
coarse aggregate than normal Portland cement concrete.
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Concrete Structures and Foundations
1.12.10.4.5 Entrained Air
The amount of admixture required to entrain the desired amount of air should be determined by tests as part of
the design of the concrete mixture.
SECTION 1.13 MIXING
1.13.1 GENERAL (2009)
a.
The concrete shall be mixed only in the quantity required for immediate use. Concrete that has
developed an initial set shall not be used.
b. The first batch of concrete materials placed in the mixer shall contain a sufficient excess of cement, sand,
and water to coat the inside of the drum without reducing the required mortar content of the mix. The
mixer shall be thoroughly cleaned if mixing is interrupted for a period that would permit initial set to
take place.
c.
Concrete may be mixed at the site of construction, at a central point, and/or in truck mixers.
d. The ingredients shall be thoroughly mixed to specification.
1.13.2 SITE-MIXED CONCRETE (2009)
a.
Unless authorized by the Engineer, the concrete shall be mixed in a batch mixer of approved type and
size which will ensure a uniform distribution of the material throughout the mass. The equipment at the
mixing plant shall be so constructed that all materials (including the water) entering the drum can be
accurately measured and weighed. The batch shall be fully discharged from the mixer before recharging.
The volume of the mixed material per batch shall not exceed the manufacturer’s rated capacity of the
mixer. Mixing of each batch shall continue for the periods noted below, during which time the drum shall
rotate at a peripheral speed as recommended by the manufacturer. The mixing time shall be measured
from the time when all of the solid materials are in the mixer drum, provided that all of the mixer water
has been introduced before one-fourth of the mixing time has elapsed. The mixer shall have a timing
device with a bell or other suitable warning device adjusted to give a clearly audible signal each time the
lock is released. In case of failure of the timing device, the contractor shall be permitted to operate while
it is being repaired, provided an approved timepiece equipped with minute and second readings is
furnished. If the timing device is not placed in good working order within 24 hours, further use of the
mixer will be prohibited until repairs are made.
b. Minimum mixing time shall be as follows:
(1) For mixers of a capacity of 1 cubic yard (0.8 cubic meter) or less – 90 seconds unless a shorter time is
shown to be satisfactory in accordance with concrete uniformity test requirements of ASTM C94.
(2) For mixers of a capacity greater than 1 cu yd (0.8 cubic meter), the time of mixing shall be increased
25 seconds for each cubic yard (0.8 cubic meter) of capacity or fraction thereof or as determined by
the concrete uniformity test requirements of ASTM C94.
c.
The production of concrete shall meet the applicable requirements of ASTM C94.
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Materials, Tests and Construction Requirements
1.13.3 READY-MIXED CONCRETE (2009)
Ready mixed concrete shall be mixed and delivered to the site by any of three methods of operation: central
mixing, shrink mixing or truck mixing. The production of ready-mixed concrete shall conform to the
requirements of ASTM C94. The batch plant providing ready-mixed concrete shall be certified by the National
Ready Mix Concrete Association.
1.13.4 DELIVERY (2009)
a.
The organization supplying concrete shall have sufficient plant capacity and transporting equipment to
ensure continuous delivery at the rate required. The rate of delivery of concrete during concrete
operations shall be such as to provide for the proper handling, placing, and finishing of the concrete. The
methods of delivering and handling concrete shall facilitate placing with minimum rehandling and
without damage to the structure or concrete.
b. The Contractor shall submit records to the Engineer showing the time and date of each batch produced
and the mix proportions and the approximate location within the structure of each batch.
1.13.5 REQUIREMENTS WHEN USING SILICA FUME IN CONCRETE (2009)
1.13.5.1 Material Handling Procedures When Using Silica Fume
It is recommended that persons handling silica fume use protective equipment and procedures to minimize the
generation and accumulation of dust. Manufacturers’ material safety data sheets should be consulted for
specific health and safety practices to be followed.
1
1.13.5.2 Workability of Delivered Concrete
Tests for slump and entrained air content should be carried out at the site before placing concrete containing
silica fume to ensure that specification limits are met.
3
SECTION 1.14 DEPOSITING CONCRETE
4
1.14.1 GENERAL (2000)
Before beginning placement of concrete, hardened concrete and foreign materials shall be removed from the
inner surfaces of the mixing and conveying equipment. Before depositing any concrete all debris shall be
removed from the space to be occupied by the concrete, and mortar splashed upon the reinforcement and
surfaces of forms shall be removed. Reinforcement shall be checked for position and fastening and approval of
the Engineer obtained. Where concrete is to be placed on a rock foundation, all loose rock, clay, mud, etc., shall
be removed from the surface of the rock. Any unusual conditions or excess fissures shall be treated as directed
by the Engineer. Water shall be removed from the space to be occupied by the concrete before concrete is
deposited, unless otherwise directed by the Engineer. Any flow of water into an excavation shall be diverted
through proper side drains to a sump, or be removed by other approved methods which will avoid washing the
freshly deposited concrete. If directed by the Engineer water ventpipes and drains shall be filled by grouting or
otherwise after the concrete has thoroughly hardened. All temporary runways for delivery of concrete must be
supported free from all reinforcing steel. The supervisor of the concrete placing crew shall maintain
certification by the American Concrete Institute as a Concrete Flatwork Finisher, or Concrete Transportation
Construction Inspector.
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1.14.2 HANDLING AND PLACING (1993)
a.
Concrete shall be handled from the mixer, or in case of ready-mixed concrete, from the transporting
vehicle, to the place of final deposit as rapidly as practicable by methods which will prevent the
separation or loss of the ingredients. Special care shall be taken to fill each part of the forms by
depositing concrete as near final position as possible, to work the coarser aggregates back from the face
and to force the concrete under and around the reinforcement without displacing it. Concrete shall not
have a free fall of more than 4 feet unless permitted by the Engineer. Depositing a large quantity at any
point and working it to final position, shall not be permitted.
b. Concrete shall be placed in horizontal layers and each layer shall be placed and compacted before the
preceding layer has taken initial set so as to prevent formation of a joint. It shall be so deposited as to
maintain, until the completion of the unit, a plastic surface approximately horizontal, except in arch
rings. Temporary struts or braces within the form shall be removed when concrete has reached an
elevation rendering their further service unnecessary. These temporary members shall be entirely
removed from the forms and not buried in the concrete. After the concrete has taken its initial set, care
shall be exercised to avoid jarring the forms or placing any strain on the ends of the projecting
reinforcement. Under no circumstances shall concrete that has partially hardened be deposited in the
work.
c.
In placing concrete for an arch ring, the work shall be carried on symmetrically with respect to the
center line, and the working faces of the completed courses shall be on approximately radial planes. This
requirement applies whether or not the arch is placed in voussoir sections with allowance for key
sections for final placement.
d. In order to allow for shrinkage or settlement, at least 2 hours shall elapse after placing concrete in walls,
columns or stems of deep T-beams before depositing concrete in girders, beams or slabs supported
thereon, unless otherwise specified or shown on the plans. If the columns are structural steel encased in
concrete, the lapse of time to allow for shrinkage or settlement need not be observed.
e.
Concrete in girders, slabs and shallow T-beam construction shall be placed in one continuous operation
for each span, unless otherwise provided. Concrete shall be deposited uniformly for the full length of the
span and brought up evenly in horizontal layers.
f.
No concrete shall be placed in the superstructure until the pier forms have been stripped sufficiently to
determine the character of the concrete in the piers, and the load of the superstructure shall not be
allowed to come upon abutments, piers and column bents until they have been in place at least 7 days,
unless otherwise permitted by the Engineer.
1.14.3 CHUTING (1993)
When concrete is conveyed by chuting, the plant shall be of such size and design as to insure a practically
continuous flow in the chute. The chutes shall be of metal or metal lined. The angle of the chute with the
horizontal and the shape of the chute shall be such as to allow the concrete to slide without separation of the
ingredients. The delivery end of the chute shall be as close as possible to the point of deposit. When the
operation is intermittent, the chute shall discharge into a hopper. The chute shall be thoroughly flushed with
water before and after each run: the water used for this purpose shall be discharged outside the forms. Chutes
must be properly baffled or hooded at the discharging end to prevent separation of the aggregates.
1.14.4 PNEUMATIC PLACING (SHOTCRETING) (1993)
Shotcrete construction shall be in accordance with ACI Standard “Guide to Shotcrete” (ACI 506) and ACI
Standard “Specification for Materials, Proportioning, and Application of Shotcrete” (ACI 506.2) of the ACI.
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Materials, Tests and Construction Requirements
1.14.5 PUMPING CONCRETE (1993)
a.
The pump and all appurtenances shall be so designed and arranged that the specified concrete can be
transported and placed in the forms without segregation. The pump shall be capable of developing a
working pressure of at least 300 psi and the pipeline and fittings shall be designed to withstand twice the
working pressure.
b. Where it is necessary to lay the pipe on a down grade, a reducer shall be placed at the discharge end of
the pipe to provide a choke and thus produce a continuous flow of concrete. When the type of pump is
such that it discharges the concrete in small batches, or “belching,” a baffle box shall be provided into
which the concrete shall be discharged. This box should preferably be of metal, about 2 feet square, with
open sides so as to permit the concrete to flow into the forms at right angles to line of discharge. The pipe
shall be not less than 6 inches nor more than 8 inches outside diameter, and the line shall be laid with as
few bends as possible. When changes in direction are necessary they shall be made with bends of 45
degrees or less, unless greater bends are specifically permitted. If greater bends are permitted in special
cases, they shall be long-radius bends. The maximum distance of delivery of concrete by pumping shall
be 1000 feet horizontally and 100 feet vertically, unless otherwise specifically permitted by the Engineer.
(A 90-degree bend is figured as equivalent to 40 feet of horizontal piping. A 45-degree bend is equivalent
to 20 feet. A 22.5-degree bend is equivalent to 10 feet.) When pumping is completed, the concrete
remaining in the pipeline if it is to be used, shall be ejected in such a manner that there will be no
contamination of the concrete or separation of the ingredients. The pipeline and equipment must then
be thoroughly cleaned. The pipeline can be cleaned by either water or air. If water is used, a pump shall
be provided with a capacity of at least 80 gpm and capable of developing a pressure of 400 psi. Cleaning of
the pipe can also be accomplished by the use of a “go-devil” which is propelled through the line by water
or air pressure. (The “go-devil” is a dumbbell shaped piece with a rubber cup on each end. The cups are
turned toward the liquid, or air, and the seal is the same as in a simple plunger pump.) If water is used, it
must be discharged outside of the forms. On important work duplicate pumping equipment and
additional pipe shall be provided to prevent delay due to breakdown of equipment.
1.14.6 COMPACTING (1993)
a.
3
Concrete shall be thoroughly compacted during and immediately after depositing by vibrating the
concrete internally by means of mechanical vibrating equipment, unless otherwise directed by the
Engineer.
b. Internal mechanical vibrators shall be of a type approved by the Engineer. They shall be of sturdy
construction, adequately powered, capable of transmitting vibration to the concrete in frequencies of not
less than 3500 impulses per minute and shall produce a vibration of sufficient intensity to consolidate
the concrete into place without a separation of the ingredients.
c.
1
The vibratory elements shall be inserted into the concrete at the point of deposit and in the areas of
freshly placed concrete. The time of vibration shall be of sufficient duration to accomplish thorough
consolidation, complete embedment of the reinforcement, the production of smooth surfaces free from
honeycomb and air bubbles, and to work the concrete into all angles and corners of the forms. However,
over-vibration shall be avoided, and vibration shall continue in a spot only until the concrete has become
uniformly plastic and shall not continue to the extent that pools of grout are formed. The length of time
of vibration depends upon the frequency of the vibration (impulses per minute), size of vibrators and the
slump of the concrete. This length of time must be determined in the field.
d. The internal vibrators shall be applied at points uniformly spaced, not farther apart than the radius over
which the vibration is visibly effective, and shall be applied close enough to the forms effectively to
vibrate the surface concrete. The vibration shall not be dissipated in lateral motion but shall be
concentrated in vertical settlement in consolidation of the concrete.
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Concrete Structures and Foundations
e.
The vibrator shall not be used to push or distribute the concrete laterally. The vibrating element shall be
inserted in the concrete mass a sufficient depth to vibrate the bottom of each layer effectively, in as
nearly a vertical position as practicable. It shall be withdrawn completely from the concrete before being
advanced to the next point of application.
f.
To secure even and dense surfaces, free from aggregate pockets or honeycomb, vibration shall be
supplemented by working or spading by hand in the corners and angles of forms and along form surfaces
while the concrete is plastic under the vibratory action.
g.
A sufficient number of vibrators shall be employed so that, at the required rate of placement, thorough
consolidation is secured throughout the entire volume of each layer of concrete. Extra vibrators shall be
on hand for emergency use and for use when other vibrators are being serviced.
h. The use of surface vibrators to supplement internal vibration will be permitted when satisfactory
surfaces cannot be obtained by the internal vibrations alone and when the contractor has obtained the
approval of the Engineer of the equipment to be used. Surface vibrators shall be applied only long
enough to embed the coarse aggregate and to bring enough mortar to the surface for satisfactory
finishing.
i.
The use of approved form vibrators will be permitted by the Engineer only when it is impossible to use
internal vibrators. They shall be attached to or held on the forms in such a manner as to effectively
transmit the vibration to the concrete and so that the principal path of motion of the vibration is in a
horizontal plane.
1.14.7 TEMPERATURE (1993)
a.
Concrete when deposited shall have temperatures within the limits shown in Table 8-1-13.
Table 8-1-13. Concrete Temperature Limits
Temperature of Air
Degrees - F
Temperature of Concrete
When Placed–Degrees F
Minimum
Maximum
Below 30
70
90
Between 30 and 45
60
90
Above 45
50
90
b. The method of controlling the temperature of the concrete shall be approved by the Engineer.
1.14.8 CONTINUOUS DEPOSITING (1993)
Concrete shall be deposited continuously and as rapidly as practicable until the unit of operation approved by
the Engineer is completed. Construction joints in addition to those provided on the plans will not be allowed
unless authorized by the Engineer. If so authorized, they shall be made in accordance with Section 1.11,
Concrete Jointing.
1.14.9 BONDING (1993)
Before new concrete is placed against hardened concrete, the surface of the hardened concrete shall be cleaned
and all laitance removed. Immediately before new concrete is placed, the existing surfaces shall be thoroughly
wetted and all standing water removed. Prior to placing fresh concrete, apply a bonding layer of mortar, usually
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Materials, Tests and Construction Requirements
1/8 inch to 1/2 inch in thickness, which is spread on the moist and prepared hardened concrete surface. In lieu
of mortar, a suitable commercial bonding agent may be used, when applied in accordance with manufacturer’s
recommendations.
1.14.10 PLACING CYCLOPEAN CONCRETE (1993)
Cyclopean aggregate shall be thoroughly embedded in the concrete. The individual stones shall not be closer
than 12 inches to any surface or adjacent stones. Stratified stone shall be laid on its natural bed. Cyclopean
aggregate shall be carefully placed to avoid injury to forms or adjoining masonry.
1.14.11 PLACING RUBBLE CONCRETE (1993)
Rubble aggregate shall be thoroughly embedded in the concrete. The individual stones shall not be closer than
4 inches to any surface or adjacent stones. Rubble aggregate shall be carefully placed to avoid injury to forms or
adjacent masonry.
1.14.12 PLACING CONCRETE CONTAINING SILICA FUME (2004)1
1.14.12.1 Protection from Moisture Loss
Protection of concrete from early moisture loss is to begin at the first opportunity after placement and may
require that such measures precede the curing phase of the work. Evaporation retarders, fogging and
protection from the wind during the placement stage, or immediate curing, may be options included in the
project specifications. Appropriate measures to protect against early moisture loss in concrete containing silica
fume should be included and stressed in the project specifications. Subgrade moistening may be required to
prevent excessive drying from the underside of the concrete.
1
1.14.12.2 Consolidation
Careful attention to effective vibration is required for concrete containing silica fume.
3
1.14.13 PLACING CONCRETE CONTAINING FLY ASH (2004)
1.14.13.1 Air Entrainment
Tests shall be performed at the site to verify that the required amount of entrained air is present at the time of
depositing the concrete.
1.14.14 WATER GAIN (1993)
Water gain is characterized by an accumulation of water at the surface. Whenever water gain appears in the
concrete placed, the succeeding batches must be placed sufficiently dry to correct the over-wet condition by the
reduction of the water cement ratio without changing the proportions of the other ingredients.
1
See C - Commentary
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SECTION 1.15 DEPOSITING CONCRETE UNDER WATER
1.15.1 GENERAL (1993)
a.
The methods specified in Section 1.14, Depositing Concrete shall be used except when the space to be
filled with concrete contains water which cannot be removed in some practical way. In such cases, and
when authorized by the Engineer, concrete shall be deposited under water in accordance with the
following.
b. The methods, equipment and materials proposed to be used, shall be submitted first to the Engineer for
approval before the work is started. The methods used shall be such as will prevent the washing out of
the cement from the concrete mixture, minimize the segregation of materials and the formation of
laitance, and prevent the flow of water through or over the new concrete until it has fully hardened.
Concrete shall not be placed in water having a temperature below 35 degrees F.
1.15.2 CAPACITY OF PLANT (1993)
Sufficient mixing, transporting and placing equipment shall be provided to insure that the depositing of all
underwater concrete for each predetermined section or unit of the work to be done, shall be continuous until
completion.
1.15.3 STANDARD SPECIFICATIONS (1993)
The materials, preparations and methods to be used in making concrete to be deposited under water shall all
conform to the requirements of these specifications except as modified or supplemented by the following
Articles.
1.15.4 CEMENT (1993)
Not less than 610 lb of cement per cubic yard of concrete shall be used.
1.15.5 COARSE AGGREGATES (1993)
Aggregate for this work shall be of exceptionally good quality, strong and durable. The maximum size of
aggregate preferably shall be 2 inches and shall not exceed 3 inches. The coarse aggregate shall be well graded
in such proportions that the weight of the coarse aggregate shall be not less than 1.25 nor more than 2.0 times
that of the fine aggregate.
1.15.6 MIXING (1993)
The cement and aggregates shall be mixed for a period of 2 minutes with sufficient water to produce a concrete
having a slump of not less than 6 inches nor more than 8 inches for concrete placed by tremies, and not less
than 3 inches nor more than 6 inches for concrete placed by bottom dump buckets or for concrete placed in
sacks.
1.15.7 CAISSONS, COFFERDAMS OR FORMS (1993)
Caissons, cofferdams or forms shall be sufficiently tight to prevent loss of mortar or flow of water through the
space in which the concrete is to be deposited. Pumping will not be permitted while concrete is being deposited,
nor until a minimum of 24 hours thereafter or longer period if required by the Engineer.
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Materials, Tests and Construction Requirements
1.15.8 LEVELING AND CLEANING THE BOTTOM TO RECEIVE CONCRETE (1993)
a.
Before starting to deposit concrete under water, the condition of the bottom shall be examined and
reported upon to the Engineer by a competent diver, and shall be approved by the Engineer.
b. The surface of the bottom, whether of clay, rock, or other material, shall be leveled as directed by the
Engineer, before depositing concrete under water.
c.
Where the bottom on which concrete is to be deposited under water is, or is likely to be, covered with silt,
such material shall be removed down to solid material before any concrete is placed. The method to be
used to clean the bottom of silt or similar material, shall be subject to the approval of the Engineer.
1.15.9 CONTINUOUS WORK (1993)
Concrete shall be deposited continuously until it is brought up to the required elevation. While depositing, the
top surface shall be kept as nearly level as possible, and the formation of laitance planes avoided.
1.15.10 METHODS OF DEPOSITING (1993)
a.
Tremie. When concrete is to be deposited under water by means of a tremie, the top section of the tremie
shall be a hopper large enough to hold one entire batch of the mix or the entire contents of the
transporting bucket, when one is used. The tremie pipe shall be not less than 8 inches in diameter and
shall be large enough to allow a free flow of concrete and strong enough to withstand the external
pressure of the water in which it is suspended, even if a partial vacuum develops inside the pipe.
Preferably, flanged steel pipe should be used, of adequate strength to sustain the greatest length and
weight required for the job. A separate lifting device shall be provided for each tremie pipe with its
hopper at the upper end. Unless the lower end of the pipe is equipped with an approved automatic check
valve, the upper end of the pipe shall be plugged with an approved material, before delivering the
concrete to the tremie pipe through the hopper, which plug will be forced to and out of the bottom end of
the pipe by filling the pipe with concrete. It will be necessary to slowly raise the tremie in order to cause
a uniform flow of the concrete, but the tremie shall not be emptied so that water enters above the
concrete in the pipe. At all times after the start of placing the concrete and until all concrete is placed,
the lower end of the tremie pipe shall be below the top surface of the plastic concrete. This will cause the
concrete to build up from below instead of flowing out over the surface thus avoiding formation of
laitance layers. If the charge in the tremie is lost while depositing, the tremie shall be raised above the
concrete surface, and unless sealed by a check valve it shall be replugged at the top end, as at the
beginning, before refilling for depositing concrete.
NOTE:
Experience has shown that tremie concrete can be placed as above specified, so that it will flow
as much as 50 feet horizontally from the discharge end of the tremie with a slope of less than 3
feet in 50 feet.
b. Bottom Dump Bucket. Where concrete is to be deposited under water by means of a bottom dump bucket,
the bucket shall be of the type that cannot be dumped until after it has rested, with its load, on the
surface upon which the concrete is to be deposited. The bottom doors shall be so equipped as to be
automatically unlatched by the release of tension on the supporting line or cable of the bucket, and the
bottom doors shall then open downward and outward as the bucket is raised. The top of the bucket shall
be fitted with double, overlapping canvas flaps, or other approved covers, to cover the contained concrete
and to protect it from wash when it enters the water and as the bucket descends to the bottom. The
bucket, preferably, should be so designed that the hinged bottom doors will operate inside of a steel skirt,
which skirt will surround the bucket while the bottom doors are shut and will extend below the bucket
as the bottom doors open and hence minimize turbulence and motion while the concrete is being
deposited. The bucket shall be submerged slowly until it is completely under water. The normal line
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speed after that shall not exceed 200 feet per minute. After the bucket has reached the surface on which
the concrete is to be deposited, it shall be raised slowly for the first 6 or 8 feet while the concrete is being
deposited.
c.
Placing Sacks of Concrete. Where a relatively small amount of concrete is to be placed that does not
warrant the equipment required for other tremie or open-bottom bucket methods, concrete may be
placed under water in sacks or bags. In such case the space shall be filled with sacks of concrete carefully
placed by hand in header and stretcher formation, so that the whole mass becomes interlocked. Sacks
used for this purpose shall be made of jute or other coarse material free from deleterious materials, and
shall be filled about two-thirds full of concrete and the sack openings securely tied.
d. Grouted Aggregate. Installed by placing course aggregate in the forms, then injecting cement grout
through pipes which extend to the bottom of the forms. The pipes are withdrawn as grouting proceeds.
The grout forces the water from the forms and fills interstices in the aggregate.
(1) Grout insert pipe system shall be designed and installed to deliver grout to the entire mass. Vent
pipes shall be required to relieve entrapped water or air. Sounding wells should be provided to
determine the location of grout surface during the grout injection.
(2) The coarse aggregate shall be placed in horizontal layers of such maximum thickness as will provide
a dense fill without segregation and shall be well compacted.
(3) The grout mixture shall be applied under such pressure and at such consistency as will insure
complete filling of voids, and group pipes shall be properly spaced to be consistent with this
requirement.
(4) Mineral fillers and admixtures may be added to the grout mixture if approved by the Engineer.
(5) The grout mixture required for this class of work necessitates the use of special mixers and agitators
to deliver suitable grout in place. This equipment and all grout lines shall be maintained in good
operating condition. After every shift or work stoppage, they shall be cleaned of all grout.
1.15.11 SOUNDINGS (1993)
During the time that concrete is being deposited under water, soundings shall be continuously taken to the
surface of the deposited concrete and recorded. The surface of the deposited concrete shall be maintained
relatively level over the area being covered.
1.15.12 REMOVING LAITANCE (1993)
Upon completing a unit or section of underwater concrete, any laitance or silt collecting on the upper surface of
the same shall be removed and the concrete surface thoroughly cleaned, if additional concrete is to be deposited
on that surface.
1.15.13 CONCRETE SEALS (1993)
Under favorable conditions it is possible to place underwater concrete of a limited thickness in the bottoms of
caissons or cofferdams and so completely seal the structures that after the concrete has set, all water can be
pumped out. In such cases, if it is economical to do so, the water shall be pumped out, the exposed surfaces
cleaned and the balance of the concrete deposited in air.
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Materials, Tests and Construction Requirements
SECTION 1.16 CONCRETE IN SEA WATER
1.16.1 CONCRETE (2004)
a.
Unless otherwise specifically provided, concrete for structures in, or exposed to, sea water shall be airentrained in accordance with Article 1.12.4, and shall be made with Type II or IIA portland cement
having a maximum tricalcium aluminate content of 8%. Concrete in sea water or exposed directly along
the sea coast shall contain a minimum of 560 lb of portland cement per cubic yard. The concrete shall be
mixed for a period of not less than 2 minutes and the water content of the mixture shall be carefully
controlled and regulated so as to produce concrete of maximum impermeability. Porous or weak
aggregates shall not be used.
b. When concrete mix designs include cementitious materials other than portland cement, the resistance to
the harmful effects of exposure to sea water shall be determined by tests, or by experience from using
materials from the same sources.
1.16.2 DEPOSITING IN SEA WATER (1993)
Between levels of extreme low water and extreme high water as determined by the Engineer, sea water shall
not come in direct contact with the concrete for a period of not less than 30 days. Sea water shall not be allowed
to come in contact with other concrete that will be in or exposed to sea water until it is hardened for at least 4
days. Concrete may be deposited in sea water only when so approved by the Engineer. The original surface, as
the forms are removed from the concrete, shall be left undisturbed.
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1.16.3 CONSTRUCTION JOINTS (1993)
Concrete shall be placed in such a manner that no construction joints shall be formed between levels of extreme
low water and extreme high water as determined by the Engineer. Construction joints outside the level between
extreme low water and extreme high water shall be held to the minimum necessary, and all construction joints
shall be made as described in Section 1.11, Concrete Jointing and Section 1.14, Depositing Concrete,
Article 1.14.9.
3
1.16.4 MINIMUM COVER (1993)
Reinforcing steel or other corrodible metal shall have a cover of not less than 4 inches of concrete.
4
1.16.5 PROTECTING CONCRETE IN SEA WATER (1993)
Where severe climatic conditions or severe abrasions are anticipated, the face of the concrete from 2 feet below
low water to 2 feet above high water, or from a plane below to a plane above wave action, shall be protected by
stone of suitable quality, dense vitrified shale brick as designated or as required by the Engineer, or in special
cases the protection may be creosoted timber.
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SECTION 1.17 CONCRETE IN ALKALI SOILS OR ALKALI WATER
1.17.1 CONDITION OF EXPOSURE (1993)
In areas where concrete may be exposed to injurious concentrations of sulfates from soils and waters, concrete
shall be made with sulfate resisting cement. Table 8-1-14 gives limitations on tricalcium aluminate content in
cement for various exposure conditions, severity of conditions may be judged by the extent of deterioration
which has occurred to concrete previously used in the immediate vicinity or from the sulfate concentrations
found in either the soil or the water.
Table 8-1-14. Recommendations For Concrete In Sulfate Exposures
Normal Weight
Aggregate
Concrete
Sulfate Concentration as SO4
Sulfate
Exposure
Maximum
Tricalcium
Aluminate in Maximum WaterCement,
Percent Cementitious
In Soil, Percent
In Solution, PPM
(Note
1)
by Weight
Material Ratio,
by Weight
Lightweight
Aggregate
Concrete
Minimum
Compression
Strength, f¢ c,
psi
Moderate
0.10–0.20
150–1500
8
0.50
3750
Severe
0.20–2.00
1500–10,000
5
0.45
4000
Very Severe
over 2.00
over 10,000
5 plus pozzolan
(Note 2)
0.45
4000
Note 1: Maximum tricalcium aluminate content of cement for concrete in seawater shall be 8%.
Note 2: Use a pozzolan which has been determined by tests to improve sulfate resistance when used in
concrete containing a cement with a maximum tricalcium aluminate content of 5% or less.
1.17.2 CONCRETE FOR MODERATE EXPOSURE (1993)
Concrete for moderate sulfate exposure shall be made from Type II or specified portland blast furnace slag
cement Type IS (MS), and portland pozzolan cement Type IP (MS) may be used to meet the 8% tricalcium
aluminate limitation. Concrete shall contain not less than 610 lb of cement per cu yd. The concrete shall be airentrained in accordance with Section 1.12, Proportioning, Article 1.12.4.
1.17.3 CONCRETE FOR SEVERE EXPOSURE (1993)
Concrete for severe sulfate exposure shall be made using Type V portland cement with a 5% maximum
tricalcium aluminate content. Concrete shall contain not less than 660 lb of cement per cu yd. The concrete
shall be air-entrained in accordance with Section 1.12, Proportioning, Article 1.12.4.
1.17.4 CONCRETE FOR VERY SEVERE EXPOSURE (1993)
Concrete for very severe exposure shall be made using Type V portland cement with a 5% maximum tricalcium
aluminate content plus pozzolan. The pozzolan used should have been determined by tests to improve the
sulfate resistance of concrete containing a cement with a maximum tricalcium aluminate content of 5% or less.
The concrete shall contain not less than 660 lb of cement per cu yd. The concrete shall be air-entrained in
accordance with Section 1.12, Proportioning, Article 1.12.4.
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Materials, Tests and Construction Requirements
NOTE:
Type III may also be specified to meet either the 5% or 8% tricalcium aluminate
limitation. In certain areas the tricalcium aluminate content of other types of cement may
be less than 5% or 8%. Sulfate resisting cement will not increase resistance to some
chemically aggressive solutions, for example ammonium nitrate. The special provisions of
the project specifications shall cover all special cases.
1.17.5 CONCRETE FOR ALKALI SOILS OR ALKALI WATER (2004)
When concrete mix designs include cementitious materials other than portland cement, resistance to the
harmful effects of exposure to alkali soils or alkali water shall be determined by tests, or by experience from
using materials from the same sources.
1.17.6 CONSTRUCTION JOINTS (1993)
Wherever possible, placing of concrete shall be continuous until completion of the section or until the concrete
is at least 18 inches above ground or water level. If construction joints are required they shall be minimized,
and all construction joints shall be made as described in Section 1.11, Concrete Jointing and Section 1.14,
Depositing Concrete, Article 1.14.9.
1.17.7 MINIMUM COVER (1993)
Reinforcing steel or other corrodible metal shall have a cover of not less than 4 inches of concrete.
1
1.17.8 PLACEMENT OF CONCRETE (1993)
Alkaline water or soils shall not be in contact with the concrete during placement and for a period of at least 72
hours thereafter.
3
SECTION 1.18 CURING
1.18.1 GENERAL (2000)
a.
In freezing weather, or when there is likelihood of freezing temperatures within the specified curing
period, suitable and sufficient means must be provided before concreting, for maintaining all concrete
surfaces at a temperature of not less than 50 degrees F (10 degrees C) for a period of not less than 7 days
after the concrete is placed when Type I, IA, II or IIA portland cement is used, and not less than 3 days
when Type III or IIIA portland cement is used.
b. The temperature of concrete surfaces shall be determined by thermometers placed against the surface of
the concrete. Provision shall be made in form construction to permit the removal of small sections of
forms to accommodate the placing of thermometers against concrete surfaces at locations designated by
the Engineer. After thermometers are placed, the apertures in forms shall be covered in a way to
simulate closely the protection afforded by the forms.
c.
In determining the temperatures at angles and corners of a structure, thermometers shall be placed not
more than 8 inches (200 mm) from the angles and corners. In determining temperatures of horizontal
surfaces, thermometers shall rest upon the surface under the protection covering normal to section
involved.
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d. Temperature readings shall be taken and recorded at intervals to be designated by the Engineer, over the
entire curing period specified, and the temperatures so recorded shall be interpreted as the temperature
of the concrete surfaces when the thermometers were placed.
e.
When protection from cold is needed to insure meeting these specification requirements, all necessary
materials for covering or housing must be delivered at the site of the work before concreting is started
and must be effectively applied or installed, and such added heat must be furnished as may be necessary
without depending in any way upon the heat of hydration during the first 24 hours after concrete is
placed when Type I, IA, II or IIA portland cement is used, or the first 18 hours when Type III or IIIA
portland cement is used. The methods of heating and protecting the concrete shall be approved by the
Engineer. Chemicals or other foreign materials shall not be mixed with the concrete for the purpose of
preventing freezing, unless approved by the Engineer.
f.
When heat is supplied by steam or salamanders, covering or housing of the structure shall be so placed as
to permit free circulation of air above and around the concrete within the enclosure, but to the exclusion
of air currents from without, except that where salamanders are used, sufficient ventilation shall be
provided to carry off gases. Special care shall be exercised to maintain the specified temperature
continuously and uniformly in all parts of the structure enclosures, and to exclude cold drafts from
angles and corners and from all projecting reinforcing steel. All exposed surfaces in the heated enclosure
shall be kept continuously wet during the heating period unless heat is supplied in the form of live
steam.
g.
The supervisor responsible for curing procedures shall maintain certification by the American Concrete
Institute as a Concrete Flatwork Finisher or Concrete Transportation Construction Inspector.
1.18.2 HOT WEATHER CURING (1993)
a.
The temperature of concrete at times of placement shall not exceed 90 degrees F (32 degrees C). When
the temperature of the concrete approaches 90 degrees F (32 degrees C), special efforts to prevent too
rapid drying out must be made.
b. Continuous wet curing is preferred and shall commence as soon as the concrete has hardened sufficiently
to resist surface damage. Wet curing shall be carried out in accordance with the practice recommended
under Article 1.18.3. Curing water shall not be much cooler than the concrete to avoid temperaturechange stresses resulting in cracking. Exposed, unformed concrete surfaces shall be protected from wind
and direct sun.
1.18.3 WET CURING (1993)
a.
All concrete surfaces when not protected by forms, or membrane curing compounds, must be kept
constantly wet for a period of not less than 7 days after concrete is placed when Type I, IA, II or IIA
portland cement is used, or not less than 3 days when Type III or IIIA portland cement is used.
b. The wet curing period for all concrete which will be in contact with brine drip, sea water, salt spray,
alkali or sulfate-bearing soils or waters, or similar destructive agents, shall be increased to 50% more
than the periods specified for normal exposures. Salt water and corrosive waters and soils shall be kept
from contact with the concrete during placement and for the curing period.
c.
When wood forms are left in place during the curing period they shall be kept sufficiently damp at all
times to prevent openings at the joints and drying of the concrete.
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Materials, Tests and Construction Requirements
1.18.4 MEMBRANE CURING1 (1993)
a.
In lieu of wet curing, a concrete curing compound in full conformance to ASTM C309 may be used, with
the approval of the Engineer.
b. Liquid Membrane-Forming Curing Compounds shall meet the requirements of ASTM C309:
(1) Type 1 (Clear).
(2) Type 1D (Clear with Fugitive Dye).
(3) Type 2 (White Pigmented).
(4) Class B (Solids Restricted to Resin Only).
c.
The compounds shall be applied to all exposed concrete surfaces except those areas where concrete or
other materials are to be bonded, such as construction joints or areas to be dampproofed or
waterproofed.
d. The compound shall be sprayed on finished surfaces as soon as the surface water has disappeared.
Spraying equipment shall be of the pressure-tank type with mist producing spray orifice. If forms are
removed during the curing period, concrete shall be sprayed lightly with water and the moistening
continued until the surface will not readily absorb more water. The curing compound shall then be
sprayed on the concrete surface as soon as the moisture film has disappeared.
1
1.18.5 STEAM CURING (1993)
Steam curing shall be done in an enclosure capable of containing the live steam in order to minimize moisture
and heat losses. The application of the steam shall be delayed from 2 to 4 hours after final placement of
concrete to allow the initial set of the concrete to take place. If retarders are used, the waiting period before
application of the steam may be increased to 4 to 6 hours. The steam shall be at 100% relative humidity to
prevent loss of moisture and to provide excess moisture for proper hydration of the cement. Application of the
steam shall not be directly on the concrete. During application of the steam, the ambient air temperature shall
increase at a rate not to exceed 40 degrees F (4.5 degrees C) per hour until a maximum temperature of 140
degrees F to 160 degrees F (60 degrees C to 70 degrees C) is reached. This temperature shall be held for 12 to 18
hours or until the concrete has reached the required strength. In discontinuing the steam, the ambient air
temperature shall decrease at a rate not to exceed 40 degrees F (4.5 degrees C) per hour until a temperature has
been reached about 20 degrees F (-7 degrees C) above the temperature of the air to which the concrete will be
exposed. The concrete shall not be exposed to temperatures below freezing for 6 days after casting.
1.18.6 CURING CONCRETE CONTAINING SILICA FUME (2003)2
1.18.6.1 Delays in Implementing Curing
Curing of freshly placed concrete as outlined in this Article should be implemented immediately upon having
placed the concrete or other measures should be taken to minimize the opportunity for shrinkage cracking to
occur.
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2
See C - Commentary
See C - Commentary
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1.18.7 CURING CONCRETE CONTAINING GROUND GRANULATED BLAST-FURNACE
SLAG (2004)1
1.18.7.1 General
Curing time may have to be extended due to slower strength gain during the initial curing period.
1.18.7.2 Delays in Implementing Curing
Curing of freshly placed concrete as outlined in this Article may require implementation sooner than normal if
the mix exhibits less bleed water than normal.
1.18.8 CURING CONCRETE CONTAINING FLY ASH (2004)2
Curing procedures and times should be determined from the concrete mix design requirements.
SECTION 1.19 FORMED SURFACE FINISH
1.19.1 GENERAL (2005)
The following requirements, except as modified by the Plans or as approved by the Engineer, shall apply to the
construction of concrete surfaces exposed upon the completion of the structure:
a.
Construct all face forms smooth and watertight. If constructed of wood, size the face boards to a uniform
thickness and dress all offsets or inequalities to a smooth surface. Fill and point flush all openings and
cracks, as approved by the Engineer, to prevent leakage and the formation of fins.
b. Cast concrete in one continuous operation between prescribed construction limits, true to line with
sharp, unbroken edges beveled or rounded as specified. Make joints not shown on the plans only if
approved by the Engineer.
c.
Mix, place and consolidate concrete so that the aggregate is uniformly distributed and a full surface of
mortar, free from air pockets and void spaces, is brought against the form.
d. Remove the forms carefully. Remove any fins or projections neatly as approved by the Engineer. If any
small pits or openings appear in the exposed surface of the concrete, or if the removal of bolts used for
securing the forms leave small holes, thoroughly saturate the surface with water and neatly fill all such
holes, pits, etc., with an approved mortar. Smooth with a wooden float to achieve an even finish. Mix the
pointing mortar in small quantities, and use while still plastic.
1
2
e.
Perform all work in connection with the correction of damaged sections, voids or honeycomb as approved
by the Engineer.
f.
Do not apply mortar or cement to the surface except to fill pits or voids, tie bolt holes, etc., as provided
above, and not by plastering.
See C - Commentary
See C - Commentary
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Materials, Tests and Construction Requirements
1.19.2 RUBBED FINISH (2005)
a.
Do not rub the surface unless called for on the plans or directed by the Engineer.
b. Fill all voids. Then thoroughly wet the surface and rub with a carborundum brick, or similar abrasive, to
a smooth, even finish of uniform appearance without applying any cement or other coating.
SECTION 1.20 UNFORMED SURFACE FINISH
1.20.1 GENERAL (2005)
a.
After placing and consolidating concrete, strike off and finish with floats and trowels or finishing
machines in a manner approved by the Engineer. Finish edges with an edging tool satisfactory to the
Engineer. Take care to avoid an excess of water in the concrete and drain or otherwise promptly remove
any water that accumulates on the surface. Do not sprinkle dry cement, or a mixture of cement and sand,
directly onto the surface.
b. Slope all horizontal surfaces of bridge seats to drain, except those directly under bearing plates.
c.
Require the supervisor responsible for finishing unformed surfaces to have and maintain certification by
the American Concrete Institute as a Concrete Flatwork Finisher.
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1.20.2 SIDEWALK FINISH (2005)
Float and trowel the top surface of all walks to a smooth finish with a steel trowel. After the water sheen has
disappeared, final finish the surface by brushing with a bristle brush. Draw the brush across the walk, at right
angles to the edge of the walk. Adjacent strokes should slightly overlap, to produce a uniform surface,
moderately roughened by parallel brush marks. The stiffness of the bristles and the time at which the surface is
finished shall leave well defined brush marks. Keep the brush clean at all times to avoid depositing mortar
picked up during previous strokes.
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1.20.3 FINISHING CONCRETE CONTAINING SILICA FUME (2004)1
For concrete containing silica fume, trial placements and finishing may be required prior to the start of the
project.
1.20.4 FINISHING CONCRETE CONTAINING GROUND GRANULATED BLAST-FURNACE
SLAG (2004)2
Finishing techniques may have to be adjusted to account for reduced amounts of bleed water.
1.20.5 FINISHING CONCRETE CONTAINING FLY ASH (2004)
Finishing may have to be delayed unless the concrete mix was proportioned to avoid delayed setting.
1
2
See C - Commentary
See C - Commentary
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SECTION 1.21 DECORATIVE FINISHES
Construct special or decorative finishes as called for on the Plans and as set forth in a special specification or
special provision.
SECTION 1.22 PENETRATING WATER REPELLENT TREATMENT
OF CONCRETE SURFACES1
1.22.1 GENERAL (1993)
When called for on the plans, in the specifications or ordered by the Engineer the following requirements shall
be applicable to the treatment of exposed concrete surfaces upon completion of the structure or precast
member. Water repellent treatment is not intended to be used on surfaces subject to hydrostatic pressure.
1.22.2 SURFACE PREPARATION (2003)
a.
Concrete surfaces shall be cleaned by light sand or shot blasting, followed by vacuum cleaning to remove
all traces of curing compounds, laitance, dirt, salt, oil, grease, fluids or other foreign material that would
prevent penetration or adhesion of the sealer.
b. Concrete surface shall be clean and dry or as recommended by manufacturer. If concrete is subjected to
rain or moisture the surface should be allowed to air dry for a minimum of forty-eight (48) hours before
treatment.
c.
The cleaning process shall not alter the existing surface finish unless specified by the Engineer as an
intentional part of the design.
1.22.3 ENVIRONMENTAL REQUIREMENTS (2003)
a.
Volatile Organic Compound regulations may vary by individual state. Therefore, it is mandatory that
materials selected for use be in total conformance to the applicable legislation of the state within which
the work will be performed.
b. Ambient and surface temperatures at time of application shall be as specified by the manufacturer but
not less than 40 degrees F (5 degrees C) or greater than 100 degrees F (38 degrees C).
c.
No rain shall be predicted for a minimum of 12 hours after completion of water repellent treatment.
d. No precipitation shall occur within 24 hours preceding application.
1
e.
No wind shall be predicted of velocity, per the manufacturer, greater than that which will cause an
improper application rate to drift, etc.
f.
Adjoining surfaces of other materials shall be protected unless solvent carrier is certified as harmless to
these materials by water repellent manufacturer.
See C - Commentary
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1.22.4 APPLICATION (2003)
a.
The penetrating water repellent treatment solution shall be applied in strict accordance with
manufacturer’s instructions and not diluted or altered unless specified by the manufacturer. Equipment
for the application of the water-repellent treatment shall be clean of foreign materials and approved by
the Engineer before use. The sealer shall be applied by brushing, spraying or rolling, as recommended
by the manufacturer.
b. Surface treatment of new concrete prior to 28 days curing is not permitted, unless approved by the
manufacturer and the Engineer.
c.
The sealer manufacturer should be consulted on the recommended treatment of cracks.
d. Follow all safety precautions required by occupational jurisdiction.
e.
A minimum of two (2) coats of water-repellent treatment is recommended to achieve uniform coverage.
The second and each additional coat shall be applied perpendicular to the previous coat. Care shall be
taken when applying each coat, such that running or puddling does not occur. Each coat shall be allowed
to dry for a minimum of two (2) hours before the next coat is applied. The final coat shall be allowed to
dry according to the manufacturer’s instructions before applying ballast and track.
1.22.5 MATERIALS (2003)
a.
The penetrating water repellent material shall consist of an isobutyltrialkoxy silane, n-octyltrialkoxy
silane or iso-octytrialkoxy silane dissolved in a suitable solvent that will produce a hydrophobic surface
covalently bonded to the concrete. Only one (1) brand and specific type of penetrating sealer shall be
used on each individual concrete element (i.e., each pier, deck, abutment, etc.). The penetrating sealer
must be a one part liquid, with no field blending required.
b. Qualities of the material to be furnished for the project shall be tested and results certified by an
independent testing laboratory with report provided to the owner. The following tests shall be performed
on standardized laboratory specimens:
1
3
(1) Water Penetration. ASTM C642–50 Day Soak less 1% Absorption (untreated specimen 4%, 0.2%
absorption).
(2) Water Penetration. National Cooperative Highway Research Program Report 244–21 Day Soak–
Effective Average Minimum 80% (Series II).
(3) Vapor Transmission. National Cooperative Highway Research Program Report 244–Minimum 100%.
(4) Surface Appearance. No change in surface appearance or texture.
(5) Penetration. Oklahoma DOT OHD L-34 Visible Average 0.15 inches.
(6) Drying Time. Dry and ready for use 1 hour after application.
(7) Accelerated Weathering. ASTM G23–2000 hours are weatherometer–Maximum 3% loss of
effectiveness.
(8) Water Penetration. Alberta DOT Type 1 Class B minimum.
