The information presented in this publication has been developed by Michael
Winarta, Engineering Manager, and Greg Davis, Design Engineer, New
Millennium Building Systems, in conjunction with the SJI’s Health and Safety
Committee and Perry S. Green, PhD, Technical Director of the Steel Joist
Institute and is produced in accordance with recognized engineering principles
and is for general information only. The SJI and its committees have made a
concerted effort to present accurate, reliable, and useful information on the
erection of steel joists and Joist Girders. The information contained in this digest
should not be used or relied upon for any specific project without competent
professional assessment of its accuracy, suitability and applicability by a licensed
professional engineer or architect. The publication of the material contained in
this Technical Digest is not intended as a representation or warranty on the part
of the Steel Joist Institute. Any person making use of this information does so at
one’s own risk and assumes all liability arising from such use.
Federal Regulations Governing Erection of Joist Products
Steel joists and Joist Girders must be erected in accordance with the
Occupational Safety and Health Administration (OSHA), U.S. Department of
Labor 29 CFR Part 1926 Safety Standards for Steel Erection. The erection of
Open Web Steel Joists is governed by Section 1926.