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(9) Salt Water Ponding. AASHTO T-259–Maximum 1.50 lb per cubic yard at 1/16 inch to 1/2 inch; 0.75 lb
per cubic yard at 1/2 inch to 1 inch.
(10) Traction – ASTM E303. No change when treated surface is compared to control surface. Measured in
British Pendulum Numbers.
1.22.6 QUALITY ASSURANCE (1993)
a.
The manufacturer shall provide written certification of the quality of the product being offered and issue
a warranty as to its effectiveness when it is applied in accordance with the manufacturer’s specifications.
b. Manufacturer shall have an established Quality Assurance Program with the Program available to the
owner or buyer.
c.
Pre-Test. An eight square feet (0.75 square meter) test panel on the job shall be treated and evaluated in
accordance with the primary water repellent manufacturer’s recommendations and written test
procedures which would allow the water repellent to cure for a minimum of 5 days. Two test cores
(minimum 3 inches (75 mm) diameter and 3 inches (75 mm) deep) should be taken at locations
determined by the Engineer. In the presence of the manufacturer, or one of its representatives, the cores
should be split by chisel. One core should be retained by the Engineer. The water repellent material shall
have penetrated the core at least 1/8 inch (3 mm) (avg) and shall appear as a band of non-wettable
concrete.
d. Test Data. All test data submitted by the water repellent manufacturer must be data generated by an
independent testing laboratory. Product tests must be totally controlled by the testing laboratory.
Specimens cannot be pre-treated by the manufacturer.
1.22.7 DELIVERY, STORAGE AND HANDLING (1995)
a.
Materials shall be delivered to job site in manufacturer’s original undamaged containers with labels and
seals intact.
b. Materials shall be stored in accordance with manufacturer’s requirements and in a dry area with a
temperature range of not less than 32 degrees F (0 degrees C) and not more than 120 degrees F (49
degrees C). Adequate ventilation shall be provided, away from sources of ignition.
c.
Manufacturer’s application instructions and Material Safety Data Sheet shall be consulted for additional
safety instructions.
SECTION 1.23 REPAIRS AND ANCHORAGE USING REACTIVE RESINS1
1.23.1 GENERAL (2003)
a.
1
This recommended practice covers reactive resin polymer materials (i.e. epoxy) used for concrete repairs
and installation of anchor bolts and other miscellaneous items in concrete.
See C - Commentary
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b. The material shall be a non-metallic, non-shrinking polymer resin supplied in prepackaged and/or premeasured containers. It shall contain no rust or corrosion promoting agents and shall be moisture
insensitive.
c.
Packaged stability of each component in original unopened containers stored in temperatures between
40 degrees F (5 degrees C) and 90 degrees F (32 degrees C) shall be a minimum of six months. The
mixing instructions, setting time and expiration date of the material shall appear on each container.
1.23.2 SURFACE PREPARATION (2003)
a.
The surface of the concrete should be prepared per the manufacturer’s recommendations for the type of
application being conducted.
b. The concrete surface shall be clean and dry, with no traces of curing compounds, laitance, dirt, salt, oil,
or grease.
1.23.3 APPLICATION (2003)
a.
The reactive resins should be chosen to provide the requirements (i.e. viscosity, strength, flexibility,
adhesion etc.) of the specific repair to be performed. The specific type, grade and class of material is to be
selected by the Engineer in accordance with the recommendations of the manufacturer.
1
SECTION 1.24 HIGH STRENGTH CONCRETE1
1.24.1 GENERAL (1995)
a.
The following specifications shall apply to structures with a minimum specified concrete compressive
strength of 6,000 psi (41 MPa) and made with portland cement concrete. These provisions do not apply to
“exotic” materials and techniques such as polymer-impregnated concrete, polymer concrete, or concrete
with artificial aggregates.
b. The compressive strength of production concrete shall be tested at 7 and 28 days and at other times as
required by the Engineer in accordance with ASTM C39.
1.24.2 MATERIALS (1995)
Trial batches containing the materials to be used on the job shall be prepared at the proposed slump and tested
to determine compressive strength. Unless tests on additional trial batches are performed, materials shall be of
the same type, brand and source of supply throughout the duration of the project.
1.24.2.1 Cement
a.
Cement mill test reports shall be submitted by cement suppliers for each shipment of cement. Silo test
certificates shall be submitted for the previous 6 to 12 months. Cement uniformity in accordance with
ASTM C917 shall be reported. Variations shall be limited to the following:
Tricalcium silicate (C3S). . . . . . . . . . . . . . . . . . . . . .
1
4%
See C - Commentary
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Ignition Loss. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5%
Fineness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 cm2/g (Blaine)
Sulfate (SO3). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20% of optimum
b. Mortar cube tests shall be performed in accordance with ASTM C109.
1.24.2.2 Chemical Admixtures
Chemical admixtures shall conform to the following ASTM specifications:
Air-entraining admixtures . . . . . . . . . . . . . . . . . . . . ASTM C260
Retarders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM C494, Types B and D
Normal-setting water reducers . . . . . . . . . . . . . . . . ASTM C494, Type A
High-range water reducers . . . . . . . . . . . . . . . . . . . ASTM C494, Types F and G
Accelerators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM C494, Types C and E
1.24.2.3 Mineral Admixtures
Mineral admixtures consist of fly ash (Class C and F), silica fume and ground granulated blast-furnace slag. Fly
ash shall conform to ASTM C618 specifications. Methods for sampling and testing of fly ash shall conform to
ASTM C311. Silica fume shall conform to ASTM C1240. Slag shall conform to ASTM C989.
1.24.2.4 Aggregates
Fine and coarse aggregate shall meet the requirements of ASTM C33.
1.24.2.5 Water
Water for use in high-strength concrete shall conform to Section 1.5, Water. Acceptance requirements specified
in Table 1 of ASTM C94 shall be met.
1.24.3 CONCRETE MIXTURE PROPORTIONS (1995)
Trial batches shall be performed to generate sufficient data to obtain optimum mixture proportions.
SECTION 1.25 SPECIALTY CONCRETES
1.25.1 GENERAL
This manual article describes and provides requirements for specialty concretes that may be used in railroad
construction. Before any specialty concrete is used, additional investigation of specific and detailed
specifications shall be made.
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1.25.2 SULFUR CONCRETE1
1.25.2.1 General
Sulfur concrete is a thermoplastic material produced by mixing heated aggregate 350F to 400F (177C to 204C)
with modified sulfur cement and fine mineral filler (ambient temperature) to prepare a well-mixed concrete
that is maintained within a temperature range of 270F to 285F (132C to 141C) until placed. The ACI Manual of
Concrete Practice contains detailed information.
1.25.2.2 Design
a.
Mixture design for sulfur concrete is different from portland cement concrete.
b. Aggregate for sulfur concrete shall conform with ASTM C33.
c.
Reinforcement may be with reinforcing steel, epoxy-coated reinforcing steel or with fibers.
1.25.2.3 Handling
The requirements for mixing/transporting equipment are defined by the unique thermoplastic characteristic of
sulfur concrete. Sulfur concrete must be maintained in a molten state and continuously monitored to maintain
the temperature range of 270F (133C) to 285F (147C). The concrete mixture must be thoroughly mixed so the
molten sulfur cement adequately coats the fine and coarse aggregate and mineral filler.
1
1.25.2.4 Placing
Sulfur concrete can be placed in either wooden or metal forms.
1.25.3 HEAVYWEIGHT CONCRETE
3
1.25.3.1 Design
Heavyweight concrete, unless otherwise stipulated, shall conform to the other requirements of Chapter 8, Part
1, shall be made with Type II cement, and shall be proportioned as directed by the Engineer, with not more
than 6 gal. (22.7 L) of water per 94 lb (42.8 kg) of cement. Where heavyweight concrete is required for
counterweights, the coarse aggregate shall be trap rock, iron ore, or other heavy material or the concrete may
incorporate steel punchings or scrap metal. The mortar shall be composed of 1 part of cement and 2 parts of
fine aggregate. Fine metallic aggregate shall consist of commercial chilled-iron or steel shot or ground iron,
meeting SAE J 444a. All metallic aggregate shall have a specific gravity of 6.50 or greater and be clean and free
from foreign coatings of grease, oil, machine shop compounds, zinc chromate, loose scale, and dirt. The
maximum weight of heavy concrete shall be 315 lb per cu feet (5,050 kg per cu m).
1.25.3.2 Placing
a.
1
Heavyweight concrete shall be placed in layers and consolidated with vibrators or tampers. Heavyweight
concrete usually will not “flow” in a form and must be placed uniformly throughout the area and
compacted in place with a minimum of vibration. Under no circumstances shall an attempt be made to
move heavyweight concrete during consolidation with vibration equipment. Layers shall be limited to a
maximum 12 inch (300 mm) thickness. Consolidation shall be by internal vibrators to achieve uniform
and optimum density. In heavyweight concrete vibrators have a smaller effective area, or radius of
action; therefore greater care shall be exercised to insure that the concrete is properly consolidated.
See C - Commentary
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Vibrators shall be inserted at closely spaced intervals and only to a depth sufficient to cause complete
intermixing of adjacent layers. Counterweights containing punchings or scrap metal or iron ore
aggregates shall be enclosed in steel boxes.
b. Heavyweight concrete not enclosed in steel boxes shall be adequately reinforced.
1.25.3.3 Determining Weight
For ascertaining the weight of the concrete, test blocks having a volume of not less than 0.1 cu m (4 cu feet) for
ordinary concrete, and 1 cu feet (0.03 cu m) for heavy concrete, and 1 cu feet (0.03 cu m) for the mortar for
heavy concrete, shall be cast at least 30 days before concreting is begun. Two test blocks of each kind shall be
provided, and one weighed immediately after casting and the other after it has cured for 28 days.
C - COMMENTARY
The purpose of this part is to furnish the technical explanation of various Articles in Part 1, Materials, Tests
and Construction Requirements. In the numbering of Articles of this section, the numbers after the “C-”
correspond to the Section/Article being explained.
C - SECTION 1.2 CEMENT
C - 1.2.2 SPECIFICATIONS (2004)
The use of slag cement Types ‘S’ and ‘S(A)’ as defined in Standard Specification C 595 is not included in this
recommended practice as these cements are not intended to be used alone in producing structural concrete.
C - SECTION 1.3 OTHER CEMENTITIOUS MATERIALS
C - 1.3.3.1(a) Silica Fume
One of the primary benefits of including silica fume in a concrete mix design is to reduce the permeability of the
hardened concrete. Porosity will be significantly reduced if proper proportioning, pre-construction testing, and
curing methods are used. Long term durability, resistance to chemical attack including sulphate attack, and
penetration of chloride ions can all be favorably affected.
Other possible benefits include improved resistance to abrasion. Silica fume has been used to obtain both of
these properties. However, the replacement method may inhibit other special properties.
C - 1.3.3.1(b) Fly Ash
All fly ashes contain pozzolanic materials, but some fly ashes also exhibit cementitious properties of their own.
Factors affecting this are the glass content, its fineness and gradation, and silica or silica-plus-alumina content.
There is therefore a wide variation in pozzolanic and cementitious efficiency of different fly ashes, which
cannot be predicted by selecting Class C, Class F or Class N. Direct tests of strength development, and tests to
determine the efficiency of fly ash to produce special properties such as sulphate resistance, or resistance to
alkali-silica reactions, are necessary.
Possible benefits of using fly ash in a concrete mix which is properly designed, deposited and cured include
increased long-term strength potential, improved workability and pumpability, reductions in the heat of
hydration when using fly ash as a replacement for some of the cement that would otherwise be used, a finer
pore structure which reduces the ingress of chloride ions, and improved resistance to sulphate attack and to
alkali silica reactions. Possible difficulties in using fly ash include a need to adjust the dosage of air entraining
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admixture, reduced bleeding of fresh concrete, reduced rate of strength gain which could effect form and/or
falsework removal parameters, and a need to delay finishing of unformed surfaces under some circumstances.
C - 1.3.3.2 Ground Granulated Blast-Furnace Slag
When used as provided in this recommended practice, replacement of part of the portland cement that would
otherwise be required in a concrete mix design with ground granulated blast-furnace slag may impart several
benefits. These include a much reduced permeability, with a consequent reduction of penetration of chloride
ions and reductions in corrosion of reinforcement; reduced heat of hydration at early ages; improved sulphate
resistance; and reduced levels of alkali silica reactivity. Reductions in alkali silica reactivity are due to reduced
permeability, reductions in available alkali, chemical effects, and other effects.
C - SECTION 1.4 AGGREGATES
C - 1.4.2.1 General
Use of lightweight fine aggregates is not allowed because of their poor performance in all lightweight concrete,
and the many difficulties and restrictions to their use.
C - SECTION 1.5 WATER
Non-potable water (not fit for human consumption) is being used as mixing water in hydraulic cement concrete
to a much larger extent than when the AREMA recommendation effective in 2009 was written. Use of a nonpotable water source requires limiting the solids content of the water. ASTM C1603, which is referenced by
ASTM C1602, provides a test method for measurement of the solids content of water by means of measuring
the water’s density.
1
In addition to limiting the amount of solids in mixing water, maximum concentrations of other materials that
impact the quality of concrete must be limited. These include levels of chloride ions, sulfates, and alkalies. ACI
318-08, R 3.4.1 is the requirement that water used to mix concrete must comply with ASTM C1602. As
indicated in ACI 318-08, R 3.4.1, ASTM C1602 permits the use of potable water without testing.
3
The chief concern over high chloride content is the possible effect of chloride ions on the corrosion of embedded
reinforcing steel, prestressing tendons, aluminum embedments or stay-in-place galvanized metal forms.
Limitations placed on the maximum concentration of chloride ions that are contributed by the ingredients
including water, aggregates, cement, and admixtures are given in ACI 318-08, Chapter 4, Table 4.3.1. ASTM
C1602 limits the chloride ions in ppm (parts per million) and only applies to that contributed by the mixing
water.
4
Test results for non-potable water shall be furnished to the Engineer and approved prior to use.
C - SECTION 1.6 REINFORCEMENT
C - 1.6.4 BENDING AND STRAIGHTENING (2003)
a.
Field bending and straightening of partially embedded reinforcement bars is discouraged but when this
operation is required it should be closely controlled. Construction conditions that make field bending or
straightening necessary also make it difficult to control the conditions under which it is done thus
making field inspection even more critical.
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b. There are numerous papers written on this subject with varying opinions on the best procedures to use.
There is ongoing research that should supply additional test results to clarify current assumptions. A few
of the current known factors that affected these standards are that:
(1) Application of heat appears to be necessary to bend or straighten larger sized rebar but either over
heating (above 1800 F (980 C)) or under heating between 450 F (230 C) and 650 F (340 C) can create
much reduced rebar strength or even cause failure.
(2) Repeated bending and straightening weakens the metal and will result in failure even under the best
controlled conditions.
(3) Tight bending diameters decreases the metal’s strength.
c.
The reworking of reinforcing bars that are partially embedded in concrete involves some level of risk and
is not encouraged. Risks may be minimized by using reinforcing bars of a more ductile steel such as A
706 rather than A 615 in locations where field bending and/or straightening will be required. This is
awkward from a constructability standpoint.
d. When field bending and straightening of partially embedded bars, for A 615 grade 40 or grade 60 steel, is
permitted by the Engineer, an example procedural guideline is the following:
(1) Bars of size #3 (#10) through #7 (#22).
(a) Bend or straighten bars cold (bars should be above freezing temperature).
(b) Do not allow more than one cycle of bending and straightening.
(c) Diameter of bends should conform to Part 2, Reinforced Concrete Design, Table 8-2-6. Bends
should not exceed 90 degrees.
(d) Bending should be done with as smooth an application of force as possible.
(e) Straightening should be accomplished by using a steel pipe pushed tight against the bend and
with application of force and reset periodically as follows:
1 Steel pipe should have inside diameter 1/8 inch to 3/8 inch (3 mm to 9 mm) larger than outside
diameter of bar to be straightened.
2 Steel pipe should be a minimum length of 8 inches (200 mm) times the bar number size of the
bar to be straightened to provide sufficient leverage.
3 Straightening pipe should be reset against the bar at 45 degrees for #4 (#13) and smaller bars
and at 30 degrees and 60 degrees for #5 to #7 (#16 to #22) bars.
4 Workers must have a firm base from which to apply straightening pressure to reduce the risk
of injury if the bar suddenly fails.
(2) Bars of size #8 through #11 (#25 through #36).
(a) Bend or straighten bars after preheating to 1100 degrees F to 1500 degrees F (590 degrees to 810
degrees C) as measured with temperature sticks.
(b) Concrete must be protected from exposure to excessive heat. If necessary protective insulation
should be used.
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(c) Atmospherically cool bars. Do not expose to water or other cooling mediums.
(d) Do not allow more than one cycle of bending and straightening.
(e) Diameter of bends should conform to Part 2, Reinforced Concrete Design, Table 8-2-6.
(f) Bending should be done with as smooth an application of force as possible.
(g) Straightening should be accomplished by using a steel pipe pushed tight against the bend and
with application of force and reset periodically.
(h) Steel pipe should have inside diameter 1/8 inch to 3/8 inch (3 mm to 9 mm) larger than outside
diameter of bar to be straightened.
1 Steel pipe should be long enough to provide sufficient leverage.
2 Straightening pipe should be reset progressively against the bar around the bend.
3 Workers must have a firm base from which to apply straightening pressure to reduce the risk
of injury if the bar suddenly fails.
C - SECTION 1.12 PROPORTIONING
C - 1.12.10 SPECIAL PROVISIONS WHEN USING CEMENTITIOUS MATERIALS OTHER
THAN PORTLAND CEMENT (2009)
1
C - 1.12.10.2 Requirements When Using Silica Fume in Concrete
ACI 211.1 provides guidance for proportioning concrete containing silica fume.
C - 1.12.10.2.2 High-Range Water Reducing Admixtures
3
Concrete containing silica fume will have a greater water demand to maintain workability than concrete not
containing silica fume. However, this additional water is rarely provided since it would negate the potential
benefits of using silica fume. High range water reducers (superplasticizers) are commonly used instead. If a
superplasticizer is not used, then the fresh concrete would appear sticky and not consolidate properly. Concrete
containing silica fume is more cohesive and less prone to segregation than other fresh concretes. It is common
to increase the slump by 2 inches (50mm) from what would otherwise be provided.
The use of a high range water reducing admixture will also benefit the rate of strength gain. Initial strength
gain will be slower when using silica fume. Twenty-eight (28) to ninety (90) day strengths can be enhanced
using silica fume, however, as long as the water to cementitious material ratio is kept low by using a high range
water reducing admixture.
C - 1.12.10.2.3 Entrained Air
Concrete containing silica fume will require more air entraining admixture than normal concrete to obtain the
desired result. The amount will depend upon the amount of silica fume and the type of air entraining
admixture used.
C - 1.12.10.3 Requirements When Using Fly Ash in Concrete
ACI 211.1 provides guidance for proportioning concrete containing fly ash.
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C - 1.12.10.3.3 Testing to Verify Mix Design
Reduced bleeding rates in fresh concrete may result in raising the possibility of plastic shrinkage cracking.
Initial setting time and the rate of early strength gain may be retarded by the use of fly ash. Setting time
requirements can also delay finishing. The rate of early strength gain can be satisfactory with a properly
designed and tested mix, which usually includes increases in the total cementitious material (fly ash plus
portland cement) content. The proportion of fly ash to cement may be varied from winter to summer.
Air entraining admixture requirements will be different for concrete containing fly ash to achieve the same
amount of air that would have resulted in concrete not containing fly ash.
The heat of hydration can be reduced if the fly ash is used to replace some of the portland cement instead of
being added as additional cementitious material.
The long term strength of the hardened concrete may be enhanced using fly ash.
Improved performance against sulphate attack and resistance to alkali aggregate reactivity will require the
addition of sufficient quantities of cementitious materials other than portland cement that may exceed the
proportions of what would be used otherwise.
C - 1.12.10.3.4 Water to Cementitious Materials Ratio
The improved workability and pumpability of concrete containing fly ash will permit reductions in the amount
of water. This is due to the spherical shape of the fly ash particles imparting improved workability; and to the
reduced unit weight of fly ash as compared with cement which can result in increased paste content when
cement replacement with fly ash is by weight. Reductions in the amount of water can also reduce the
possibility of plastic shrinkage. The measurement of water as a proportion of total cementitious material by
weight provides a consistent approach which is also applicable when using blended cements.
C - 1.12.10.4 Requirements When Using Ground Granulated Blast-Furnace Slag in Concrete
ACI 211.1 provides guidance for proportioning concrete containing ground granulated blast-furnace slag.
C - 1.12.10.4.1 General
The amount of ground granulated blast-furnace slag as a proportion of the total cementitious material
normally varies between 25% and 70%, with approximately 40% to 50% being a common proportional amount.
A maximum amount of 50% can also be applicable, per Table 8-1-12.
Final concrete properties will also be determined by the portland cement used, the grade or reactivity of the
ground granulated blast-furnace slag, curing conditions, and the special properties for which the material was
used, such as reduced early heat of hydration.
C - 1.12.10.4.2 Water-Reducing Admixtures
Concrete containing ground granulated blast-furnace slag will have a slower rate of strength gain than normal
portland cement concretes, especially at early ages, unless the water content is reduced.
C - 1.12.10.4.3 Accelerators
Significant retardation has been observed at low temperatures when using ground granulated blast-furnace
slag. Accelerating admixtures can be used to counter this effect. However, the source and reactivity of the
ground granulated blast-furnace slag, the ratio of ground granulated blast-furnace slag to normal portland
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cement, the characteristics of the cement, and the water to cementitious material ratio will also influence set
time. Therefore the need for pre-construction tests, as noted previously, is also confirmed here.
C - 1.12.10.4.4 Proportioning of Aggregates
Portland cement concrete containing ground granulated blast-furnace slag will have a higher volume of paste
than normal portland cement concrete when both mixes are proportioned by weight (mass). The proportional
difference is due to ground granulated blast-furnace slag being lighter than portland cement. The coarse to
fine aggregate ratio can therefore be increased or the water to cementitious material ratio can be reduced.
Increases in the amount of coarse aggregate may be beneficial to finishing, which may aid in reducing
shrinkage and potential for scaling. The natural tendency of concrete containing ground granulated blastfurnace slag is to be more workable and easier to place and consolidate. This will compensate for some
increases in the proportion of coarse aggregate.
C - SECTION 1.13 MIXING
C - 1.13.5 REQUIREMENTS WHEN USING SILICA FUME IN CONCRETE (2009)
C - 1.13.5.2 Workability of Delivered Concrete
Refer to Commentary for Article 1.12.10.2.2.
C - SECTION 1.14 DEPOSITING CONCRETE
1
C - 1.14.12 PLACING CONCRETE CONTAINING SILICA FUME (2004)
C - 1.14.12.1 Protection from Moisture Loss
Fresh concrete containing silica fume displays significantly less bleeding than normal concrete. There is
therefore the potential that shrinkage cracking will occur if the evaporation rate exceeds the bleeding rate.
Increased amounts of silica fume will increase the potential for such shrinkage cracking. Other conditions
including adverse temperatures, wind, or low humidity could also increase the potential for shrinkage cracking.
Evaporation retarders, fogging, and protection from the wind during the placement stage are options which
may be included in the project specifications to counter this. Measures to protect against early moisture loss in
concrete containing silica fume should included in the project specifications. Shrinkage cracking can be
eliminated through the use of proper procedures.
C - 1.14.12.2 Consolidation
The cohesive nature of concrete containing silica fume makes it susceptable to excessive entrapment of air, even
with higher slumps. Proper placing techniques are essential to achieving any special properties for which silica
fume is specified.
C - SECTION 1.18 CURING
C - 1.18.4 MEMBRANE CURING (1993)
a.
With the emergence of legislation designed to limit the amounts of Volatile Organic Compound (V.O.C.)
emission, it is incumbent upon specifying Engineers to be cognizant of these new laws.
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b. Volatile Organic Compound regulations may vary by individual state. Therefore, it is mandatory that
materials selected for use be in total conformance to the applicable legislation of the state within which
the work will be performed.
C - 1.18.6 CURING CONCRETE CONTAINING SILICA FUME (2003)
C - 1.18.6.1 Delays in Implementing Curing
Refer to the commentary concerning Article 1.14.12.1.
C - 1.18.7 CURING CONCRETE CONTAINING GROUND GRANULATED BLASTFURNACE SLAG (2004)
C - 1.18.7.1 General
Strength gain may be slower at low temperatures during the initial curing period when the ground granulated
blast-furnace slag is used to replace part of the portland cement in a mix. The amount of retardation will
depend upon the temperature, the proportions and characteristics of each of the cementitious materials, the
total content of cementitious material and other factors. Little, if any, retardation occurs at temperatures
above about 70° F (21° C), and the behavior of concretes containing ground granulated blast-furnace slag
under elevated curing temperatures has been reported to be good.
Refer also to the commentary concerning accelerators, in Article 1.12.10.4.3.
C - 1.18.7.2 Delays in Implementing Curing
Ground granulated blast-furnace slags that are finer than portland cements are likely to produce mixes with
reduced bleed water when the combined amount of cementitious material is not also reduced.
C - 1.18.8 CURING CONCRETE CONTAINING FLY ASH (2004)
Time of setting and the rate of early strength gain will have been prescribed in arriving at the mix design and
proportioning. This will have determined the water to cementitious material ratio that, if high, may require
special curing measures to avoid plastic shrinkage cracking. Special curing requirements may also result if a
minimum specified strength is to be attained before subjecting the hardened concrete to freeze-thaw cycles or
to chlorides.
C - SECTION 1.20 UNFORMED SURFACE FINISH
C - 1.20.3 FINISHING CONCRETE CONTAINING SILICA FUME (2004)
The tackiness and lack of bleed water of concrete containing 10% to 20% silica fume will make finishing of
unformed surfaces more difficult and may require trial placements in order to determine finishing methods.
The use of evaporation retarders and other methods to reduce evaporation will aid the finishing process.
C - 1.20.4 FINISHING CONCRETE CONTAINING GROUND GRANULATED BLASTFURNACE SLAG (2004)
See the commentary for Article 1.18.7.2 regarding delays in implementing curing procedures.
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Materials, Tests and Construction Requirements
C - SECTION 1.22 PENETRATING WATER REPELLENT TREATMENT OF CONCRETE
SURFACES
C - 1.22.1 GENERAL (1993)
a.
Penetrating sealers are primarily intended for use in sealing the surface of concrete structures against
intrusion of water and chlorides, while having a minimum effect on the concrete’s ability to breathe
(transfer water vapor). Of the 21 materials tested and addressed in National Cooperative Highway
Research Program Report 244, only the silane exhibited a measurable penetration effect.
NCHRP Report 244:
“This silane material produces a non-wettable concrete surface to a depth of 0.10 inch (2.5 mm). The
other materials tested in this project, including boiled linseed oil, generally do not produce a measurable
penetration or a measurable thickness of non-wettable concrete. Most of these other materials are
coatings and should not be referred to in specifications as ‘penetrating sealers’.”
b. With the emergence of new legislation designed to limit the amounts of Volatile Organic Compound
(V.O.C.) emission, it is incumbent upon specifying Engineers to be cognizant of these new laws.
C - 1.22.2 SURFACE PREPARATION (2003)
a.
Good surface preparation, prior to applying the sealer, is essential to achieve the desired maximum
penetration into the concrete. When the sealers penetrate below the surface of the concrete, they
chemically bond to the concrete and prevent water and chlorides from entering the concrete.
Contaminants must be totally removed and the surface allowed to dry. Properly applied sealers shall
provide protection from the ingress of water and chlorides for a period of five (5) years.
1
b. Surface preparation may be accomplished by:
(1) High pressure water (hot or cold).
3
(2) Chemical cleaners.
(3) Sandblasting.
(4) Shotblasting.
c.
When high pressure water is employed, all surfaces shall be free of standing water or moisture at the
time of the treatment which could restrict surface penetration. Care must be taken when using highpressure water steam to avoid excessive exposure of coarse aggregate.
C - 1.22.3 ENVIRONMENTAL REQUIREMENTS (2003)
There is some question of the effects of high temperature on water repellent treatments as one author states
that high temperatures actually speed up the condensation reaction of monomeric silanes into oligomeric
siloxanes. Because of this, application of treatment at temperatures over 100 degrees F should be carefully
considered.
C - 1.22.4 APPLICATION (2003)
Consult the manufacturer’s material safety data sheet and application instructions for further safety
information.
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Concrete Structures and Foundations
C - 1.22.6 QUALITY ASSURANCE (1993)
a.
The owner of a concrete structure or buyer of a concrete sealer shall be satisfied that the manufacturer
can furnish the quality assurance claimed. This can be done by comparing test results of the product
against test results obtained by independent test studies, several of which are listed in the References
found at the end of this Chapter. The buyer or owner should also be satisfied that an agent or distributor
who makes such claims or offers such a warranty has the full authority to do so by the manufacturer.
b. The owner of a concrete structure or buyer of a concrete sealer should seek out an applicator (either
owner’s own employee or outside contractor) approved by the manufacturer in order to validate its
warranty.
C - SECTION 1.23 REPAIRS AND ANCHORAGE USING REACTIVE RESINS
a.
Reactive resins may be selected for inclusion with fine and/or coarse aggregate in polymer concrete or
included with a clean, dry, fine aggregate in a polymer mortar. Reactive resins can be used in chemical
bonding systems as an adhesive for concrete or as a binder for mortars or concrete.
b. Reactive resins may also be used neat (without the addition of aggregate) as a bonding agent, as a
bonding coat for adhesion, as well as anchoring between metallic inserts and concrete when the spacing
between the metallic insert and the interior wall of the bored hole in the concrete is 1/8 inch (3.2 mm)
minimum. While the general rule for anchor bolt embedment is ten (10) to fifteen (15) times the bolt
diameter, the embedment shall be designed based upon loads to be carried.
C - SECTION 1.24 HIGH STRENGTH CONCRETE
C - 1.24.1 GENERAL (1995)
a.
With the advances in concrete technology during the last few decades, the commonly achievable limits of
concrete strength have steadily increased. The use of high-strength concrete in construction has also
increased. Concrete compressive strengths approaching 20,000 psi (138 MPa) have been used in cast-inplace concrete buildings. High-strength concrete has also been used in bridge structures. Research has
been conducted on the performance of high-strength prestressed concrete in bridges.
b. Because of the continuing advances in technology, the definition of the minimum concrete compressive
strength for high-strength concrete is changing with time. Different geographic locations may also have
varying limits for what they consider as high-strength concrete. The ACI Committee 363 report on highstrength concrete (ACI 363R-92) defines high-strength as having compressive strengths of 6,000 psi (41
MPa) or greater.
c.
The ACI Committee 363 report on high-strength concrete provides detailed information on material and
structural aspects of high-strength concrete.
C - 1.24.2 MATERIALS (1995)
a.
To achieve adequate consistency and quality of high-strength concrete, stringent control of constituent
materials is necessary. Variations in type, brand and source of supply of the components can have major
influences on the properties of high-strength concrete. Therefore, emphasis is placed on the preparation
of trial batches and maintenance of the same component materials throughout the project.
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Materials, Tests and Construction Requirements
b. Testing and comparison of laboratory and production-sized trial batches are needed to establish the
required strength of laboratory trial batches. This is because the laboratory trial batches have often
exhibited significantly higher strength than production batches.
C - 1.24.2.1 Cement
The quality and consistency of cement used in high-strength concrete need verification through mill test
reports, and mortar cube tests. The most suitable types of cement for high-strength concrete are Type I or Type
III with minimum 7-day cube compressive strength of 4500 psi (31 MPa). In addition, cement should not show
signs of false set.
C - 1.24.2.2 Chemical Admixtures
a.
Chemical admixtures are commonly used in high-strength concrete to increase compressive strength
through reduction of water, control rate of hardening, accelerate strength gain, and improve workability
and durability. Performance of all materials in high-strength concrete as a whole should be considered
when selecting the type, brand and dosage of any admixtures.
b. Air-entraining admixtures (ASTM C260) are used to improve durability and freeze-thaw resistance.
However, air voids have the effect of reducing compressive strength and their use is therefore
recommended only when durability is a concern. Incorporation of entrained air may reduce strength at a
rate of 5% to 7% for each percent of air in the mix.
c.
Retarders (ASTM C494, Types B and D) are used to control early hydration and hardening of concrete.
Factors such as an increase in strength and temperature effects should be considered.
1
d. Normal-setting water reducers (ASTM C494, Type A) are used to increase strength without affecting the
rate of hardening. High-range water reducers (ASTM C494, Types F and G) are used to increase
strength (decrease water demand) especially high early strength (24 hours) or increase slump. Matching
the admixture to the cement used (both in type and dosage rate) is an important consideration.
e.
High-range water reducers (ASTM C494, Types F and G) are often used in high-strength concrete
mixtures and are essential with the very high-strength concretes to ensure adequate workability with
low water-cementitious ratios. Further information is available in ACI SP-68.
f.
Accelerators (ASTM C494, Types C and E) are not normally used in high strength concrete except when
early form removal is critical. Accelerators will normally be counterproductive in long-term strength
development.
C - 1.24.2.3 Mineral Admixtures
a.
Mineral admixtures such as fly ash, silica fume, and ground granulated blast-furnace slag have been
widely used in high-strength concrete. Variations in physical and chemical properties of mineral
admixtures (even when within tolerance of specifications) can have a major influence on properties of
high-strength concrete.
b. Fly ash generally reduces early strength gain and improves late age strength of concrete. There are two
(2) classes of fly ash available (ASTM C618). Class F fly ash is generally available in eastern U.S. and
Canada and has pozzolanic properties, but little or no cementitious properties. Class C fly ash is
generally available in western U.S. and Canada and has pozzolanic and some autogenous cementitious
properties. An ignition loss of 3% or less is desirable, although ASTM C618 permits a higher value.
ASTM C311 provides standard test methods for sampling and testing of fly ash or natural pozzolans.
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c.
Silica fume consists of very fine spherical particles, approximately 100 times smaller than the average
cement particle, and is a highly effective pozzolanic material. It is used in concrete in applications where
abrasion resistance and low permeability are desired. Normally, silica fume content ranges from 5% to
15% of portland cement content. The availability of high-range water reducers has facilitated the use of
silica fume in high-strength concrete. However, concrete with silica fume has an increased tendency to
develop plastic shrinkage cracks. Therefore steps should be taken to prevent rapid water evaporation.
d. Ground granulated blast furnace slag (ASTM C989) is used as a partial replacement for portland cement
in various proportions to enhance different properties of concrete. Research has shown promise for its
use in high-strength concrete.
C - 1.24.2.4 Aggregates
a.
The optimum gradation of fine aggregates for high-strength concrete is mainly determined by its effect
on water requirement rather than physical packing. High-strength concrete has high contents of fine
cementitious materials and therefore the grading of fine aggregates is relatively unimportant compared
to conventional concrete. Fine aggregates with rounded particle shapes and smooth texture require less
mixing water and are therefore preferred in high-strength concrete.
b. The desirable maximum size of coarse aggregate should be 1/2 inch (13 mm) or 3/8 inch (10 mm). Mix
designs with maximum size aggregate of 3/4 inch (19 mm) and 1 inch (25 mm) have also been
successfully used. Many studies have shown that crushed stone produces higher strengths than rounded
gravel because of improved mechanical bond in angular particles. However, accentuated angularity can
result in higher water requirement and reduced workability and therefore should be avoided. The ideal
aggregate should be clean, cubical, angular, 100% crushed aggregate with a minimum of flat and
elongated particles. It would also be beneficial if the aggregate has moderate absorption capability to
provide added curing water for high-strength concrete.
c.
High-strength concrete requires high-strength aggregates. However, this trend holds only true until the
limit of the bonding potential of the cement-aggregate combination is reached.
C - 1.24.3 CONCRETE MIXTURE PROPORTIONS (1995)
a.
High-strength concrete mix proportioning is a more critical process than the design of normal-strength
concrete mixtures. Generally, chemical admixtures and pozzolanic materials are added and the
attainment of low water-cementitious ratio is essential. Trial batches are often required to optimize
constituent materials and mixture proportions. Additional information can be found in ACI 211.1, ACI
211.4, and ACI Publication SP-46.
b. The relationship between water-cementitious ratio and compressive strength in high-strength concrete
is similar to that identified for normal-strength concrete. The use of high-range water reducers has
provided lower water-cementitious ratios and higher slumps. Water-cementitious ratios by weight for
high-strength concrete typically have ranged from approximately 0.27 to 0.50. The compressive strength
of concrete at a given water-cementitious ratio varies widely depending on the cement, aggregates and
admixtures used. The quantity of liquid admixtures, particularly high-range water reducers, has
sometimes been included in the calculation of water-cementitious ratio. When silica fume as a slurry is
used, its water content must be included in the water-cementitious ratio.
c.
Typical cement contents in high-strength concrete range from 660 lb/cy (390 kg/m3) to 940 lb/cy (560
kg/m3). For any given set of materials in a concrete mixture, there may be an optimum cement content
that produces maximum concrete strength. The strength of concrete may decrease if cement is added in
excess of the optimum level. The strength for any given cement content will vary with the water demand
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Materials, Tests and Construction Requirements
of the mixture and the strength-producing characteristics of that particular cement. Loss of workability
(stickiness) will be increased as higher cement amounts are used.
d. The maximum temperature desired in the concrete element may limit the quantity or type of cement.
Addition of ice, set retarders or pozzolans may be considered.
C - 1.24.3.1 Aggregate Proportions
Table 3.1 in the ACI 363R-92 suggests the amounts of coarse aggregate based on the fineness modulus of sand
for the purpose of initial proportioning. In general, the least sand consistent with necessary workability has
given the best strengths for a given paste. The use of smaller coarse aggregates (maximum 3/8 inch (10 mm) to
1/2 inch (13 mm)) are generally beneficial, and crushed aggregates seem to bond best to the cementitious paste.
C - 1.24.3.2 Proportioning of Admixtures
a.
In high-strength concrete, pozzolanic admixtures have been used to supplement the portland cement
from 10% to 40% by weight of the cement content. The use of fly ash has often reduced the water
demand of the mixture. Silica fume, on the other hand, dramatically increases the water demand of the
mixture which has made the use of retarding and high-range water-reducing admixture
(superplasticizing) admixtures a requirement.
b. The amount of conventional water reducers and retarders in high-strength concrete varies depending on
the particular admixture and application. In general, the tendency has been to use maximum quantities
of these admixtures. Typically, water reductions of 5% to 8% may be increased to 10%. Corresponding
increases in fine aggregate content have been made to compensate for the loss of volume due to the
reduction of water.
c.
Most high-strength concretes contain both mineral admixtures and chemical admixtures. It is common
for these mixtures to contain combinations of chemical admixtures. High-range water reducers have
performed better in high-strength concretes when used in combination with conventional water reducers
or retarders.
1
3
C - 1.24.3.3 Workability
a.
High-strength concrete mixtures tend to lose slump more rapidly than lower-strength concrete. If slump
is to be used as a field control, testing should be done at a prescribed time after mixing. Concrete should
be discharged before the mixture becomes unworkable.
4
b. High-strength concrete, often placed with 1/2 inch (13 mm) maximum size aggregate and with a high
cementitious content, is inherently placeable provided attention is given to optimizing the ratio of fine to
coarse aggregate. Local material characteristics have a marked effect on proportions. Cement fineness
and particle size distribution influence the character of the mixture. Appropriate admixtures improve
the placeability of the mixture.
c.
Mixtures that were proportioned properly but appear to change in character and become more sticky
should be considered suspect and checked for proportions, possible false setting of cement, undesirable
air-entrainment, or other changes. A change in the character of a high-strength mixture could be a
warning sign for quality control.
C - 1.24.3.4 Trial Batches
Frequently, the development of a high-strength concrete program has required a large number of trial batches.
In addition to laboratory trial batches, field-sized trial batches have been used to simulate typical production
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Concrete Structures and Foundations
conditions. Once a desirable mixture has been formulated in the laboratory, field testing with production-sized
batches should be preformed.
C - 1.25.2 SULFUR CONCRETE
C - 1.25.2.1 General
c.
Sulfur concrete is generally not resistant to alkalis or oxidizers. However sulfur concrete exhibits
excellent characteristics of:
(1) High strength [in excess of 62 MPa (9,000 psi)] and fatigue resistance;
(2) Excellent corrosion resistance against salts and most acids;
(3) Extremely rapid set and strength gains and achieves a minimum of 70% to 80% of ultimate
compressive strength within 24 hours;
(4) Placement year round, above and below freezing temperatures;
(5) Very low water permeability.
C - 1.25.2.2 Handling
Extreme care should be used when handling sulfur concrete to avoid burns.
C - 1.25.2.3 Placing
Wall construction should be given special consideration to preclude poor consolidation. Preheating the
reinforcing steel and forms using infrared or suitable heaters, plus using insulation on the outside of wall forms
should be utilized to retain heat during placement.
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8
Part 2
Reinforced Concrete Design1
— 2010 —
TABLE OF CONTENTS
Section/Article
Description
Page
2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.1 Scope (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.2 Design Methods (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.3 Highway Bridges (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.4 Buildings (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.5 Pier Protection (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.6 SuperStructure Protection (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.7 Skewed Concrete Bridges (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-5
8-2-5
8-2-5
8-2-5
8-2-6
8-2-6
8-2-6
8-2-7
2.2 Notations, Definitions and Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.1 Notations (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.2 D e f i ni ti on s (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.3 Design Loads (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.4 Loading Combinations (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-8
8-2-8
8-2-11
8-2-12
8-2-19
2.3 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.1 Concrete (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.2 Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-20
8-2-20
8-2-21
Details of Reinforcement
2.4 Hooks and Bends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4.1 Standard Hooks (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4.2 Minimum Bend Diameter (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-21
8-2-21
8-2-21
2.5 Spacing of Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-22
2.6 Concrete Protection for Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6.1 Minimum Concrete Cover (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6.2 Concrete Cover for Bar Bundles (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-22
8-2-22
8-2-23
1
References, Vol. 31, 1930, pp. 1148, 1787; Vol. 48, 1947, p. 418; Vol. 50, 1949, pp. 291, 757; Vol. 54, 1953, pp. 794, 1341; Vol. 57, 1956, p.
996; Vol. 63, 1962, pp. 278, 688; Vol. 68, 1967, p. 313; Vol. 71, 1970, pp. 230, 242; Vol. 72, 1971, p. 136; Vol. 76, 1975, p. 205; Vol. 80, 1979,
p. 91; Vol. 90, 1989, p. 53; Vol. 91, 1990, p 63; Vol. 93, 1992, pp. 78, 92; Vol. 94, 1994, p. 98.
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Concrete Structures and Foundations
TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
Concrete Cover for Corrosive and Marine Environments (1992) . . . . . . . . . . . . . . . . . . .
Corrosion Protection (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-23
8-2-23
2.7 Minimum Reinforcement of Flexural Members (1992) . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-23
2.8 Distribution of Reinforcement in Flexural Members (2005) . . . . . . . . . . . . . . . . . . . . .
8-2-23
2.9 Lateral Reinforcement of Flexural Members (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-24
2.10 Shear Reinforcement – General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.10.1 Minimum Shear Reinforcement (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.10.2 Types of Shear Reinforcement (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.10.3 Spacing of Shear Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-25
8-2-25
8-2-25
8-2-25
2.11 Limits for Reinforcement of Compression Members . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.11.1 Longitudinal Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.11.2 Lateral Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-26
8-2-26
8-2-26
2.12 Shrinkage and Temperature Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-27
2.6.3
2.6.4
Development and Splices of Reinforcement
2.13 Development Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.13.1 General (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.13.2 Positive Moment Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.13.3 Negative Moment Reinforcement (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.13.4 Special Members (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-28
8-2-28
8-2-28
8-2-29
8-2-29
2.14 Development Length of Deformed Bars and Deformed Wire in Tension (2005) . . . . .
8-2-29
2.15 Development Length of Deformed Bars in Compression (2005) . . . . . . . . . . . . . . . . . .
8-2-31
2.16 Development Length of Bundled Bars (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-31
2.17 Development of Standard Hooks in Tension (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-31
2.18 Combination Development Length. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-33
2.19 Development of Welded Wire Fabric in Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.19.1 Deformed Wire Fabric (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.19.2 Smooth Wire Fabric (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-33
8-2-33
8-2-33
2.20 Mechanical Anchorage (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-34
2.21 Anchorage of Shear Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-34
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-2-2
AREMA Manual for Railway Engineering
Reinforced Concrete Design
TABLE OF CONTENTS (CONT)
Section/Article
Description
2.22 Splices of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.22.1 Lap Splices (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.22.2 Welded Splices and Mechanical Connections (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.22.3 Splices of Deformed Bars and Deformed Wire in Tension (2005). . . . . . . . . . . . . . . . . . . .
2.22.4 Splices of Deformed Bars in Compression (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.22.5 End Bearing Splices (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.22.6 Splices of Welded Deformed Wire Fabric in Tension (2005) . . . . . . . . . . . . . . . . . . . . . . . .
2.22.7 Splices of Welded Smooth Wire Fabric in Tension (2005) . . . . . . . . . . . . . . . . . . . . . . . . . .
Page
8-2-35
8-2-35
8-2-35
8-2-36
8-2-37
8-2-37
8-2-37
8-2-37
Analysis and Design – General Considerations
2.23 Analysis Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.1 General (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.2 Expansion and Contraction (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.3 Stiffness (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.4 Modulus of Elasticity (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.5 Thermal and Shrinkage Coefficients (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.6 Span Length (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.7 Computation of Deflections (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.8 Bearings (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.9 Composite Concrete Flexural Members (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.10 T-Girder Construction (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.23.11 Box Girder Construction (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-38
8-2-38
8-2-38
8-2-38
8-2-38
8-2-38
8-2-39
8-2-39
8-2-40
8-2-40
8-2-41
8-2-41
2.24 Design Methods (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-43
3
Service Load Design
2.25 General Requirements (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-43
2.26 Allowable Service Load Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.26.1 Concrete (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.26.2 Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-43
8-2-43
8-2-44
2.27 Flexure (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-45
2.28 Compression Members with or without Flexure (1992) . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-45
2.29 Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.29.1 Shear Stress (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.29.2 Permissible Shear Stress (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.29.3 Design of Shear Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.29.4 Shear-Friction (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.29.5 Horizontal Shear Design for Composite Concrete Flexural Members (2005) . . . . . . . . . .
2.29.6 Special Provisions for Slabs and Footings (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.29.7 Special Provisions for Brackets and Corbels (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-45
8-2-45
8-2-46
8-2-48
8-2-48
8-2-50
8-2-51
8-2-52
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
1
8-2-3
4
Concrete Structures and Foundations
TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
Load Factor Design
2.30 Strength Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.30.1 Required Strength (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.30.2 Design Strength (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-53
8-2-53
8-2-53
2.31 Design Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.31.1 Strength Design (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-54
8-2-54
2.32 Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.32.1 Maximum Reinforcement of Flexural Members (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.32.2 Rectangular Sections With Tension Reinforcement Only (2005) . . . . . . . . . . . . . . . . . . .
2.32.3 I- and T-Sections With Tension Reinforcement Only (2005) . . . . . . . . . . . . . . . . . . . . . . .
2.32.4 Rectangular Sections With Compression Reinforcement (2005) . . . . . . . . . . . . . . . . . . . .
2.32.5 Other Cross Sections (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-55
8-2-55
8-2-55
8-2-55
8-2-56
8-2-57
2.33 Compression Members with or without Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.33.1 General Requirements (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.33.2 Compression Member Strengths (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.33.3 Biaxial Loading (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-57
8-2-57
8-2-58
8-2-59
2.34 Slenderness Effects in Compression Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.34.1 General Requirements (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.34.2 Approximate Evaluation of Slenderness Effects (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-60
8-2-60
8-2-60
2.35 Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.35.1 Shear Strength (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.35.2 Permissible Shear Stress (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.35.3 Design of Shear Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.35.4 Shear-Friction (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.35.5 Horizontal Shear Design for Composite Concrete Flexural Members (2005). . . . . . . . . .
2.35.6 Special Provisions for Slabs and Footings (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.35.7 Special Provisions for Brackets and Corbels (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-62
8-2-62
8-2-62
8-2-64
8-2-65
8-2-66
8-2-67
8-2-69
2.36 Permissible Bearing Stress (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-70
2.37 Serviceability Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.37.1 Application (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.37.2 Service Load Stresses (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-70
8-2-70
8-2-70
2.38 Fatigue Stress Limit for Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-70
2.39 Distribution of Flexural Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-71
2.40 Control of Deflections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.40.1 General (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.40.2 Superstructure Depth Limitations (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-71
8-2-71
8-2-71
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-72
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-2-4
AREMA Manual for Railway Engineering
Reinforced Concrete Design
LIST OF FIGURES
Figure
Description
8-2-1 Cooper E 80 (EM 360) Axle Load Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-2 Reinforcement Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-3 Standard Hook Bars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-4 #6, 7, or 8 Stirrups (fy > 40,000 psi) (#19, 22, or 25) (fy > 280 MPa) . . . . . . . . . . . . . . . . . . . .
C-8-2-1 Pier Protection: Minimum Crash Wall Requirements (Not To Scale) . . . . . . . . . . . . . . . . . . . .
C-8-2-2 Comparison of Impact Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Page
8-2-13
8-2-31
8-2-32
8-2-35
8-2-74
8-2-75
LIST OF TABLES
Table
Description
Page
8-2-1
8-2-2
8-2-3
8-2-4
8-2-5
8-2-6
8-2-7
8-2-8
8-2-9
8-2-10
Coefficient for Nose Inclination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coefficient for Design Ice Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Temperature Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Group Loading Combinations – Service Load Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Group Loading Combinations – Load Factor Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Minimum Diameter of Bend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Minimum Concrete Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Development Length for Deformed Bars and Wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tension Lap Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Recommended Minimum Thickness For Constant Depth Members . . . . . . . . . . . . . . . . . . . . .
8-2-18
8-2-18
8-2-19
8-2-20
8-2-20
8-2-22
8-2-23
8-2-30
8-2-36
8-2-42
SECTION 2.1 GENERAL
1
3
2.1.1 SCOPE (2005)
These recommended practices shall govern the design of reinforced concrete members of railway structures
supporting or protecting tracks and shall govern both SERVICE LOAD DESIGN and LOAD FACTOR DESIGN.
4
2.1.2 DESIGN METHODS (2005)
a.
The design of reinforced concrete members shall be made either with reference to service loads and
allowable service load stresses as provided in the Service Load Design Section or, alternately, with
reference to load factors and strength as provided in the Load Factor Design section. The design method
to be used, SERVICE LOAD DESIGN or LOAD FACTOR DESIGN, shall be as directed by the Engineer.
2.1.3 HIGHWAY BRIDGES (2005)
Unless otherwise specified by highway authority, all highway bridges shall be designed in accordance with the
latest Specifications for Highway Bridges adopted by the American Association of State Highway and
Transportation Officials.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-2-5
Concrete Structures and Foundations
2.1.4 BUILDINGS (2005)
Unless otherwise specified by local governing ordinances or state codes, all concrete railway buildings shall be
designed in accordance with the latest “Building Code Requirements for Reinforced Concrete (ACI 318)” of the
American Concrete Institute, subject to design loads conforming to railway requirements.
2.1.5 PIER PROTECTION (2005)
2.1.5.1 Adjacent to Railroad Tracks1
a.
To limit damage by the redirection and deflection of railroad equipment, piers supporting bridges over
railways and with a clear distance of 25 feet (7600 mm) or less from the centerline of a railroad track
shall be of heavy construction (defined below) or shall be protected by a reinforced concrete crash wall.
Crash walls for piers from 12 to 25 feet (3600 to 7600 mm) clear from the centerline of track shall have a
minimum height of 6 feet (1800 mm) above the top of rail. Piers less than 12 feet (3600 mm) clear from
the centerline of track shall have a minimum crash wall height of 12 feet (3600 mm) above the top of rail.
b. The crash wall shall be at least 2¢ -6² (760 mm) thick and at least 12 feet (3600 mm) long. When two or
more columns compose a pier, the crash wall shall connect the columns and extend at least 1 foot (300
mm) beyond the outermost columns parallel to the track. The crash wall shall be anchored to the
footings and columns, if applicable, with adequate reinforcing steel and shall extend to at least 4 feet
(1200 mm) below the lowest surrounding grade.
c.
Piers shall be considered of heavy construction if they have a cross-sectional area equal to or greater
than that required for the crash wall and the larger of its dimensions is parallel to the track.
d. Consideration may be given to providing protection for bridge piers over 25 feet (7600 mm) from the
centerline of track as conditions warrant. In making this determination, account shall be taken of such
factors as horizontal and vertical alignment of the track, embankment height, and an assessment of the
consequences of serious damage in the case of a collision.
2.1.5.2 Over Navigable Streams
Piers located adjacent to channels of navigable waterways shall have a protection system in accordance with
Part 23 Pier Protection Systems at Spans Over Navigable Streams.
2.1.6 SUPERSTRUCTURE PROTECTION (2010)2
2.1.6.1 General Requirements
a.
An evaluation of a railroad bridge over a roadway should be performed when the risk potential and
consequence from a vehicular collision with a railroad superstructure is deemed necessary by the
Engineer. Factors to be considered in the evaluation should include but not limited to railroad safety and
operational requirements, vertical clearance over roadway surface, roadway functional classification,
roadway design speed, roadway sight distance, traffic data, and other reasonable data for the specific
location. Reasonable protection of the superstructure should be determined based upon results from the
evaluation and approval by the Engineer.
b. A re-evaluation of the grade separation requirements should be performed when changes in conditions at
the location or other factors warrant.
1
2
See Commentary
See Commentary
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-2-6
AREMA Manual for Railway Engineering
Reinforced Concrete Design
2.1.7 SKEWED CONCRETE BRIDGES (2005)1
a.
The skew angle, on most concrete bridges, is the smallest angle measured between a line perpendicular
to the centerline of bridge and the centerline of the abutments or piers. Skewed concrete bridges should
be avoided when possible. When skewed bridges are unavoidable, cast-in-place concrete bridges are
preferable. The following table illustrates the maximum recommended skew for different types of
concrete bridges.
TYPE OF STRUCTURE
SKEW IN DEGREES
Precast concrete slabs and box girders
15
Precast concrete I-girders and T-girders
30
Cast-in-place concrete slabs and girders
60
b. When interior diaphragms are used on concrete girder bridges, they should be placed perpendicular to
the web of the girder.
c.
Abutments may be skewed, provided there is either a haunch in the backwall of the abutment, or an
approach slab is provided for each track. The end of the haunch in the backwall of the abutment and the
end of the approach slab shall be set perpendicular to the center of the track.
d. Concrete bridges with a curved superstructure should not be skewed. Piers and abutments for these
bridges should be placed radial to the centerline of the bridge.
e.
The ends of concrete slabs and concrete box girders with flange widths 5’-0” (1525 mm) and wider may
be skewed. Skews on the ends of concrete I-girders, concrete T-girders and concrete box girders with
flange widths less than 5’-0” (1525 mm) should be avoided.
f.
All concrete bridges that differ from these guidelines should be evaluated on a case by case basis.
1
3
4
1
See Commentary
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-2-7
Concrete Structures and Foundations
SECTION 2.2 NOTATIONS, DEFINITIONS AND DESIGN LOADS
2.2.1 NOTATIONS (2005)
a
= depth of equivalent rectangular stress block, inches (mm). See Article 2.31.1f
ab
= depth of equivalent rectangular stress block for balanced strain conditions, inches (mm). See
Article 2.33.2
av
= shear span, distance between concentrated load and face of support, inches (mm). See Article 2.29.7
and Article 2.35.7
A
= effective tension area of concrete surrounding the main tension reinforcing bars and having the same
centroid as that reinforcement, divided by the number of bars, square inches (mm2). When the main
reinforcement consists of several bar sizes the number of bars shall be computed as the total steel area
divided by the area of the largest bar used. See Section 2.39
Ab = area of an individual bar, square inches (mm2). See Section 2.14
Ac
= area of the core of a spirally reinforced compression member measured to the outside diameter of the
spiral, square inches (mm2). See Article 2.11.2
Af
= area of reinforcement in bracket or corbel resisting moment, square inches (mm2). See Article 2.29.7
and Article 2.35.7
Ag = gross area of section, square inches (mm2).
Ah = area of shear reinforcement parallel to flexural tension reinforcement, square inches (mm2). See
Article 2.29.7 and Article 2.35.7
An = area of reinforcement in bracket or corbel resisting tensile force, Nc(Nuc), square inches (mm2). See
Article 2.29.7 and Article 2.35.7
As
= area of tension reinforcement, square inches (mm2)
A¢ s = area of compression reinforcement, square inches (mm2)
Asf = area of reinforcement to develop compression strength of overhanging flanges of I- and T-sections,
square inches (mm2). See Article 2.32.3
Ask = area of skin reinforcement per unit height in one side face, square inches/foot (mm2/m). See
Section 2.8
Ast = total area of longitudinal reinforcement, square inches (mm2). See Article 2.33.1 and 2.33.2
Av
= area of shear reinforcement within a distance s, square inches (mm2)
Avf = area of shear-friction reinforcement, square inches (mm2). See Article 2.29.4 and Article 2.35.4
Aw = area of individual wire to be developed or spliced, square inches (mm2)
b
= width of compression face of member, inches (mm)
bo
= perimeter of critical section for slabs and footings, inches (mm). See Article 2.29.6 and Article 2.35.6
bv
= width of cross section being investigated for horizontal shear, inches (mm). See Article 2.29.6 and
Article 2.35.5
bw = web width, or diameter of circular section. For tapered webs, the average width or 1.2 times the
minimum width, whichever is smaller, inches (mm). See Article 2.29.1 and Article 2.35.1
c
= distance from extreme compression fiber to neutral axis, inches (mm). See Article 2.31.1
Cm = a factor relating the actual moment diagram to an equivalent uniform moment diagram. See
Article 2.34.2
d
= distance from extreme compression fiber to centroid of tension reinforcement, inches (mm)
d¢
= distance from extreme compression fiber to centroid of compression reinforcement, inches (mm)
d²
= distance from centroid of gross section neglecting the reinforcement, to centroid of tension
reinforcement, inches (mm)
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db
= diameter of bar or wire, inches (mm)
dc
= thickness of concrete cover measured from extreme tension fiber to center of bar located closest
thereto, inches (mm). See Section 2.39
dp
= diameter of round pile or cross sectional depth of H-pile at footing base, inches (mm). See
Article 2.29.6 and Article 2.35.6
Ec
= modulus of elasticity of concrete, psi (MPa). See Article 2.23.4
EI = flexural stiffness of compression member. See Article 2.34.2
Es
= modulus of elasticity of steel, psi (MPa). See Article 2.23.4
fb
= average bearing stress in concrete on loaded area, psi (MPa). See Article 2.26.1 and Section 2.36
fc
= extreme fiber compressive stress in concrete at service loads, psi (MPa). See Article 2.26.1
f ¢ c = specified compressive strength of concrete, psi (MPa)
f¢ c= square root of specified compressive strength of concrete, psi (MPa)
fct
= average splitting tensile strength of lightweight aggregate concrete, psi (MPa)
fmin = algebraic minimum stress level, tension positive, compression negative, psi (MPa). See Section 2.38
fr
= modulus of rupture of concrete, psi (MPa). See Article 2.26.1
ff
= stress range in steel reinforcement, ksi (MPa). See Section 2.38 and Article 2.26.2
fs
= tensile stress in reinforcement at service loads, psi (MPa). See Article 2.26.2
f ¢ sb = stress in compression reinforcement at balanced strain conditions, psi (MPa). See Article 2.32.4 and
Article 2.33.2
ft
= extreme fiber tensile stress in concrete at service loads, psi (MPa). See Article 2.26.1
fy
= specified yield strength of reinforcement, psi (MPa)
h
= overall thickness of member, inches (mm)
hf
= compression flange thickness of I- and T-sections, inches (mm)
1
Icr = moment of inertia of cracked section transformed to concrete. See Article 2.23.7
Ie
= effective moment of inertia for computation of deflection. See Article 2.23.7
Ig
= moment of inertia of gross concrete section about centroidal axis, neglecting reinforcement
Io
= moment of inertia of reinforcement about centroidal axis of member cross section
k
= effective length factor for compression member. See Article 2.34.2
la
= additional embedment length at support or at point of inflection, inches (mm). See Article 2.13.2
ld
= development length, inches (mm). See Section 2.13 through Section 2.22
3
ldh = development length of standard hook in tension, measured from critical section to outside end of hook
(straight embedment length between critical section and start of hook [point of tangency] plus radius
of bend and one bar diameter), inches (mm).
lhb x applicable modification factors
lhb = basic development length of standard hook in tension, inches (mm).
lu
= unsupported length of compression member. See Section 2.34
M
= computed moment capacity as defined in Article 2.13.2
Ma = maximum moment in member at section for which deflection is being computed. See Article 2.23.7
Mb = nominal moment strength of a section at balanced strain conditions. See Article 2.33.2
Mc = moment to be used for design of compression member. See Article 2.34.2
Mcr = cracking moment. See Article 2.23.7
Mn = nominal moment strength of a section
Mnx = nominal moment strength of a section considered about the x axis. See Article 2.33.3
Mny = nominal moment strength of a section considered about the y axis. See Article 2.33.3
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Mu = factored moment at section £ FMn
Mux = factored moment component in direction of x axis. See Article 2.33.3
Muy = factored moment component in direction of y axis. See Article 2.33.3
M1b = value of small end moment on compression member due to loads that result in no appreciable side
sway, calculated by conventional elastic frame analysis, positive if member is bent in single curvature,
negative if bent in double curvature. See Article 2.34.2
M2b = value of larger end moment on compression member due to loads that result in no appreciable side
sway, calculated by conventional elastic frame analysis, always positive. See Article 2.34.2
M2s = value of larger end moment on compression member due to loads that result in appreciable side sway,
calculated by conventional elastic frame analysis, always positive. See Article 2.34.2
n
= modular ratio = Es/Ec. See Article 2.27
N
= design axial load normal to cross section occurring simultaneously with V to be taken as positive for
compression, negative for tension, and to include the effects of tension due to shrinkage and creep. See
Article 2.29.2
Nc = design tensile force applied at top of bracket or corbel acting simultaneously with V, to be taken as
positive for tension. See Article 2.29.7
Nu = factored axial load normal to the cross section occurring simultaneously with Vu to be taken as positive
for compression, negative for tension, and to include the effects of tension due to shrinkage and creep.
See Article 2.35.2
Nuc = factored tensile force applied at top of bracket or corbel acting simultaneously with Vu, to be taken as
positive for tension. See Article 2.35.7
Pb = nominal axial load strength of a section at balanced strain conditions. See Article 2.33.2
Pc
= critical load. See Article 2.34.2
Pn = nominal axial load strength at given eccentricity.
Pnx = nominal axial load strength corresponding to Mnx with bending considered about the x axis only. See
Article 2.33.3
Pny = nominal axial load strength corresponding to Mny with bending considered about the y axis only. See
Article 2.33.3
Pnxy = nominal axial load strength with biaxial loading. See Article 2.33.3
Po
= nominal axial load strength of a section at zero eccentricity. See Article 2.33.2 and Article 2.33.3
Pu = factored axial load at given eccentricity £ F Pn
r
= radius of gyration of cross section of compression member. See Article 2.34.2
s
= tie spacing, inches (mm). See Article 2.22.4
s
= shear reinforcement spacing in a direction parallel to the longitudinal reinforcement, inches (mm)
sw
= spacing of wire to be developed or spliced, inches (mm)
S
= span length as defined in Article 2.23.6, feet (meters)
v
= design shear stress at section. See Section 2.29
vc
= permissible shear stress carried by concrete. See Section 2.29 and Section 2.35
vdh = design horizontal shear stress at any cross section. See Article 2.29.5
vh
= permissible horizontal shear stress. See Article 2.29.5 and Article 2.35.5
vu
= factored shear stress at section. See Section 2.35
vuh = factored horizontal shear stress at any cross section. See Article 2.35.5
V
= design shear force at section. See Section 2.29
Vu = factored shear force at section. See Section 2.35
wc = weight of concrete, pounds per cubic foot (kg/m3)
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yt
= distance from centroidal axis of gross section, neglecting reinforcement, to extreme fiber in tension,
inches (mm). See Article 2.23.7
Z
= a quantity limiting distribution of flexural reinforcement. See Section 2.39
a
= angle between inclined shear reinforcement and longitudinal axis of member
af
= angle between shear-friction reinforcement shear plane. See Article 2.29.4 and Article 2.35.4
bb
= ratio of area of bars cut off to total area of bars at the section. See Article 2.13.1
bc
= ratio of long side to short side of concentrated load or reaction area. See Article 2.29.6 and
Article 2.35.6
bd
= ratio of maximum factored axial dead load to maximum total factored axial load, where the load is due
to gravity effects only in the calculation of Pc in EQ 2-43, or ratio of the maximum factored sustained
lateral load to the maximum total factored lateral load in that level in the calculation of Pc in EQ 2-43.
See Article 2.34.2
b1
= a factor defined in Article 2.31.1
db
= Moment magnification factor for members braced against sidesway to reflect effects of member
curvature between ends of compression member.
ds
= Moment magnification factor for members not braced against sidesway to reflect lateral drift resulting
from lateral and gravity loads.
l
= correction factor related to unit weight of concrete. See Article 2.29.4 and Article 2.35.4
m
= coefficient of friction. See Article 2.29.4 and Article 2.35.4
r
= tension reinforcement ratio = As/bd
1
r¢
= compression reinforcement ratio = A¢ s/bd
rb
= reinforcement ratio producing balanced strain conditions. See Article 2.32.1
rs
= ratio of volume of spiral reinforcement to total volume of core (out-to-out of spirals) of a spirally
reinforced compression member. See Article 2.11.2
rv
= ratio of tie reinforcement area to area of contact surface
r w = reinforcement ratio (As/bwd) used in EQ 2-15 and EQ 2-46. See Article 2.29.2 and Article 2.35.2
F
3
= strength reduction factor. See Article 2.30.2
2.2.2 DEFINITIONS (2005)
The following terms are for general use in Part 2 Reinforced Concrete Design. Specialized terms appear in
individual paragraphs. Refer to the Chapter 8 Glossary located at the end of the chapter for definitions.
Compressive Strength of Concrete (f ¢ c)
Nominal Strength
Deformed Reinforcement
Plain Reinforcement
Design Load
Required Strength
Design Strength
Service Load
Development Length
Spiral
Embedment Length
Stirrups or Ties
Embedment Length, Equivalent (le)
Yield Strength or Yield Point (fy)
End Anchorage
Concrete, Structural Lightweight
Factored Load
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Concrete Structures and Foundations
2.2.3 DESIGN LOADS (2009)
a.
General.
(1) The following loads and forces shall be considered in the design of railway concrete structures
supporting tracks:
D
= Dead Load
F
= Longitudinal Force due to Friction
or Shear Resistance at Expansion
Bearings
L
= Live Load
I
= Impact
CF
= Centrifugal Force
EQ
= Earthquake (Seismic)
E
= Earth Pressure
SF
= Stream Flow Pressure
B
= Buoyancy
ICE = Ice Pressure
W
= Wind Load on Structure
OF
WL
= Wind Load on Live Load
LF
= Longitudinal Force from Live Load
= Other Forces (Rib Shortening,
Shrinkage, Temperature and/or
Settlement of Supports)
(2) Each member of the structure shall be designed for that combination of such loads and forces that
can occur simultaneously to produce the most critical design condition as specified in Article 2.2.4.
b. Dead Load.
(1) The dead load shall consist of the estimated weight of the structural member, plus that of the track,
ballast, fill, and other portions of the structure supported thereby.
(2) The unit weight of materials comprising the dead load, except in special cases involving unusual
conditions or materials, shall be assumed as follows:
• Track rails, inside guardrails and fastenings – 200 lb per linear foot of track. (3kN/m)
• Ballast, including track ties – 120 lb per cubic foot. (1900 kg/m3)
• Reinforced concrete – 150 lb per cubic foot. (2400 kg/m3)
• Earthfilling materials – 120 lb per cubic foot. (1900 kg/m3)
• Waterproofing and protective covering – estimated weight.
c.
Live Load.
(1) The recommended live load for each track of main line structure is Cooper E 80 (EM 360) loading
with axle loads and axle spacing as shown in Figure 8-2-1. On branch lines and in other locations
where the loading is limited to the use of light equipment, or cars only, the live load may be reduced,
as directed by the engineer. For structures wherein the material in the primary load-carrying
members is not concrete, the E loading used for the concrete design shall be that used for the
primary members.
(2) The axle loads on structures may be assumed as uniformly distributed longitudinally over a length of
3 feet (900 mm), plus the depth of ballast under the tie, plus twice the effective depth of slab, limited,
however, by the axle spacing.
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Figure 8-2-1. Cooper E 80 (EM 360) Axle Load Diagram
(3) Live load from a single track acting on the top surface of a structure with ballasted deck or under
fills shall be assumed to have uniform lateral distribution over a width equal to the length of track
tie plus the depth of ballast and fill below the bottom of tie, unless limited by the extent of the
structure.
(4) The lateral distribution of live load from multiple tracks shall be as specified for single tracks and
further limited so as not to exceed the distance between centers of adjacent tracks.
(5) The lateral distribution of the live load for structures under deep fills carrying multiple tracks, shall
be assumed as uniform between centers of outside tracks, and the loads beyond these points shall be
distributed as specified for single track. Widely separated tracks shall not be included in the multiple
track group.
1
(6) In calculating the maximum live loads on a structural member due to simultaneous loading on two
or more tracks, the following proportions of the specified live load shall be used:
• For two tracks – full live load,
3
• For three tracks – full live load on two tracks and one-half on the other track,
• For four tracks – full live load on two tracks, one-half on one track, and one-fourth on the
remaining track.
(7) The tracks selected for full live load in accordance with the listed limitations shall be those tracks
which will produce the most critical design condition on the member under consideration.
d. Impact Load.1
(1) Impact forces, applied at the top of rail, shall be added to the axle loads specified. For rolling
equipment without hammer blow (diesels, electric locomotives, tenders alone, etc.), the impact shall
be equal to the following percentages of the live load:
1
See Commentary
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Concrete Structures and Foundations
(U.S. Customary)
For L £14 feet
I = 60
For 14 feet < L £127 feet
I =225 ¤ ( L )
For L > 127 feet
I = 20
(Metric)
For L £4 meters
I = 60
For 4 meters < L £39 meters
I =125 ¤ ( L )
For L > 39 meters
I = 20
Where L is the span length in feet (meters).
This formula is intended for ballasted-deck spans and substructure elements as required.
(2) For continuous structures, the impact value calculated for the shortest span shall be used
throughout.
(3) Impact may be omitted in the design for massive substructure elements which are not rigidly
connected to the superstructure.
(4) For steam locomotives with hammer blow, the impact calculated according to Article 2.2.3d(1) shall
be increased by 20%.
e.
Centrifugal Force.
(1) On curves, a centrifugal force corresponding to each axle load shall be applied horizontally through a
point 8 feet (2450 mm) above the top of rail measured along a line perpendicular to the line joining
the tops of the rails and equidistant from them. This force shall be the percentage of the live load
computed from the formulas below.
(2) On curves, each axle load on each track shall be applied vertically through the point defined in the
first paragraph of this article.
(3) The greater of loads on high and low sides of a superelevated track shall be used for the design of
supports under both sides.
(4) The relationships between speed, degree of curve, centrifugal force and a superelevation which is 3
inches (75 mm) less than that required for zero resultant flange pressure between wheel and rail are
expressed by the formulas:
C = 0.00117 S2D
C = 0.000452 S2D
EQ 2-1
EQ 2-1M
E = 0.0007 S2D – 3
E = 0.0068 S2D – 75
EQ 2-2
EQ 2-2M
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Reinforced Concrete Design
S =
E+3
----------------------0.0007D
EQ 2-3
S =
E + 75
----------------------0.0068D
EQ 2-3M
where:
C = Centrifugal force in percentage of the live load
D = Degree of curve (Degrees based on 100 foot (30 m) chord)
E = Actual superelevation in inches (mm)
S = Permissible speed in miles per hour (km/hr)
f.
Earth Pressure. Earth pressure forces to be applied to the structure shall be determined in accordance
with the provisions of Part 5 Retaining Walls, Abutments and Piers.
g.
Buoyancy. Buoyancy shall be considered as it affects the design of either substructure, including piling,
or the superstructure.
h. Wind Load on Structure. The base wind load acting on the structure is assumed to be 45 lb per square
foot (2160 Pa) on the vertical projection of the structure applied at the center of gravity of the vertical
projection in any horizontal direction. A base wind velocity of 100 miles per hour (160 km/h) was used to
determine the base wind load. If an increase in the design wind velocity is made, the design wind
velocity and design wind load shall be shown on the plans.
1
For Group II and Group V loadings, when a design wind velocity greater than 100 miles per hour (160
km/h) is advisable the base wind load may be increased by the ratio of the square of the design wind
velocity to the square of the base wind velocity. This increase shall not apply to Group III and Group VI
Loadings.
3
i.
Wind Load on Live Load. A wind load of 300 lb per linear foot (4.4 kN/m) on the train shall be applied 8
feet (2450 mm) above the top of rail in a horizontal direction perpendicular to the centerline of the track.
j.
Longitudinal Force.1
(1) The longitudinal force for E-80 (EM 360) loading shall be taken as the larger of:
4
– Force due to braking, as prescribed by the following equation, acting 8 feet (2450 mm) above top
of rail.
Longitudinal braking force (kips) = 45+1.2L
(Longitudinal braking force (kN) = 200+17.5L)
where L is the length in feet (meters) of the portion of the bridge under consideration
– Force due to traction, as prescribed by the following equation, acting 3 feet (900 mm) above top
of rail.
Longitudinal traction force (kips) = 25 L
1
See Commentary
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Concrete Structures and Foundations
(Longitudinal traction force (kN) = 200 L )
where L is the length in feet (meters) of the portion of the bridge under consideration
For design loads other than E-80 (EM 360), these forces shall be scaled proportionally. The points of
force application shall not be changed.
(2) The effective longitudinal force shall be distributed to the various components of the supporting
structure, taking into account their relative stiffness. The resistance of the backfill behind the
abutments shall be utilized where applicable. The mechanisms (rail, bearings, load transfer devices,
etc.) available to transfer the force to the various components shall also be considered.
(3) The longitudinal deflection of the superstructure due to longitudinal force computed in (1) above
shall not exceed 1 inch (25 mm) for E-80 (EM 360) loading. For design loads other than E-80 (EM
360), the maximum allowable longitudinal deflection shall be scaled proportionally. In no case,
however, shall the longitudinal deflection exceed 1-1/2 inches (38 mm).
k. Longitudinal Force Due to Friction or Shear Resistance at Expansion Bearings. Provisions shall be made
to accommodate forces due to friction or shear resistance due to expansion bearings.
l.
Earthquake. In regions where earthquakes may be anticipated, structures may be designed to resist
earthquake motions by considering the relationship of the site to active faults, the seismic response of
the soils at the site, and the dynamic response characteristics of the total structure. Refer to Chapter 9
Seismic Design for Railway Structures for additional guidance.
m. Stream Flow Pressure. All piers and other portions of structures which are subject to the force of flowing
water or drift shall be designed to resist the maximum stresses induced thereby.
(1) Stream Pressure
The effect of flowing water on piers and drift build up, assuming a second-degree parabolic velocity
distribution and thus a triangular pressure distribution, shall be calculated by the formula:
Pavg = K(Vavg)2
EQ 2-4
where:
Pavg = average stream pressure, in pounds per square foot, (Pa)
Vavg = average velocity of water in feet per second, (m/s) computed by dividing the flow rate
by the flow area,
K = a constant, being 1.4 (or 725 for metric) for all piers subjected to drift build up and
square-ended piers, 0.7 (or 360 for metric) for circular piers, and 0.5 (or 260 for
metric) for angle-ended piers where the angle is 30 degrees or less.
The maximum stream flow pressure, Pmax, shall be equal to twice the average stream flow pressure,
Pavg, computed by EQ 2-4. Stream flow pressure shall be a triangular distribution with Pmax located
at the top of water elevation and a zero pressure located at the flow line.
(2) The stream flow forces shall be computed by the product of the stream flow pressure, taking into
account the pressure distribution, and the exposed pier area. In cases where the corresponding top
of water elevation is above the low beam elevation, stream flow loading on the superstructure shall
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be investigated. The stream flow pressure acting on the superstructure may be taken as Pmax with a
uniform distribution.
(3) Pressure Components
When the direction of stream flow is other than normal to the exposed surface area, or when bank
migration or a change of stream bed meander is anticipated, the effects of the directional
components of stream flow pressure shall be investigated.
(4) Drift Lodge Against Pier
Where a significant amount of drift lodge against a pier is anticipated, the effects of this drift build
up shall be considered in the design of the bridge opening and the bridge components. The overall
dimensions of the drift build up shall reflect the selected pier locations, site conditions, and known
drift supply upstream. When it is anticipated that the flow area will be significantly blocked by drift
build up, increases in high water elevations, stream velocities, stream flow pressures, and the
potential increases in scour depths shall be investigated.
n. Ice Pressure. The effects of ice pressure, both static and dynamic, shall be accounted for in the design of
piers and other portions of the structure where, in the judgment of the Engineer, conditions so warrant.
(1) General. Ice forces on piers shall be selected having regard to site conditions and the mode of ice
action to be expected. Consideration shall be given to the following modes:
(a) dynamic ice pressure due to moving ice sheets and floes carried by streamflow, wind or currents;
1
(b) static ice pressure due to thermal movements of continuous stationary ice sheets onlarge bodies
of water;
(c) static pressure resulting from ice jams;
3
(d) static uplift or vertical loads resulting from adhering ice in waters of fluctuating level.
The expected thickness of ice, the direction of its movement, and the height at which it acts shall be
determined by field investigations, published records, aerial photography and other means.
Consideration shall be given to the worst expected combination of height, thickness and pressure, to
the possibility of unusual thicknesses resulting from special circumstances or operations, and to the
natural variability of ice conditions from year to year.
(2) Dynamic Ice Pressure. Horizontal forces resulting from the pressure of moving ice are to be
calculated by the formula:
EQ 2-5
F = Cnptw
where:
F = horizontal ice force on pier; pounds (N)
Cn = coefficient for nose inclination from Table 8-2-1;
p = ice pressure as indicated below; psi (MPa)
t = thickness of ice in contact withpier; inches (mm)
w = width of pier or diameter of circular-shaft pier at the level of ice action; inches (mm)
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Table 8-2-1. Coefficient for Nose Inclination
Inclination of Nose to Vertical
Cn
0 degrees to 15 degrees
1.00
15 degrees to 30 degrees
0.75
30 degrees to 45 degrees
0.50
(3) The ice pressure “p” shall normally be taken in the range of 100 psi (0.7 MPa) to 400 psi (2.8 MPa)
on the assumption that crushing or splitting of the ice takes place on contact with the pier. The
value used shall be based on an assessment of the probable condition of the ice at time of movement,
on previous local experience, and on assessment of existing structure performance. Relevant ice
conditions include the expected temperature of the ice at time of movement, the size of moving
sheets and floes and the velocity at contact. Due consideration shall be given to probability of
extreme rather than average conditions at the site in question.
NOTE:
The following values of ice pressure appropriate to various situations may be
used as a guide:
(a) In the order of 100 psi (0.7 MPa) where break-up occurs at melting temperatures and where the
ice runs as small “cakes” and is substantially disintegrated in its structure;
(b) In the order of 200 psi (1.4 MPa) where break-up occurs at melting temperatures, but the ice
moves in large pieces and is internally sound;
(c) In the order of 300 psi (2.1 MPa) where at break-up there is an initial movement of the ice sheet
as a whole or where large sheets of sound ice may strike the piers;
(d) In the order of 400 psi (2.8 MPa) where break-up or major ice movement may occur with ice
temperature significantly below the melting point.
(4) The ice pressure values listed above apply to piers of substantal mass and dimensions. The values
shall be modified as necessary for variations inpier width or pile diameter, and design ice thickness
by multiplying by the appropriate coefficient obtained from Table 8-2-2.
Table 8-2-2. Coefficient for Design Ice Thickness
b/t
Coefficient
0.5
1.8
1.0
1.3
1.5
1.1
2.0
1.0
3.0
0.9
4.0 or greater
0.8
where:
b = width of pier or diameter of pile;
t = design ice thickness.
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(5) Piers should be placed with their longitudinal axes parallel to the principal direction of ice action.
The force calculated by the formula shall then be taken to act along the direction of the long axis. A
force transverse to the longitudinal axis and amounting to not less than 15% of the longitudinal force
shall be considered to act simultaneously.
(6) Where the longitudinal axis of a pier cannot be placed parallel to the principal direction of ice action,
or where the direction of ice action may shift, the total force on the pier shall be figured by the
formula and resolved into vector components. In such conditions, forces transverse to the
longitudinal axis of the pier shall in no case be taken as less than 20% of the total force.
(7) In the case of slender and flexible piers, consideration should be given to the vibrating nature of
dynamic ice forces and to the possibility of high momentary pressures and structural resonance.
(8) Ice pressure on piers frozen into ice sheets on large bodies of water shall receive special consideration
where there is reason to believe that the ice sheets are subject to significant thermal movements
relative to the piers.
o.
Other Forces (Rib Shortening, Shrinkage, Temperature and/or Settlement of Supports).
(1) The structure shall be designed to resist the forces caused by rib shortening, shrinkage, temperature
rise and/or drop and the anticipated settlement of supports.
(2) The range of temperature shall generally be as shown in Table 8-2-3.
1
Table 8-2-3. Temperature Ranges
Climate
Temperature Rise
Temperature Fall
Moderate
30 degrees F (17 degrees C) 40 degrees F (22 degrees C)
Cold
35 degrees F (20 degrees C) 45 degrees F (25 degrees C)
4
2.2.4 LOADING COMBINATIONS (2005)
a.
General. The following groups represent various combinations of loads and forces to which a structure
may be subjected. Each component of the structure, or the foundation on which it rests, shall be
proportioned for the group of loads that produce the most critical design condition.
b. Service Load Design.
(1) The group loading combinations for SERVICE LOAD DESIGN are as shown in Table 8-2-4.
(2) No increase in allowable unit stresses shall be permitted for members or connections carrying wind
load only. If predictability of service load conditions is different from the specifications, this
difference should be accounted for in the appropriate service load analyses or in the unit stress
increase percentages.
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Concrete Structures and Foundations
Table 8-2-4. Group Loading Combinations – Service Load Design
Item
Allowable Percentage
of Basic Unit Stress
I
D + L + I + CF + E + B + SF
100
II
D + E + B + SF + W
125
III
Group I + 0.5W + WL + LF + F
125
IV
Group I + OF
125
V
Group II + OF
140
VI
Group III + OF
140
VII
Group I + ICE
140
VIII
Group II + ICE
150
Group
c.
Load Factor Design.
(1) The group loading combinations for LOAD FACTOR DESIGN are as shown in Table 8-2-5.
Table 8-2-5. Group Loading Combinations – Load Factor Design
Group
I
Item
1.4 (D + 5/3 (L + I) + CF + E + B + SF)
IA
1.8 (D + L + I + CF + E + B + SF)
II
1.4 (D + E + B + SF + W)
III
1.4 (D + L + I + CF + E + B + SF + 0.5W + WL + LF
+ F)
IV
1.4 (D + L + I + CF + E + B + SF + OF)
V
Group II + 1.4 (OF)
VI
Group III + 1.4 (OF)
VII
1.0 (D + E + B + EQ)
VIII
1.4 (D + L + I + E + B + SF + ICE)
IX
1.2 (D + E + B + SF + W + ICE)
(2) The load factors given are only intended for designing structural members by the load factor concept.
The actual loads should not be increased by these factors when designing for foundations (soil
pressure, pile loads, etc.). The load factors are not intended to be used when checking for foundation
stability (safety factors against overturning, sliding, etc.) of a structure. The load factors given above
represent usual conditions and should be increased if, in the Engineer’s judgment, the predictability
of loads is different than anticipated by the specifications.
SECTION 2.3 MATERIALS
2.3.1 CONCRETE (1992)
a.
Compressive strength of concrete f ¢ c for which each part of the structure is designed, shall be shown on
the plans.
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b. Specified compressive strength of concrete f ¢ c shall be the basis for acceptance. Requirements for f ¢ c
shall be based on tests of cylinders made and tested in accordance with the methods as prescribed in Part
1 Materials, Tests and Construction Requirements.
2.3.2 REINFORCEMENT (2005)
a.
Yield strength or grade of reinforcement used in design shall be shown on the plans.
b. Reinforcement to be welded shall be indicated on the plans and the welding procedure to be used shall be
specified. ASTM steel specifications, except for ASTM A706, shall be supplemented to require a report of
material properties (chemical analysis) necessary to conform to welding procedures specified in
“Structural Welding Code–Reinforcing Steel” (AWS D 1.4) of the American Welding Society. If coated bars
are to be welded, the Engineer should specify any additional requirements to those contained in AWS D
1.4, such as removal of zinc or epoxy coating for welding and field application of new coatings in the weld
region if protection is required.
c.
Designs shall not be based on a yield strength fy in excess of 60,000 psi (420 MPa).
d. Only deformed reinforcement shall be used except that plain bars or smooth wire may be used as spirals.
e.
Reinforcement shall conform to the specifications listed in Part 1 Materials, Tests and Construction
Requirements, except that, for reinforcing bars, the yield strength shall correspond to that determined by
tests on full-size bars.
1
DETAILS OF REINFORCEMENT
3
SECTION 2.4 HOOKS AND BENDS
2.4.1 STANDARD HOOKS (2005)
The term “standard hook” as used herein, shall mean one of the following:
a.
4
180-degree bend plus 4db extension, but not less than 2-1/2 inches (60 mm) at free end of bar.
b. 90-degree bend plus 12db extension at free end of bar.
c.
For stirrup and tie hooks:
(1) #5 (#16) bar and smaller, 90-degree bend plus 6db extension at free end of bar, or
(2) #6, #7, and #8 (#19, #22, #25) bar, 90-degree bend plus 12db extension at free end of bar, or
(3) #8 (#25) bar and smaller, 135-degree bend plus 6db extension at free end of bar.
2.4.2 MINIMUM BEND DIAMETER (2005)
a.
Diameter of bend measured on the inside of the bar, other than for stirrups and ties in sizes #3 (#10)
through #5 (#16), shall not be less than the values in Table 8-2-6.
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Concrete Structures and Foundations
Table 8-2-6. Minimum Diameter of Bend
Bar Size
#3 through #8 (#10 through #25)
Minimum Diameter
6 bar diameters
#9, #10 and #11 (#29, #32 and #36) 8 bar diameters
#14 and #18 (#43 and #57)
10 bar diameters
b. Inside diameter of bends for stirrups and ties shall not be less than 4db for #5 (#16) bar and smaller. For
bars larger than #5 (#16), diameter of bend shall be in accordance with Table 8-2-6.
c.
Inside diameter of bend in welded wire fabric, smooth or deformed, for stirrups and ties shall not be less
than four wire diameters for deformed wire larger than D6 and two wire diameters for all other wires.
Bends with inside diameter of less than eight wire diameters shall not be less than four wire diameters
from the nearest welded intersection.
SECTION 2.5 SPACING OF REINFORCEMENT (2005)
a.
For cast-in-place concrete the clear distance between parallel bars in a layer shall not be less than one
and one-half times the diameter of the bars, two times the maximum size of the coarse aggregate, nor 11/2 inches (40 mm).
b. For precast concrete (manufactured under plant control conditions) the clear distance between parallel
bars in a layer shall be not less than the diameter of the bars, one and one-third times the maximum size
of the coarse aggregate, nor 1 inch (25 mm).
c.
Where positive or negative reinforcement is placed in two or more layers, bars in the upper layers shall
be placed directly above those in the bottom layer with the clear distance between layers not less than 1
inch (25 mm).
d. Clear distance limitation between bars shall also apply to the clear distance between a contact lap splice
and adjacent splices or bars.
e.
Groups of parallel reinforcing bars bundled in contact to act as a unit shall be limited to four in any one
bundle. Bars larger than #11 (#36) shall not be bundled in beams. Bundled bars shall be located within
stirrups or ties. Individual bars in a bundle cut off within the span of a member shall terminate at
different points with at least 40 bar diameters stagger. Where spacing limitations are based on bar size, a
unit of bundled bars shall be treated as a single bar of a diameter derived from the equivalent total area.
f.
In walls and slabs the principal reinforcement shall be spaced not farther apart than one and one-half
times the wall or slab thickness, nor more than 18 inches (450 mm).
SECTION 2.6 CONCRETE PROTECTION FOR REINFORCEMENT
2.6.1 MINIMUM CONCRETE COVER (2005)
Table 8-2-7 defines the minimum concrete cover that shall be provided for reinforcement.
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Table 8-2-7. Minimum Concrete Cover
Condition of Concrete
Minimum Cover
(Inches)
Minimum Cover
(mm)
Concrete cast against and permanently exposed to earth
3
75
Concrete exposed to earth or weather
Principal reinforcement
Stirrups, ties and spirals
2
1-1/2
50
40
Concrete bridge slabs
Top reinforcement
Bottom reinforcement
2
1-1/2
50
40
Concrete not exposed to weather or in contact with ground
Principal reinforcement
Stirrups, ties and spirals
1-1/2
1
40
25
2.6.2 CONCRETE COVER FOR BAR BUNDLES (2005)
For bar bundles, minimum concrete cover shall be equal to the lesser of the equivalent diameter of the bundle
or 2 inches (50 mm), but not less than that given in Article 2.6.1.
2.6.3 CONCRETE COVER FOR CORROSIVE AND MARINE ENVIRONMENTS (1992)
In corrosive or marine environments or other severe exposure conditions, the amount of concrete protection
shall be suitably increased, and the denseness and nonporosity of the protecting concrete shall be considered, or
other protection shall be provided.
1
2.6.4 CORROSION PROTECTION (1992)
Exposed reinforcing bars, inserts, and plates intended for bonding with future extensions shall be protected
from corrosion.
SECTION 2.7 MINIMUM REINFORCEMENT OF FLEXURAL MEMBERS (1992)
a.
4
At any section of a flexural member where tension reinforcement is required by analysis, the
reinforcement provided shall be adequate to develop a design moment strength FMn at least 1.2 times
the cracking moment calculated on the basis of the modulus of rupture for normal weight concrete
specified in Article 2.26.1a.
b. The requirements of Section 2.7a may be waived if the area of reinforcement provided at the section
under consideration is at least one-third greater than that required by analysis based on the load factors
specified in Article 2.2.4c.
SECTION 2.8 DISTRIBUTION OF REINFORCEMENT IN FLEXURAL MEMBERS (2005)
a.
Flexural tension reinforcement shall be well distributed in the zones of maximum tension.
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Concrete Structures and Foundations
(1) For T-girder and box-girder flanges, tension reinforcement shall be distributed over an effective
tension flange width equal to 1/10 the girder span length, or a width as defined in Article 2.23.10b,
whichever is smaller. If the actual slab width, center-to-center of girder webs, exceeds the effective
tension flange width, and for excess portions of deck slab overhang, additional longitudinal
reinforcement having a total area at least equal to 0.4% of excess slab area shall be provided in the
outer portions of the slab.
(2) For integral bent caps of T-girder and box girder construction, tension reinforcement shall not be
placed outside the bent cap web farther than an overhanging slab width on each side of the bent cap
equal to 1/4 the average spacing of intersecting girder webs or a width as defined in Article 2.23.10b
for integral bent caps, whichever is smaller.
b. If the depth of web exceeds 3 feet (900 mm), longitudinal skin reinforcement shall be uniformly
distributed along both side faces of the member for a distance d/2 nearest the flexural tension
reinforcement. The area of skin reinforcement Ask per foot (m) of height on each side face shall be
³0.012(d-30) (or Ask ³ 0.3 (d-750) in metric). The maximum spacing of the skin reinforcement shall be
the smaller of d/6 or 12 inches (300 mm). Such reinforcement may be included in strength computations
if a strain compatibility analysis is made to determine stresses in the individual bars or wires. The total
area of longitudinal skin reinforcement in both faces need not exceed one-half of the required flexural
tensile reinforcement.
c.
For LOAD FACTOR DESIGN, the distribution of flexural reinforcement requirements of Article 2.39
shall also apply.
SECTION 2.9 LATERAL REINFORCEMENT OF FLEXURAL MEMBERS (2005)
a.
Compression reinforcement used to increase the strength of flexural members shall be enclosed by ties
or stirrups, at least #3 (#10) in size for longitudinal bars #10 (#32) or smaller, and at least #4 (#13) in
size for #11, #14, #18 (#36, #43, #57) and bundled longitudinal bars, or by welded wire fabric of
equivalent area. Spacing of the ties shall not exceed 16 longitudinal bar diameters. Such stirrups or ties
shall be provided throughout the distance where the compression reinforcement is required.
b. Torsion reinforcement, where required, shall consist of closed stirrups, closed ties, or spirals, combined
with longitudinal bars.
c.
Closed stirrups or ties may be formed in one piece by overlapping standard stirrup or tie end hooks
around a longitudinal bar, or formed in one or two pieces lap spliced with a Class C splice (lap of 1.7ld).
d. In seismic areas, where an earthquake of such magnitude as to cause major damage to construction has a
high probability of occurrence, lateral reinforcement shall be designed and detailed to provide adequate
strength and ductility to resist anticipated seismic movements.
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SECTION 2.10 SHEAR REINFORCEMENT – GENERAL REQUIREMENTS
2.10.1 MINIMUM SHEAR REINFORCEMENT (2005)
a.
A minimum area of shear reinforcement shall be provided in all flexural members, except slabs, footings,
and shallow beams, where the design shear stress is greater than one-half the permissible shear stress vc
carried by concrete. Beams where total depth does not exceed either 10 inches (250 mm), 2-1/2 times the
thickness of the flange, or one-half the width of the web shall be considered shallow beams.
b. Where shear reinforcement is required by Article 2.10.1a, or by analysis, the area provided shall not be
less than
EQ 2-6
EQ 2-6M
Av = 60 bws/fy
Av = 0.42 bws/fy
where:
bw = inches (mm)
s = inches (mm)
c.
Minimum shear reinforcement requirements may be waived if it is shown by test that the required
ultimate flexural and shear strength can be developed when shear reinforcement is omitted.
1
2.10.2 TYPES OF SHEAR REINFORCEMENT (1992)
a.
Shear reinforcement may consist of:
(1) Stirrups perpendicular to axis of member or making an angle of 45 degrees or more with the
longitudinal tension reinforcement.
3
(2) Welded wire fabric with wires located perpendicular to axis of member.
(3) Longitudinal bars with a bent portion making an angle of 30 degrees or more with the longitudinal
tension bars.
4
(4) Combinations of stirrups and bent bars.
(5) Spirals.
b. Shear reinforcement shall be anchored at both ends in accordance with requirements of Section 2.21.
2.10.3 SPACING OF SHEAR REINFORCEMENT (2005)
Where shear reinforcement is required and is placed perpendicular to axis of member, it shall be spaced not
further apart than 0.50d, but not more than 24 inches (600 mm). Inclined stirrups and bent bars shall be so
spaced that every 45 degree line, extending toward the reaction from the mid-depth of the member, 0.50d, to
the longitudinal tension bars, shall be crossed by at least one line of shear reinforcement.
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Concrete Structures and Foundations
SECTION 2.11 LIMITS FOR REINFORCEMENT OF COMPRESSION MEMBERS
2.11.1 LONGITUDINAL REINFORCEMENT (2005)
a.
Longitudinal reinforcement for compression members shall not be less than 0.01 nor more than 0.08
times the gross area of Ag of the section. The minimum number of longitudinal reinforcing bars shall be
six for bars in a circular arrangement and four for bars in a rectangular arrangement. The minimum size
of bar shall be #5 (#16).
b. When the cross section is larger than that required by consideration of loading, a reduced effective area
may be used. The reduced effective concrete area shall not be less than that which would require 1% of
longitudinal reinforcement to carry the loading.
2.11.2 LATERAL REINFORCEMENT (2005)
a.
Spirals. Spiral reinforcement for compression members shall conform to the following:
(1) Spirals shall consist of evenly spaced continuous bar or wire, with a minimum diameter of 3/8 inch
(10 mm).
(2) Ratio of spiral reinforcement r s shall not be less than the value given by:
f¢ c
Ag
r s = 0.45 æ ------- – 1ö -------èA
ø f
y
c
EQ 2-7
where:
fy = the specified yield strength of spiral reinforcement but not more than 60,000 psi
(420 MPa)
(3) Clear spacing between spirals shall not exceed 3 inches (75 mm) nor be less than 1-1/2 inches (40
mm) or 2 times the maximum size of coarse aggregate used.
(4) Anchorage of spiral reinforcement shall be provided by 1-1/2 extra turns of spiral bar or wire at each
end of a spiral unit.
(5) Spirals shall extend from top of footing or other support to level of lowest horizontal reinforcement
in members supported above.
(6) Splices in spiral reinforcement shall be welded splices, or they shall be lap splices not less than the
larger of 12 inches (300 mm) and the length indicated in one of (a) through (e) below:
(a) deformed uncoated bar or wire......................................................................................................48db
(b) plain uncoated bar or wire.............................................................................................................72db
(c) epoxy-coated deformed bar or wire...............................................................................................72db
(d) plain uncoated bar or wire with a standard stirrup or tie hook in accordance with Article 2.4.1c
at ends of lapped spiral reinforcement. The hooks shall be embedded within the core confined by
the spiral reinforcement................................................................................................................48db
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(e) epoxy-coated deformed bar or wire with a standard stirrup or tie hook in accordance with
Article 2.4.1c at ends of lapped spiral reinforcement. The hooks shall be embedded within the
core confined by the spiral reinforcement....................................................................................48db
(7) Spirals shall be of such size and so assembled to permit handling and placing without distortion from
designed dimensions.
(8) Spirals shall be held firmly in place and true to line by vertical spacers. For spiral bar or wire smaller
than 5/8 inch (16 mm) diameter, a minimum of two spacers shall be used for spirals less than 20
inches (500 mm) in diameter, three spacers for spirals 20 to 30 inches (500 to 750 mm) in diameter,
and four spacers for spirals greater than 30 inches (750 mm) in diameter. For spiral bar or wire 5/8
inch (16 mm) diameter or larger, a minimum of three spacers shall be used for spirals 24 inches (600
mm) or less in diameter, and four spacers for spirals greater than 24 inches (600 mm) in diameter.
b. Ties. Tie reinforcement for compression members shall conform to the following:
(1) All bars shall be enclosed by lateral ties, at least #3 (#10) in size for longitudinal bars #10 (#32) or
smaller, and at least #4 (#13) in size for #11, #14, #18 (#36, #43, #57), and bundled longitudinal
bars. Deformed wire or welded wire fabric of equivalent area may be used.
(2) Vertical spacing of ties shall not exceed the least dimension of the compression member or 12 inches
(300 mm). When bars larger than #10 (#32) are bundled more than two in any one bundle, tie
spacing shall be one-half that specified above.
(3) Ties shall be located vertically not more than half a tie spacing above the footing or other support
and shall be spaced as provided herein to not more than half a tie spacing below the lowest
horizontal reinforcement in members supported above.
(4) At each tie location, the lateral ties shall be so arranged that no longitudinal bar is farther than
2 feet (600mm) on either side along the tie from a bar with lateral support provided by the corner of
a tie having an included angle of not more than 135 degrees. Where longitudinal bars are located
around the perimeter of a circle, a complete circular tie may be used.
c.
1
3
In a compression member which has a larger cross section than required by conditions of loading, the
lateral reinforcement requirements may be waived where structural analysis or tests show adequate
strength feasibility of construction.
d. In seismic areas, where an earthquake of such magnitude as to cause major damage to construction has a
high probability of occurrence, lateral reinforcement for column piers shall be designed and detailed to
provide adequate strength and ductility to resist anticipated seismic movements.
SECTION 2.12 SHRINKAGE AND TEMPERATURE REINFORCEMENT (2005)
Reinforcement for shrinkage and temperature stresses shall be provided near exposed surfaces of walls and
slabs not otherwise reinforced. The total area of reinforcement provided shall be at least 0.25 in2/ft (530
mm2/m) measured in the direction perpendicular to the direction of the reinforcement and be spaced not
farther apart than three times the wall or slab thickness, nor 18 inches (450 mm).
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Concrete Structures and Foundations
DEVELOPMENT AND SPLICES OF REINFORCEMENT
SECTION 2.13 DEVELOPMENT REQUIREMENTS
2.13.1 GENERAL (2005)
a.
The calculated tension or compression in the reinforcement at each section shall be developed on each
side of that section by embedment length or end anchorage or a combination thereof. For bars in tension,
hooks may be used in developing the bars.
b. Tension reinforcement may be anchored by bending it across the web and making it continuous with the
reinforcement on the opposite face of the member, or anchoring it there.
c.
Critical sections for development of reinforcement in flexural members are at points of maximum stress
and at points within the span where adjacent reinforcement terminates, or is bent. The provisions of
Article 2.13.2c must also be satisfied.
d. Reinforcement shall extend beyond the point at which it is no longer required to resist flexure for a
distance equal to the effective depth of the member, 15 bar diameters, or 1/20 of the clear span,
whichever is greater, except at supports of simple spans and at the free end of cantilevers.
e.
Continuing reinforcement shall have an embedment length not less than the development length ld
beyond the point where bent or terminated tension reinforcement is no longer required to resist flexure.
f.
Flexural reinforcement located within the width of a member used to compute the shear strength shall
not be terminated in a tension zone unless one of the following conditions is satisfied.
(1) Shear at the cutoff point does not exceed one-half of the design shear strength, FVn, including the
shear strength of furnished shear reinforcement.
(2) Stirrup area in excess of that required for shear is provided along each terminated bar over a
distance from the termination point equal to three-fourths the effective depth of the member. The
excess stirrups shall be proportioned such that their (Av/bws)fy is not less than 60 psi (0.42 MPa).
The resulting spacings shall not exceed d/(8bb) where bb is the ratio of the area of bars cut off to the
total area of bars at the section.
(3) For #11 (#36) and smaller bars, the continuing bars provide double the area required for flexure at
the cutoff point and shear does not exceed three-fourths of the design shear strength, FVn.
2.13.2 POSITIVE MOMENT REINFORCEMENT (2005)
a.
At least one-half the positive moment reinforcement in simple members and one-fourth the positive
moment reinforcement in continuous members shall extend along the same face of the member into the
support. In beams, such reinforcement shall extend into the support a distance of 12 or more bar
diameters, or shall be extended as far as possible into the support and terminated in standard hooks or
other adequate anchorage.
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b. When a flexural member is part of the lateral load resisting system, the positive reinforcement required
to be extended into the support by Article 2.13.2a shall be anchored to develop the full fy in tension at the
face of the support.
c.
At simple supports and at points of inflection, positive moment tension reinforcement shall be limited to
a diameter such that ld computed for fy by Section 2.14 satisfies EQ 2-8; except EQ 2-8 need not be
satisfied for reinforcement terminating beyond centerline of simple supports by a standard hook, or a
mechanical anchorage at least equivalent to a standard hook.
M
ld £----- + la
V
EQ 2-8
where:
M = the computed moment capacity assuming all positive moment tension reinforcement at the
section to be fully stressed
V = the maximum applied design shear at the section
la = the embedment length beyond center of support or point of inflection
la at a point of inflection shall be limited to the effective depth of the member 12d b , whichever is greater.
The value of M/V in the development length limitation may be increased 30% when the ends of the
reinforcement are confined by a compressive reaction.
1
2.13.3 NEGATIVE MOMENT REINFORCEMENT (1994)
a.
Tension reinforcement in a continuous, restrained, or cantilever member, or in any member of a rigid
frame, shall be anchored in or through the supporting member by embedment length, hooks, or
mechanical anchorage.
3
b. Negative moment reinforcement shall have an embedment length into the span as required by
Article 2.13.1a and Article 2.13.1d.
c.
At least one-third the total reinforcement provided for negative moment at the support shall have an
embedment length beyond the point of inflection not less than the effective depth of the member, 12 bar
diameters, or one-sixteenth of the clear span, whichever is greater.
4
2.13.4 SPECIAL MEMBERS (1994)
Adequate end anchorage shall be provided for tension reinforcement in flexural members where reinforcement
stress is not directly proportional to moment, such as: sloped, stepped, or tapered footings; brackets; deep
beams; or members in which the tension reinforcement is not parallel to the compression face.
SECTION 2.14 DEVELOPMENT LENGTH OF DEFORMED BARS AND DEFORMED WIRE
IN TENSION (2005)
Development length ld, in inches (mm), of deformed bars and deformed wire in tension shall be computed as the
product of the basic development length of Section 2.14a and the applicable modification factor or factors of
Section 2.14b through Section 2.14e, but ld shall be not less than that specified in Section 2.14f.
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a.
The basic development length is shown in Table 8-2-8.
Table 8-2-8. Development Length for Deformed Bars and Wire
Type
For #11 or smaller bars
Development Length
0.04A b f y
-----------------------f¢ c
(Note 1)
but not less than:
0.0004dbfy (Note 2)
For #14 bars
For #18 bars
For deformed wire
0.085f y
-------------------f¢ c
(Note 3)
0.11f y
---------------f¢ c
(Note 3)
0.03d b f y
----------------------f¢ c
Note 1: The constant carries the unit of 1/inch.
Note 2: The constant carries the unit of inch2/lb.
Note 3: The constant carries the unit of inch.
b. The basic development length shall be multiplied by a factor of 1.4 for top reinforcement.
NOTE:
c.
Top reinforcement is horizontal reinforcement so placed that more than 12 inches (300 mm) of
concrete is cast in the member below the bar.
When lightweight aggregate concrete is used, the basic development lengths in Section 2.14a shall be
multiplied by 1.18, or the basic development length may be multiplied by
6.7 f¢ c ¤ f ct
(or
0.56 f¢ c ¤ f ct in metric), but not less than 1.0, when fct is specified. The factors of Section 2.14b and
Section 2.14d shall also be applied.
d. The basic development length may be multiplied by the applicable factor or factors for:
Reinforcement being developed in length under consideration and spaced laterally at
least 6 inches (150 mm) on center with at least 3 inches (75 mm) clear from face of
member to edge bar, measured in the direction of the spacing (Figure 8-2-2). . . . . . . . . . . 0.8
Bars enclosed within a spiral which is not less than 1/4 inch (6 mm) diameter and not
more than 4 inch (100 mm) pitch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.75
e.
The basic development length for bars coated with epoxy with cover less than 3 bar diameters or clear
spacing between bars less than 6 bar diameters shall be multiplied by a factor of 1.5. The basic
development length for all other epoxy coated bars shall be multiplied by a factor of 1.15. The product
obtained when combining the factor for top reinforcement with the applicable factor for epoxy coated
reinforcement need not be taken greater than 1.7.
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f.
The development length ld shall be taken as not less than 12 inches (300 mm) except in the computation
of lap splices by Article 2.22.3 and anchorage of shear reinforcement by Section 2.21.
Figure 8-2-2. Reinforcement Spacing
SECTION 2.15 DEVELOPMENT LENGTH OF DEFORMED BARS IN COMPRESSION (2005)
The development length ld for bars in compression shall be computed as 0.02f y d b ¤ ( f ¢ c) (or f y d b ¤ 4 ( f ¢ c) in
metric), but shall not be less than 0.0003 fydb or 8 inches [or (0.04 dbfy) or 200 mm in metric]. Where excess bar
area is provided the ld length may be reduced by the ratio of required area to area provided. The development
length may be reduced 25% when the reinforcement is enclosed by spirals not less than 1/4 inch (6 mm) in
diameter and not more than 4 inch (100 mm) pitch.
1
3
SECTION 2.16 DEVELOPMENT LENGTH OF BUNDLED BARS (1990)
The development length of each bar of bundled bars shall be that for the individual bar, increased by 20% for a
three-bar bundle, and 33% for a four-bar bundle.
4
SECTION 2.17 DEVELOPMENT OF STANDARD HOOKS IN TENSION (2005)
a.
Development length ldh, in inches (mm), for deformed bars in tension terminating in a standard hook
(Article 2.4.1) shall be computed as the product of the basic development length lhb of Section 2.17b and
the applicable modification factor or factors of Section 2.17c but ldh shall not be less than 8db or 6 inches
(150 mm), whichever is greater.
b. Basic development length lhb for a hooked bar with fy equal to 60,000 psi (420 MPa) shall be
1200d b ¤ ( f ¢ c) (or 100d b ¤ ( f ¢ c) in metric).
c.
Basic development length lhb shall be multiplied by applicable modification factor or factors for:
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-2-31
Concrete Structures and Foundations
(1) Bar yield strength
Bars with fy other than 60,000 psi (420 MPa) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . fy/60,000
(fy/420)
(2) Concrete cover
For #11 (#36) bar and smaller, side cover (normal to plane of hook) not less than 2-1/2
inches (60 mm), and for 90 degree hook, cover on bar extension beyond hook not less
than 2 inches (50 mm).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7
(3) Ties or stirrups
For #11 (#36) bar and smaller, hook enclosed vertically or horizontally within ties or
stirrup-ties spaced along full development length ldh not greater than 3db, where db is
diameter of hooked bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.8
(4) Excess reinforcement
Where anchorage or development for fy is not specifically required,
( A s required )
reinforcement in excess of that required by analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . ------------------------------------( A s provided )
(5) Lightweight aggregate concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3
d. For bars being developed by a standard hook at discontinuous ends of members with both side cover and
top (or bottom) cover over hook less than 2-1/2 inches (60 mm), hooked bar shall be enclosed within ties
or stirrups spaced along full development length ldh not greater than 3db, where db is diameter of hooked
bar (Figure 8-2-3). For this case, factor of Section 2.17c(3) shall not apply.
e.
Hooks shall not be considered effective in developing bars in compression.
Figure 8-2-3. Standard Hook Bars
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8-2-32
AREMA Manual for Railway Engineering
Reinforced Concrete Design
SECTION 2.18 COMBINATION DEVELOPMENT LENGTH
Information deleted in 1990 revision.
SECTION 2.19 DEVELOPMENT OF WELDED WIRE FABRIC IN TENSION
2.19.1 DEFORMED WIRE FABRIC (2005)
a.
Development length ld, in inches (mm), of welded deformed wire fabric measured from point of critical
section to end of wire shall be computed as the product of the basic development length of Article 2.19.1b
or Article 2.19.1c and applicable modification factor or factors of Section 2.14b, Section 2.14c and
Section 2.14d; but ld shall not be less than 8 inches (200 mm) except in computation of lap splices by
Article 2.22.6 and development of shear reinforcement by Section 2.21.
b. Basic development length of welded deformed wire fabric, with at least one cross wire within the
development length not less than 2 inches (50 mm) from point of critical section, shall be
0.03d b ( f y – 20, 000 ) ¤
0.36d b ( f y – 140 ) ¤
f¢
f¢ c
NOTE: The 20,000 has units of psi.
NOTE: The 140 has units of MPa.
EQ 2-9
EQ 2-9M
1
but not less than
0.20A w æ f y ö
-------------------- ç ------------÷
s w è f¢ ø
c
c.
EQ 2-10
3
Basic development length of welded deformed wire fabric, with no cross wires within the development
length, shall be determined as for deformed wire.
2.19.2 SMOOTH WIRE FABRIC (2005)
Yield strength of welded smooth wire fabric shall be considered developed by embedment of two cross wires
with the closer cross wire not less than 2 inches (50 mm) from point of critical section. However, development
length ld measured from point of critical section to outermost cross wire shall not be less than
0.27A w æ f y ö
-------------------- ç ------------÷
s w è f¢ ø
c
EQ 2-11
3.3A w æ f y ö
---------------- ç ------------÷
s w è f¢ ø
c
EQ 2-11M
modified by a factor of Section 2.14c for lightweight aggregate concrete, but ld shall not be less than 6 inches
(150 mm) except in computation of lap splices by Article 2.22.7.
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Concrete Structures and Foundations
SECTION 2.20 MECHANICAL ANCHORAGE (1992)
a.
Any mechanical device shown by tests to be capable of developing the strength of reinforcement without
damage to concrete may be used as anchorage.
b. Development of reinforcement may consist of a combination of mechanical anchorage plus additional
embedment length of reinforcement between point of maximum bar stress and the mechanical
anchorage.
SECTION 2.21 ANCHORAGE OF SHEAR REINFORCEMENT (2005)
a.
Shear reinforcement shall extend to a distance d from the extreme compression fiber and shall be carried
as close to the compression and tension surfaces of the member as cover requirements and the proximity
of other reinforcement permit. Shear reinforcement shall be anchored at both ends for its design yield
strength.
b. The ends of single leg, single U-, or multiple U-stirrups shall be anchored by one of the following means:
(1) For #5 (#16) bar and D31 wire, and smaller, and for #6, #7, and #8 (#19, #22, and #25) bars with
fy of 40,000 psi (280 MPa) or less, a standard hook around longitudinal reinforcement.
(2) See Figure 8-2-4. For #6, #7, and #8 (#19, #22, and #25) stirrups with fy greater than 40,000 psi
(280 MPa), a standard hook around a longitudinal bar plus an embedment between mid-height of the
member and the outside end of the hook equal to or greater than 0.014d b f y ¤ f ¢ c
( 0.17d b f y ¤ f ¢ c in metric).
(3) For each leg of welded plain wire fabric forming single U-stirrups, either:
(a) Two longitudinal wires spaced at 2 inch (50 mm) spacing along the beam at the top of the U.
(b) One longitudinal wire located not more than d/4 from the compression face and a second wire
closer to the compression face and spaced at least 2 inches (50 mm) from the first wire. The
second wire may be located beyond a bend or on a bend which has an inside diameter of at least 8
wire diameters.
c.
Pairs of U-stirrups or ties so placed as to form a closed unit shall be considered properly spliced when the
laps are 1.7 ld.
d. Between the anchored ends, each bend in the continuous portion of a transverse single U- or multiple Ustirrup shall enclose a longitudinal bar.
e.
Longitudinal bars bent to act as shear reinforcement shall, in a region of tension, be continuous with the
longitudinal reinforcement and in a compression zone shall be anchored, above or below the mid-depth
d/2 as specified for development length in Section 2.14 for that part of the stress in the reinforcement
needed to satisfy EQ 2-21 or EQ 2-52.
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8-2-34
AREMA Manual for Railway Engineering
Reinforced Concrete Design
Figure 8-2-4. #6, 7, or 8 Stirrups (fy > 40,000 psi) (#19, 22, or 25) (fy > 280 MPa)
1
SECTION 2.22 SPLICES OF REINFORCEMENT
Splices of reinforcement shall be made only as shown on design drawings, or as specified, or as authorized by
the Engineer.
3
2.22.1 LAP SPLICES (2005)
a.
Lap splices shall not be used for bars larger than #11 (#36).
b. Lap splices of bundled bars shall be based on the lap splice length required for individual bars within a
bundle, increased 20% for a 3-bar bundle and 33% for a 4-bar bundle. Individual bar splices within a
bundle shall not overlap.
c.
Bars spliced by noncontact lap splices in flexural members shall not be spaced transversely farther apart
than 1/5 the required lap splice length, nor 6 inches (150 mm).
2.22.2 WELDED SPLICES AND MECHANICAL CONNECTIONS (2005)
a.
Welded splices and other mechanical connections may be used. Except as provided herein, all welding
shall conform to “Structural Welding Code–Reinforcing Steel” (AWS D1.4).
b. A full welded splice shall have bars butted and welded to develop in tension at least 125% of specified
yield strength fy of the bar.
c.
A full mechanical connection shall develop in tension or compression, as required, at least 125% of
specified yield strength fy of the bar.
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Concrete Structures and Foundations
d. Welded splices and mechanical connections not meeting requirements of Article 2.22.2b or
Article 2.22.2c may be used in accordance with Article 2.22.3d.
2.22.3 SPLICES OF DEFORMED BARS AND DEFORMED WIRE IN TENSION (2005)
a.
Minimum length of lap for tension lap splices shall be as required for Class A, B, or C splice, but not less
than 12 inches (300 mm),
where:
Class A splice = 1.0ld
Class B splice = 1.3ld
Class C splice = 1.7ld
where:
ld = the tensile development length for the specified yield strength fy in accordance with
Section 2.14.
b. Lap splices of deformed bars and deformed wire in tension shall conform to Table 8-2-9.
Table 8-2-9. Tension Lap Splices
(As Provided/As Required)
(Note 1)
Maximum Percent of As Spliced within Required Lap Length
50
75
100
Equal to or greater than 2
Class A
Class A
Class B
Less than 2
Class B
Class C
Class C
Note 1: Ratio of area of reinforcement provided to area of reinforcement required by analysis at
splice location.
c.
Welded splices or mechanical connections used where area of reinforcement provided is less than twice
that required by analysis shall meet requirements of Article 2.22.2b or Article 2.22.2c.
d. Welded splices or mechanical connections used where area of reinforcement provided is at least twice
that required by analysis shall meet the following:
(1) Splices shall be staggered at least 24 inches (600 mm) and in such manner as to develop at every
section at least twice the calculated tensile force at that section but not less than 20,000 psi (140
MPa) for total area of reinforcement provided.
(2) In computing tensile force developed at each section, spliced reinforcement may be rated at the
specified splice strength. Unspliced reinforcement shall be rated at that fraction of fy defined by the
ratio of the shorter actual development length to ld required to develop the specified yield strength
fy.
e.
Splices in “tension tie members” shall be made with a full welded splice or full mechanical connection
and splices in adjacent bars shall be staggered at least 30 inches (750 mm).
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AREMA Manual for Railway Engineering
Reinforced Concrete Design
2.22.4 SPLICES OF DEFORMED BARS IN COMPRESSION (2005)
a.
Minimum length of lap for compression lap splices shall be 0.0005fydb, in inches (or 0.07fydb in
millimeters), but not less than 12 inches (300 mm). For f ¢ c less than 3000 psi (20 MPa), length of lap
shall be increased by/1/3.
b. In tied reinforced compression members, where ties throughout the lap splice length have an effective
area not less than 0.0015hs, lap splice length may be multiplied by 0.83, but lap length shall not be less
than 12 inches (300 mm). Tie legs perpendicular to dimension h shall be used in determining effective
area.
c.
In spirally reinforced compression members, lap splice length of bars within a spiral may be multiplied
by 0.75, but lap length shall not be less than 12 inches (300 mm).
d. Welded splices or mechanical connections used in compression shall meet requirements of Article 2.22.2b
or Article 2.22.2c.
2.22.5 END BEARING SPLICES (1992)
In bars required for compression only, compressive stress may be transmitted by bearing of square cut ends
held in concentric contact by a suitable device. Bar ends shall terminate in flat surfaces within 1-1/2 degrees of
a right angle to the axis of the bars and shall be fitted within 3 degrees of full bearing after assembly. End
bearing splices shall be used only in members containing closed ties, closed stirrups, or spirals.
1
2.22.6 SPLICES OF WELDED DEFORMED WIRE FABRIC IN TENSION (2005)
a.
Minimum length of lap for lap splices of welded deformed wire fabric measured between the end of each
fabric sheet shall not be less than 1.7ld nor 8 inches (200 mm), and the overlap measured between
outermost cross wires of each fabric sheet shall not be less than 2 inches (50 mm). ld shall be the
development length for the specified yield strength fy, in accordance with Article 2.19.1.
3
b. Lap splices of welded deformed wire fabric, with no cross wires within the lap splice length, shall be
determined as for deformed wire.
2.22.7 SPLICES OF WELDED SMOOTH WIRE FABRIC IN TENSION (2005)
Minimum length of lap for lap splices of welded smooth wire fabric shall be in accordance with the following:
a.
When area of reinforcement provided is less than twice that required by analysis at splice location,
length of overlap measured between outermost cross wires of each fabric sheet shall not be less than one
spacing of cross wire plus 2 inches (50 mm), nor less than 1.5ld nor 6 inches (150 mm). ld shall be the
development length for the specified yield strength fy in accordance with Article 2.19.2.
b. When area of reinforcement provided is at least twice that required by analysis at splice location, length
of overlap measured between outermost cross wires of each fabric sheet shall not be less than 1.5ld nor 2
inches (50 mm). ld shall be the development length for the specified yield strength fy in accordance with
Article 2.19.2.
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AREMA Manual for Railway Engineering
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Concrete Structures and Foundations
ANALYSIS AND DESIGN – GENERAL CONSIDERATIONS
SECTION 2.23 ANALYSIS METHODS
2.23.1 GENERAL (1992)
a.
All members of continuous and rigid frame structures shall be designed for the maximum effects of the
loads specified in Article 2.2.3 as determined by the theory of elastic analysis.
b. Consideration shall be given to the effects of forces due to shrinkage, temperature changes, creep, and
unequal settlement of supports.
2.23.2 EXPANSION AND CONTRACTION (2005)
a.
In general, provision for temperature changes shall be made in simple spans when the span length
exceeds 40 feet (12 m).
b. In continuous bridges, provision shall be made in the design to resist thermal stresses induced or means
shall be provided for movement caused by temperature changes.
c.
Movements not otherwise provided for shall be provided by rockers, sliding plates, elastomeric pads or
other means.
2.23.3 STIFFNESS (1992)
a.
Any reasonable assumptions may be adopted for computing the relative flexural and torsional stiffnesses
of continuous and rigid frame members. The assumptions made shall be consistent throughout the
analysis.
b. Effect of haunches shall be considered both in determining moments and in design of members.
2.23.4 MODULUS OF ELASTICITY (2005)
a.
Modulus of elasticity Ec for concrete may be taken as w c
1.5
33 f ¢ c , in psi (or w c
1.5
0.043 f ¢ c in MPa), for
values of wc between 90 and 155 pcf (1500 and 2500 kg/m3). For normal weight concrete (wc = 145 pcf,
wc = 2300 kg/m3), Ec may be considered as 57, 000 f ¢ c (or 4700 f ¢ c in metric) .
b. Modulus of elasticity of nonprestressed steel reinforcement may be taken as 29,000,000 psi (200 GPa).
2.23.5 THERMAL AND SHRINKAGE COEFFICIENTS (2005)
a.
Thermal coefficient for normal weight concrete may be taken as 0.000006 per degree F (or 0.0000105 per
degree C).
b. Shrinkage coefficient for normal weight concrete may be taken as 0.0002.
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Reinforced Concrete Design
c.
Thermal and shrinkage coefficients for lightweight concrete shall be determined for the type of
lightweight aggregate used.
2.23.6 SPAN LENGTH (1992)
a.
Span length of members not built integrally with supports shall be considered the clear span plus depth
of member, but need not exceed distance between centers of supports.
b. In analysis of continuous and rigid frame members, center-to-center distances shall be used in the
determination of moments. Moments at faces of support may be used for member design. When fillets
making an angle of 45 degrees or more with the axis of a continuous or restrained member are built
monolithic with the member and support, face of support shall be considered at a section where the
combined depth of the member and fillet is at least one and one-half times the thickness of the member.
No portion of a fillet shall be considered as adding to the effective depth.
c.
Effective span length of slabs shall be as follows:
(1) Slabs monolithic with beams or walls (without haunches), S = clear span.
(2) Slabs supported on steel stringers, S = distance between edges of flanges plus 1/2 the stringer flange
width.
2.23.7 COMPUTATION OF DEFLECTIONS (2005)
a.
Where deflections are to be computed, they shall be based on the cross-sectional properties of the entire
superstructure section except railings, curbs, sidewalks or any element not placed monolithically with
the superstructure section before falsework removal. Deflections of composite members shall take into
account shoring during erection, differential shrinkage of the elements and the magnitude and duration
of load prior to the beginning of effective composite action.
b. Computation of live load deflection may be based on the assumption that the superstructure flexural
members act together and have equal deflection. The live loading shall consist of all tracks loaded as
specified in Article 2.2.3c. The live loading shall be considered uniformly distributed to all longitudinal
flexural members.
c.
1
3
Computation of Immediate Deflection.
(1) Deflections that occur immediately on application of load shall be computed by the usual methods of
formulas for elastic deflections. Unless values are obtained by a more comprehensive analysis,
deflections shall be computed taking the modulus of elasticity for concrete as specified in
Article 2.23.4a for normal weight or lightweight concrete and taking the effective moment of inertia
as follows, but not greater than Ig.
M cr 3
M cr 3
I c = æ ----------ö I g + 1 – æ ----------ö I cr
èM ø
èM ø
a
a
EQ 2-12
fr Ig
Mcr= ---------yt
EQ 2-13
where:
fr = modulus of rupture of concrete specified in Article 2.26.1a
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Concrete Structures and Foundations
(2) For continuous spans, the effective moment of inertia may be taken as the average of the values
obtained from EQ 2-12 for the critical positive and negative moment sections.
2.23.7.1 Computation of Long-time Deflection
Unless values are obtained by more comprehensive analysis, the additional long-term deflection for both
normal weight and lightweight concrete flexural members shall be obtained by multiplying the immediate
deflection caused by the sustained load considered, computed in accordance with Article 2.23.7c, by the factor
æ 2 – 1.2 A¢
---------s-ö ³ 0.6
è
A ø
s
2.23.8 BEARINGS (2005)
Bearing devices shall be designed in accordance with Part 18 Elastomeric Bridge Bearings and Chapter 15,
Part 10 and Part 11. Bearing stresses in concrete shall not exceed the values given in Section 2.26 or
Section 2.36.
2.23.9 COMPOSITE CONCRETE FLEXURAL MEMBERS (1992)
a.
Application. Composite flexural members consist of concrete elements constructed in separate
placements but so interconnected that the elements respond to loads as a unit.
b. General Considerations.
(1) The total depth of the composite member or portions thereof may be used in resisting the shear and
the bending moment. The individual elements shall be investigated for all critical stages of loading.
(2) If the specified strength, unit weight, or other properties of the various components are different, the
properties of the individual components, or the most critical values, shall be used in design.
(3) In calculating the flexural strength of a composite member by load factor design, no distinction shall
be made between shored and unshored members.
(4) All elements shall be designed to support all loads introduced prior to the full development of the
design strength of the composite member.
(5) Reinforcement shall be provided as necessary to control cracking and to prevent separation of the
components.
c.
Shoring. When used, shoring shall not be removed until the supported elements have developed the
design properties required to support all loads and limit deflections and cracking at the time of shoring
removal.
d. Vertical Shear.
(1) When the total depth of the composite member is assumed to resist the vertical shear, the design
shall be in accordance with the requirements of Section 2.29 or Section 2.35 as for a monolithically
cast member of the same cross-sectional shape.
(2) Shear reinforcement shall be fully anchored in accordance with Section 2.21. Extended and anchored
shear reinforcement may be included as ties for horizontal shear.
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AREMA Manual for Railway Engineering
Reinforced Concrete Design
e.
Horizontal Shear. In a composite member, full transfer of the shear forces shall be assured at the
interfaces of the separate components. Design for horizontal shear shall be in accordance with the
requirements of Article 2.29.5 or Article 2.35.5.
2.23.10 T-GIRDER CONSTRUCTION (1992)
a.
In T-girder construction, the girder web and slab shall be built integrally or otherwise effectively bonded
together. Full transfer of shear forces shall be assured at the interface of web and slab. Where applicable,
the design requirements of Article 2.23.9 for composite concrete members shall apply.
b. Compression Flange Width.
(1) The effective slab width acting as a T-girder flange shall not exceed one-fourth of the span length of
the girder, and its overhanging width on either side of the girder shall not exceed six times the
thickness of the slab or one-half the clear distance to the next girder.
(2) For girders having a slab on one side only, the effective overhanging flange width shall not exceed
1/12 of the span length of the girder, nor 6 times the thickness of the slab, nor one-half the clear
distance to the next girder.
(3) Isolated T-girders in which the flange is used to provide additional compression area shall have a
flange thickness not less than one-half the width of the girder web and a total flange width not more
than four times the width of the girder web.
(4) For integral bent caps, the effective overhanging slab width on each side of a bent cap web shall not
exceed six times the least slab thickness, nor 1/10 the span length of the bent cap. For cantilevered
bent caps, the span length shall be taken as two times the length of cantilever span.
c.
Diaphragms. Diaphragms shall be used at span ends. Intermediate diaphragms shall be used where
required in the judgment of the Engineer.
1
3
2.23.11 BOX GIRDER CONSTRUCTION (2005)
a.
In box girder construction, the girder web and top and bottom slab shall be built integrally or otherwise
effectively bonded together. Full transfer of shear forces shall be assured at the interfaces of the girder
web with the top and bottom slab. Design shall be in accordance with the requirements of Article 2.23.9.
When required by design, changes in girder web thickness shall be tapered for a minimum distance of 12
times the difference in web thickness.
b. Compression Flange Width.
(1) For box girder flanges, the entire slab width shall be assumed effective for compression.
(2) For integral bent caps, the effective overhanging slab width on each side of a bent cap web shall not
exceed six times the least slab thickness, nor 1/10 the span length of the bent cap. For cantilevered
bent caps, the span length shall be taken as two times the length of cantilever span.
c.
Top and Bottom Slab Thickness.
(1) The thickness of the top slab shall be designed for loads specified in Article 2.2.3c, but shall be not
less than the minimum specified in Table 8-2-10.
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Concrete Structures and Foundations
Table 8-2-10. Recommended Minimum Thickness For Constant Depth Members
(Note 1)
Minimum Thickness
In Feet (Note 2)
Minimum Thickness
In Meters (Note 2)
S + 10
---------------20
but not less than 0.75
S+3
------------20
but not less than 0.23
T-Girders
S+9
------------15
S + 2.75
--------------------15
Box Girders
S + 10
---------------17
S+3
------------17
Superstructure Type
Bridge slabs with main reinforcement
parallel or perpendicular to traffic
Note 1: When variable depth members are used, table values may be adjusted to account for change in
relative stiffness of positive and negative moment sections.
Note 2: Recommended values for simple spans; continuous spans may be about 90% of thickness given.
S = span length as defined in Article 2.23.6, in feet (meters).
(2) The thickness of the bottom slab shall be not less than 1/16 of the clear span between girder webs or
6 inches (150 mm), whichever is greater, except that the thickness need not be greater than the top
slab unless required by design.
d. Top and Bottom Slab Reinforcement.
(1) Minimum distributed reinforcement of 0.4% of the flange area shall be placed in the bottom slab
parallel to the girder span. A single layer of reinforcement may be provided. The spacing of such
reinforcement shall not exceed 18 inches (450 mm).
(2) Minimum distributed reinforcement of 0.5% of the cross-sectional area of the slab, based on the least
slab thickness, shall be placed in the bottom slab transverse to the girder span. Such reinforcement
shall be distributed over both surfaces with a maximum spacing of 18 inches (450 mm). All
transverse reinforcement in the bottom slab shall extend to the exterior face of the outside girder
web in each group and be anchored by a standard 90 degree hook.
(3) At least 1/3 of the bottom layer of the transverse reinforcement in the top slab shall extend to the
exterior face of the outside girder web in each group and be anchored by a standard 90 degree hook.
If the slab extends beyond the last girder web, such reinforcement shall extend into the slab
overhang and shall have an anchorage beyond the exterior face of the girder web not less than that
provided by a standard hook.
e.
Diaphragms. Diaphragms shall be used at span ends. Intermediate diaphragms shall be used where
required in the judgment of the Engineer. Diaphragm spacing for curved girders shall be given special
consideration.
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AREMA Manual for Railway Engineering
Reinforced Concrete Design
SECTION 2.24 DESIGN METHODS (1992)
The design methods to be used, SERVICE LOAD DESIGN or LOAD FACTOR DESIGN, shall be as directed by
the Engineer.
SERVICE LOAD DESIGN
(APPLICABLE TO Section 2.25 THROUGH Section 2.29)
SECTION 2.25 GENERAL REQUIREMENTS (1992)
a.
For reinforced concrete members designed with reference to service loads and allowable stresses, the
service load stresses shall not exceed the values given in Section 2.26.
b. Development and splices of reinforcement shall be as required under Development and Splices of
Reinforcement.
1
SECTION 2.26 ALLOWABLE SERVICE LOAD STRESSES
2.26.1 CONCRETE (2005)
3
For service load design, stresses in concrete shall not exceed the following:
a.
Flexure:
Extreme fiber stress in compression fc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.40 f ¢ c
4
Extreme fiber stress in tension for plain concrete, ft . . . . . . . . . . . . . . . . . . . . . 0.21 fr
Modulus of rupture f r, from tests, or if data are not available:
Normal weight concrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 f ¢ c
0.62 f ¢ c (metric)
Lightweight concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 f ¢ c
0.52 f ¢ c (metric)
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Concrete Structures and Foundations
b. Shear:
NOTE:
For more detailed analysis of permissible shear stress vc carried by concrete, and shear values
for lightweight aggregate concrete – see Article 2.29.2.
Beams and one-way slabs and footings:
Shear carried by concrete vc, but not to exceed 95 psi (0.66 MPa) 0.95 f ¢ c
0.079 f ¢ c (metric)
Maximum shear carried by concrete plus shear reinforcement
vc + 4 f ¢ c
v c + 0.33 f ¢ c (metric)
Two-way slabs and footings:
(If shear reinforcement is provided see Article 2.29.6d)
2ö
æ 0.8 + ---- f¢ c
è
bø
Shear carried by concrete vc
c
æ 0.066 + 0.17
-----------ö f ¢ c (metric)
è
b ø
c
but not greater than
1.8 f ¢ c
0.15 f ¢ c (metric)
c.
Bearing on loaded area fb, but not to exceed 1050 psi (7.2 MPa) . . . . . . . . . . . . . 0.30 f ¢ c
Minimum distance from edge of bearing to edge of supporting concrete shall be 6 inches (150 mm).
2.26.2 REINFORCEMENT (2005)
a.
For service load design, tensile stress in reinforcement fs shall not exceed the following:
Grade 40 (Grade 280) reinforcement
20,000 psi (140 MPa)
Grade 60 (Grade 420) reinforcement
24,000 psi (170 MPa)
b. Fatigue Stress Limit.
(1) The range between a maximum tensile stress and minimum stress in straight reinforcement caused
by live load plus impact shall not exceed the value obtained from:
ff = 21 – 0.33fmin + 8 (r / h)
ff = 145 – 0.33fmin + 55 (r / h)
(metric)
where:
ff = stress range in steel reinforcement, ksi (MPa).
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Reinforced Concrete Design
fmin = algebraic minimum stress level, tension positive, compression negative, ksi (MPa).
r/h = ratio of base radius to height of rolled-on transverse deformations; when the actual
value is not known, use 0.3.
(2) Bends in primary reinforcement shall be avoided in regions of high stress range.
SECTION 2.27 FLEXURE (2005)
For investigation of service load stresses, the straight-line theory of stress and strain in flexure shall be used
and the following assumptions shall be made:
a.
A section plane before bending remains plane after bending; strains vary as the distance from the
neutral axis.
b. Stress-strain relation of concrete is a straight line under service loads within the allowable service load
stresses. Stresses vary as the distance from the neutral axis except, for deep flexural members with
overall depth-clear-span ratios greater than 2/5 for continuous spans and 4/5 for simple spans, a
nonlinear distribution of stress should be considered.
c.
Steel takes all the tension due to flexure.
1
d. Modular ratio n = Es/Ec may be taken as the nearest whole number (but not less than 6). Except in
calculations for deflections, the value of n for lightweight concrete shall be assumed to be the same as for
normal weight concrete of the same strength.
e.
In doubly reinforced flexural members, an effective modular ratio of 2Es/Ec shall be used to transform
the compression reinforcement for stress computations. The compressive stress in such reinforcement
shall not be greater than the allowable tensile stress.
SECTION 2.28 COMPRESSION MEMBERS WITH OR WITHOUT FLEXURE (1992)
The combined axial load and moment capacity of compression members shall be taken as 35% of that computed
in accordance with the provisions of Section 2.33. Slenderness effects shall be included according to the
requirements of Section 2.34. The term Pu in Article 2.33.1b shall be replaced by 2.85 times the design axial
load. In using the provisions of Section 2.33 and Section 2.34, F shall be taken as 1.0.
SECTION 2.29 SHEAR
2.29.1 SHEAR STRESS (2005)
a.
Design shear stress v shall be computed by:
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V
v = ----------bw d
EQ 2-14
where:
bw = the width of web
d = the distance from the extreme compression fiber to the centroid of the longitudinal tension
reinforcement.
For a circular section, bw shall be taken as the diameter and d shall be taken as 0.8 times the diameter of
the section.
b. When the reaction in the direction of the applied shear introduces compression into the end region of the
member, sections located less than a distance d from the face of the support may be designed for the
same shear v as that computed at a distance d. An exception occurs when major concentrated loads are
imposed between that point and the face of support. In that case sections closer than d to the support
shall be designed for V at distance d plus the major concentrated loads.
c.
Shear stress carried by concrete vc shall be calculated according to Article 2.29.2. When v exceeds vc,
shear reinforcement shall be provided according to Article 2.29.3. Whenever applicable, the effects of
torsion shall be added.
d. For tapered webs, bw shall be the average width or 1.2 times the minimum width, whichever is smaller.
2.29.2 PERMISSIBLE SHEAR STRESS (2005)
NOTE:
The value of
f ¢ c used in computing vc in this paragraph shall not be taken greater than
100 psi (0.69 MPa).
a.
Shear stress carried by concrete vc shall not exceed 0.95 f ¢ c (or 0.079 f ¢ c in metric) unless a more
detailed analysis is made in accordance with Article 2.29.2b or Article 2.29.2c. For members subject to
axial tension, vc shall not exceed the value given in Article 2.29.2d. For lightweight concrete, the
provisions of Article 2.29.2f shall apply.
b. Shear stress carried by concrete vc, for members subject to shear and flexure only, may be computed by:
Vd
v c = 0.9 f ¢ c + 1100r w -------M
EQ 2-15
Vd
v c = 0.075 f ¢ c + 7.58r w -------M
EQ 2-15M
Vd
but vc shall not exceed 1.6 f ¢c (or 0.13 f ¢c in metric). The quantity -------- shall not be taken greater than
M
1.0, where M is the design moment occurring simultaneously with V at the section considered.
c.
For members subject to axial compression, vc may be computed by:
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Reinforced Concrete Design
0.0006N
v c = 0.9 æ 1 + -----------------------ö f ¢ c
è
Ag ø
EQ 2-16
0.0006N
v c = 10.8 æ 0.0069 + -----------------------ö f ¢ c
è
Ag ø
EQ 2-16M
N
The quantity ------- shall be expressed in psi (MPa).
Ag
d. For members subject to significant axial tension, shear reinforcement shall be designed to carry the total
shear, unless a more detailed analysis is made using:
0.004N
v c = 0.9 æ 1 + --------------------ö f¢ c
è
Ag ø
EQ 2-17
0.004N
v c = 10.8 æ 0.0069 + --------------------ö f¢ c
è
Ag ø
EQ 2-17M
where:
N = negative for tension
e.
N
The quantity ------- shall be expressed in psi (MPa).
Ag
Special provisions for slabs of box culverts. For slabs of box culverts under 2 feet (600 mm) or more fill,
shear stress vc may be computed by:
Vd
f¢ c + 2200r -------M
EQ 2-18
Vd
v c = 0.083 f¢ c + 15.2r -------M
EQ 2-18M
vc =
but vc shall not exceed 1.8 f¢ c (or 0.15 f¢ c in metric). For single cell box culverts only, vc need not be
taken less than 1.4 f¢ c (or 0.12 f¢ c in metric) for slabs monolithic with walls or 1.2 f¢ c (or 0.10 f¢ c
Vd
in metric) for slabs simply supported. The quantity of -------- shall not be taken greater than 1.0, where M is
M
moment occurring simultaneously with V at section considered.
f.
The provisions for shear stress vc carried by concrete apply to normal weight concrete. When lightweight
aggregate concretes are used, one of the following modifications shall apply:
(1) When fct is specified, shear stress vc shall be modified by substituting fct/6.7 (or 1.8 fct in metric) for
f¢ c but the value of fct/6.7 (or 1.8 fct in metric) used shall not exceed
f¢ c.
(2) When fct is not specified, shear stress vc shall be multiplied by 0.85.
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2.29.3 DESIGN OF SHEAR REINFORCEMENT (2005)
a.
Shear reinforcement shall conform to the general requirements of Section 2.10. When shear
reinforcement perpendicular to the axis of the member is used, required area shall be computed by:
( v – v c )b w s
A v = -----------------------------fs
EQ 2-19
b. When inclined stirrups or bent bars are used as shear reinforcement the following provisions apply:
(1) When inclined stirrups are used, required area shall be computed by:
( v – v c )b w s
A v = ----------------------------------------f s ( sin a + cos a)
EQ 2-20
(2) When shear reinforcement consists of a single bar or a single group of parallel bars, all bent up at the
same distance from the support, required area shall be computed by:
( v – v c )b w d
A v = ------------------------------f s sin a
EQ 2-21
in which (v – vc) shall not exceed 1.5 f¢ c (or 0.12 f¢ c in metric).
(3) When shear reinforcement consists of a series of parallel bent-up bars or groups of parallel bent-up
bars at different distances from the support, required area shall be computed by Article 2.29.3b(1).
(4) Only the center three-fourths of the inclined portion of any longitudinal bar that is bent shall be
considered effective for shear reinforcement.
c.
Where more than one type of shear reinforcement is used to reinforce the same portion of the member,
required area shall be computed as the sum for the various types separately. No one type shall resist
more than 2/3 of the total shear resisted by reinforcement. In such computations, vc shall be included
only once.
d. When (v – vc) exceed 2 f¢ c (or 0.17 f¢ c in metric), maximum spacings given in Article 2.10.3 shall be
reduced by one-half.
e.
The value of (v – vc) shall not exceed 4 f¢ c (or 0.33 f¢ c in metric).
f.
When flexural reinforcement located within the width of a member used to compute the shear strength
is terminated in a tension zone, shear reinforcement shall be provided in accordance with Article 2.13.1f.
2.29.4 SHEAR-FRICTION (2005)
a.
Provisions for shear-friction are to be applied where it is appropriate to consider shear transfer across a
given plane, such as: an existing or potential crack, an interface between dissimilar materials, or an
interface between two concretes cast at different times.
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Reinforced Concrete Design
b. A crack shall be assumed to occur along the shear plane considered. Required area of shear-friction
reinforcement Avf across the shear plane may be designed using either Article 2.29.4c or any other shear
transfer design methods that result in prediction of strength in substantial agreement with results of
comprehensive tests. Provisions of Article 2.29.4d through Article 2.29.4h shall apply for all calculations
of shear transfer strength.
c.
Shear-friction design method.
(1) Shear-friction reinforcement is perpendicular to shear plane, area of shear-friction reinforcement Avf
shall be computed by:
V
A vf = ------fs m
EQ 2-22
where:
m = the coefficient of friction in accordance with Article 2.29.4c(3).
(2) When shear-friction reinforcement is inclined to shear plane such that the shear force produces
tension in shear-friction reinforcement, area of shear-friction reinforcement Avf shall be computed
by:
V
A vf = -----------------------------------------------f s ( m sin af + cos af )
EQ 2-23
1
where:
af = angle between shear-friction reinforcement and shear plane.
3
(3) Coefficient of friction m in EQ 2-22 and EQ 2-23 shall be
concrete placed monolithically. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4l
concrete placed against hardened concrete with surface intentionally
roughened as specified in Article 2.29.4g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0l
4
concrete placed against hardened concrete not intentionally roughened . . . . 0.6l
concrete anchored to as-rolled structural steel by headed studs or by
reinforcing bars (see Article 2.29.4h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7l
where:
l = 1.0 for normal weight concrete and 0.85 for lightweight concrete.
d. Shear stress v on area of concrete section resisting shear transfer shall not exceed 0.09 f ¢ c nor 360 psi
(2.5 MPa).
e.
Net tension across shear plane shall be resisted by additional reinforcement. Permanent net compression
across shear plane may be taken as additive to the force in the shear-friction reinforcement A v f f s , when
calculating required A v f .
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Concrete Structures and Foundations
f.
Shear-friction reinforcement shall be appropriately placed along the shear plane and shall be anchored to
develop the specified yield strength on both sides by embedment, hooks, or welding to special devices.
g.
For the purpose of Article 2.29.4, when concrete is placed against previously hardened concrete, the
interface for shear transfer shall be clean and free of laitance. If m is assumed equal to 1.0l, interface
shall be roughened to a full amplitude of approximately 0.25 inches (6 mm).
h. When shear is transferred between as-rolled steel and concrete using headed studs or welded reinforcing
bars, steel shall be clean and free of paint.
2.29.5 HORIZONTAL SHEAR DESIGN FOR COMPOSITE CONCRETE FLEXURAL
MEMBERS (2005)
a.
In a composite member, full transfer of horizontal shear forces shall be assured at contact surfaces of
interconnected elements.
b. Design of cross sections subject to horizontal shear may be in accordance with provisions of
Article 2.29.5c or Article 2.29.5d, or any other shear transfer design method that results in prediction of
strength in substantial agreement with results of comprehensive tests.
c.
Design horizontal shear stress vdh at any cross section may be computed by:
V
v dh = ----------bw d
EQ 2-24
where:
V = design shear force at section considered
d = depth of entire composite section
Horizontal shear vdh shall not exceed permissible horizontal shear vh in accordance with the following:
(1) When contact surface is clean, free of laitance, and intentionally roughened, shear stress vh shall not
exceed 36 psi (0.25 MPa).
(2) When minimum ties are provided in accordance with Article 2.29.5e, and contact surface is clean and
free of laitance, but not intentionally roughened, shear stress vh shall not exceed 36 psi (0.25 MPa).
(3) When minimum ties are provided in accordance with Article 2.29.5e, and contact surface is clean,
free of laitance, and intentionally roughened to a full amplitude of approximately 1/4 inch (6 mm),
shear stress vh shall not exceed 160 psi (1.1 MPa).
(4) For each percent of tie reinforcement crossing the contact surface in excess of the minimum required
by Article 2.29.5e, permissible vh may be increased by 72fy /40,000 psi (or 72fy /280 MPa in metric).
d. Horizontal shear may be investigated by computing, in any segment not exceeding one-tenth of the span,
the actual change in compressive or tensile force, and provisions made to transfer that force as
horizontal shear between interconnected elements. Horizontal shear shall not exceed the permissible
horizontal shear stress vh in accordance with Article 2.29.5c.
e.
Ties for horizontal shear.
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Reinforced Concrete Design
(1) A minimum area of tie reinforcement shall be provided between interconnected elements. Tie area
shall not be less than 50bws/fy (or 0.35bws/fy in metric), and tie spacing ‘s’ shall not exceed 4 times
the least web width of support element, nor 24 inches (600 mm).
(2) Ties for horizontal shear may consist of single bars or wire, multiple leg stirrups, or vertical legs of
welded wire fabric (smooth or deformed). All ties shall be adequately anchored into interconnected
elements by embedment or hooks.
(3) All beam shear reinforcement shall extend into cast-in-place deck slabs. Extended shear
reinforcement may be used in satisfying the minimum tie reinforcement.
2.29.6 SPECIAL PROVISIONS FOR SLABS AND FOOTINGS (2005)
a.
Shear capacity of slabs and footings in the vicinity of concentrated loads or reactions shall be governed
by the more severe of two conditions:
(1) The slab or footing acting as a wide beam, with a critical section extending in a plane across the
entire width and located at a distance d from the face of the concentrated load or reaction area. For
this condition, the slab or footing shall be designed in accordance with Article 2.29.1 through
Article 2.29.3.
(2) Two-way action for the slab or footing, with a critical section perpendicular to the plane of the slab
and located so that its perimeter is a minimum and approaches no closer than d/2 to the perimeter of
the concentrated load or reaction area. For this condition, the slab or footing shall be designed in
accordance with Article 2.29.6b and Article 2.29.6c.
1
(3) At footings supported on piles the shear on the critical section shall be determined in accordance
with:
(a) Entire reaction from any pile whose center is located dp/2 or more outside the critical section
shall be considered as producing shear on that section.
3
(b) Reaction from any pile whose center is located dp/2 or more inside the critical section shall be
considered as producing no shear on that section.
(c) For intermediate positions of pile center, the portion of the pile reaction to be considered as
producing shear on the critical section shall be based on linear interpolation between full value
at dp/2 outside the section and zero value at dp/2 inside the section.
b. Design shear stress for two-way action shall be computed by:
V
v = --------bo d
EQ 2-25
where:
V and bo = are taken at the critical section defined in Article 2.29.6a(2).
c.
Design shear v shall not exceed the smallest vc given by EQ 2-26 or EQ 2-27 unless shear reinforcement
is provided in accordance with Article 2.29.6d.
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2
v c = æ 0.8 + -----ö f¢ c ; f’c in psi
è
b cø
0.17
v c = æ 0.066 + -----------ö
è
bc ø
EQ 2-26
EQ 2-26M
f¢ c ; f’c in MPa
or
as d
v c = æ 0.8 + ---------ö f¢ c ; f’c in psi
è
b ø
EQ 2-27
as d f¢ c
v c = æ 0.8 + ---------ö ------------ ; f’c in MPa
è
b o ø 12
EQ 2-27M
o
but not greater than 1.8 f¢ (or 0.15 f¢ in metric). bc is the ratio of long side to short side of
c
c
concentrated load or reaction area. as is 20 for interior concentrated loads or reaction areas, 15 for edge
concentrated loads or reaction areas and 10 for corner concentrated loads or reaction areas.
d. If shear reinforcement consisting of bars or wires is provided in accordance with Article 2.29.3, vc at any
section shall not exceed 0.9 f¢ c (or 0.075 f¢ c in metric) and v shall not exceed 3 f¢ c (or 0.25 f¢ c in
metric). Shear stresses shall be investigated at the critical section defined in Article 2.29.6a(2) and at
successive sections more distant from the support.
2.29.7 SPECIAL PROVISIONS FOR BRACKETS AND CORBELS (2005)
a.
The following provisions shall apply to brackets and corbels with a shear span-to-depth ratio av/d not
greater than unity, and subject to a horizontal tensile force Nc not larger than V. Distance d shall be
measured at face of support.
b. Depth at outside edge of bearing area shall not be less than 0.5d.
c.
Section at face of support shall be designed to resist simultaneously a shear V, a moment
[Vav + Nc(h-d)], and a horizontal tensile force Nc.
(1) Design of shear-friction reinforcement Avf to resist shear V shall be in accordance with Article 2.29.4.
For normal weight concrete, shear stress v shall not exceed 0.09f ¢ c nor 360 psi (2.5 MPa). For “sandlightweight” concrete, shear stress v shall not exceed (0.09 – 0.03av/d)f ¢ c nor (360 – 126av/d) psi (or
2.5 – 0.09av/d) MPa in metric).
(2) Reinforcement Af to resist moment [Vav + Nc(h-d)] shall be computed in accordance with
Section 2.26 and Section 2.27.
(3) Reinforcement An to resist tensile force Nc shall be computed by An = Nc /fs. Tensile force Nc shall
not be taken less than 0.2V unless special provisions are made to avoid tensile forces.
(4) Area of primary tension reinforcement As shall be made equal to the greater of (Af + An), or
(2Av f / 3 + An).
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d. Closed stirrups or ties parallel to As, with a total area Ah not less than 0.5 (As – An), shall be uniformly
distributed within two-thirds of the effective depth adjacent to As.
e.
Ratio r = As/bd shall not be taken less than 0.04 (f ¢ c /fy).
f.
At front face of bracket or corbel, primary tension reinforcement As shall be anchored by one of the
following:
(1) a structural weld to a transverse bar of at least equal size; weld to be designed to develop specified
yield strength fy of As bars;
(2) bending primary tension bars As back to form a horizontal loop, or
(3) some other means of positive anchorage.
g.
Bearing area of load on bracket or corbel shall not project beyond straight portion of primary tension
bars As, nor project beyond interior face of transverse anchor bar (if one is provided).
LOAD FACTOR DESIGN
1
(APPLICABLE TO Section 2.30 THROUGH Section 2.39)
SECTION 2.30 STRENGTH REQUIREMENTS
2.30.1 REQUIRED STRENGTH (2005)
3
Structures and structural members shall be designed to have design strengths at all sections at least equal to
the required strengths calculated for the factored loads and forces in such combinations as stipulated in
Article 2.2.4c, which represent various combinations of loads and forces to which a structure may be subjected.
Each part of such structure shall be proportioned for the group loads that are applicable, and the maximum
design required shall be used. Members shall also follow all other requirements of this Chapter to ensure
adequate performance at service load levels.
2.30.2 DESIGN STRENGTH (1992)
a.
For reinforced concrete members designed with reference to load factors and strengths, the design
strength provided by a member, its connections to other members, and its cross sections, in terms of
flexure, axial load, and shear, shall be taken as the nominal strength calculated in accordance with the
requirements and assumptions of LOAD FACTOR DESIGN, multiplied by a strength reduction factor f.
b. Strength reduction factor f shall be taken as follows:
For flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . f = 0.90
For shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . f = 0.85
For spirally reinforced compression members, with or
without flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . f = 0.75
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For tied reinforced compression members with or without flexure . . . f = 0.70
NOTE:
The value of f may be increased linearly from the value for
compression members to the value for flexure as the axial load
strength Pn decreases from Pb to zero.
For bearing on concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . f = 0.70
NOTE:
Development and splices of reinforcement specified in Section 2.13 through Section 2.22 do not
require a f factor.
SECTION 2.31 DESIGN ASSUMPTIONS
2.31.1 STRENGTH DESIGN (2005)
Strength design of members for flexure and axial loads shall be based on the assumptions given in this article,
and on satisfaction of the applicable conditions of equilibrium and compatibility of strains.
a.
Strain in the reinforcing steel and concrete shall be assumed directly proportional to the distance from
the neutral axis.
b. Maximum usable strain at the extreme concrete compression fiber shall be assumed equal to 0.003.
c.
Stress in reinforcement below the specified yield strength fy for the grade of steel used shall be taken as
Es times the steel strain. For strains greater than that corresponding to fy the stress in the
reinforcement shall be considered independent of strain and equal to fy.
d. Tensile strength of concrete shall be neglected in flexural calculations of reinforced concrete.
e.
The relationship between concrete compressive stress distribution and concrete strain may be assumed
to be a rectangle, trapezoid, parabola, or any other shape which results in prediction of strength in
substantial agreement with the results of comprehensive tests.
f.
The requirements of Article 2.31.1e may be considered satisfied by an equivalent rectangular concrete
stress distribution defined as follows: A concrete stress of 0.85 f ¢ c shall be assumed uniformly
distributed over an equivalent compression zone bounded by the edges of the cross section and a straight
line located parallel to the neutral axis at a distance (a = b1c) from the fiber of maximum compressive
strain. The distance c from the fiber of maximum strain to the neutral axis is measured in a direction
perpendicular to that axis. The factor b1 shall be taken as 0.85 for concrete strength f¢ c up to and
including 4000 psi (28 MPa). For strengths above 4000 psi (28 MPa) b1 shall be reduced continuously at a
rate of 0.05 for each 1000 psi (7 MPa) of strength in excess of 4000 psi (28 MPa), but b1 shall not be taken
less than 0.65.
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SECTION 2.32 FLEXURE
2.32.1 MAXIMUM REINFORCEMENT OF FLEXURAL MEMBERS (1992)
a.
For flexural members, the reinforcement r provided shall not exceed 0.75 of that ratio r b which would
produce balanced strain conditions for the section under flexure.
For flexural members with compression reinforcement, the portion of r b balanced by compression
reinforcement need not be reduced by the 0.75 factor.
b. Balanced strain conditions exist at a cross section when the tension reinforcement reaches its specified
yield strength fy just as the concrete in compression reaches its assumed ultimate strain of 0.003.
2.32.2 RECTANGULAR SECTIONS WITH TENSION REINFORCEMENT ONLY (2005)
a.
For rectangular sections, when r £0.75 r b the design moment strength FMn may be computed by:
0.6r f y
FM n = F A s f y d æ 1 – -----------------ö
è
f¢ c ø
EQ 2-28
a
= F A s f y æ d – ---ö
è
2ø
EQ 2-29
1
where:
As fy
a = ----------------------0.85f¢ c b
3
b. The balanced reinforcement ratio r b for rectangular sections with tension reinforcement only is given
by:
0.85b 1 f¢ c 87, 000
r b = -------------------------- æ --------------------------------ö
è 87, 000 + f ø
fy
y
EQ 2-30
0.85b 1 f¢ c 600
r b = -------------------------- æ ---------------------ö
è 600 + f ø
fy
y
EQ 2-30M
2.32.3 I- AND T-SECTIONS WITH TENSION REINFORCEMENT ONLY (2005)
a.
When the compression flange thickness is equal to or greater than the depth of the equivalent
rectangular stress block a and r £0.75 r b, the design moment strength FMn may be computed by the
equations given in Article 2.32.2.
b. When the compression flange thickness is less than a, the design moment strength FMn may be
computed by:
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Concrete Structures and Foundations
FM n = F ( A s – A sf )f y æ d – --a-ö + A sf f y ( d – 0.5h f )
è
2ø
EQ 2-31
where:
h
Asf = 0.85f¢ c ( b – b w ) -----f
fy
( A s – A sf )f y
a = ------------------------------0.85f¢ c b w
c.
The balanced reinforcement ratio r b for I- and T-sections with tension reinforcement only is given by:
b w 0.85b 1 f¢ c 87, 000
r b = ------- -------------------------- æ --------------------------------ö + r f
è 87, 000 + f ø
b
fy
y
EQ 2-32
b w 0.85b 1 f¢ c 600
r b = ------- -------------------------- æ ---------------------ö + r f
è 600 + f ø
b
fy
y
EQ 2-32M
where:
A sf
r f = ----------bw d
d. When the compression flange thickness is greater than a, the design moment strength, FMn, may be
computed by using the equations in Article 2.32.2.
e.
For T-girder and box-girder construction defined by Article 2.23.10 and Article 2.23.11, the width of the
compression face b shall be equal to the effective slab width.
2.32.4 RECTANGULAR SECTIONS WITH COMPRESSION REINFORCEMENT (2005)
a.
For rectangular sections when r £0.75 r b, the design moment strength FMn may be computed by:
FM n = F ( A s – A¢ s )f y æ d – --a-ö + A¢ s f y ( d – d¢ )
è
2ø
EQ 2-33
where:
( A s – A¢ s )f y
a = -------------------------------0.85f¢ c b
and the following condition shall be satisfied:
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AREMA Manual for Railway Engineering
Reinforced Concrete Design
A s – A¢ s 0.85b 1 f¢ c d ¢ æ 87, 000 ö
---------------------- ³ --------------------------------- -------------------------------è 87, 000 – f ø
fy d
bd
y
EQ 2-34
A s – A¢ s 0.85b 1 f¢ c d ¢ æ 600 ö
----------------------- ³ --------------------------------- -------------------è 600 – f yø
fy d
bd
EQ 2-34M
b. When the value of (As – A¢ s)/bd is less than the value given by EQ 2-34, so that the stress in the
compression reinforcement is less than the yield strength fy or when effects of compression
reinforcement are neglected, the moment strength may be computed by the equations in Article 2.32.2,
except when a general analysis is made based on stress and strain compatibility using the assumptions
given in Section 2.31.
c.
The balanced reinforcement ratio r b for rectangular section with compression reinforcement is given by:
0.85b 1 f¢ c æ 87, 000 ö r ¢ f¢ sb
- -------------------------------- + -----------------r b = ------------------------è 87, 000 – f yø
fy
fy
EQ 2-35
0.85b 1 f¢ c æ 600 ö r ¢ f¢ sb
- -------------------- + -----------------r b = ------------------------è 600 – f yø
fy
fy
EQ 2-35M
1
where:
f ¢ sb is stress in compression reinforcement at balanced strain conditions
f ¢ sb
=
f ¢ sb
=
d¢
87, 000 – ------- ( 87, 000 – f y ) £f y
d
d¢
600 – ------- ( 600 – f y ) £f y
d
3
(metric)
2.32.5 OTHER CROSS SECTIONS (1992)
For other cross sections the design moment strength FMn shall be computed by a general analysis based on
stress and strain compatibility using the assumptions given in Section 2.31. The requirements of Article 2.32.1
shall also be satisfied.
SECTION 2.33 COMPRESSION MEMBERS WITH OR WITHOUT FLEXURE
2.33.1 GENERAL REQUIREMENTS (2005)
a.
Design of cross sections subject to axial load or to combined flexure and axial load shall be based on
stress and strain compatibility using the assumptions given in Section 2.31. Slenderness effects shall be
included in accordance with Section 2.34.
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b. Members subject to compressive axial load shall be designed for the maximum moment that can
accompany the axial load. The factored axial load Pu at given eccentricity shall not exceed that given in
Article 2.33.1c. The maximum factored moment Mu shall be magnified for slenderness effects in
accordance with Section 2.34.
c.
Design axial load strength FPa of compression members shall not be taken greater than the following:
(1) For members with spiral reinforcement conforming to Article 2.11.2a:
EQ 2-36
FP a (max) = 0.85F[ 0.85f¢ c ( A g – A st ) + f y A st ]
(2) For members with tie reinforcement conforming to Article 2.11.2b:
EQ 2-37
FP a (max) = 0.80F[ 0.85f¢ c ( A g – A st ) + f y A st ]
2.33.2 COMPRESSION MEMBER STRENGTHS (2005)
The following provisions may be used as a guide to define the range of the load-moment interaction relationship
for members subjected to combined flexure and axial load.
a.
Pure Compression.
(1) The design axial load strength at zero eccentricity FPo may be computed by:
EQ 2-38
FP o = F[ 0.85f¢ c ( A g – A st ) + A st f y ]
(2) For design, pure compression strength is a hypothetical loading condition since Article 2.33.1c limits
the axial load strength of compression members to 85% and 80% of the design axial load strength at
zero eccentricity.
b. Pure Flexure. The assumptions given in Section 2.31, or the applicable equations for flexure given in
Section 2.32 may be used to compute the design moment strength FMn in pure flexure.
c.
Balanced Strain Conditions. Balanced strain conditions for a cross section are defined in Article 2.32.1b.
For a rectangular section with reinforcement in one or two faces and located at approximately the same
distance from the axis of bending, the balanced load strength FPb and balanced moment strength FMb
may be computed by:
EQ 2-39
FP b = F[ 0.85f¢ c ba b + A¢ s f¢ sb – A s f y ]
and
a
FM b = F 0.85f¢ c ba b æ d – d² – -----b-ö + A¢ s f¢ sb ( d – d¢ – d² ) + A s f y d²
è
2ø
EQ 2-40
where:
87, 000
ab = æè --------------------------------öø b 1 d
87, 000 + f y
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Reinforced Concrete Design
600
ab = æè ---------------------öø b 1 d
600 + f y
(metric)
f ¢ sb = 87, 000 – d¢
------- ( 87, 000 + f y ) £ f y
d
f ¢ sb = 600 – d¢
------- ( 600 + f y ) £ f y
d
(metric)
d. Combined Flexure and Axial Load.
(1) The design strength under combined flexure and axial load shall be based on stress and strain
compatibility using the assumptions given in Section 2.31. The strength of a cross section is
controlled by tension when the nominal axial load strength Pn is less than Pb. The strength of a cross
section is controlled by compression when the nominal axial load strength Pn is greater than Pb.
(2) The nominal values of axial load strength Pn and moment strength Mn must both be multiplied by
the appropriate strength reduction factor F for spirally reinforced or tied compression members as
given in Article 2.30.2. The value of F may be increased linearly from the value for compression
members to the value for flexure as the design axial load strength FPn decreases from 0.10f ¢ c A g or
FPb whichever is smaller, to zero.
2.33.3 BIAXIAL LOADING (1992)
1
In lieu of a general section analysis based on stress and strain compatibility for a loading condition of biaxial
bending, the strength of non-circular members subject to biaxial bending may be computed by the following
approximate expressions:
1
P nxy = --------------------------------------------------------1 -ö – æ -----1ö
1 -ö + æ --------æ --------èP ø èP ø èP ø
nx
ny
o
EQ 2-41
3
where the factored axial load,
P u ³ 0.1f¢ c A g
4
or
M uy
M ux
--------------- £1
+ -------------FM nx FM ny
EQ 2-42
when the factored axial load,
P u < 0.1f¢ c A g
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Concrete Structures and Foundations
SECTION 2.34 SLENDERNESS EFFECTS IN COMPRESSION MEMBERS
2.34.1 GENERAL REQUIREMENTS (2005)
a.
Design of compression members shall be based on forces and moments determined from an analysis of
the structure. Such an analysis shall take into account the influence of axial loads and variable moment
of inertia on member stiffness and fixed-end moments, the effect of deflections on the moments and
forces, and the effects of the duration of the loads.
b. In lieu of the procedure described in Article 2.34.1a, the design of compression members may be based on
the approximate procedure given in Article 2.34.2.
2.34.2 APPROXIMATE EVALUATION OF SLENDERNESS EFFECTS (2005)
a.
Unsupported length lu of a compression member shall be taken as the clear distance between slabs,
girders, or other members capable of providing lateral support for the compression member. When
haunches are present, the unsupported length shall be measured to the lower extremity of the haunch in
the plane considered.
b. Radius of gyration r may be taken equal to 0.30 times the overall dimension in the direction in which
stability is being considered for rectangular compression members, and 0.25 times the diameter for
circular compression members. For other shapes, r may be computed from the gross concrete section.
c.
For compression members braced against sidesway, the effective length factor k shall be taken as 1.0,
unless an analysis shows that a lower value may be used. For compression members not braced against
sidesway, the effective length factor k shall be determined with due consideration of cracking and
reinforcement on relative stiffness, and shall be greater than 1.0.
d. For compression members braced against sidesway, the effects of slenderness may be neglected when
klu/r is less than 34 – 12M1b/M2b. For compression members not braced against sidesway, the effects of
slenderness may be neglected when klu/r is less than 22. For all compression members with klu/r greater
than 100, an analysis as defined in Article 2.34.1a shall be made. M1b = value of smaller end moment on
compression member calculated from a conventional elastic analysis, positive if member is bent in single
curvature, negative if bent in double curvature, M2b = value of larger end moment on compression
member calculated from a conventional elastic analysis, always positive.
e.
Compression members shall be designed using the factored axial load Pu from a conventional frame
analysis and a magnified factored moment Mc defined by EQ 2-43. For members braced against sidesway,
ds shall be taken as 1.0. For members not braced against sidesway, db shall be evaluated as for a braced
member and ds as for an unbraced member.
EQ 2-43
M c = db M 2b + ds M 2s
where:
db =
Cm
------------------ ³ 1.0
Pu
1 – --------fP c
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Reinforced Concrete Design
ds =
1 - ³ 1.0
---------------------SP u
1 – -----------fSP c
Pc =
p EI
---------------2
( kl u )
and
2
In lieu of a more precise calculation, EI may be taken either as
Ec Ig
----------- + Es Is
5
EI = -----------------------------1 + bd
or conservatively
Ec Ig
-----------2.5 EI = --------------1 + bd
1
For members braced against sidesway and without transverse loads between supports, Cm may be taken
as:
M 1b
- but not less than 0.4.
C m = 0.6 + 0.4 ---------M 2b
EQ 2-44
3
For all other cases Cm shall be taken as 1.0.
f.
g.
When a group of compression members on one level composes a bent, or when they are connected
integrally to the same superstructure, and all collectively resist the sidesway of the structure, the value
of ds shall be computed for the member group with SPu and SPc equal to the summations for all
compression members in the group.
If computations show that there is no moment at both ends of a compression member or that computed
end eccentricities are less than (0.6 + 0.03h) inches ((15 + 0.03h)mm); M2b in EQ 2-43 shall be based on
a minimum eccentricity of (0.6 + 0.03h) inches ((15 + 0.03h)mm) about each principal axis separately.
Ratio M1b /M2b in EQ 2-44 shall be determined by either of the following:
(1) When computed end eccentricities are less than (0.6 + 0.03h) inches ((15 + 0.03h)mm), computed
end moments may be used to evaluate M1b /M2b in EQ 2-44.
(2) If computations show that there is essentially no moment at both ends of a compression member, the
ratio M1b/M2b shall be taken equal to one.
h. When compression members are subject to bending about both principal axes, the moment about each
axis shall be amplified by d computed from the corresponding conditions of restraint about that axis.
i.
In structures which are not braced against sidesway, the flexural members shall be designed for the total
magnified end moments of the compression members at the joint.
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Concrete Structures and Foundations
SECTION 2.35 SHEAR
2.35.1 SHEAR STRENGTH (2005)
a.
Factored shear stress vu shall be computed by:
Vu
v u = -------------Fb w d
EQ 2-45
where:
bw = the width of web
d = the distance from the extreme compression fiber to the centroid of the longitudinal tension
reinforcement
For a circular section, bw shall be taken as the diameter, and d need not be taken less than the distance
from the extreme compression fiber to the centroid of the longitudinal reinforcement in the opposite half
of the member.
b. When the reaction in the direction of the applied shear introduces compression into the end region of the
member and loads are applied at or near the top of the member, sections located less than a distance d
from the face of the support may be designed for the same shear vu as that computed at a distance d. An
exception occurs when major concentrated loads are imposed between that point and the face of support.
In that case sections closer than d to the support shall be designed for Vu at distance d plus the major
concentrated loads.
c.
Shear stress carried by concrete vc shall be calculated according to Article 2.35.2. When vu exceeds vc,
shear reinforcement shall be provided according to Article 2.35.3. Whenever applicable, the effects of
torsion shall be added.
NOTE:
The design criteria for combined shear and torsion given in “Building Code Requirements for
Reinforced Concrete – ACI318-02” may be used.
d. For tapered webs, bw shall be the average width or 1.2 times the minimum width, whichever is smaller.
2.35.2 PERMISSIBLE SHEAR STRESS (2010)
NOTE:
a.
The value f’c used in computing vc shall not be taken greater than 10,000 psi (69 MPa).
Shear stress carried by concrete vc shall not exceed 2 f¢ c (or 0.17 f¢ c in metric) unless a more detailed
analysis is made in accordance with Article 2.35.2b or Article 2.35.2c. For members subject to axial
tension, vc shall not exceed the value given in Article 2.35.2d. For lightweight concrete, the provisions of
Article 2.35.2f shall apply.
b. Shear stress carried by concrete vc, for members subject to shear and flexure only, may be computed by:
Vu d
v c = 1.9 f¢ c + 2500r w ---------M
EQ 2-46
u
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Reinforced Concrete Design
Vu d
v c = 0.16 f¢ c + 17r w ---------M
EQ 2-46M
u
Vu d
- shall not be taken greater
but vc shall not exceed 3.5 f¢ c (or 0.29 f¢ c in metric). The quantity ---------M
u
than 1.0, where Mu is the factored moment occurring simultaneously with Vu at the section considered.
c.
For members subject to axial compression, vc may be computed by:
N
v c = 2 æ 1 + 0.0005 -------u-ö f¢ c
è
Ag ø
N
v c = 0.17 æ 1 + 0.072 -------u-ö
è
A ø
f¢ c
EQ 2-47
EQ 2-47M
g
N
The quantity -------u- shall be expressed in psi (MPa).
Ag
d. For members subject to significant axial tension, shear reinforcement shall be designed to carry the total
shear, unless a more detailed analysis is made using
N
v c = 2 æ 1 + 0.002 -------u-ö
è
Ag ø
f¢ c
N
v c = 0.17 æ 1 + 0.29 -------u-ö
è
A ø
1
EQ 2-48
3
f¢ c
EQ 2-48M
g
where:
Nu is negative for tension
4
N
the quantity -------u- shall be expressed in psi (MPa).
Ag
e.
Special provisions for slabs of box culverts. For slabs of box culverts under 2 feet (600 mm) or more fill,
shear stress vc may be computed by:
Vu d
v c = 2.14 f¢ c + 4600r ---------M
EQ 2-49
Vu d
v c = 0.18 f¢ c + 32r ---------M
EQ 2-49M
u
u
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Concrete Structures and Foundations
1
but vc shall not exceed 4 f¢ c (or --- f¢ c in metric). For single cell box culverts only, vc need not be taken
3
f¢ c
5
less than 3 f¢ c (or ------------ in metric) for slabs monolithic with walls or 2.5 f¢ c (or ------ f¢ c in metric) for
24
4
Vu d
- shall not be taken greater than 1.0, where Mu is factored
slabs simply supported. The quantity ---------Mu
moment occurring simultaneously with Vu at section considered.
f.
The provisions for shear stress vc carried by concrete apply to normal weight concrete. When lightweight
aggregate concretes are used, one of the following modifications shall apply:
(1) When fct is specified, shear stress vc shall be modified by substituting fct/6.7 (or 1.8fct in metric) for
f¢ c , but the value of fct/6.7 (or 1.8fct in metric) used shall not exceed
f¢ c.
(2) When fct is not specified, shear stress vc shall be multiplied by 0.85 for sand-lightweight concrete.
2.35.3 DESIGN OF SHEAR REINFORCEMENT (2005)
a.
Shear reinforcement shall conform to the general requirements of Section 2.10. When shear
reinforcement perpendicular to the axis of the member is used, required area shall be computed by:
( v u – v c )b w s
A v = --------------------------------fy
EQ 2-50
b. When inclined stirrups or bent bars are used as shear reinforcement the following provisions apply:
(1) When inclined stirrups are used, required area shall be computed by:
( v u – v c )b w s
A v = ----------------------------------------f y ( sin a + cos a)
EQ 2-51
(2) When shear reinforcement consists of a single bar or a single group of parallel bars, all bent up at the
same distance from the support, required area shall be computed by:
( v u – v c )b w d
A v = ---------------------------------f y sin a
EQ 2-52
f¢ c
in which (vu – vc) shall not exceed 3 f¢ c (or ------------ in metric).
4
(3) When shear reinforcement consists of a series of parallel bent-up bars or groups of parallel bent-up
bars at different distances from the support, required area shall be computed using
Article 2.35.3b(1).
(4) Only the center three-fourths of the inclined portion of any one longitudinal bar that is bent shall be
considered effective for shear reinforcement.
c.
When more than one type of shear reinforcement is used to reinforce the same portion of the member,
required area shall be computed as the sum for the various types separately. No one type shall resist
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Reinforced Concrete Design
more than 2/3 of the total shear resisted by reinforcement. In such computations, vc shall be included
only once.
f¢ c
d. When (vu – vc) exceeds 4 f¢ c (or ------------ in metric), maximum spacings given in Article 2.10.3 shall be
3
reduced by one-half.
e.
f.
2 f¢ c
The value of (vu – vc) shall not exceed 8 f¢ c (or ---------------- in metric).
3
When flexural reinforcement located within the width of a member used to compute the shear strength
is terminated in a tension zone, shear reinforcement shall be provided in accordance with Article 2.13.1f.
2.35.4 SHEAR-FRICTION (2005)
a.
Provisions for shear-friction are to be applied where it is appropriate to consider shear transfer across a
given plane, such as: an existing or potential crack, an interface between dissimilar materials, or an
interface between two concretes cast at different times.
b. A crack shall be assumed to occur along the shear plane considered. Required area of shear-friction
reinforcement Avf across the shear plane may be designed using either Article 2.35.4c or any other shear
transfer design method that results in prediction of strength in substantial agreement with results of
comprehensive tests. Provisions of Article 2.35.4d through Article 2.35.4h shall apply for all calculations
of shear transfer strength.
c.
1
Shear-friction design method.
(1) When shear-friction reinforcement is perpendicular to shear plane, area of shear-friction
reinforcement Avf shall be computed by:
Vu
A vf = ----------ff y m
3
EQ 2-53
where:
4
m = the coefficient of friction in accordance with Article 2.35.4c(3).
(2) When shear-friction reinforcement is inclined to shear plane such that the shear force produces
tension in shear-friction reinforcement, area of shear friction reinforcement Avf shall be computed
by:
Vu
A vf = --------------------------------------------------ff y ( m sin af + cos af )
EQ 2-54
where:
af = angle between shear-friction reinforcement and shear plane
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(3) Coefficient of friction m in EQ 2-53 and EQ 2-54 shall be:
concrete placed monolithically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4l
concrete placed against hardened concrete with surface
intentionally roughened as specified in Article 2.35.4g . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0l
concrete placed against hardened concrete not intentionally roughened . . . . . . . . . . . . . 0.6l
concrete anchored to as-rolled structural steel by headed studs or by
reinforcing bars (see Article 2.35.4h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7l
where l = 1.0 for normal weight concrete and 0.85 for sand-lightweight concrete.
d. Shear stress vu on area of concrete section resisting shear transfer shall not exceed 0.2f ¢ c nor 800 psi
(5.5 MPa).
e.
Net tension across shear plane shall be resisted by additional reinforcement. Permanent net compression
across shear plane may be taken as additive to the force in the shear-friction reinforcement A v f f y, when
calculating required A v f .
f.
Shear-friction reinforcement shall be appropriately placed along the shear plane and shall be anchored to
develop the specified yield strength on both sides by embedment, hooks, or welding to special devices.
g.
For the purpose of this paragraph, when concrete is placed against previously hardened concrete, the
interface for shear transfer shall be clean and free of laitance. If m is assumed equal to 1.0l, interface
shall be roughened to a full amplitude of approximately 1/4 inch (6 mm).
h. When shear is transferred between as-rolled steel and concrete using headed studs or welded reinforcing
bars, steel shall be clean and free of paint.
2.35.5 HORIZONTAL SHEAR DESIGN FOR COMPOSITE CONCRETE FLEXURAL
MEMBERS (2005)
a.
In a composite member, full transfer of horizontal shear forces shall be assured at contact surfaces of
interconnected elements.
b. Design of cross sections subject to horizontal shear may be in accordance with provisions of
Article 2.35.5c or Article 2.35.5d, or any other shear transfer design method that results in prediction of
strength in substantial agreement with results of comprehensive tests.
c.
Design horizontal shear stress vuh at any cross section may be computed by
Vu
v uh = ----------fb v d
EQ 2-55
where:
Vu = factored shear force at section considered
d = depth of entire composite section
Horizontal shear vuh shall not exceed permissible horizontal shear vh in accordance with the following:
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(1) When contact surface is clean, free of laitance, and intentionally roughened, shear stress vh shall not
exceed 80 psi (0.55 MPa).
(2) When minimum ties are provided in accordance with Article 2.35.5e, and contact surface is clean and
free of laitance, but not intentionally roughened, shear stress vh shall not exceed 80 psi (0.55 MPa).
(3) When ties are provided in accordance with Article 2.35.5e and contact surfaces are clean, free of
laitance and intentionally roughened to a full amplitude of 1/4 inch (6 mm), shear stress, vh, shall be
taken equal to (260 + 0.6r vfy) l in psi [(1.8 + 0.6r vfy) l in MPa]; but not greater than 500 psi (3.5
MPa).
(4) When factored shear stress, vu, at section considered exceeds f 500 psi (f 3.5 in MPa), design for
horizontal shear shall be in accordance with Article 2.35.4.
d. Horizontal shear may be investigated by computing, in any segment not exceeding one-tenth of the span,
the actual change in compressive or tensile force to be transferred, and provisions made to transfer that
force as horizontal shear between interconnected elements. The factored horizontal shear stress shall
not exceed the horizontal shear strength vuh in accordance with Article 2.35.5c, except that length of
segment considered shall be substituted for d.
e.
Ties for horizontal shear.
(1) A minimum area of tie reinforcement shall be provided between interconnected elements. Tie area
shall not be less than 50bws/fy (or 0.35bws/fy in metric), and tie spacing s shall not exceed 4 times the
least web width of support element, nor 24 inches (600 mm).
1
(2) Ties for horizontal shear may consist of single bars or wire, multiple leg stirrups, or vertical legs of
welded wire fabric (smooth or deformed). All ties shall be adequately anchored into interconnected
elements by embedment or hooks.
(3) All beam shear reinforcement shall extend into cast-in-place deck slabs. Extended shear
reinforcement may be used in satisfying the minimum tie reinforcement.
3
2.35.6 SPECIAL PROVISIONS FOR SLABS AND FOOTINGS (2005)
a.
Shear strength of slabs and footings in the vicinity of concentrated loads or reactions shall be governed
by the more severe of the following conditions:
(1) The slab or footing acting as a wide beam, with a critical section extending in a plane across the
entire width and located at a distance d from the face of the concentrated load or reaction area. For
this condition, the slab or footing shall be designed in accordance with Article 2.35.1 through
Article 2.35.3.
(2) Two-way action for the slab or footing, with a critical section perpendicular to the plane of the slab
and located so that its perimeter is a minimum and approaches no closer than d/2 to the perimeter of
the concentrated load or reaction area. For this condition, the slab or footing shall be designed in
accordance with Article 2.35.6b and Article 2.35.6c.
(3) For footings supported on piles the shear on the critical section shall be determined in accordance
with:
(a) Entire reaction from any pile whose center is located dp/2 or more outside the critical section
shall be considered as producing shear on that section.
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Concrete Structures and Foundations
(b) Reaction from any pile whose center is located dp/2 or more inside the critical section shall be
considered as producing no shear on that section.
(c) For intermediate positions of pile center, the portion of the pile reaction to be considered as
producing shear on the critical section shall be based on linear interpolation between full value
at dp/2 outside the section and zero value at dp/2 inside the section.
b. Factored shear stress for two-way action shall be computed by:
Vu
v u = ------------Fb o d
EQ 2-56
where:
Vu and bo = are taken at the critical section defined in Article 2.35.6a(2).
c.
Factored shear stress vu shall not exceed vu given by EQ 2-57, EQ 2-58, or EQ 2-59 unless shear
reinforcement is provided in accordance with Article 2.35.6d.
as d
- + 2ö
v c = æ -------èb
ø
o
f¢ c
EQ 2-57
f¢
as d
- + 2ö ------------c
v c = æ -------èb
ø 12
o
EQ 2-57M
4-ö f¢
v c = æ 2 + ---c
è
b cø
EQ 2-58
f¢ c
2
v c = æ 1 + -----ö -----------è
b cø 6
EQ 2-58M
v c = 4 f¢ c
EQ 2-59
1
v c = --- f¢ c
3
EQ 2-59M
bc is the ratio of long side to short side of concentrated load or reaction area. as is 40 for interior
concentrated loads or reaction areas, 30 for edge concentrated loads or reaction areas, and 20 for corner
concentrated loads or reaction areas.
d. If shear reinforcement consisting of bars or wires is provided in accordance with Article 2.35.3, vc at any
1
1
section shall not exceed 2 f¢ c (or --- f¢ c in metric) and vu shall not exceed 6 f¢ c (or --- f¢ c in metric).
6
2
Shear stresses shall be investigated at the critical section defined in Article 2.35.6a(2) and at successive
sections more distant from the support.
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Reinforced Concrete Design
2.35.7 SPECIAL PROVISIONS FOR BRACKETS AND CORBELS (2005)
a.
The following provisions shall apply to brackets and corbels with a shear span-to-depth ratio and av/d not
greater than unity, and subject to a horizontal tensile force Nuc not larger than Vu. Distance d shall be
measured at face of support.
b. Depth at outside edge of bearing area shall not be less than 0.5d.
c.
Section at face of support shall be designed to resist simultaneously a shear Vu, a moment
[Vuav + Nuc(h – d)], and a horizontal tensile force Nuc .
(1) In all design calculations in accordance with this paragraph, strength reduction factor f shall be
taken equal to 0.85.
(2) Design of shear-friction reinforcement Avf to resist shear Vu shall be in accordance with
Article 2.35.4. For normal weight concrete, shear stress vu shall not exceed 0.2 f ¢ c nor 800 psi (5.5
MPa). For “sand-lightweight” concrete, shear stress vu shall not exceed (0.2 – 0.07a v /d) f ¢ c nor (800
– 280a v /d) psi (5.5 – 1.9a v /d MPa).
(3) Reinforcement Af to resist moment [Vuav + Nuc(h – d)] shall be computed in accordance with
Section 2.31 and Section 2.32.
(4) Reinforcement An to resist tensile force Nuc shall be computed by An = Nuc/ffy. Tensile force Nuc
shall not be taken less than 0.2Vu unless special provisions are made to avoid tensile forces.
1
(5) Area of primary tension reinforcement As shall be made equal to the greater of (Af + An), or
(2 A v f /3 + An).
d. Closed stirrups or ties parallel to As, with a total area of Ah not less than 0.5(As – An), shall be uniformly
distributed within two-thirds of the effective depth adjacent to As.
e.
Ratio r = As/bd shall not be taken less than 0.04 (f ¢ c /fy).
f.
At front face of bracket or corbel, primary tension reinforcement As shall be anchored by one of the
following:
(1) a structural weld to a transverse bar of at least equal size; weld to be designed to develop specified
yield strength fy of As bars;
(2) bending primary tension bars As back to form a horizontal loop, or
(3) some other means of positive anchorage.
g.
Bearing area of load on bracket or corbel shall not project beyond straight portion of primary tension
bars As, nor project beyond interior face of transverse anchor bar (if one is provided).
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AREMA Manual for Railway Engineering
8-2-69
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4
Concrete Structures and Foundations
SECTION 2.36 PERMISSIBLE BEARING STRESS (2005)
Design bearing stress shall not exceed f (0.85f ¢ c), except when the supporting surface is wider on all sides than
the loaded area, then the design bearing stress on the loaded area shall be permitted to be multiplied by
A 2 ¤ A 1, but not more than 2,
where:
A1 = load area
A2 = the area of the lower base of the largest frustrum of a pyramid, cone, or tapered
wedge contained wholly within the support and having for its upper base the
loaded area, and having side slopes of 1 vertical to 2 horizontal.
Minimum distance from edge of bearing to edge of supporting concrete shall be 6 inches (150 mm).
SECTION 2.37 SERVICEABILITY REQUIREMENTS
2.37.1 APPLICATION (1992)
For flexural members designed with reference to load factors and strengths by LOAD FACTOR DESIGN,
stresses at service load shall be limited to satisfy the requirements for fatigue in Section 2.38, and the
requirements for distribution of reinforcement in Section 2.39. The requirements for deflection control in
Section 2.40 shall also apply.
2.37.2 SERVICE LOAD STRESSES (1992)
For investigation of service load stresses to satisfy the requirements of Section 2.38 and Section 2.39, the
straight-line theory of stress and strain in flexure shall be used, and the assumptions given in Section 2.27 shall
apply.
SECTION 2.38 FATIGUE STRESS LIMIT FOR REINFORCEMENT (2005)
a.
The range between a maximum tension stress and minimum stress in straight reinforcement caused by
live load plus impact at service load shall not exceed:
ff = 21 – 0.33fmin + 8(r/h)
ff = 145 – 0.33fmin + 55(r/h)
(metric)
where:
ff = stress range in steel reinforcement, ksi (MPa)
fmin = algebraic minimum stress level, tension positive, compression negative, ksi (MPa)
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-2-70
AREMA Manual for Railway Engineering
Reinforced Concrete Design
r/h = ratio of base radius to height of rolled-on transverse deformations; when the actual value is
not known, use 0.3
b. Bends in primary reinforcement shall be avoided in regions of high stress range.
SECTION 2.39 DISTRIBUTION OF FLEXURAL REINFORCEMENT (2005)
a.
Tension reinforcement shall be well distributed in the zones of maximum tension. When the design yield
strength fy for tension reinforcement exceeds 40,000 psi (280 MPa), cross sections of maximum positive
and negative moment shall be so proportioned that the calculated stress in the reinforcement at service
load fs in ksi (MPa), does not exceed the value computed by:
Z - but f shall not be greater than 0.5 f
f s = -------------s
y
3 d A
c
EQ 2-60
where:
A = effective tension area of concrete surrounding the main tension reinforcing bars and having
the same centroid as that reinforcement, divided by the number of bars, square inches (mm2).
When the main reinforcement consists of several bar sizes the number of bars shall be
computed as the total steel area divided by the area of the largest bar used
1
dc = thickness of concrete cover measured from extreme tension fiber to center of bar located
closest thereto, inches (mm), but dc shall not exceed (2 inches + 1/2 db) (or (50 mm + 1/2 db) in
metric).
b. The quantity Z in EQ 2-60 shall not exceed 170 kips per inch (30 kN/mm) for members in moderate
exposure conditions and 130 kips per inch (23 kN/mm) for members in severe exposure conditions.
Where members are exposed to very aggressive exposure or corrosive environments, such as deicer
chemicals, the denseness and nonporosity of the protecting concrete should be considered, or other
protection, such as a waterproof protecting system, should be provided in addition to satisfying EQ 2-60.
3
4
SECTION 2.40 CONTROL OF DEFLECTIONS
2.40.1 GENERAL (1992)
Flexural members of bridge structures shall be designed to have adequate stiffness to limit deflections or any
deformations which may adversely affect the strength or serviceability of the structure at service load.
2.40.2 SUPERSTRUCTURE DEPTH LIMITATIONS (1992)
The minimum thicknesses stipulated in Table 8-2-10 are recommended unless computation of deflection
indicates that lesser thickness may be used without adverse effects.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-2-71
Concrete Structures and Foundations
C - COMMENTARY
The purpose of this part is to furnish the technical explanation of various paragraphs in Part 2 Reinforced
Concrete Design. In the numbering of paragraphs of this section, the numbers after the “C-” correspond to the
section/paragraph being explained.
C - SECTION 2.1 GENERAL
C - 2.1.5 PIER PROTECTION (2005)
C - 2.1.5.1 Adjacent to Railroad Tracks
a.
The provisions of this section are not intended to create a structure that will resist the full impact of a
direct collision by a loaded train at high speed. Rather, the intent is to reduce the damage caused by
shifted loads or derailed equipment. This is accomplished by: deflecting or redirecting the force from the
pier; providing a smooth face; providing resisting mass; and distributing the collisions forces over several
columns.
b. Research by the National Transportation Safety Board found no clear break point in the distribution of
the distance traveled from the centerline of the track by derailed equipment. It was therefore decided to
retain the existing 25 feet (7600 mm) distance within which collision protection is required. In addition,
it is recognized that the distance traveled by equipment in a derailment is related to the speed of the
train, the weight of the equipment, whether the side slopes tend to restrain or distribute the equipment
and the alignment of the track. In cases where these factors would cause the equipment to travel farther
than normal in a derailment, the required distance should be increased. Structures not otherwise
requiring protection under this section along the railroad right-of-way may also warrant protection by
using crash walls or earthen berms.
c.
Where the risk of serious damage to the overhead structure is estimated to be higher than normal in case
of an impact, this distance should also be increased. Among the factors to be considered in this
evaluation are: the height of the pier, bearing type, redundancy of the structure, length of the span and
consequences of loss of use of the structure.
d. Examples of crash walls and pier protection for tracks on one side of piers are shown in Figure C-8-2-1.
Where tracks are on both sides of the pier the wall shall protect both sides.
C - 2.1.6 SUPERSTRUCTURE PROTECTION (2010)
C - 2.1.6.1 General Requirements
a.
The purpose for this guideline stems from the fact that many existing railroad bridge superstructures
have been struck by trucks and other over-height loads and vehicles. Many of these bridges play a
pivotal role in the day-to-day operations of the railroads and the transportation of goods. Railway
networks are less extensive than those of other modes of transportation to the extend that unplanned
shutdowns can have an adverse impact on railroad operations, particularly along core routes of a railway
network. Protection of railroad bridge superstructures to abate impacts to daily railroad operations is
critical and should be evaluated.
Parameters that affect railroad operational requirements include:
(1) The availability of other routes between linked markets
(2) The freight tonnage hauled over the route relative to the rest of the rail network
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AREMA Manual for Railway Engineering
Reinforced Concrete Design
(3) The types of commodity handled on the line
(4) Future growth of freight or passenger traffic between the served markets or terminals
(5) The density of passenger traffic on the line
Roadway functional classification, which is influenced by traffic volume and type of service it provides
for the community, determines:
(1) Vehicular design speed
(2) Vertical and horizontal alignment of the roadway
(3) Cross section of the roadway
C - 2.1.7 SKEWED CONCRETE BRIDGES (2005)
b. There is no supporting documentation for the maximum recommended skew angles given. The
information was compiled from a questionnaire that was sent to several Chief Bridge Engineers of Class
I railroad companies. The skew angle recommendations resulted from the Chief Engineers’ past
experience. The preference to use cast-in-place concrete for skewed bridges is due to the high torsional
stiffness of concrete bridges and the flexibility of forming the concrete to fit the bearing area. The
maximum recommended skew angle is reduced for precast slabs and box beams since the bearing area of
precast box beams and slabs is longer. This longer bearing area can result in warping of the section
during precasting due to the varying cambers.
c.
3
The placement of interior diaphragms perpendicular to the webs is recommended since they allow for
easier construction or installation of transverse post-tensioning.
d. On skewed abutments, the end of the haunch in the backwall of the abutment or the end of the approach
slab is set perpendicular to the centerline of track to ensure adequate stiffness for the last tie off the
bridge.
e.
1
The ends of concrete slabs and concrete box girders with flanges 5’-0” wide and wider may be skewed to
reduce the width of pier cap or abutment seat.
C - 2.2.3 DESIGN LOADS (2008)
C - 2.2.3 (d.) IMPACT LOAD
Previously, different impact formulas were included in the Manual for reinforced concrete in Part 2 and
prestressed concrete in Part 17. It was known however that impact values should be similar for both types of
structures (ref. 1). In order to resolve this discrepancy, a new impact formula was developed based on work in
Europe (ref. 1) and Canada (ref. 6, 7). The resulting impact is generally lower than that recommended
previously for reinforced concrete, particularly for longer spans. It is generally higher than that recommended
previously for prestressed concrete, particularly for shorter spans. This is illustrated in Figure C-8-2-2.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-2-73
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AREMA Manual for Railway Engineering
© 2011, American Railway Engineering and Maintenance-of-Way Association
Concrete Structures and Foundations
8-2-74
Figure C-8-2-1. Pier Protection: Minimum Crash Wall Requirements (Not To Scale)
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-2-75
Reinforced Concrete Design
Figure C-8-2-2. Comparison of Impact Formulas
Concrete Structures and Foundations
According to the ORE report (ref. 1) the impact can be expressed as:
I = 0.65 x K / (1 - K + K2)
where K = V/(2/Lf)
V = speed of train in feet/second (meters/second)
L = span length in feet (meters)
f = natural frequency of the loaded bridge in hertz
In order to get the impact value as a percentage, this formula is multiplied by 100
I = 65 x K / (1 - K + K2)
For simply supported undamped beams, the natural frequency of the bridge can be estimated (see ref. 5) as:
f = 3.5 ¤ ( d) where d is the deflection due to dead and live load in inches or;
f = 5.6 ¤ ( d) where d is in centimeters.
NOTE:
Limited data exist for impact on continuous structures. The ORE has done one test on such
structures which suggests that impact values do not normally exceed those for simple spans.
Article 2.2.3d(2) recommends using for the entire continuous structure the impact value
calculated for the shortest of the continuous spans.
Assuming the deflection under dead and live load is equal to L/750 (where L is the span length) and the speed is
100 miles per hour (160 kilometers per hour) and transforming to consistent units we get:
K = V/(2Lf) = 2.64/ L
where L is the span length in feet or;
K = V/(2Lf) = 1.47/ L
where L is in meters
Replacing this value for K in the ORE impact formula and considering the fact that the denominator is
practically a constant for the range of span lengths where the formula is applicable, the impact formula is
simplified to:
I = 225/ L
where L is the span length in feet or;
I = 125/ L
where L is in meters
This formula was validated by the ORE with tests on 37 reinforced concrete, prestressed concrete and steel
bridges, small scale models and theoretical calculations. It was found that the formula gave a good
representation of the mean impact values for European railway bridges. For North American bridges, the
formula had to be adjusted for higher impacts due to different track and equipment maintenance standards. It
was decided to address this issue by using in the ORE formula a design speed of 100 mph (160 km/h) which is
higher than the actual speed for North American freight operations. Therefore, for bridge rating purposes, one
should not attempt to input actual train speeds in the ORE formula. Impact reduction for bridge rating
purposes is given in Part 19. The different safety factors given in the Manual for impact loading will cover the
cases where the impact would be higher than the mean value.
For piers and abutments, where the weight of the substructure is much greater than the live load, the effects of
impact will generally be minimal and therefore can be neglected in the design.
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AREMA Manual for Railway Engineering
Reinforced Concrete Design
When the substructure and superstructure are rigidly connected together, the superstructure will undergo
additonal rotation due to the impact loading at the point where it is connected to the substructure. In order to
maintain compatibility of deformations, the substructure will experience the same additional rotations.
Therefore, impact must be used in this case for the design of the substructure.
Particular attention should be given to short structural members spanning in the direction perpendicular to the
track and located next to the bridge approach. These members will be subjected to higher impacts due to the
transition in stiffness of the riding surface between the bridge and the approach. Members such as concrete
deck slabs and flanges of precast concrete beams are known to experience higher impacts. However, very
limited test data is available to evaluate accurately the level of impact experienced by these members. Some
Railways design these members for impacts as high as 100 percent.
It should be noted that direct fixation can result in much higher impacts than reflected by the formula. This
formula is intended for ballasted deck spans and substructure elements as required. For bridges with direct
fixation, refer to Part 27 Concrete Slab Track.
The Association of American Railroads (AAR) conducted a series of tests on nine prestressed concrete bridges
in the late 1950s and early- to mid-1960s from which impact data was gathered. Spans varied from 18 feet to 70
feet in length. This data is summarized in the Committee 30 report found in AREA Bulletin 597, January 1966.
The highest impacts measured were 45 percent in a 30 foot span. Other spans tested al had impacts less than
30 percent.
The AAR performed further testing on three prestressed concrete bridges in the early 1990s [ref. 5]. Tests
included cars equipped with flat wheels or out-of-round wheels near the condemning limit. Impacts up to 51
percent were measured on an 18-foot span.
1
References
(1) Office de Recherche et d’Essais (ORE), ORE Committee D23 - Report No. 17 Final Report, Utrecht,
April 1970.
3
(2) Skaberna, S., “A Review of Studies of Impact in Concrete Railway Bridges”, Railway Track &
Structures, November 1988, pp. 23-25.
(3) Sharma, V., Gamble, W.G., and Choros, J., Impact Factor Measurements for Three Precast
Pretensioned Concrete Railway Bridges, Association of American Railroads, Report No. R-824,
January 1993.
4
(4) Sharma, Vinaya, Flat Wheel Impacts and TLV Tests on a Prestressed Concrete Bridge, Technology
Digest TD 94-016, Association of American Railroads, September 1994.
(5) Fryba, Ladislav, “Dynamics of Railway Bridges”, Thomas Telford Services, London, P. 92, 1996.
(6) Skaberna, S. AREA correspondence, April 24 1986.
(7) Skaberna, S. AREA correspondence, January 18 1988.
C - 2.2.3 (j.) LONGITUDINAL LOAD. (2008) (References 33, 34, 35, 45, 51, 54, 65, 66, 67, 68,
and 102)
a.
Longitudinal loads due to train traffic can vary tremendously from train to train. These loads are
dependent on train handling and operating practices. The greatest longitudinal loads result from
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AREMA Manual for Railway Engineering
8-2-77
Concrete Structures and Foundations
starting or stopping a train, or moving a train up or down a grade. The longitudinal loads applied to a
bridge from normal train operations could be small in comparison to the design loads.
b. Maximum adhesion between wheel and rail for train braking is about 15 percent. This level of adhesion
would typically be reached with an emergency application of the train air brakes. The equation for train
braking is derived using 15 percent of the Cooper E-80 (EM 360) live loading.
c.
Longitudinal load due to braking acts at the center of gravity of the live load. Center of gravity height is
taken as 8 feet (2450 mm) above top of rail. This load is transferred from vehicle to rail as a horizontal
force at the top of rail and a vertical force couple transmitted through the wheels.
d. Locomotive traction can be applied at levels of adhesion approaching 50 percent, particularly with
locomotives using AC traction motors. Locomotive tractive effort is generally limited by drawbar and
coupler capacity to less than about 500 kips (2200 kN), depending on equipment. Large applications of
dynamic braking effort (which generate tractive forces) are also possible. The greatest locomotive
tractive efforts are generally reached at speeds below 25 mph (40 km/h). Above this speed, locomotive
horsepower generally governs, and available tractive effort drops.
e.
Longitudinal load due to locomotive traction acts at the drawbar. Drawbar height is taken as 3 feet (900
mm) above top of rail. As with braking, this force is transferred from vehicle to rail as a horizontal force
at the top of rail and a vertical force couple transmitted through the wheels.
f.
The equation for longitudinal load due to locomotive traction is based on maximum values from AAR
measurements on bridges tested with AC locomotives. The equipment used in the tests was
approximately equivalent to a Cooper E-60 (EM 270) loading on the spans tested. The formula has been
scaled to be consistent with the E-80 (EM 360) design loading.
g.
Longitudinal deflection limits are required to increase serviceability of the structure. They can also
potentially reduce track problems (buckling, ballast degradation, etc.) on or just beyond the ends of the
bridge.
h. The longitudinal deflection is computed assuming the entire bridge acts as a unit. The stiffness of
individual substructure components must be considered. Stiffer components deflect the same amount as
more flexible components; the stiffer components resist more load.
i.
For the case where longitudinal deflection controls the design of fairly tall flexible pile bents, the
designer should consider adding longitudinal bracing to some of the double bents to stiffen them above
the ground line, and thus reduce longitudinal deflection. Battering or increasing the batter of piles,
and/or adding more piles can also reduce deflection.
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-2-78
AREMA Manual for Railway Engineering
8
Part 3
Spread Footing Foundations1
— 1995 —
TABLE OF CONTENTS
Section/Article
Description
Page
3.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.1 General (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.2 Classification (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-3-2
8-3-2
8-3-2
3.2 Information Required. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.1 Field Survey (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.2 Controlling Dimensions (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.3 Loads (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2.4 Character of Subsurface Materials (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-3-4
8-3-4
8-3-4
8-3-4
8-3-5
3.3 Depth of Base of Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.1 Selection of Tentative Depths (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.2 Revision of Depths of Footings (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-3-7
8-3-7
8-3-7
3.4 Sizing of Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.1 Definitions (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.2 Safety Factors (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.3 Shallow Footings on Granular Material (Cohesion = 0) (1995) . . . . . . . . . . . . . . . . . . . . .
3.4.4 Shallow Footings on Saturated Clay (f = 0) (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.5 Footings on Unsaturated Silts and Clays (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.6 Footings on Non-Homogeneous Deposits (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4.7 Footings on Soils with Cohesion and Friction (Preconsolidated Clays) (1989) . . . . . . . . .
8-3-7
8-3-7
8-3-8
8-3-8
8-3-10
8-3-11
8-3-11
8-3-12
3.5 Footings with Eccentric Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.1 Loads Eccentric in One Direction (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.2 Loads Eccentric in Two Directions (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5.3 Sizing Footings with Eccentric Loads (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-3-12
8-3-12
8-3-13
8-3-13
3.6 Footing Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.1 Loads Eccentric in Two Directions (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-3-14
8-3-14
1
References, Vol. 58, 1957, pp. 633, 1182; Vol. 59, 1958, pp. 676, 1188; Vol. 62, 1961, pp. 438, 860; Vol. 74, 1973, p. 138; Vol. 76, 1975, p.
206; Vol. 78, 1977, p. 108; Vol. 90, 1989, pp. 53, 56; Vol. 96, p. 59. Revised 1995.
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3
Concrete Structures and Foundations
TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
3.7 Field Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.1 Modification of Design (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.2 Reinforcement (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.3 Footings at Varying Levels (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.4 Drainage (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.5 Treatment of Bottom of Excavation (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.6 Stresses (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.7 Information on Drawings (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-3-14
8-3-14
8-3-14
8-3-14
8-3-14
8-3-15
8-3-15
8-3-15
3.8 Combined Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.1 Uses and Types (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.2 Allowable Soil Pressures (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.3 Column Loads (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.4 Sizing Combined Footings (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-3-15
8-3-15
8-3-15
8-3-16
8-3-16
LIST OF FIGURES
Figure
8-3-1
8-3-2
8-3-3
8-3-4
Description
Page
Factors Affected by Depth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Extreme Frost Penetration, in Inches, Based upon State Averages. Source:
U.S. National Weather Records Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Relationship Among f, N, and Bearing Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Types of Combined Footings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-3-3
8-3-6
8-3-9
8-3-16
SECTION 3.1 DEFINITIONS
3.1.1 GENERAL (1995)
a.
A spread footing is a structural unit which transfers and distributes a load to the underlying soil or rock
at a pressure consistent with the requirements of the structure and the supporting capacity of the soil or
rock. The general approach to sizing footings on soil is to assure that the contact pressure defined in
Article 3.4.1 is equal to or less than the allowable soil pressure defined in Article 3.4.1.
b. Sizing of footings on rock is not discussed. The designer should be aware that the approaches presented
here are for the least complicated situations; and where unusual geology or loadings are encountered,
geotechnical engineering specialists should be consulted.
3.1.2 CLASSIFICATION (1995)
a.
Spread footings may be classified according to their structural arrangement:
(1) An individual column footing which supports a single column or isolated load.
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(2) A wall footing or continuous footing which supports a wall.
(3) A combined footing which supports more than one column.
(4) A raft or mat footing, which supports all the columns in a structure or a large portion thereof.
b. Spread footings may be classified according to their depth and dimensions:
(1) Shallow footings for which the depth of foundation, Df, defined as the minimum vertical distance
from the base of the footing to the surface of the surrounding ground or floor, does not exceed the
least width, B, of the footing. See Figure 8-3-1.
(2) Deep footings, for which the depth, Df, is greater than the width, B, are described in Part 4, Pile
Foundations and Part 24, Drilled Shaft Foundations.
c.
Spread footings may be classified with respect to the subsurface material from which they derive their
support:
(1) Footings on granular, non-cohesive soils.
(2) Footings on saturated clay or plastic silt.
(3) Footings on unsaturated clay or silt.
1
(4) Footings on nonhomogeneous deposits.
(5) Footings on preconsolidated clay.
3
4
NO REDUCTION IN ALLOWABLE
SETTLEMENT PRESSURE IS
REQUIRED WHEN WATER
TABLE IS BELOW THIS
ELEVATION - SEE ARTICLE
3.4.3.3A(3).
Reduction in allowable pressure on footing on granular material.
Figure 8-3-1. Factors Affected by Depth
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Concrete Structures and Foundations
SECTION 3.2 INFORMATION REQUIRED
3.2.1 FIELD SURVEY (1995)
a.
All available information shall be furnished in the form of a topographic map, in order to adapt the
structural requirements to the field conditions. The locations and dimensions of underground utilities,
existing foundations, roads, tracks, or other structures shall be indicated. In connection with footings for
river crossings, the records of normal high water, low water, floodwater level, depth of scour, stream
velocities, and alignment of the stream shall be provided.
b. All available information concerning the nature of the foundations of neighboring structures, the nature
of the underlying materials, and of the settlement and behavior of these foundations shall be assembled
and condensed as a guide to the judgment of the engineer in the design of the new structure.
3.2.2 CONTROLLING DIMENSIONS (1995)
Information shall be assembled concerning the proposed arrangement of the column, piers, abutments or
equipment to be supported; the depths of basements, tunnels, and other excavations; the surface elevation of
fill areas; and all other factors that may affect or be affected by the construction.
3.2.3 LOADS (1995)
a.
The loads to be supported by the foundations shall be indicated. These shall be subdivided into the
following categories:
(1) Dead load.
(2) Normal live load, defined as the live load that is likely to be transmitted to the foundation
throughout the greater portion of the useful lifetime of the structure, is commonly used when the
foundation soil is a saturated clay.
(3) Maximum live load, defined as the greatest live load that may be anticipated at any time during the
lifetime of the structure, is commonly used when the foundation soil is a freely draining sand.
(4) Longitudinal and lateral forces.
(5) Snow load.
(6) Ice load.
(7) Earthquake load.
(8) Wind load.
(9) Loads from pore water pressures including buoyancy and seepage forces.
(10) Area load, defined as any load transmitted to the supporting soil by the addition of fill or adjacent
structures.
(11) Impact normally is not considered in the design of a footing except for special circumstances.
(12) Vibratory loads to footings on granular material shall be considered.
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b. An estimate shall be made of the duration of each loading, because the settlement of some types of
subsurface materials depends upon the proportion of the total time the loads are active.
c.
The character, frequency, and amplitude of any vibratory loads including earthquakes shall be noted for
further analysis. If such loads are an important consideration, the foundation design shall be referred to
a geotechnical engineer with expertise in dynamics.
d. Footings shall be designed by using the following combinations of loads:
(1) Primary: Dead + Live + Centrifugal Force + Earth Pressure + Pore Water Pressures + Area Load
+ Special Vibratory Loads.
(2) Secondary: Longitudinal Force + Wind + Ice and Stream Flow Pressures + Seismic Forces.
3.2.4 CHARACTER OF SUBSURFACE MATERIALS (1989)
3.2.4.1 General
a.
Pertinent supplementary data with respect to local geological or foundation conditions, including aerial
photographs and agricultural soil maps, should be assembled if available. Data concerning changes in
groundwater level should also be investigated.
b. The data concerning subsurface materials shall be assembled in suitable graphical form, such as cross
sections through the various deposits, showing the probable arrangement and sequence of lenses or
strata, the pertinent physical properties of each element of the deposit, and the location of the
groundwater table.
1
3.2.4.2 Field Investigation
a.
The nature and extent of the various formations of soil and rock beneath the site and the depth to
groundwater shall be determined by means of test borings or probes and physical tests of a type and to
an extent appropriate to the character and importance of the structure and the nature of the subsurface
materials. The borings shall be made in accordance with the AREMA recommendations in Part 22,
Geotechnical Subsurface Investigation.
b. For major structures, at least one boring should, if practicable, extend into bedrock. Borings should at
least extend to a depth equal to three times the least footing width plus the depth of the footing from the
ground surface. For major structures on cohesive soils undisturbed samples should generally be
recovered for laboratory testing. The recovery of undisturbed samples in granular soil has not proven
satisfactory. In site tests may provide useful data for foundation design. These tests include standard
penetration test, vane shear test, Dutch cone penetration test (static penetration test), pressuremeter
test, and other tests as described in Part 22, Geotechnical Subsurface Investigation.
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4
Concrete Structures and Foundations
3.2.4.3 Depth of Frost and Volume Change
a.
The maximum depth of frost penetration shall be determined, usually on the basis of local experience
and records. Figure 8-3-2 is a map showing the depths of frost penetration in the contiguous 48 states.
Similarly, in regions of excessively swelling or shrinking soils, the depth to which significant volume
changes occur as a result of seasonal variations in moisture content shall be determined.
b. Permafrost, or permanently frozen ground, exists in the northern hemisphere in arctic and subarctic
regions. Although the southern boundary of permafrost is irregular, it may extend as far south as the
50th parallel. Foundations for structures, in areas of permafrost, should be designed in such a way as to
not disturb the permanently frozen ground; or if this is impossible, the influence of the foundation on
the permafrost should be predicted so the effect of the changes can be accommodated in the design. A
geotechnical engineer with experience in these ground conditions should be consulted for design of
foundations to be placed on permafrost.
Figure 8-3-2. Extreme Frost Penetration, in Inches, Based upon State Averages. Source:
U.S. National Weather Records Center
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SECTION 3.3 DEPTH OF BASE OF FOOTINGS
3.3.1 SELECTION OF TENTATIVE DEPTHS (1995)
On the basis of the data concerning the subsurface materials, tentative elevations for the bases of the footing
should be selected. Unless special provisions are made, the depth shall not be less than the depth of frost
penetration, scour, or, in expansive clay subsoils, less than the thickness of the zone of significant volume
change of the subsoil due to seasonal moisture variations. Footings should be placed below disturbed shallow
soils, uncontrolled fills, collapse susceptible soils, and organic soils.
3.3.2 REVISION OF DEPTHS OF FOOTINGS (1995)
After the preliminary depths have been selected, the allowable soil pressure shall be determined and the sizes of
the footings proportioned to the pressures. If the resulting design is not feasible or economical, similar studies
shall be made for footings established at other depths until the most suitable and economical arrangement is
determined. In considering the relative economy of footings at various levels, the cost and difficulty of
excavation below groundwater level in pervious soils shall be taken into account. The economy and suitability
of other types of foundations, such as piles or drilled shafts, shall also be considered. For deep foundations, the
designer should refer to Part 4, Pile Foundations and Part 24, Drilled Shaft Foundations.
SECTION 3.4 SIZING OF FOOTINGS
1
3.4.1 D E F I N I T I O N S (1995)
The following definitions will be used in the design procedures described below.
• Net Bearing Capacity. The ultimate pressure at which the supporting material will fail in shear
beneath the footing, less the pressure due to the weight of the soil at that depth.
3
• Allowable Bearing Capacity. The net bearing capacity divided by an appropriate factor of safety.
• Allowable Settlement Pressure. The maximum pressure to which the footings of the structure may be
subjected without producing excessive settlement or excessive differential settlement of the structure.
This settlement consists of two stages:
– Initial Settlement or Elastic Settlement. Occurs shortly after loading.
– Consolidation. Occurs over an extended time period.
The pressures for settlement are net pressures; that is, they represent pressures at the base level of
the footing in excess of pressures at the same level due to the weight of the surrounding soil
immediately adjacent to the footing.
• Allowable Soil Pressure. Shall be taken as the smaller of the allowable bearing capacity or the
allowable pressure for settlement.
• Contact Pressure. The total load divided by the area for vertically loaded footings and the maximum
pressure applied by the combined effects of vertical and horizontal loads for eccentrically loaded
footings as described in Part 3, Spread Footing Foundations, Section 3.5, Footings with Eccentric
Loads.
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Concrete Structures and Foundations
3.4.2 SAFETY FACTORS (1995)
The safety factor for Primary Loads shall not be less than 3; for Primary + Secondary Loads the safety factor
shall not be less than 2. Additional consideration shall be taken of load duration in relation to foundation soil
type and groundwater conditions when selecting a safety factor.
3.4.3 SHALLOW FOOTINGS ON GRANULAR MATERIAL (COHESION = 0) (1995)
3.4.3.1 General
a.
The allowable soil pressure for a shallow footing on granular material depends on the width B of the
footing, the shape of the footing, the depth of foundation Df, the unit weight of the foundation material,
and the position of the groundwater table.
b. The location of the present and/or future groundwater level will noticeably affect the bearing capacity
and allowable settlement pressure of the footing. Due consideration should be given to the future
groundwater level.
c.
Vibrational loads can cause severe settlement of a footing founded on loose to medium granular soils. If
future construction in the immediate area will require pile driving, vibratory compaction of subsoil, or
other vibrations, then consideration should be given to a more extensive vibratory analysis and a
geotechnical engineer knowledgeable in soil dynamics should be consulted.
3.4.3.2 Net Bearing Capacity of a Footing on Granular Material (Cohesion = 0)
a.
The net bearing capacity of a footing on sand can be calculated from the following formulae:
For a continuous footing:
Q u = 0.5gBN g + D f g ( N q – 1 )
For a square footing:
Q u = 0.4gBN g + D f g ( N q – 1 )
For a circular footing:
Q u = 0.3gBN g + D f g ( N q – 1 )
where:
Qu = the net bearing capacity in lb/square foot
B = the footing width in feet
Df = the footing depth in feet
g = the unit weight of the sand in lb/cubic foot
Ng and Nq = dimensionless bearing capacity factors which are a function of f, the internal angle of
friction, or of N, the standard penetration blow count.
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The standard penetration blow count is described in Part 22, Geotechnical Subsurface Investigation. The
relationships between f, N, and the bearing capacity factors are shown in Figure 8-3-3 as proposed by
Peck, Hanson and Thornburn.
b. For saturated sands the buoyant unit weight should be used in the equations above.
1
3
4
Figure 8-3-3. Relationship Among f, N, and Bearing Capacity
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Concrete Structures and Foundations
3.4.3.3 Allowable Settlement Pressure for Sand
a.
An empirical equation by Meyerhof may be used to estimate the allowable settlement pressure, Qs, of a
footing on sand.
(1) For B £ 4 feet:
Q s = Ns
------8
(2) For B > 4 feet:
B + 1)
ö (-----------------Q s = æ Ns
è ------ø
12
B
where:
Qs = is in tons/square foot
N = the standard penetration blow count
B = the footing width in feet
s = the allowable settlement in inches
(3) The presence of a water table will have the effect of reducing the allowable settlement pressure as
the effective stress is lowered. Therefore the allowable settlement pressure shall be reduced 50% if
the water table is at the base of the footing and 0% if the water table is at a depth greater than B.
The reduction for intermediate depths can be interpolated.
3.4.3.4 Sizing Footings on Granular Material
A trial footing size is used to determine the net bearing capacity from Article 3.4.3.2 and the allowable bearing
capacity described in Article 3.4.1 is calculated by dividing the net bearing capacity by the appropriate safety
factor from Article 3.4.2. The trial footing size is used to determine the allowable settlement pressure defined in
Article 3.4.3.3. The loads defined in Article 3.2.3 are divided by the trial footing area to give the contact
pressure defined in Article 3.4.1. If the contact pressure is greater than either the allowable bearing capacity or
the allowable settlement pressure, the footing size must be increased until the contact pressure is less than the
allowable soil pressure defined in Article 3.4.1.
3.4.4 SHALLOW FOOTINGS ON SATURATED CLAY (f = 0) (1989)
3.4.4.1 Net Bearing Capacity (Qu)
a.
The net bearing capacity of shallow footings on saturated clays or clayey soils depends on the footing
width, B; the footing length, L; the depth, Df, of the footing below the surface and on the unconfined
compressive strength, qu, of the clay. The net bearing capacity for a footing may be determined by means
of the following equations.
(1) For a continuous footing:
Qu = 2.7qu
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(2) For a square or rectangular footing:
Qu = 2.7qu (1 + 0.3 B/L)
(3) For a circular footing:
Qu = 3.5qu
b. In these equations, Qu and qu are expressed in tons/square foot. The value of qu shall be taken as the
average unconfined compressive strength of the clay within a depth B below the base of the footing;
provided, however, that the strength of the clay does not decrease significantly with increasing depth
below the footing. In the event that soft material underlies stiffer material, a special investigation of the
bearing capacity of this level shall be undertaken.
3.4.4.2 Sizing Footings on Clay
The correct factor of safety as indicated in Article 3.4.1 and Article 3.4.2 shall be used in order to obtain an
allowable bearing capacity. The required footing area is determined by dividing the column or wall load by the
allowable bearing capacity.
3.4.4.3 Settlement Characteristics
a.
For footings located on or above medium clays, (qu below 2.0 tons per square foot) settlement analysis
should generally be undertaken using the footing size and contact pressure determined in Article 3.4.1.
In certain cases, large settlements will occur by consolidation of an underlying layer under very small
additional loads. If any doubt exists concerning the consolidation characteristics of the soil, one or more
consolidation tests should be undertaken. Settlement by “consolidation” of underlying clay layers can be
many times the initial “elastic settlement.” Both the consolidation and elastic settlements can be
estimated by laboratory analysis. If the estimated settlement is greater than the allowable settlement,
the footing size shall be increased to bring the estimated settlement below the allowable limit or a deep
foundation shall be used.
1
3
b. The effect of subsidance due to drainage of the soil shall be considered in the design of the structure.
3.4.5 FOOTINGS ON UNSATURATED SILTS AND CLAYS (1989)
a.
Accurate determination of the bearing capacity of such soils is very difficult; and complicated laboratory
testing is required. Due to the existence of hairline cracks in the soil structure, and unknown pore-air
pressures, an extensive field investigation may be required. Each structure will have a different solution.
Careful evaluation is necessary in order to arrive at a satisfactory footing design. A rise in the
groundwater table will reduce the allowable capacity and complicate the analysis.
b. Where loadings on footings are light, or in the case of a floor slab, roadway, walks or other similar lightly
loaded areas, due consideration to swelling of a clay soil shall be given. This may be especially important
if the percent of soil with particle diameters less than 0.001 mm is greater than 15%.
3.4.6 FOOTINGS ON NON-HOMOGENEOUS DEPOSITS (1989)
a.
Footings established above stratified or other non-homogeneous formations shall be proportioned on the
assumption that the most unfavorable condition disclosed by the subsurface exploration may be present
under the most heavily loaded footings, unless detailed information is obtained concerning the actual
conditions beneath each footing.
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Concrete Structures and Foundations
b. Subsoil of this type requires extensive knowledge and investigation in order to obtain an accurate
solution. However, in many cases using the above assumption in order to simplify the solution is
satisfactory.
3.4.7 FOOTINGS ON SOILS WITH COHESION AND FRICTION
(PRECONSOLIDATED CLAYS) (1989)
a.
Many soils fit this category and an accurate analysis can be carried out. The investigation must be
undertaken without the use of the simplifying assumptions made for granular or cohesive soils, and
more extensive laboratory information is required. Triaxial shear tests are required for this analysis.
b. At times, it will be satisfactory to assume the soil alternately only granular or cohesive and use the lower
value for allowable pressure.
SECTION 3.5 FOOTINGS WITH ECCENTRIC LOADS
3.5.1 LOADS ECCENTRIC IN ONE DIRECTION (1989)
a.
In cases where a footing is subjected to moments in addition to vertical loads, the line of action of the
resultant force is located some distance from the centerline of the footing. This distance, called
eccentricity, e, is calculated by the equation
M
e = ----P
where:
M = the moment
P = the total vertical load
The total vertical load is equal to live load plus dead load. The eccentricity shall have a maximum value
of B/6.
b. The pressure distribution beneath a footing subjected to moment will be non-uniform and the maximum
pressure, Pmax and minimum pressure, Pmin, can be calculated from:
P
6M
P max = ------- + ----------BL B 2 L
P – 6M
P min = ------- ----------BL B 2 L
where:
B = the footing width
L = the footing length
M = the moment
P = the total vertical load
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3.5.2 LOADS ECCENTRIC IN TWO DIRECTIONS (1989)
a.
In cases where a footing is subjected to moments in two directions, the vertical load, P, is calculated by
adding dead loads to live loads. Horizontal loads and their lines of action in each direction are
determined, and the moments in the two directions are computed by multiplying the force times the
moment arm for each load. The eccentricity in each direction is computed by dividing the moment in
each direction by the vertical load as follows:
M
M
e x = -------x- and e y = -------yP
P
where:
ex and ey = the eccentricities in the two directions
Mx and My = the moments in the respective directions
b. Next, select trial footing dimensions B and L, where B is the footing dimension parallel to the x direction
and L is parallel to the y direction. Using these dimensions, the previously determined eccentricities, and
the vertical load, calculate the maximum and minimum contact pressures beneath the footing according
to:
6e
6e
P
P max = -------- æ 1 + --------x- + --------y-ö
è
B
L ø
BL
1
6e 6e
P
P min = -------- æ 1 – --------x- – --------y-ö
è
BL
B
L ø
3
where all terms are as previously defined.
c.
If Pmin is negative, that corner of the footing is in tension and so larger footing dimensions should be
tried. The computations of maximum and minimum pressures are repeated with new trial dimensions
until Pmin is positive. This indicates that the entire footing is in compression and the entire surface area
will contribute to the footing’s load carrying capacity.
4
3.5.3 SIZING FOOTINGS WITH ECCENTRIC LOADS (1989)
a.
Footings shall be designed using Primary Loads with the required factor of safety and checked by using
Primary + Secondary Loads with their required factor of safety. Both design criteria must be met.
b. If the footing is subjected to eccentric loads, the maximum footing contact pressure as determined in
either Article 3.5.1 or Article 3.5.2 is compared with the allowable soil pressure determined from either
Article 3.4.3.3 or Article 3.4.3.4 for sands, or Article 3.4.4.2 for clays. In the case of clays, the settlement
should be estimated according to Article 3.4.4.3. If the contact pressures are less than allowable
pressures and the amount of settlement is acceptable, the footing size is adequate; however, if the
maximum contact pressure exceeds the allowable soil pressures or if the settlement is excessive, the
footing size shall be increased in order to decrease maximum contact pressure and settlement. If the
resulting footing size is too large to be practical, deep foundations, such as piles as described in Part 4,
Pile Foundations or drilled shafts as described in Part 24, Drilled Shaft Foundations, shall be considered.
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SECTION 3.6 FOOTING STRESSES
3.6.1 LOADS ECCENTRIC IN TWO DIRECTIONS (1989)
a.
For computation of the stress within the footing itself, the pressures on the foundation may be calculated
by the procedure given in Article 3.5.2:
6e
6e
P
P = -------- æ 1 ± --------x- ± --------y-ö
x
y ø
BL è
b. However it is desirable, if possible, to proportion the footing for an equal pressure distribution.
c.
A more detailed study may be required for a flexible, combined, or mat footing. In actual practice the
pressure distribution may vary materially from this ideal distribution. The correct distribution of the
reaction is dependent upon the rigidity of the footing, distribution of the loading, characteristics of the
soil, and the factor of safety.
SECTION 3.7 FIELD CONDITIONS
3.7.1 MODIFICATION OF DESIGN (1989)
If excavation discloses soils or soil conditions different from those upon which the design of the footings has
been based, the design shall be altered as necessary. The plans for the footing should indicate the type of soil
and soil pressure upon which the design is based.
3.7.2 REINFORCEMENT (1989)
Wherever the concrete of a reinforced footing is in contact with the soil, steel reinforcement shall be provided
with a cover of not less than 3 inches. If the concrete is placed against a seal coat or against steel sheeting that
is to remain in place, the cover shall be not less than 2 inches.
3.7.3 FOOTINGS AT VARYING LEVELS (1989)
If the footings for two adjacent parts of a structure are established at different levels, the difference in elevation
of the bases of adjacent footings, divided by the least horizontal clear distance between the footings, shall not
exceed a value appropriate to the characteristics of the subsoil, and in general should not exceed 1.0. An
increased load on the lower footing will result from this configuration.
3.7.4 DRAINAGE (1989)
Unless underwater construction is specified, surface water or groundwater shall not be permitted to
accumulate in excavations for footings. Such water shall be conducted to sumps located outside the boundaries
of the footing and removed. If the water cannot be handled by this procedure, groundwater lowering should be
accomplished by well points, a tremie seal coarse, or other appropriate means.
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3.7.5 TREATMENT OF BOTTOM OF EXCAVATION (1995)
a.
Care shall be exercised to prevent disturbance of the materials at the bottom of the excavation by
equipment or by the feet of the workmen. The bottom 2 inches of concrete in the footing shall be
neglected for strength calculations.
b. On soft clayey or silty soils a working platform or mud coat of lean concrete, from 2 inches to 3 inches in
thickness, is recommended if disturbance is probable. Otherwise, final excavation of the last 3 inches to 6
inches above grade should be deferred until immediately before placement of the reinforcement. The
concrete in a working platform or mud coat shall not be considered as contributing to the strength of the
footing.
c.
If a tremie seal is to be placed to permit dewatering of the cofferdam for pier, the thickness of the seal
shall be adequate to withstand the upward pressure of the water beneath the seal at the time of
dewatering. This uplift force shall be determined by a rational analysis.
3.7.6 STRESSES (1995)
Concrete and steel allowable stresses shall be in accordance with Part 2, Reinforced Concrete Design.
3.7.7 INFORMATION ON DRAWINGS (1995)
Design drawings shall indicate the allowable soil pressure, type of soil, grade of the reinforcing steel, strength of
concrete, minimum cement factor, and other pertinent data.
1
SECTION 3.8 COMBINED FOOTINGS
3.8.1 USES AND TYPES (1995)
a.
3
Combined footings are those which carry more than one column and are used for reasons such as:
(1) Wall column is so close to property line or obstruction(s) that it is impossible to center column on
footing.
(2) Allowable soil pressures are so low or column loads so large that individual footings would overlap.
b. Combined footing types are illustrated in Figure 8-3-4 and include: rectangular, trapezoidal, and strap
footings.
3.8.2 ALLOWABLE SOIL PRESSURES (1995)
a.
Allowable soil pressures defined in Article 3.4.1 are determined from Article 3.4.3.3 or Article 3.4.3.4 for
sands and Article 3.4.4.2 for clays. For clays, settlements should be estimated according to Article 3.4.4.3.
For combined footings a minimum safety factor is 3.
b. A combined footing is ideally proportioned such that the centroid of the contact area lies on the line of
action of the resultant of column loads, thereby producing a uniform pressure distribution. In situations
where it is impossible to produce a uniform pressure distribution, the pressure distribution is computed
and the footing sized according to the principles outlined in Section 3.5, Footings with Eccentric Loads.
The dimensions of the footing are selected so that the allowable soil pressure is not exceeded.
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Concrete Structures and Foundations
Figure 8-3-4. Types of Combined Footings
3.8.3 COLUMN LOADS (1995)
Combined footings should be proportioned for uniform soil pressure under dead load plus the amount of live
load that is likely to govern settlement as recommended in Article 3.2.3. The centroid of the footing must lie on
the line of action of the resultant column loads consisting of dead load plus a fraction of live load specified by
the specifications or building code if applicable.
3.8.4 SIZING COMBINED FOOTINGS (1995)
3.8.4.1 Rectangular Footings
A rectangular footing is used if the rectangle can extend beyond each column the distance necessary to make
the centroid of the rectangle coincide with the point where the resultant of the column loads intersects the
base.
3.8.4.2 Trapezoidal Footings
A trapezoidal footing is used if a rectangular footing cannot project the required distance beyond one or both
columns.
3.8.4.3 Strap Footings
The strap footing is considered as two individual footings connected by a beam.
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-3-16
AREMA Manual for Railway Engineering
8www.nbm.
Part 4
Pile Foundations1
— 1994 —
TABLE OF CONTENTS
Section/Article
Description
Page
4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.1.1 Scope (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4-2
8-4-2
4.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.1 Loads (1994). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.2 Loads on Piles (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.3 Eccentricity of Loads (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.4 Uplift on Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.5 Spacing of Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.6 Batter Piles (1990). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2.7 Scour (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4-2
8-4-2
8-4-3
8-4-3
8-4-3
8-4-4
8-4-4
8-4-5
4.3 Allowable Load on Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.1 Subsurface Investigation (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.2 End Bearing Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.3 Friction Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.4 Lateral Support (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.5 Pile Length Determination (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.6 Pile Driving and Loading Tests (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4-5
8-4-5
8-4-5
8-4-5
8-4-6
8-4-6
8-4-8
4.4 Pile Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.1 General (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.2 Timber Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.3 Steel Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.4 Precast Concrete Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.5 Cast-in-Place Concrete Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4.6 Augered Cast-in-Place Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4-9
8-4-9
8-4-9
8-4-10
8-4-11
8-4-11
8-4-13
4.5 Installation of Piles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.1 Driven Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5.2 Augered Cast-in-Place Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4-14
8-4-14
8-4-16
1
References, Vol. 40, 1939, pp. 418, 764; Vol. 41, 1940, pp. 369, 843; Vol. 49, 1948, p. 254; Vol. 50, 1949, pp. 311, 758; Vol. 52, 1951, pp. 382,
861; Vol. 63, 1962, pp. 276, 687; Vol. 64, 1963, pp. 226, 624; Vol. 80, 1979, p. 136; Vol. 91, 1990, pp. 63, 74; Vol. 94, 1994, p. 99.
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TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
4.6 Inspection of Pile Driving (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4-16
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4-16
LIST OF TABLES
Table
8-4-1
Description
Page
Recommended Pile Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4-13
SECTION 4.1 GENERAL
4.1.1 SCOPE (1994)
a.
This part of the Manual covers the investigation, design and construction of pile foundations.
b. For the purpose of this part, a pile shall be considered as a relatively slender structural member
continuously driven or augered into the earth. Drilled shafts placed in predrilled holes are addressed in
Part 24, Drilled Shaft Foundations.
c.
In this part, factors of safety are suggested; however, where information on loads or soil conditions is
limited, larger factors of safety should be used.
SECTION 4.2 DESIGN
4.2.1 LOADS (1994)
a.
Pile foundations shall be designed to carry the entire superimposed load, including the weight of the
footing and overlying loads supported by the footing.
b. Pile foundations shall be designed for that reasonable combination of the following loads and forces
which produce maximum load and in accordance with Section 4.3, Allowable Load on Piles:
4.2.1.1 Primary Loads and Forces
a.
Dead.
b. Live – Vertical.
c.
Live – Horizontal due to surcharge.
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d. Centrifugal force.
e.
Earth pressure.
f.
Buoyancy.
g.
Negative skin friction.
NOTE:
Live Load Impact shall be considered only in Case A of Article 4.2.2 for steel or concrete
piles above the ground line where they are rigidly connected to the member supporting
the superstructure.
4.2.1.2 Secondary Loads and Forces (Occasional)
a.
Wind and other lateral forces.
b. Ice and Stream flow.
c.
Longitudinal forces.
d. Seismic forces.
4.2.2 LOADS ON PILES (1994)
a.
1
Pile foundations shall be designed using the most restrictive of the following load capacity cases:
• Case A: The capacity of an individual pile as a structural member.
• Case B: The capacity of the pile to transfer its load to the ground.
• Case C: The capacity of the ground to support the load from the pile or piles.
3
b. When pile foundations are designed for primary and secondary loads in combination, as defined in
Article 4.2.1, the allowable loads may be increased 25% for Load Cases A, B, and C, but the number of
piles shall not be less than is required for primary forces alone with no increases in allowable stress for
Case A and the minimum factor of safety shall be 2.0 for Cases B and C. For group friction piles, the
factor of safety for Case C shall not fall below 2.0 for primary and secondary load combinations.
4
4.2.3 ECCENTRICITY OF LOADS (1990)
The maximum design pile load under eccentric loading shall not exceed the allowable load as determined under
Section 4.3, Allowable Load on Piles with the appropriate factors of safety stipulated in Article 4.2.2. The piles
shall be so spaced that the eccentric load on the piles, due to primary forces, will be distributed as equally as
practicable to the piles in the group. Pile loads due to combinations of primary and secondary forces shall not
exceed that permitted by Article 4.2.2.
4.2.4 UPLIFT ON PILES (1990)
a.
In special cases when piles or pile groups are subjected to uplift, and sufficient bond and anchorage are
provided between the pile and the supported structure, the uplift shall be considered in the design of the
pile foundation. The pile foundation shall be designed for uplift considering load capacity Cases A, B, and
C of Article 4.2.2. The factor of safety for Cases B and C shall be a minimum of 2.0 for combinations of
primary and secondary forces, and a minimum of 3.0 for combinations of secondary forces with dead load
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alone. The capacity of the pile as a structural member (Case A) shall be based on allowable stresses
established in the applicable AREMA Specifications for Timber Structures, Chapter 7, Timber
Structures; in Part 2, Reinforced Concrete Design; or in the AREMA Specifications for Steel Structures,
Chapter 15, Steel Structures. The allowable stresses may be increased 25% for combinations of primary
and secondary forces.
b. The ultimate uplift value of an individual pile shall be determined by jacking test piles of identical type
and dimension to that used in the design, and measuring the pull required per square foot of embedded
surface area to raise the pile. When a tension pile group is involved, a group analysis shall also be
undertaken. The maximum capacity of a tension pile group shall be considered to be the smaller of (1)
the capacity of a single pile multiplied by the number of piles in the group, or (2) the weight of the block
of soil contained within the perimeter of the groups, each with a minimum safety factor of 2.0, except as
noted in paragraph a.
4.2.5 SPACING OF PILES (1990)
a.
Piles shall be spaced to nearly equalize their load consistent with economical design of the footings. The
spacing of piles shall depend upon: the type of pile, that is whether friction or end bearing; the pile’s
structural and crushing strength; and the type of material sustaining the pile. Generally, piles should be
spaced, center-to-center, at least three times the minimum butt width of the pile. Piles should be spaced
far enough apart, or other suitable means used, to prevent heaving or uplifting of adjacent piles during
driving.
b. In small groups, the piles may be battered to enlarge the area sustaining the group, thereby increasing
the load-carrying capacity of the group without unreasonably increasing the size of the foundation. Endbearing piles may be spaced in accordance with the capacity of the pile and the end-bearing stratum that
will carry the design load. When closely spaced friction piles are contemplated, their total group capacity
shall be verified by an acceptable geotechnical method which considers the capacity of the engaged soil
mass to support the applied pile loads.
c.
When determining spacing of piles in granular soils, consideration should be given to the increased
difficulty of driving due to the increased soil density that will occur because of soil packing or
consolidation within the pile group.
4.2.6 BATTER PILES (1990)
a.
Piles may be battered to help resist horizontal forces. Primary horizontal forces on pile foundations shall
be resisted by batter piles where practicable. Such piles shall be designed to carry horizontal forces
combined with their share of the vertical loads. In general, batter should not exceed 3 (horizontal) to 12
(vertical), due to increased difficulty in driving piles with a greater batter.
b. Secondary horizontal forces on pile foundations may be accommodated by the shear resistance of the
vertical piles, passive soil pressure, or friction between the soil/foundation interface where these
resisting forces can be determined to exist for a particular foundation system. Where these resisting
forces cannot be shown to be reliable over the expected life of the structure, batter piles or other
dependable means of resisting these forces shall be used.
c.
Where large pile groups are involved, where clearance problems limit the pile foundation area, where
secondary horizontal loads are small or in areas of the country where earthquake loading makes use of
batter piles undesirable, the foundation shall be specially designed to include the horizontal forces as
acting on the vertical piles. In such a case, the piles shall be designed to resist all loads, and the structure
designed for the horizontal movement to be encountered.
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Pile Foundations
4.2.7 SCOUR (1990)
a.
The possible effects of scour to pile foundations located in or adjacent to water should be reviewed as
part of the total foundation design.
b. When there is a possibility that the upper portion of the soil formations may be removed by scour, the
piles or pile group shall be designed to have adequate bearing capacity and lateral support below the
projected depth of scour. The free standing portions of the exposed piles shall be designed as columns.
c.
Determination of the probable depth of scour at a given location may have to be based largely on past
records of stream bed erosion or wave action in the area, and how it has affected existing structures.
SECTION 4.3 ALLOWABLE LOAD ON PILES
4.3.1 SUBSURFACE INVESTIGATION (1990)
a.
Test borings shall be made at enough locations and to a sufficient depth below the anticipated tip
elevation of the piles to determine adequately the character of the material through which the piles are
to be driven and of the materials underlying the pile tips. The results of the borings and soil tests, taken
into consideration with the function of the piles in service, will assist in determining the type, spacing,
and length of piles that should be used and whether the piles will be end bearing, friction or a
combination of both types.
1
b. The subsurface investigation should be made in accordance with provisions outlined in Part 22,
Geotechnical Subsurface Investigation.
4.3.2 END BEARING PILES (1990)
a.
A pile may be considered end bearing when it passes through soil having low frictional resistance, and
has its tip resting on relatively impenetrable material such as rock, or enters other material that offers
rapidly increasing resistance to further penetration. The capacity of end-bearing piles depends on the
bearing capacity of soil or rock material underlying the piles, and upon the structural capacity of the pile.
The dynamic characteristics of the soil-hammer cushion-pile system coupled with the installation
technique will determine the ability of the pile to penetrate overlaying strata to reach the bearing
stratum.
b. Allowable stresses for pile materials are given elsewhere in this part. When end-bearing piles pass
through unconsolidated material, consideration should be given in design to the additional load (negative
skin friction) that may be imposed on the pile as the material consolidates above the bearing stratum.
The bearing stratum must be of sufficient thickness and strength to support the entire pile group
loading. The design load shall preferably be determined by loading test piles. In addition, an analysis of
the group of piles must show that the allowable load on the soil or rock supporting material is not
exceeded.
4.3.3 FRICTION PILES (1990)
a.
A friction pile derives its support principally from the surrounding soil through the development of
shearing or frictional resistance. The capacity of friction piles depends upon the ability of the soil to
carry the load distributed by the piles within the limits of settlement that can be tolerated by the
structure.
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Concrete Structures and Foundations
b. The design load shall preferably be determined by loading test piles in accordance with the provisions of
Article 4.3.6. Where groups of piles are driven into plastic materials, consideration should be given not
only to the allowable load per pile, but also to the total load that can be safely assigned to the group. The
design load shall be determined by loading a group of piles or by making an allowance for the difference
between the capacity of a single pile and a group of piles by means of a block analysis. A single row of
piles need not be considered as a group, provided the piles are spaced at least three times their butt
width.
c.
In many cases, a study of the borings and the estimation of approximate soil constants will determine the
ability of the soil to carry the applied loads. In foundations involving cohesive soils, the load-settlement
relationship should be investigated by recognized geotechnical methods and procedures.
4.3.4 LATERAL SUPPORT (1990)
A fully embedded pile can generally be considered laterally supported. A pile that is not fully embedded, or may
be as a result of scour, in air or water, or which may be in muck, peat, thin mud, or fluid material, shall be
investigated for the allowable capacity by the methods given in the Report of ACI Committee 543
“Recommendations for Design, Manufacture, and Installation of Concrete Piles” or other acceptable method
approved by the engineer.
4.3.5 PILE LENGTH DETERMINATION (1990)
The determination of the most satisfactory and economical length of piles is one of the key factors in securing
an adequate foundation. In addition to information that can be developed through soil borings, pile driving
tests, pile load tests, and pile driving formulas, the use of the one-dimensional wave equation can be a valuable
tool on large or difficult foundations, and is recommended for design and field control purposes (Reference 71).
Pile driving records of nearby adjacent piles may also be used in determining pile length if definite correlation
between the existing and proposed piles as to type, loading, and use can be determined as well as the veracity of
the previous pile driving record. The use of pile driving records to establish pile lengths without the benefit of a
subsurface investigation and geotechnical analysis on projects which are not relatively small and where the
conditions above cannot be met is not recommended.
4.3.5.1 Estimated Tip Elevation and Estimated Length
a.
At each boring location, using recognized geotechnical methods, the theoretical length of piles shall be
computed considering contributions from both bearing and frictional resistance. Piles in very deep
deposits are likely to receive support primarily through friction, whereas relatively shallow hardpan or
rock conditions are likely to provide support primarily through end bearing. Many foundation conditions
will provide both bearing and frictional support.
b. At each individual boring, an estimated tip elevation and an estimated pile length shall be selected and
tabulated based on the design cutoff elevation.
4.3.5.2 Minimum Tip Elevation
a.
At each boring location, a minimum tip elevation shall be computed above which no structure piles will
be permitted to stop. The minimum tip elevation reflects the design intent of the pile foundation design
and is determined by an experienced foundation engineer’s review of the estimated tip elevations,
recognizing practical aspects of foundation construction practice. As an example, if geotechnical
calculations demonstrate that piles should penetrate into a hardpan layer at varying depths, the
minimum tip elevation will be shown at the top of this layer. In certain cases, field conditions during
driving may modify this elevation.
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b. The minimum tip elevation will usually be above the estimated tip elevation.
4.3.5.3 Wave Equation
a.
The use of the one dimensional wave equation will greatly assist the engineer and contractor in
determining the foundation adequacy and the construction of the project as planned.
b. By the use of this tool, several values will be obtained:
(1) the ability of the soil-hammer cushion-pile system to obtain the required design capacity,
(2) the estimated blows per foot needed to obtain the required ultimate load at the estimated depth,
(3) the means whereby the required blows per foot at other depths can be evaluated,
(4) a means of evaluating the required blows per foot when the hammer fails to produce the
manufacturer’s rated energy.
c.
When this procedure is followed, the engineer can have the opportunity to modify his design before
construction is started, and the contractor can be appraised of his hammer requirement.
d. This procedure is recommended for all large and/or important projects.
4.3.5.4 Pile Driving Formulas
1
Many dynamic pile driving formulas have been developed as an aid in determining pile capacities. While such
formulas serve a useful purpose, particularly on smaller projects, greater accuracy, and economy can usually be
obtained by use of the wave equation method as described in Article 4.3.5.3. If pile driving formulas are
proposed for use, formulas that take into account the relationship between the weight of pile and weight of the
pile hammer striking parts should be used.
3
4.3.5.5 Plan Tip Elevations
4.3.5.5.1 Friction Piles
For those piles which can be considered to act as true friction piles, i.e. no end bearing stratum is in evidence
within reasonable depths, only a design tip elevation is required. In uniform soils, where a complete soil
investigation has determined the tip elevation, no further driving criteria is required, except the statement that
the piles must be driven to the design tip elevation. A variation in the expected rate of penetration at the
required tip elevation would indicate a variable soil layer, and a reappraisal of the tip elevation will be required.
4.3.5.5.2 Combined Bearing and Friction Piles, or Bearing Piles
Plans and specifications should require that all piles be driven to the minimum tip elevation shown on the
plans. At the minimum tip elevation, driving shall be continued until the required resistance is achieved, as
determined by the load tests, a wave equation analysis, or some pile driving formula specified by the engineer.
The latter provision will insure against variations in the consistency and depth of the bearing layer. An
important judgement factor is selection of required hammer energy-type, and cushion. This decision can best be
achieved by a wave equation analysis.
4.3.5.5.3 Estimated Lengths
The plans should show estimated lengths which have been used for calculation of the engineer’s estimate, and
will provide the bidders with a reasonable basis for pricing the pile foundations.
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4.3.6 PILE DRIVING AND LOADING TESTS (1990)
4.3.6.1 Driving Tests
a.
Where variable soil conditions are known to exist, the following procedure is suggested. A few of the
structure piles should be selected, including at least one from each substructure unit of the bridge or
structure, and they should be driven first before other service piles are ordered. Their installations
should be designated as Pile Driving Tests. A separate pay item should be provided, to cover piles
installed by Pile Driving Tests.
b. Where practical, piles installed by driving tests should have their tips carried five to ten feet below the
estimated tip elevation for the service piles at each particular location. Driving records for each foot of
driving of each pile shall be kept and plotted in the field to provide exploratory information. The plot
should be on a log containing the generalized information from the nearest structure boring. This record
will provide an immediate correlation of driving resistance and subsoil conditions for the pile, hammer
and cushion arrangement being used. The record will also provide information on where to select
suitable locations for future load tests if required. (Load tests should be applied only to standard service
piles, not to piles installed by pile driving tests. This is because piles installed by pile driving tests are
deliberately overdriven and, therefore, are not typical of the service piles.)
c.
Piles installed by driving tests are recommended both for the situation where later load tests are to be
performed and where load tests are not expected to be performed. The driving tests are of particular
importance where load tests are not contemplated, because in that case, they provide the only correlation
between soil boring data and driving data.
d. If possible, piles installed by driving tests should be placed in a position where they can serve as service
piles in the completed structure. It is permissible on small projects to overdrive all service piles (similar
to the installation of driving tests described above) in lieu of load testing which, from a cost standpoint,
may not be practical.
4.3.6.2 Pile Load Tests
a.
Pile load tests are considered essential for large or important jobs, or in subsurface conditions where
there is little precedent for major construction. To date, they give the best knowledge of the probable
capacity of an individual pile.
b. It is preferred that load tests be carried to failure to determine the true factor of safety for the proposed
design. If the margin of safety is higher or lower than desired, driving and elevation criteria can be
modified. If, due to very high loads, tests to failure are not practicable, testing should be carried to not
less than twice the design load. Test loads should not exceed the ultimate capacity of the pile as a
structural member, or the capacity of the jack frame.
c.
The test apparatus and procedure shall be in accordance with the current ASTM Designation: D1143
“Standard Method of Testing Piles under Axial Compressive Load.”
d. By analyzing and interpreting the load tests with the driving test data and subsoil information, it will be
possible to affirm the adequacy of the design and the installation criteria and introduce field
modifications as may be necessary.
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Pile Foundations
SECTION 4.4 PILE TYPES
4.4.1 GENERAL (1990)
a.
Selection of the type of foundation pile for a particular structure should be based on the following
criteria:
(1) Design load per pile or pile group.
(2) Type of foundation material to be penetrated.
(3) Relative costs of the piles and pile driving.
(4) Equipment available for driving piles.
(5) Availability of desired pile type.
(6) Special considerations based on specific job conditions, including, but not limited to:
(a) Restricted space for pile driving.
(b) Possible damage to existing structures.
1
(c) Exposure to sea water.
(d) Possible damage from marine organisms.
(e) Chemical attack.
(f) Possible damage to adjacent structures caused by vibration or soil movement during driving.
3
(g) Noise level during driving.
b. Full-length piles shall be used wherever practicable, but if splices cannot be avoided, an approved
method of splicing shall be used which will develop the full strength of the pile. Piles shall not be spliced
except by permission of the engineer, who must also approve all splice locations.
4
4.4.2 TIMBER PILES (1990)
a.
Timber piles shall conform to the AREMA specifications for wood piles, Chapter 7, Timber Structures,
Part 1, Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners,
Timber Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood and Part 3,
Rating Existing Wood Bridges and Trestles. If treatment is required, it shall conform to AREMA
specifications for wood preservation – Chapter 30, Ties, Section 3.6, Wood Preserving.
b. For a timber pile which is primarily a friction pile, the maximum allowable load in pounds shall be
computed by multiplying the tip area in square inches (small end) by the figure 1,200; the maximum load
thus being equivalent to 1,200 psi acting at the tip.
c.
For a timber pile that is primarily a point bearing pile, the maximum allowable load shall be computed as
above, but using the figure 800 instead of 1,200.
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Concrete Structures and Foundations
4.4.3 STEEL PILES (1990)
4.4.3.1 Types
This type of piling shall include all steel H-section piles and open-end steel pipe piles.
4.4.3.2 Material
All steel used for the piles shall conform to the current ASTM Designations: A36 for H-pile sections, and A252
for pipe sections. Special steels may be used for corrosion protection or other purposes, but where welding is
required weldability must be assured.
4.4.3.3 Size
a.
The minimum depth of a steel H-section shall be 8 inches. The minimum thickness of metal in the flange
or web shall be 3/8 inch. The flange width shall be not less than 85% of the depth of the section.
b. The minimum outside diameter of open-end pipe piles shall be 8-5/8 inches. The minimum wall thickness
shall be 3/8 inch.
4.4.3.4 Pile Caps
In general, steel bearing caps are not required on steel H-piles embedded at least 1 foot in concrete, providing
the footing reinforcement is adequately designed to transmit the imposed loads.
4.4.3.5 Protection Against Corrosion
a.
Steel piles that will be exposed to corrosive environments shall be protected by concrete encasement or
other suitable means; such as specially formulated epoxy or bituminous coatings, or additional steel
thickness. Protection at ground surfaces or normal water lines shall be provided and shall extend at least
1 foot above and 3 feet below the ground surface or low-water line. Concrete protection, where provided
shall have a minimum thickness of 4 inches and shall contain nominal steel reinforcement.
b. Structural steel piles shall not be used through active corrosion-inducing material or where electrolysis
may occur, without adequate provision for the protection of such piles.
4.4.3.6 Allowable Stresses
The allowable load per pile shall be determined as specified in Section 4.3, Allowable Load on Piles, but the unit
stresses due to axial load shall not exceed 12,600 psi. Due allowance shall be made for any bending stresses
caused by horizontal or eccentric loads and consideration shall be given to any column action of an unsupported
pile.
4.4.3.7 Pile Tip Reinforcement
Pile tip reinforcement may be required to prevent damage to H-piles when driving through heavy gravel,
boulders, or formations known to contain obstructions, or when driving end bearing piles. Heavy cast steel tips
are recommended for this purpose where the conditions so justify their use.
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AREMA Manual for Railway Engineering
Pile Foundations
4.4.4 PRECAST CONCRETE PILES (1990)
4.4.4.1 General
a.
This type of piling includes both conventionally reinforced concrete piles and prestressed concrete piles.
Both types can be formed by either casting, centrifugal casting, or extrusion methods. They are made in
various cross section shapes such as square, octagonal, and round. Often such piles are cast with a hollow
core. The piles are usually of constant cross section but may have a tapered tip.
b. Precast concrete piles must be designed and manufactured to withstand handling and driving stresses in
addition to service loads. The workmanship, material, and proportioning shall conform to the
requirements specified in Part 1, Materials, Tests and Construction Requirements.
4.4.4.2 Design
The minimum acceptable diameter or side dimension for driven piles is usually 8 inches. This may be
satisfactory for short piles which are lightly loaded, however, as a general rule, it is recommended that the
minimum average dimension be 10 inches, except that the pile tip may be 8 inches. Piles may be pointed or not
as directed by the engineer.
4.4.4.3 Manufacture
The manufacture of the various types of precast concrete piles shall be in accordance with the current Chapter
4 of American Concrete Institute (ACI) Committee 543 report titled “Recommendations for Design,
Manufacture, and Installation of Concrete Piles.”
1
4.4.4.4 Cut-Off
Precast piles shall be driven to or cut off within 2 inches of the elevation shown on the plans, but in all cases,
the cutoff shall be below any indication of fracture. If piles are cut off or driven below the required elevation,
they shall be built-up to the cutoff line as determined by the engineer. Standard details are to be shown on the
project plans.
3
4.4.4.5 Allowable Stresses
The allowable load per pile shall be determined as specified in Section 4.3, Allowable Load on Piles, but the
concrete unit stresses shall not exceed 0.3 f ¢c with a maximum of 1,600 psi. Other stresses shall conform to the
requirements of Part 2, Reinforced Concrete Design and Part 17, Prestressed Concrete.
4.4.5 CAST-IN-PLACE CONCRETE PILES (1990)
4.4.5.1 Types
Cast-in-place piles shall be cast in previously driven metal casings or shells which shall remain permanently in
place. They may be tapered or cylindrical, or a combination of tapered and cylindrical shapes.
4.4.5.2 Tapered Piles
Tapered piles shall not be less than 8 inches in diameter at the tip and shall be uniformly tapered at the rate of
not more than 1 inch in 8 feet, or step tapered, at the same average rate.
4.4.5.3 Cylindrical Piles
Cylindrical piles shall have a minimum diameter of 8 inches.
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AREMA Manual for Railway Engineering
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Concrete Structures and Foundations
4.4.5.4 Pipe Casings and Shells
a.
Pipe casings driven without a mandrel shall be formed of steel conforming to the current ASTM
Designation: A252, Grade 2. Metal shells driven with a mandrel shall have a thickness of not less than
No. 16 USMSG and a minimum yield strength of 30,000 psi. Casings shall be in one integral piece or
adequately spliced, and shall be of sufficient thickness to withstand installation pressures without
leakage or harmful distortion.
b. All piles shall be equipped with approved watertight flat plates or conical points welded to the tip end of
the casing. The end closures approved for cylindrical piles shall not project beyond the diameter of the
pile casing when used on friction piles.
4.4.5.5 Placing Concrete
a.
Casings or shells shall be inspected and approved by the engineer immediately before any concrete is
placed. A suitable light shall be used to inspect the entire length. Any accumulated foreign matter, or
water shall be removed before the concrete is placed. Any broken or otherwise defective shells shall be
corrected by removal and replacement, or by driving an additional pile, as directed by the engineer.
Concrete having a minimum compressive strength of at least 2,500 psi at 28 days shall be used to fill the
shell. The placing of the concrete shall be carried out as a continuous operation from the tip to the cutoff
elevation, and shall be performed in such a manner as to minimize segregation and insure complete
filling of the casing or shell.
b. No pile shall be driven within 15 feet of a pile that has been filled with concrete for more than 2 hours
but less than 24 hours. The driving procedure for any particular project shall be approved by the
engineer in charge, before commencing work.
4.4.5.6 Allowable Stresses
The allowable load per pile shall be determined as specified in Section 4.3, Allowable Load on Piles, but the unit
stresses, shall not exceed the following:
a.
Concrete. 0.3 of the ultimate compressive unit strength of the concrete used (f ¢c), but not to exceed 1,600
psi.
b. Steel. The unit stresses shall not exceed 12,600 psi.
4.4.5.7 Protection Against Corrosion
a.
When the steel casing is used in computing the strength of the pile and the piles will be exposed, they
shall be protected from corrosion as specified in Article 4.4.3.5.
b. If the strength of the steel is considered in computing the strength of the pile, the pile shall not be used
through active rust-inducing material or where electrolysis may occur without adequate provision for
the protection of such pile.
4.4.5.8 Reinforcement
Cast-in-place piles may be reinforced to provide needed bending strength, or for uplift anchorage. When used,
the reinforcing steel should be preassembled into cages and accurately placed in accordance with design
drawings. The reinforcement shall be clean of foreign material that could affect bond, and securely positioned
before concrete fill is placed.
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Pile Foundations
4.4.6 AUGERED CAST-IN-PLACE PILES (1990)
4.4.6.1 General
Augered Cast-In-Place piles are primarily used as friction piles. They are installed by rotating a continuous
flight hollow-shaft auger into the ground to a predetermined pile depth. High-strength mortar is pumped with
sufficient pressure as the auger is withdrawn, to fill the hole preventing hole collapse and causing the lateral
penetration of the mortar into soft or porous zones of the surrounding soil. A head of at least several feet of
mortar above the injection point is carried around the perimeter of the auger at all times during the raising of
the auger so that the high strength mortar has a displacing action removing any loose material from the hole.
4.4.6.2 Design
The length of pile will be determined from the examination of soil borings using the shear strength of the soil,
and preferably, verified by pile load tests as described in Article 4.3.6.2. Recommended pile loads for varying
pile diameters, depending on soil strengths, are given in Table 8-4-1.
Table 8-4-1. Recommended Pile Loads
Nominal Size of Pile
(Inches)
Normal Loadings Range
(Tons)
Normal Required Compression
Strength of Mortar
(PSI)
12
10-40
2,000-2,500
14
40-75
2,500-3,000
16
75-100
3,000-4,000
1
4.4.6.3 Materials
a.
3
The material used to fill the holes shall consist of a mixture of Portland Cement, concrete sand, fluidizer
and water proportioned and mixed as to provide a mortar capable of maintaining the solids in suspension
without appreciable water gain and which will laterally penetrate and fill any voids in the foundation
material. Portland Cement shall conform to Part 1, Materials, Tests and Construction Requirements,
Section 1.2, Cement. The fine aggregate shall conform to Section 1.3, Other Cementitious Materials,
with a fineness modulus between 1.40 and 3.40. Fluidizer shall meet the requirements of the current
Corps of Engineers, USA, Spec. No. CRDC 566.
b. The mortar shall be so proportioned as to have a minimum ultimate compressive strength of 2,000 psi at
28 days. A set of 6 mortar cubes shall be made each day and tested in accordance with the current ASTM
Designation: C109, with the exception that the mortar should be restrained from expansion by a top
plate.
4.4.6.4 Tension Piles
Where tension is required, a special continuous flight hollow-shaft auger shall be rotated into the ground to the
required depth. A steel bar shall be inserted into the hollow center shaft of the auger. The auger head closure
shall be detached allowing the steel bar to remain in place and be centered in the tension pile as the continuous
flight auger is slowly withdrawn from the hole. During this withdrawal process, high strength mortar shall be
placed under pressure through the space between the steel rod left in place and the wall of the hollow shaft
auger.
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AREMA Manual for Railway Engineering
8-4-13
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Concrete Structures and Foundations
SECTION 4.5 INSTALLATION OF PILES
4.5.1 DRIVEN PILES (1990)
Piles shall be driven with steam, air, or diesel powered hammers. Size of the type of hammer used should be
determined by guidelines noted in Article 4.5.1.1. The hammer shall be operated at all times at pressures and
speeds recommended by the manufacturer. Use of vibratory type hammers may be allowed if pile capacities
have been determined by load tests. Use of a gravity drop hammer for driving piles should be limited to
relatively unimportant foundations where uniform pile capacity is not critical.
4.5.1.1 Selection of Hammer-Cushion Combination
a.
Preliminary selection of the hammer-cushion combination for driving piles can be made with the
following guide:
(1) Steel Piles – Air or Steam Operated Hammers.
• Minimum size: 170 ft-lb of rated energy per ton of pile service load. Stiff or hard internal cushion.
• Desired size: 250-340 ft-lb of rated energy per ton of pile service load.
• Pile Cushion: Moderately stiff to soft (wood) internal cushion.
• Diesel Hammers:
– Use 100 to 135% of size determined for air or steam hammers.
– Use standard (stiff) internal cushion.
(2) Mandrel-Driven Piles – Same as Steel.
(3) Precast or Prestressed Concrete Piles – Air or Steam Operated Hammers.
• Desired size: 250 ft-lb of rated energy per ton of pile service load. The weight of the ram shall
generally not be less than one-fourth of the weight of the pile being driven. Use wood, or
equivalent, internal cushion.
• Pile Cushion: Design by one-dimensional wave theory, or by experience.
• Diesel Hammers:
– Use 100 to 135% of size determined for air or steam hammers.
– Use standard (stiff) internal cushion.
(4) Wood Piles – Air or Steam Operated Hammers.
• For normal capacity piles (up to 30 tons service load) excluding abnormally large timbers or
fabricated sections, use 15,000 ft-lb maximum rated energy with a wood internal cushion. Diesel
hammers may be rated up to 20,000 ft-lb with standard (stiff) internal cushions.
b. The foregoing preliminary selection of hammer and cushion combinations should preferably be
confirmed by a wave equation analysis of pile driving indicating the pile yield stresses are not exceeded
and that the desired ultimate load capacity can be achieved (see Article 4.3.5.3).
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Pile Foundations
4.5.1.2 Pile Leads
Pile drivers shall have firmly supported leads extending from the highest point to the lowest point that the
hammer must travel. The leads should be supported independently of the pile and constructed to guide and
stay the pile during driving.
4.5.1.3 Splicing
Driving shall be continued until the plan tip elevation is reached or until the rate of penetration specified is
obtained. If the proper resistance to driving is not attained at the plan cutoff, the driving shall be continued and
the additional length of pile required shall be supplied by splicing in such a way as to develop the full strength
of the section of the pile. The splice shall be made a sufficient distance, but not less than 1 foot above the
ground or water surface so that the splice can be observed during subsequent driving.
4.5.1.4 Jetting
Piles may be jetted, when permitted by the engineer, either by use of water jets alone or in combination with
the hammer. The volume and pressure of the water at the jet nozzles shall be sufficient to freely erode the
material adjacent to the pile. Before the desired penetration is reached, jetting shall be discontinued at the
elevation specified by the engineer and the piles driven to required penetration or resistance.
4.5.1.5 Preboring
Where piles must be installed through strata offering high resistance to driving, where jetting would cause
damage, to prevent excessive heaving of cohesive soils, for driving through relatively impenetrable material or
for other valid reasons, the engineer may require or permit holes to be bored with a power auger or other
equipment especially designed for the purpose. Depending upon the reasons for preboring, the diameter of the
hole shall be as directed by the engineer to obtain the proper pile penetration and carrying capacity. The pile
shall be inserted into the hole immediately after boring and be driven to required penetration or resistance.
1
4.5.1.6 Improperly Driven and Damaged Piles
Piles shall be driven within 3 inches of the plan location. Variations of more than 1/4 inch per foot from the
vertical, or from the batter line when batter piles are required, may be subject to rejection by the engineer. Any
pile so out of line or plumb as to impair its usefulness shall be pulled and/or an additional pile driven, as
required by the engineer. Any pile so injured in driving or handling as to impair its structural capacity as a pile
under conditions of use shall be replaced by a new pile, or the injured part shall be replaced by splicing or other
remedial measures–all as directed by the engineer.
4
4.5.1.7 Redriving of Heaved Piles
Previously driven piles shall be carefully checked during the driving of adjacent piles, and if any uplift occurs,
they shall be redriven to the required penetration or resistance as directed by the engineer.
4.5.1.8 Underwater Driving
While it is possible to drive piles underwater by use of a follower between the pile and hammer, or by use of a
submersible pile hammer, such driving methods should be avoided when it is necessary to drive piles to obtain a
predetermined bearing capacity, unless such capacity is determined by a pile load test under similar conditions.
4.5.1.9 Interrupted Driving
When driving is interrupted or the rate of blows retarded for any reason, a careful record shall be kept of the
extent of the delay or retardation. Any decrease in the penetration per blow immediately following such
stoppage, shall be cause to suspect the interpretation of the preceding blows per foot.
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Concrete Structures and Foundations
4.5.2 AUGERED CAST-IN-PLACE PILES (1990)
4.5.2.1 Augering Equipment
a.
The hole through which the high-strength mortar is pumped during the placement of the pile shall be
located at the bottom of the auger head below the bar containing the cutting teeth.
b. The auger flighting shall be continuous from the auger head to the top of auger with no gaps or other
breaks. The pitch of the auger flighting shall not exceed 9 inches.
c.
Augers over 40 feet in length shall contain a middle guide. The piling leads should be prevented from
rotating by a stabilizing arm.
4.5.2.2 Mixing and Pumping of High-Strength Cement Mortar
a.
Only approved pumping, continuous mixing, and agitating equipment shall be used in the preparation
and handling of the mortar. All oil or other rust inhibitors shall be removed from mixing drums and
mortar pumps. If ready-mix mortar is used, an agitating storage tank of sufficient size shall be used
between the ready-mix truck and the mortar pump to insure a homogeneous mix and continuity in the
pumping operations. All materials shall be such as to produce a homogeneous mortar of the desired
consistency. If there is a lapse in the operation, the mortar shall be recirculated through the pump.
b. The mortar pump shall be a positive displacement piston type pump capable of developing displacing
pressures at the pump of up to 350 psi.
4.5.2.3 Pile Top Encasement
Metal sleeves or casing of the proper diameter and at least 18 inches in length shall be placed around the pile
tops. (Special conditions may require metal sleeves of additional length.)
SECTION 4.6 INSPECTION OF PILE DRIVING (1994)
Pile driving and augering operations shall be inspected and documented completely as directed by the engineer.
Recommended techniques of inspection and records to be compiled can be found in the publication titled
“Inspection of Pile Driving Operations” Technical Report M-22, Department of the Army, Construction
Engineering Research Laboratory, Champaign, Illinois, July 1972.
C - COMMENTARY
The purpose of this part is to furnish the technical explanation of various Articles in Part 4, Pile Foundations.
In the numbering of Articles of this Section, the numbers after the “C-” correspond to the Section/Article being
explained.
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Pile Foundations
C - SECTION 4.1 GENERAL
C - 4.1.1 SCOPE (1994)
a.
Many texts and foundation reference sources consider drilled shafts as cast-in-place concrete piles. In
view of the special techniques required for the installation of drilled shafts as opposed to driven or
augered piles, they have been treated separately in Part 24, Drilled Shaft Foundations.
b. Since it is not often practical to obtain definitive geotechnical information for every part of a pile
foundation system, good engineering judgement and experience should be used to increase stated factors
of safety where warranted by local conditions.
C - SECTION 4.2 DESIGN
C - 4.2.1 LOADS (1994)
It is not possible to accurately predict the behavior of a combined pile and soil bearing footing. In most cases,
because of the pile supporting system, little load, including that of the footing, will be transferred to the
material directly under the footing after it has been cast. Therefore, in analysis, the pile system will be
considered as carrying all loads, with no load being transferred to the underlying soil.
C - 4.2.1.1 Primary Loads and Forces
Live loads are separated into two cases, vertical and horizontal due to surcharge, to ensure that these loads are
considered separately and in combination.
1
C - 4.2.1.2 Secondary Loads and Forces (Occasional) (Reference 89)
The effect of seismic events on pile foundation may not be limited in all cases to the additional loads imposed on
the piles. In certain types of water-bearing sands, a phenomenon referred to as soil liquefaction may be
precipitated by the vibrations induced by a seismic event or other source. When this occurs, soil shear strength
is eliminated and support for piles, both vertically and laterally, is diminished. In geographical areas susceptible
to seismic events, the potential for liquefaction should be evaluated through a competent geotechnical
investigation and measures to ensure the stability of foundations should be employed. Further discussion on
methods to predict the occurrence and extent of liquefaction may be found in the References.
4
C - 4.2.2 LOADS ON PILES (1994)
Cases A, B and C are listed to ensure that complete consideration is given to the possible failure modes of a pile
foundation. A safety factor of 2.0 is prescribed for Cases B and C for all primary loads or possible primary load
combinations. An increase of 25% in stresses or load capacity is allowed for individual piles in a foundation
system for combinations of secondary loads and primary loads except for Case C for group friction pile effect.
No increase is specified for this case due to greater relative uncertainty that is associated with its analysis when
compared to individual bearing pile analysis.
C - 4.2.6 BATTER PILES (1990) (Reference 79 and 94)
a.
It is intended that battered piles be used to resist lateral foundation loads due to primary forces. Where
this is not practical, the lateral resistance of vertical piles can be utilized to resist horizontal forces. The
engineer should make a careful evaluation of the pile foundation system to ascertain its lateral
resistance capacity. Much research has been done concerning the lateral resistance of vertical piles. The
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Concrete Structures and Foundations
FHWA Manual on Design of Piles and Drilled Shafts Under Lateral Load should be consulted for the
design of such pile foundations.
b. Cases A, B and C of Article 4.2.2 should be evaluated for lateral loads on vertical piles. Recent research
has indicated that under certain conditions that may be encountered during a seismic event, battered
piles should not be used. The designer should consult the AASHTO “Standard Specifications for Seismic
Design” for guidance.
C - 4.2.7 SCOUR (1990) (Reference 30, 31 and 37)
Research is continuing into the prediction of the occurrence and extent of scour. The FHWA Technical Advisory,
Scour at Bridges and publication RD78-162, Countermeasures for Hydraulic Problems at Bridges, provide
references for scour analysis.
C - SECTION 4.3 ALLOWABLE LOAD ON PILES
C - 4.3.5.3 Wave Equation (Reference 91)
The Wave Equation method of analyzing pile capacity and pile length was developed by Smith (1960). For a
detailed explanation of the Wave Equation methodology, the designer may consult FHWA documentation of the
WEAP program.
C - 4.3.5.4 Pile Driving Formulas
Historically, pile driving formulas which make use of the relationship between the hammer energy and the pile
movement when driven have been used to approximate safe pile loads. Most notably, the Engineering News
Record formula has been used extensively for this purpose. Tests have shown that these formulas do not give
consistent results whereby excessive pile lengths may be dictated in some instances while in others insufficient
factors of safety may result from their use. For these reasons, the use of these formulas should be limited to
projects whose size and importance may justify their use in lieu of the more elaborate Wave Equation method.
When these formulas are to be used, their application should be guided by good engineering judgement and
experience. Careful evaluation of the actual hammer energy applied to the pile through the hammer-pile
cushion-pile system is also required.
C - SECTION 4.4 PILE TYPES
C - 4.4.2 Timber Piles (1990)
Timber piles shall be of a length which will allow driving to the minimum specified tip elevation and which also
will allow the complete removal of timber damaged by driving.
C - 4.4.3.6 Allowable Stresses
The compressive stress at the tip of steel H-piles has been limited to 12,600 psi for design loads. It should be
recognized that stresses during driving may considerably exceed this stress. The Wave Equation formula can
predict these driving stresses. In general, driving stresses should be limited to 0.8 of the yield strength of the
pile steel.
C - 4.4.5.4 Pipe Casings and Shells
Where the pipe casing or shell is to serve only as a form for the cast-in-place concrete piles, the steel thickness
need only be sufficient to withstand soil pressures and driving forces subject to the stated minimum thickness
and strength for mandrel driven piles. If the casing or shell is to be used to compute the structural capacity of
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Pile Foundations
the pile, the plans must show the steel thickness to be used and also splicing details and the grade of steel to be
used.
C - SECTION 4.5 INSTALLATION OF PILES
C - 4.5.1.3 Splicing
a.
Piles may be spliced in a variety of methods to fully develop the strength of the pile section. The
following methods may be employed:
b. Steel Piles. The method of splicing shall be shown on the plans or as approved by the engineer. Piles may
be spliced by full penetration butt welds, by the addition of welded splice plates, by a combination of
these methods or by other means approved by the engineer which fully maintains the strength of the pile
section.
c.
Concrete Piles. Concrete piles shall preferably not be spliced, unless specifically provided for by the plans,
special provisions or by the engineer in writing. Short extensions may be added to tops of reinforced
concrete piles after completion of driving when the required capacity is not attained at the planned top of
pile elevation. These extensions shall be made by exposing the pile reinforcing steel a sufficient distance
to provide a full strength lap splice with the extension segment steel. Concrete for the extension shall be
of the same quality and strength of the pile concrete and shall be placed in forms of the same shape and
dimensions as the driven pile. Prior to placement of the new concrete, the top of the driven pile shall be
cleaned and coated with neat cement or an approved bonding agent.
1
C - SECTION 4.6 INSPECTION OF PILE DRIVING (1994) (Reference 106)
Other useful documents to aid in inspection of the pile driving may be found in:
• The Performance of Pile Driving Systems: Inspection Manual, FHWA RD-86-160.
3
• Inspectors Manual for Pile Foundations and A Pile Inspector’s Guide to Hammers, from the:
Deep Foundation Institute
P.O. Box 359
Springfield, NJ 07081
4
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Part 5
Retaining Walls, Abutments and Piers
— 2002 —
TABLE OF CONTENTS
Section/Article
Description
Page
5.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1.1 Types of Retaining Walls, Abutments and Piers (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.1.2 Scour (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-2
8-5-2
8-5-3
5.2 Information Required. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.1 Field Survey (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.2 Subsurface Exploration (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.3 Controlling Dimensions (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.4 Loads (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.5 Type of Backfill (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2.6 Character of Foundation (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-4
8-5-4
8-5-4
8-5-4
8-5-4
8-5-4
8-5-5
5.3 Computation of Applied Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.1 Loads Exclusive of Earth Pressure (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3.2 Computation of Backfill Pressure (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-5
8-5-5
8-5-6
5.4 Stability Computation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4.1 Point of Intersection of Resultant Force and Base (2002) . . . . . . . . . . . . . . . . . . . . . . . . .
5.4.2 Resistance Against Sliding (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4.3 Soil Pressure (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4.4 Settlement and Tilting (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-7
8-5-7
8-5-7
8-5-8
8-5-8
5.5 Design of Backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5.1 Drainage (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5.2 Compaction (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-8
8-5-8
8-5-8
5.6 Designing Bridges to Resist Scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.6.1 Design Philosophy and Concepts (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.6.2 Design Considerations (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.6.3 Design Procedure (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-9
8-5-9
8-5-9
8-5-9
5.7 Details of Design and Construction for Abutments and Retaining Walls . . . . . . . . . .
5.7.1 General (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.7.2 Cantilever Walls (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-11
8-5-11
8-5-11
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-5-1
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3
Concrete Structures and Foundations
TABLE OF CONTENTS (CONT)
Section/Article
Description
Page
Counterfort and Buttress Walls (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-11
5.8 Details of Design and Construction for Bridge Piers . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.8.1 Pier Spacing, Orientation and Type (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.8.2 Pier Shafts (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.8.3 Caissons (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.8.4 Bearings and Anchorage (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.8.5 Piers in Navigable Streams (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-12
8-5-12
8-5-12
8-5-13
8-5-13
8-5-13
Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-13
5.7.3
LIST OF FIGURES
Figure
Description
Page
C-8-5-1 Cases 1, 2 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C-8-5-2 Cases 4, 5 and 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C-8-5-3 Cases 7, 8 and 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C-8-5-4 Earth Pressure Computation – Walls with Heels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C-8-5-5 Earth Pressure Computation – Walls without Heels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C-8-5-6 Earth Pressure Charts for Walls Less than 20 Feet High . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-16
8-5-17
8-5-18
8-5-21
8-5-22
8-5-26
LIST OF TABLES
Table
8-5-1
8-5-2
Description
Page
Types of Backfill for Retaining Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Properties of Backfill Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-5
8-5-6
SECTION 5.1 DEFINITIONS
5.1.1 TYPES OF RETAINING WALLS, ABUTMENTS AND PIERS (2002)
a.
A retaining wall is a structure used to provide lateral support for a mass of soil which, in turn, may
provide vertical support for loads acting on or within the soil mass.
b. The principal types of retaining walls are as follows:
(1) The gravity wall, which is so proportioned that no reinforcement other than temperature steel is
required.
(2) The semi-gravity wall, which is so proportioned that some steel reinforcement is required along the
back and along the lower side of the toe.
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AREMA Manual for Railway Engineering
Retaining Walls, Abutments and Piers
(3) The cantilever wall, which has a cross section resembling an L or an inverted T, and which requires
extensive steel reinforcement.
(4) The counterfort wall, which consists of a reinforced vertical face slab supported laterally at intervals
by vertical reinforced counterforts extending into the backfill and supported by a reinforced base
slab which usually projects in front of the face slab to form a toe.
(5) The buttress wall, which is similar to the counterfort wall except that the vertical members, called
buttresses, are exposed on the face of the wall rather than buried in the backfill.
(6) The crib wall, which consists of an earth-filled assembly of individual structural units, and which
relies for its stability on the weight and strength of the earth fill. The design of such walls is treated
in Part 6, Crib Walls.
(7) Mechanically Stabilized Embankments (MSE) are covered by Part 7, Mechanically Stabilized
Embankment of this Chapter.
c.
An abutment commonly consists of a retaining wall that incorporates a bridge seat in its face. It may also
be of the spill-through type in which the bridge seat rests on horizontal beams supported by piles or
columns between which the fill is permitted to extend. Preferably, abutments shall be of the gravity or
semi-gravity type.
d. A pier is an intermediate support for the superstructure. The principal pier types are:
1
(1) Solid wall, reinforced for strength and temperature.
(2) Rigid frame, consisting of multiple columns with a cap reinforced to act as a frame.
(3) Bents, consisting of multiple piles extended to a cap.
(4) Hammerhead, consisting of a column supporting a cap which cantilevers beyond the column.
3
(5) Drilled shafts, consisting of poured concrete columns extending to a cap.
5.1.2 SCOUR (2002)1
Scour is the result of the erosive action of flowing water excavating and carrying away material from the bed
and banks of waterways. There are three types of scour all of which are likely to be present at a structure.
a.
Aggradation and Degradation. These are long term streambed elevation changes due to natural or man
induced causes within the reach of the river over which the bridge is located. Aggradation involves the
deposition of material eroded from other sections of a stream reach, whereas degradation involves the
lowering or scouring of the bed of a stream.
b. Contraction Scour.2 Contraction scour in a natural channel involves the removal of material from the
bed and banks across all or most of the channel width. This component of scour results from a
contraction of the flow, such as a change in downstream control of the water surface elevation. Increased
velocities and a resulting increase in bed shear stresses cause scour. Contraction of the flow by bridge
approach embankments encroaching onto the floodplain and/or into the main channel is the most
common cause of contraction scour.
1
2
See Commentary
See Commentary
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
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Concrete Structures and Foundations
c.
Local scour.1 Local scour involves removal of material from around piers, abutments, spurs, and
embankments. It is caused by an acceleration of flow and resulting vortices induced by flow
obstructions.
SECTION 5.2 INFORMATION REQUIRED
5.2.1 FIELD SURVEY (2002)
a.
Sufficient information shall be furnished, in the form of a profile and cross-sections or a topographic
map, to determine the structural requirements. Present grades and alignments of tracks and roads shall
be indicated, together with the records of high water, low water, and depth of scour, the location of
underground utilities, change in channel location characteristics, site history from local sources, and
information concerning the structures that may affect or be affected by this construction.
b. For bridge construction at a new location, a complete survey is required as detailed in Part 3, Spread
Footing Foundations, Article 3.2.1.
5.2.2 SUBSURFACE EXPLORATION (2002)
a.
Sufficient borings shall be made along the length of the structure to determine, with a reasonable degree
of certainty, the subsurface conditions. Irregularities found during the initial soil boring program may
dictate that additional borings be taken.
b. The subsurface investigation shall be made in accordance with the provisions of Part 22, Geotechnical
Subsurface Investigation.
5.2.3 CONTROLLING DIMENSIONS (1989)
Information shall be assembled concerning clearances, proposed grades of tracks and roads, and all other
factors that may influence the limiting dimensions of the proposed structure.
5.2.4 LOADS (2002)
Loads to be superimposed on piers, retaining walls, abutments, or on backfill, shall be determined and
indicated on the plans. See Part 2, Reinforced Concrete Design and Chapter 9 for seismic loading.
5.2.5 TYPE OF BACKFILL (2002)2
a.
Backfill is defined as all material behind the wall, whether undisturbed ground or fill, that contributes to
the pressure against the wall.
b. The backfill shall be investigated and classified with reference to the soil types described in
Table 8-5-1.
1
2
See Commentary
See Commentary
© 2011, American Railway Engineering and Maintenance-of-Way Association
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AREMA Manual for Railway Engineering
Retaining Walls, Abutments and Piers
Table 8-5-1. Types of Backfill for Retaining Walls
Backfill
Type
1
2
3
4
5
c.
Backfill Description
Coarse-grained soil without admixture of fine soil particles, very freedraining (sand, gravel or broken stone).
Coarse-grained soil of low permeability due to admixture of particles of silt
size.
Fine silty sand; granular materials with conspicuous clay content; or residual
soil with stones.
Soft or very soft clay, organic silt; or soft silty clay.
Medium or stiff clay that may be placed in such a way that a negligible
amount of water will enter the spaces between the chunks during floods or
heavy rains.
Types 4 and 5 backfill shall be used only with the permission of the Engineer. In all cases the wall design
shall be based on the type of backfill used.
5.2.6 CHARACTER OF FOUNDATION (2002)
The character of the foundation material shall be investigated as specified under Part 3, Spread Footing
Foundations of Article 3.2.4. Where pile supported foundations are required, the provisions of Article 4.3.1 of
Part 4, Pile Foundations, shall be followed for the necessary subsurface investigation.
1
3
SECTION 5.3 COMPUTATION OF APPLIED FORCES
5.3.1 LOADS EXCLUSIVE OF EARTH PRESSURE (2002)
a.
In the analysis of piers, retaining walls and abutments, due account shall be taken of all superimposed
loads carried directly on them, such as building walls, columns, or bridge structures; and of all loads
from surcharges caused by railroad tracks, highways, building foundations, or other loads supported on
the backfill. Piers must also be designed for stream flow pressures as well as ice flow pressures and
collision forces where applicable.
b. In calculating the surcharge due to track loading on an abutment and on wingwalls that are in line with
the abutment backwalls, the entire load shall be taken as distributed uniformly on the surface of the
ballast immediately below the tie, over a width equal to the length of the tie. With increased depth, the
width for distribution can be increased on slopes of 1 horizontal to 2 vertical, with surcharge loads from
the adjacent tracks not being permitted to overlap.
c.
To account for variability in backfilling and the dynamic effects of axle loads, abutment backwalls above
bridge seats shall be designed for earth pressures and live load surcharge increased by 100%. This does
not apply to the portion of the abutment below the bridge seat nor the stability of the abutment.
d. In calculating the surcharge due to track loading above a wall and parallel, or roughly parallel, to the
wall, the entire load shall be taken as distributed uniformly over a width equal to the length of the tie.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
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Concrete Structures and Foundations
e.
The stability of the abutment or wall as a whole unit, regardless of the distribution of the loads and
surcharges, shall always be checked and shall conform to the requirement of Section 5.4, Stability
Computation.
f.
Live load impact shall not be considered in the design of an abutment or pier unless the bridge bearings
are supported by a structural beam, such as the seat of a spill-through abutment or a pier cap supported
by individual columns, piles, or shafts. In such a case, the impact shall be applied to the beam only, and
not to footings, or piles.
g.
For the design of abutments and piers, consideration must be given to all forces transmitted from the
superstructure to the substructure, depending on the bearing fixity conditions.
5.3.2 COMPUTATION OF BACKFILL PRESSURE (2002)1
a.
Values of the unit weight, cohesion, and angle of internal friction of the backfill material shall be
determined directly by means of soil tests or, if the expense of such tests is not justifiable, by means of
Table 8-5-2 referring to the soil types defined in Table 8-5-1. Unless the minimum cohesive strength of
the backfill material can be evaluated reliably, the cohesion shall be neglected and only the internal
friction considered. See Part 20, Flexible Sheet Pile Bulkheads, Table 8-20-3.
Table 8-5-2. Properties of Backfill Materials
Type of Unit Weight Cohesion
Backfill Lb. Per Cu. Ft.
“c”
Angle of Internal
Friction
1
105
0
33° 42¢ (38° for broken stone)
2
110
0
30°
3
125
0
28°
4
100
0
0°
5
120
240
0°
b. The magnitude, direction and point of application of the backfill pressure shall be computed on the basis
of appropriate values of the unit weight, cohesion and internal friction.
c.
When the backfill is assumed to be cohesionless and when 1) the surcharge load, if any, on the backfill
can be converted into an equivalent uniform load or when 2) the surcharge can be converted into an
equivalent uniform earth surcharge, Rankine’s or Coulomb’s formulas may be used under the conditions
to which each applies. Formulas and charts given in the Commentary and the trial wedge methods given
in the Commentary are both applicable.
d. When the backfill cannot be considered cohesionless, when the surcharge on the backfill is irregular, or
when the surcharge cannot be converted to an equivalent uniform earth surcharge, the trial wedge
methods illustrated in the Commentary are preferable.
1
e.
If the wall or abutment is not more than 20 ft. high and if the backfill has been classified according to
Table 8-5-1, the charts given in the Commentary may be used.
f.
If the surcharge is of a lesser width than the height of the wall, a more satisfactory design can be
obtained by the use of trial wedge methods given in the Commentary.
See Commentary
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AREMA Manual for Railway Engineering
Retaining Walls, Abutments and Piers
g.
If the wall or abutment is prevented from deflecting freely at its crest, as in a rigid frame bridge, some
types of U-shaped abutments, or in laterally braced or anchored walls, the computed backfill pressure
shall be increased 25%.
h. In spill-through abutments, the increase of pressure against the columns due to the shearing strength of
the backfill shall not be overlooked. If the space between columns is not greater than twice the width
across the back of the columns, no reduction in backfill pressure shall be made on account of the
openings. No more than the active earth pressure shall be considered as the resistance offered by the fill
in front of the abutment. In computing the active earth pressure of this fill, the negative or descending
slope of the surface shall be taken into consideration.
i.
The backfilled areas behind a wall or abutment shall be designed to dissipate water pressures by the use
of free-draining backfill material in conjunction with drains. It is preferable that the free-draining
backfill material be used within a wedge behind the wall, bounded by a plane rising at 60 degrees to the
horizontal.
j.
If local conditions do not permit the construction of drains and, consequently, water may accumulate
behind the wall, the resulting additional pressure shall be taken into account. Consideration should also
be given to the eventual plugging of the drains due to infiltration of soil.
SECTION 5.4 STABILITY COMPUTATION
1
5.4.1 POINT OF INTERSECTION OF RESULTANT FORCE AND BASE (2002)
The resultant force on the base of a wall or abutment shall fall within the middle third of the structure if
founded on soil, and within the middle half if founded on rock or piles. The resultant force on any horizontal
section above the base of a solid gravity wall should intersect this section within its middle half. If these
requirements are satisfied, safety against overturning need not be investigated.
3
5.4.2 RESISTANCE AGAINST SLIDING (2002)
a.
The factor of safety against sliding at the base of the structure is defined as the sum of the forces at or
above base level available to resist horizontal movement of the structure divided by the sum of the forces
at or above the same level tending to produce horizontal movement. The numerical value of this factor of
safety shall be at least 1.5. If the factor of safety is inadequate, it shall be increased by increasing the
width of the base, by the use of a key, or by the use of batter piles.
b. In computing the resistance against sliding, the passive earth pressure of the soil in contact with the face
of the wall shall be neglected. The frictional resistance between the wall and a non-cohesive subsoil may
be taken as the normal force on the base times the coefficient of friction f of mass concrete on soil. For
coarse-grained soil without silt, f may be taken as 0.55; for coarse-grained soil with silt, 0.45; for silt,
0.35.
c.
If the wall rests upon clay, the resistance against sliding shall be based upon the cohesion of the clay,
which may be taken as one-half the unconfined compressive strength. If the clay is very stiff or hard the
surface of the ground shall be roughened before the concrete is placed.
d. If the wall rests upon rock, consideration shall be given to such features of the rock structure as may
constitute surfaces of weakness. For concrete on clean sound rock the coefficient of friction may be taken
as 0.60.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-5-7
4
Concrete Structures and Foundations
e.
The factor of safety against sliding on other horizontal surfaces below the base shall be investigated and
shall not be less than 1.5.
5.4.3 SOIL PRESSURE (1989)
The allowable soil pressure beneath the footing shall be determined in accordance with Part 3, Spread Footing
Foundations.
5.4.4 SETTLEMENT AND TILTING (2002)1
a.
The soil pressure determined in accordance with Article 5.4.3 provide for adequate safety against failure
of the soil beneath the structure. If the subsoil consists of soft clay or silt, or if a layer of such material
lies beneath the subsoil and is within the pressure zone of influence generated by the base pressure, it is
necessary to determine the compressibility of the soil and to estimate the amount of settlement.
b. If the compressibility of the subsoil would lead to excessive settlement or tilting, the movement can be
reduced by designing the wall so that the resultant of the forces acting at the base of the wall intersects
the base near its midpoint. Otherwise, pile foundations shall be considered.
SECTION 5.5 DESIGN OF BACKFILL
5.5.1 DRAINAGE (2002)
a.
The material immediately adjacent to the wall should be noncohesive and free draining. Cinders shall
not be used. If a special back drain is installed, the pore size within the drain shall be coarse enough to
permit free flow of water, but not so coarse that the fill material may ultimately move into it and clog it.
Water from the free-draining materials shall be removed, preferably by horizontal drain pipes or by weep
holes. Horizontal drain pipes, if used, shall be installed in such a position that they will function
properly. Such drains shall be accessible for cleaning. Weep holes are considered less satisfactory than
horizontal drains. If used, they shall have diameters not less than 6 inches and shall be spaced not over
10 feet.
b. Geocomposite and/or geotextile materials in conjunction with free draining backfill may be used as
approved by the Engineer.
5.5.2 COMPACTION (2002)
a.
The backfill shall preferably be placed in loose layers not to exceed 12 inches in thickness. Each layer
shall be compacted before placing the next, but overcompaction shall be avoided.2
b. It is recommended that backfill be compacted to no less than 95% of maximum dry density per ASTM
D698 and at a moisture content within 2% of optimum.
c.
1
2
No dumping of backfill material shall be permitted in such a way that the successive layers slope
downward toward the wall. The layers shall be horizontal or shall slope downward away from the wall.
See Commentary
See Commentary
© 2011, American Railway Engineering and Maintenance-of-Way Association
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AREMA Manual for Railway Engineering
Retaining Walls, Abutments and Piers
SECTION 5.6 DESIGNING BRIDGES TO RESIST SCOUR
5.6.1 DESIGN PHILOSOPHY AND CONCEPTS (2002)1
Bridges shall be designed through careful evaluation of the hydraulic, structural, and geotechnical aspects of
the bridge foundation to withstand the effects of scour from the design flood.
5.6.2 DESIGN CONSIDERATIONS (2002)
5.6.2.1 General
a.
Scour types are additive. The design shall provide for the total of all scour types at a location. Local
scour holes at piers and abutments may overlap one another. If scour holes do overlap, the local scour
shall be the total depth from both.2
b. For pile and drilled shaft designs subject to scour, consideration shall be given to using a lesser number of
longer piles or shafts as compared with a greater number of shorter piles or shafts to develop bearing
loads. This approach will provide a greater factor of safety against pile failure due to scour.
5.6.2.2 Piers
a.
Pier foundations not in the exisiting channel shall be designed in the same manner as the pier
foundations in the stream channel if there is likelihood that the channel will shift its location to include
such piers.
1
b. Consideration shall be given to changes in the flow direction during floods when determining shape and
orientation of piers.3
c.
The effects of ice and debris build-up shall be evaluated when considering use of piers in stream
channels. Use ice and debris deflectors where appropriate.4
3
5.6.2.3 Abutments
a.
Relief openings, spur dikes, and river channelization should be used where needed to minimize the
effects of adverse flow conditions at abutments.
b. Utilize riprap or other protection devices where needed to protect abutments.
c.
4
Where ice build-up is likely to be a problem, set the toe of spill-through slopes or vertical abutment walls
some distance from the edge of the channel bank to facilitate passage of the ice.
5.6.3 DESIGN PROCEDURE (2002)5
The design procedure for scour outlined in the following steps is recommended for bridge substructure units:
1
See Commentary
See Commentary
3 See Commentary
4 See Commentary
5 See Commentary
2
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(1) Select the design flood event(s). Also check the overtopping flood (if less than the design flood) and
other flood events if there is evidence that such events would create deeper scour than the design
flood or overtopping floods.1
(2) Develop water surface profiles for the flood flows in Step 1, taking care to evaluate the range of
potential tailwater conditions below the bridge which could occur during these floods.
(3) Estimate total scour for the worst condition from Steps 1 and 2 above.
(4) Plot the total scour depths obtained in Step 3 on a cross section of the stream channel and flood plain
at the bridge site.
(5) Evaluate the scour depths obtained in Steps 3 and 4 for reasonableness.2
(6) Evaluate the bridge on the basis of the scour analysis performed in Steps 3-5. Modify the design as
necessary.3
(7) Analyze the bridge foundation on the basis that all stream bed material in the scour prism above the
total scour line (Step 4) has been removed and is not available for bearing or lateral support. In the
case of a pile foundation, the piling shall be designed for reduced lateral restraint and column action
because of the increase in unsupported pile length after scour. In areas where the local scour is
confined to the proximity of the footing, the lateral ground stresses on the pile length that remains
embedded may not be significantly reduced from the pre-local scour conditions. The depth of local
scour and volume of soil removed from above the pile group shall be considered when computing pile
embedment to sustain vertical load.
(a) Spread Footings on Soil.
Place the top of the footing below the design scour line.
The bottom of the footing shall be at least 6.0 feet below the streambed.
(b) Spread Footings on Rock Highly Resistant to Scour.4
The bottom of the footing shall be placed directly on the cleaned rock surface for massive rock
formations (such as granite) that are highly resistant to scour.
(c) Spread Footings on Erodible Rock.
Carefully assess weathered or other potentially erodible rock formations for scour prior to
determining footing elevation.
(d) Spread Footings Placed on Tremie Seals and Supported on Soil.
The tremie base shall be placed at least three feet below the scour line if the tremie is structurally
capable of sustaining the imposed structural load without lateral soil support.
(e) Deep Foundations (Piling or Drilled Shafts) with Footings.5
1
See Commentary
See Commentary
3 See Commentary
4 See Commentary
5 See Commentary
2
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Preferably place the top of the footing or pile cap below the streambed a depth equal to the estimated
contraction scour depth to minimize obstruction to flood flows and resulting local scour.
(8) For certain locations and conditions it may be necessary to calculate the scour for a superflood. See
the Commentary for further discussion of superfloods.
SECTION 5.7 DETAILS OF DESIGN AND CONSTRUCTION FOR ABUTMENTS AND
RETAINING WALLS
5.7.1 GENERAL (2002)
a.
The principles of design and permissible unit stresses for walls and abutments shall conform to Part 2,
Reinforced Concrete Design, with the modifications or additions in the following Articles:
b. The width of the stem of a semi-gravity wall, at the level of the top of the footing shall be at least onefourth of its height.
c.
The base of a retaining wall, or abutment supported on soil shall be located below frost line, and in no
case at a depth less than 3 ft. below the surface of the ground in front of the toe. The base shall be located
below the anticipated maximum depth of scour. Where this is not practicable the base shall be supported
by piles or other suitable means.
1
d. To reduce temperature and shrinkage cracks in exposed surfaces, reinforcement shall be provided as
specified in Part 2 of this Chapter, irrespective of the type of structure.
e.
The backs of retaining walls and abutments shall be damp-proofed by an approved material. Particular
attention shall be given to protection of the joint where the bottom of stem meets the top of heel.
f.
At horizontal joints between the bases and stems of piers and retaining walls, raised keys should be used.
In lieu of raised shear keys, shear friction may be used.
g.
Vertical keyed expansion joints shall be placed not over 60 ft. apart to take care of temperature changes.
They shall be protected by membrane waterproofing or noncorrosive water stops.
h. The walls above the footings shall be cast as units between expansion joints, unless construction joints
are formed in accordance with the provisions of these specifications.
5.7.2 CANTILEVER WALLS (2002)
a.
The unsupported toe and heel of the base slab shall each be considered as a cantilever beam fixed at the
edge of the support.
b. The vertical section shall be considered as a cantilever beam fixed at the top of the base.
5.7.3 COUNTERFORT AND BUTTRESS WALLS (2002)
a.
The face walls of counterfort and buttress walls and parts of base slabs supported by the counterforts or
buttresses shall be designed in accordance with the requirements of a continuous slab, Part 2 of this
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4
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Chapter. Due allowance shall be made for the effect of the toe moment on shears and bending moments
in the heel slabs of counterfort walls.
b. Counterforts may be designed in accordance with the requirements of T-beams. As T-beams,
reinforcement or stirrups shall be provided to anchor the face slabs and the heel slabs to the
counterforts. Reinforcement shall be proportioned to carry the end shears of the slabs. Stirrups shall be
anchored as near to the outside face of the face walls and as near to the bottom of the base slab as the
requirements for the protective covering permit. It is desirable to run reinforcing bars through the loops
of U-shaped stirrups.
c.
Buttresses shall be designed in accordance with the requirements for rectangular beams.
SECTION 5.8 DETAILS OF DESIGN AND CONSTRUCTION FOR BRIDGE PIERS
5.8.1 PIER SPACING, ORIENTATION AND TYPE (2002)
5.8.1.1 Grade Separation Structures
a.
Piers shall be located to provide the required horizontal and vertical clearances for traffic (highway,
railway or other), to accommodate underground utilities and structures, and to permit the maintenance
of surface drainage and other surface facilities.1
b. Piers supporting bridges over railways and located less than 25 feet clear from centerline of the near
railroad track shall be provided with pier protection conforming with the requirements of Part 2, this
Chapter.
5.8.1.2 Structures over Waterways
a.
Where possible, the bridge pier axis should be parallel to the direction of the flow. When this is not
feasible, special consideration must be given to additional loads placed on the substructure by the nonparallel flow. Consideration shall also be given to scour effects.
b. Where piers are exposed to heavy flows, or ice and debris collisions, consideration should be given to
longer span lengths, the use of nose guards, starlings, or other systems to protect against damage to the
structures.
5.8.2 PIER SHAFTS (2002)
a.
Design of concrete piers shall be in accordanc with Part 2, Reinforced Concrete Design. Piers consisting
of piles or drilled shafts shall be in accordance with Part 4, Pile Foundations and Part 24, Drilled Shaft
Foundations of this Chapter.
b. The bridge seat/pier cap shall be of sufficient size to keep bearing stresses within allowances and provide
adequate edge distances.2
1
2
See Commentary
See Commentary
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c.
The depths of a pier footing shall not be less than the depth of frost penetration in that part of the
country (see Part 3, Spread Footing Foundations of this Chapter) and not less than 3 feet below grade
unless founded on solid, nonerodible rock.
5.8.3 CAISSONS (2002)
Caisson design shall meet all of the design requirements for transferring the loads from the substructure
element being supported to the soil without exceeding allowable stresses and soil pressures. In addition,
caissons shall be designed for (1) stresses during sinking, including, but not limited to, lateral soil pressures
and unequal hydrostatic pressure; (2) adequate weight or other means of overcoming skin friction of the soil;
and (3) means of support during the tremie sealing operation.
5.8.4 BEARINGS AND ANCHORAGE (2002)
The design of bearings and anchorage for steel spans shall be in accordance with Chapter 15 and Part 2,
Reinforced Concrete Design. Any uplift forces caused by buoyancy or the use of continuous spans shall be
considered in the design of a pier and its components with particular emphasis on anchorage of the
superstructure. Anchorage that is subject to uplift forces shall be designed to develop a minimum of one and
one-half times the calculated force.
5.8.5 PIERS IN NAVIGABLE STREAMS (2002)1
a.
Consideration shall be given to collision damage. Piers shall be of sufficient size and mass to withstand a
reasonable anticipated collision or be protected in accordance with Part 23, Pier Protection Systems at
Spans Over Navigable Streams.
1
b. Unprotected piers shall be solid structures capable of resisting collision impacts in all directions
including torsion.
3
COMMENTARY
The purpose of this part is to furnish the technical explanation of various articles in Part 5, Retaining Walls,
Abutments and Piers. In the numbering of articles in this section, the numbers after the “C-” correspond to the
section/article being explained.
4
C - SECTION 5.1 DEFINITIONS
C - 5.1.2 SCOUR (2002)
Different materials scour at different rates. Loose granular soils are rapidly eroded by flowing water, while
cohesive or cemented soils are more scour resistant. However, ultimate scour in cohesive or cemented soils can
be as deep as scour in sandbed streams. Scour will reach its maximum depth in sand and gravel bed material in
hours; cohesive bed material in days; glacial tills, sandstones and shales in months; limestones in years and
dense granites in centuries. Massive rock formations with few discontinuities are highly resistant to scour
during the lifetime of a typical bridge. Scour holes may not be visible during low water stages.
b.
1
Contraction scour occurs when the flow area of a stream at flood stage is decreased from the normal,
either by a natural constriction or by a bridge. With the decrease in flow area there is an increase in
average velocity and bed shear stress. Hence, there is an increase in stream power at the contraction
See Commentary
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and more bed material is transported from the contracted reach than is transported into the reach. This
increase in the transport of bed material lowers the bed elevation.
Contraction scour is typically cyclic. That is, the bed scours during the rising stage of a runoff event, and fills
on the falling stage.
Other factors that can cause contraction scour are: (1) a natural stream constriction, (2) long embankment
approaches over the flood plain to the bridge, (3) ice formation or jams, (4) a natural berm forming along the
banks due to sediment deposits, (5) island or bar formations upstream or downstream of the bridge opening, (6)
debris, and (7) the growth of vegetation in the channel or flood plain.
In a natural channel, the depth of flow is always greater on the outside of a bend. In fact, there may well be
deposition on the inner portion of the bend. If a bridge is located on or close to a bend, the contraction scour
will be concentrated on the outer part of the bend.
C - 5.1.2 (c) Local Scour
Local scour is caused by the formation of vortices at the base of an abutment or pier. The formation of these
vortices results from the pileup of water on the upstream face and the acceleration of the flow around the pier
or abutment. The action of the vortex removes bed material from the area around the base of the pier. As the
depth of the resulting scour hole increases, the strength of the vortex decreases and equilibrium is eventually
reached.
Factors affecting local scour are:
a.
Pier width has a direct influence on depth of local scour. As width of the pier perpendicular to the flow
increases, there is an increase in scour depth.
b. Projected length of an abutment into the stream affects the depth of local scour. An increase in the
projected length of an abutment into the flow increases scour. However, there is a limit on the increase
in scour depth with an increase in length. This limit is reached when the ratio of projected length into
the flow to the depth of the approach flow is 25.
c.
Pier length has no appreciable effect on local scour depth as long as the pier is aligned with the flow.
When the pier is skewed to the flow, the length has a significant effect; i.e., with the same angle of attack,
doubling the length of the pier increases scour depth 33 percent.
d. Flow depth has an effect on the depth of local scour. An increase in flow depth can increase scour depth
by a factor of 2 or greater for piers. With abutments the increase is from 1.1 to 2.15 depending on the
shape of the abutment.
e.
The approach flow velocity affects scour depth-the greater the velocity, the deeper the scour.
f.
Bed material characteristics such as grain size, gradation, and cohesion can affect local scour. Variation
in bed material within the sand size range has no effect on local scour depth. Larger size bed material
that can be moved by the flow or by the vortices and turbulence created by the pier or abutment will not
affect the maximum scour depth but only the time it takes to attain it. Very large particles in the bed
material, such as cobbles or boulders, may armor the scour hole.
Fine bed material (silts and clays) will have scour depths as deep as sand bed streams. This is true even
if bonded together by cohesion. The effect of cohesion is to influence the time it takes to reach the
maximum scour. With sand bed material, the maximum depth of scour is reached in hours and can
result from a single flood event. With cohesive bed materials it may take days, months, or even years to
reach the maximum scour depth, the result of many flood events.
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g.
The angle of attack of the flow to the pier or abutment has a significant effect on local scour, as was
pointed out in the discussion of pier length. Abutment scour is reduced when embankments are angled
downstream and increased when embankments are angled upstream.
h. Shape of the nose of a pier or an abutment has a significant effect on scour. Streamlining the front end
of a pier reduces the strength of the horseshoe vortex, thereby reducing scour depth. Streamlining the
downstream end of piers reduces the strength of the wake vortices. A square-nose pier will have
maximum scour depths about 20 percent greater than a sharp-nose pier and 10 percent greater than
either a cylindrical or round nose pier.
i.
Full retaining abutments with vertical walls on the streamside (parallel to the flow) will produce scour
depths about double that of spill-through abutments.
j.
Ice and debris accumulations potentially increase the effective width of the piers, change the shape of
piers and abutments, increase the projected length of an abutment, and cause the flow to plunge
downward against the bed. This can increase both the local and contraction scour. The magnitude of the
increase is still largely undetermined. Debris can be taken into account in the scour equations by
estimating how much debris will increase the width of the pier or length of an abutment. Debris and ice
effects on contraction scour can also be accounted for by estimating the amount of flow blockage
(decrease in width of the bridge opening) in the equations for contraction scour.
C - SECTION 5.2 INFORMATION REQUIRED
1
C - 5.2.5 TYPE OF BACKFILL (2002)
Type 1 backfill shall be used where feasible. Types 2 and 3, in declining order of preference, may be used due to
economic or other considerations.
C - SECTION 5.3 COMPUTATION OF APPLIED FORCES
3
C - 5.3.2 COMPUTATION OF BACKFILL PRESSURE (2002)
I. EARTH PRESSURE FORMULAS FROM RANKINE-COULOMB THEORIES
a.
The following formulas are applicable only to materials that may be considered cohesionless.
(1) Cases 1 to 3 are for vertical walls without heels. The pressure P is the same as the pressure on a
vertical plane in the backfill (Figure C-8-5-1). Vertical walls with heels come under Cases 4 to 6.
(2) Cases 4 to 6 are for walls with heels (Figure C-8-5-2). The wall may be vertical or may lean forward,
or may lean backward as long as the upper edge of the back of the wall is in front of the vertical plane
through the edge of the heel.
(3) Cases 7 to 9 are for walls without heels, leaning backward (Figure C-8-5-3). Walls with heels come
under Cases 4 to 6 as long as the upper edge of the back of the wall is in front of the vertical plane
through the edge of the heel; if the upper edge of the back of the wall extends back to the vertical
plane through the edge of the heel, the problem can be solved by combining the solutions of Cases 4
to 6 and 7 to 9.
b. For walls leaning forward or walls with the heel extending into the backfill, the pressure of the backfill
on a vertical plane through the back of the heel of the wall is to be combined with the weight of backfill
contained between this vertical plane and the back of the wall.
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Concrete Structures and Foundations
Figure C-8-5-1. Cases 1, 2 and 3
c.
For walls leaning toward the backfill the resultant pressure P will be horizontal for a wall without
surcharge, or for a wall with uniform surcharge, if the surface of the backfill is horizontal; and will make
an angle l with the horizontal for a wall with a sloping surcharge. The values of l will vary from d, where
the wall is vertical, to zero, where Rankine’s theory shows that the resultant pressure is horizontal.
Values of l and values of K, where P = 1/2 wh2K, are given in Figure C-8-5-3.
II. TRIAL WEDGE METHOD OF EARTH PRESSURE COMPUTATION
A. Scope
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1
3
4
Figure C-8-5-2. Cases 4, 5 and 6
The trial wedge method is applicable for backfills of soils possessing cohesion, internal friction, or both; for
backfills having any configuration of ground surface; and for surcharges located at any position on the backfill.
The procedure, illustrated in Figure C-8-5-4 and Figure C-8-5-5, is outlined in the following Articles.
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Figure C-8-5-3. Cases 7, 8 and 9
B. Computation of Total Pressure
(1) Make scale drawing of the wall with backfill and any surcharge loads.
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(2) Locate surface AB against which earth pressure is to be computed. For walls with heels use vertical
section as shown in Figure C-8-5-4. For walls without heels use back of wall as shown in Figure C-85-5.
(3) Establish direction of earth pressure with respect to line AB, by the procedure described below under
“Direction of Pressure P”.
(4) Compute depth ho of tension cracks if soil has cohesion.
(5) Draw boundaries of trial wedges BC1, BD2, etc., wherein BC, BD, etc., are assumed plane surfaces of
sliding.
(6) Compute weights of successive wedges ABC 1, ABD 2, etc., including any surcharge acting on the
ground surface within the limits of each wedge.
(7) Lay off weight vectors for successive wedges.
(8) Compute total cohesion on each surface of sliding BC, BD, etc.
(9) Lay off cohesion vectors from lower ends of weight vectors, each parallel to the surface of sliding on
which it acts.
(10)From end of each cohesion vector draw line parallel to earth pressure P.
(11)From point B in force diagram lay off of radial lines BC, BD, etc., each making an angle f with the
normal to its respective surface of sliding (as force R on surface BF).
1
(12)Locate intersections of vectors R with corresponding lines drawn in paragraph 10 and connect
intersections with smooth curve. This is the earth pressure locus.
(13)Determine maximum distance between the TT¢ and the earth pressure locus, measured parallel to
line of action of P. This distance represents the active earth pressure P.
3
C. Direction of Pressure P
4
(1) For walls with heels, the following procedure is applicable:
– Determine height h of wall, measured from point a.
– Locate point b on the surface of the backfill at the distance 2h measured horizontally from a.
– Draw line ab.
– Take direction of resultant earth pressure P as parallel to line ab.
(2) For walls without heels, where AB is the back of wall, take angle f equal to 2/3 f.
D. Point of Application Process
(1) The point of application of the resultant pressure P can be obtained by determining the approximate
pressure-distribution diagram (Figure C-8-5-4). The procedure is as follows:
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– Subdivide the line BB¢ into about 4 equal parts h1 below the depth h0 of tension cracking.
– Compute the active earth pressures, P1, P2, P3, etc., as if each of the points C¢, D¢, E¢, etc., were at
the base of the wall. The trial wedge method is used for each computation.
– Determine the average pressures P1, P2, etc., over each distance B¢C¢, C¢D¢, etc., as indicated in
Figure C-8-5-4.
– Determine the elevation of the centroid of this approximate pressure diagram. This is the
approximate elevation of the point of application of the resultant earth pressure P.
(2) If the backfill may be considered cohesionless, the point of application of pressure may be obtained as
follows:
– Determine the center of gravity of the earth and ballast in the wedge between the plane of rupture
and the vertical plane passing through the heel of the wall (Figure C-8-5-4) or the back of the wall
(Figure C-8-5-5).
– Assume the center of gravity of the surcharge loads to be located at the surface of the backfill.
– Determine the center of gravity of the combined loads and draw a line from this point parallel to the
plane of rupture to a point of intersection with the vertical plane through the heel of the wall
(Figure C-8-5-4) or the back of the wall (Figure C-8-5-5).
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1
3
4
Figure C-8-5-4. Earth Pressure Computation – Walls with Heels
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Figure C-8-5-5. Earth Pressure Computation – Walls without Heels
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C - SECTION 5.4 STABILITY COMPUTATION
C - 5.4.4 SETTLEMENT AND TILTING (2002)
If the pressure on a subsoil containing fairly thick layers of soft clay or peat is increased by the weight of the
backfill, the wall may tilt backward because of the compression of the clay or peat. The tilt may be estimated
on the basis of a knowledge of the compressibility of the subsoil. If the tilt is likely to be excessive, it is
advisable to use backfill of lightweight material, to replace the backfill by a structure, or otherwise to change
the type of construction so as to avoid overloading the subsoil.
Progressive Creep or Movement
If the weight of the backfill is greater than one-half the ultimate bearing capacity of a clay subsoil, progressive
movement of the wall or abutment is likely to occur, irrespective of the use of a key or batter piles. In such case,
it is advisable to use backfill of lightweight material, to replace the backfill by a structure, or otherwise to
change the construction so as to avoid overloading the subsoil.
C - SECTION 5.5 DESIGN OF BACKFILL
C - 5.5.2 COMPACTION (2002)
a.
For backfill type 4 and 5 a minimum number of passes is required if the moisture content is near
optimum (OCM).
1
When the water content of clayey soil is too high, lamination sometimes occurs as the number of passes
increases. This phenomenon is harmful, so it is advisable to break up layers where this has happened.
C - SECTION 5.6 DESIGNING BRIDGES TO RESIST SCOUR
3
C - 5.6.1 DESIGN PHILOSOPHY AND CONCEPTS (2002)
The principles of economic analysis and experience with actual flood damage indicate that it is almost always
cost-effective to provide a foundation that will not fail, even from a very large flood event.
C - 5.6.2 DESIGN CONSIDERATIONS (2002)
4
C - 5.6.2.1 General
a.
The top width of a local scour hole is about 2.75 times the depth of scour.
C - 5.6.2.2 Piers
b. Assess the hydraulic advantages of various pier shapes where there are complex flow patterns during
flood events.
c. Streamline pier shapes to decrease scour and minimize potential for build-up of ice and debris. Where ice
and debris build-up is an obvious problem, design mulitiple pile bents as though they were a solid pier
for purposes of estimating scour. Consider various pier types and span arrangements to minimize scour
effects.
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C - 5.6.3 DESIGN PROCEDURE (2002)
Design measures incorporated in the original construction are almost always less costly than retrofitting scour
countermeasures.
The method used to calculate the support for a spread footing foundation on weathered or potentially erodable
rock should be based on an analysis of intact rock cores including rock quality designations and local geology, as
well as hydraulic data and anticipated structure life. An important consideration may be the existence of a high
quality rock formation below a thin weathered zone. For deep deposits of weathered rock, the potential scour
depth should be estimated and the footing base placed below that depth. Excavation into weathered rock
should be made with care. If blasting is required, light, closely spaced charges should be used to minimize
overbreak beneath the footing level. Loose rock pieces should be removed and the zone filled with lean
concrete. In any event, the final footing should be poured in contact with the sides of the excavation for the full
design footing thickness to minimize water intrusion below footing level. The excavation above the top of the
spread footing should be filled with riprap sized to withstand flood flow velocities.
(1) The FHWA microcomputer software WSPRO, “Bridge Waterways Analysis Model” (21), the Corps of
Engineers HEC 2, and other current software programs are available for this task.
(5) Consider the limitations in the accuracy of the model and of the scour estimating procedures.
(6) Visualize the overall flood flow pattern at the bridge site for the design conditions. Use this mental
picture to identify those bridge elements most vulnerable to flood flows and resulting scour.
Consider any other factors that may affect scour such as prop wash, etc.
The extent of protection to be provided should be determined by:
– The degree of uncertainty in the scour prediction method.
– The potential for and consequences of failure.
– The added cost of making the bridge less vulnerable to scour.
(7b)Spread Footings on Rock Highly Resistant to Scour.
Small embedments (keying) should be avoided since blasting to achieve keying frequently damages
the sub-footing rock structure and makes it more susceptible to scour. If footings on smooth massive
rock surfaces require lateral constraint, steel dowels should be drilled and grouted into the rock
below the footing level.
(7e)Deep Foundations (Piling or Drilled Shafts) with Footings.
Even lower footing elevations may be desirable for pile supported footings when the piles could be
damaged by erosion from exposure to river currents and corrosion from the elements.
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C - SECTION 5.8 DETAILS OF DESIGN AND CONSTRUCTION FOR BRIDGE PIERS
C - 5.8.1 PIER SPACING, ORIENTATION AND TYPE (2002)
C - 5.8.1.1 Grade Separation Structures
a.
“Highway Clearances for Bridges” and “Highway Clearances for Underpasses” of the Specifications of
the American Association of State Highway and Transportation Officials, and local and state clearance
requirements are referred to for appropriate highway clearance requirements.
C - 5.8.2 PIER SHAFTS (2002)
b.
Consideration shall be given to providing a large enough seat to allow for jacking and blocking of the
proposed superstructure.
C - 5.8.5 PIERS IN NAVIGABLE STREAMS (2002)
The more massive the bridge pier, the less damage it will suffer in a collision.
The compressive and ultimate bending capacity of concrete piles can be significantly increased by increasing
the confining reinforcement. Battered exterior piles will improve the stability of the substructure as long as
there is no seismic activity.
Vertical bar splices in pier shafts are subject to bond failure during impact. For this reason, increased
development lengths or mechnical splices are recommended. Splices should be staggered as far above the pier
base as practical.
1
Laps should be tied at both ends to prevent initiating compression failure due to high bearing under the ends of
bars.
Increasing the vertical steel reinforcement in pier shafts at the junction with the base and the cap can
significantly increase ductility as well as ultimate moment capacity, especially if combined with increased
lateral reinforcement.
3
The use of redudant structural systems may allow for local failures without structure collapse.
Tension ties should be considered between the pile and the pier footing. Consideration should be given to
designing the pier footing block to develop the ultimate capacity of the piles without punching shear failure.
The following methods should be considered to increase the capacity of pier shafts to withstand collisions:
(1) Splice vertical bars at different elevations and double the development length for overlap or use
mechanical splices, certified to develop full strength of the bars under impact load.
(2) Tie bar laps at both ends.
(3) Provide confining spirals or ties, in an amount similar to that required for seismic design for
columns. Hooks of ties should be turned in and anchored in compressive zones.
(4) Increase the vertical steel reinforcement near the junction with the base and the cap.
(5) Design multiple shaft piers so that with the rupture of one shaft, the cap is so connected to the
remaining shafts that it can carry the dead load of the span as a cantilever without collapse.
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-5-25
4
Concrete Structures and Foundations
(6) Provide shear walls between two or more shafts.
(7) Utilize keys and dowels for piers founded on firm foundation soil or rock.
The charts may be used for estimating the backfill pressure if the backfill material has been classified in accordance with Table 8-5-1.
NOTE:
Numerals on Curves indicate soil types as described inTable 8-5-1.
For materials of Type 5 computations should be based on value of H four feet less than actual value.
Figure C-8-5-6. Earth Pressure Charts for Walls Less than 20 Feet High
(Sheet 1 of 2)
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-5-26
AREMA Manual for Railway Engineering
Retaining Walls, Abutments and Piers
1
3
4
Figure C-8-5-6. Earth Pressure Charts for Walls Less than 20 Feet High
(Sheet 2 of 2)
© 2011, American Railway Engineering and Maintenance-of-Way Association
AREMA Manual for Railway Engineering
8-5-27
Concrete Structures and Foundations
THIS PAGE INTENTIONALLY LEFT BLANK.
© 2011, American Railway Engineering and Maintenance-of-Way Association
8-5-28
AREMA Manual for Railway Engineering
8
Part 6
Crib Walls1
— 1997 —
TABLE OF CONTENTS
Section/Article
Description
Page
6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.1 Scope (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1.2 Definitions (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-6-2
8-6-2
8-6-2
6.2 Design of Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2.1 General (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-6-2
8-6-2
6.3 Requirements for Reinforced Concrete Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3.1 General (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3.2 Manufacture (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3.3 Installation (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-6-3
8-6-3
8-6-4
8-6-4
6.4 Requirements for Metal Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.1 General (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.2 Manufacture (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4.3 Installation (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-6-5
8-6-5
8-6-5
8-6-5
6.5 Requirements for Timber Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5.1 General (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5.2 Materials (1997). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.5.3 Installation (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-6-6
8-6-6
8-6-6
8-6-6
LIST OF FIGURES
Figure
Description
Page
8-6-1
8-6-2
8-6-3
Typical Sections through Walls of Timber Cribbing . . . . . . . . .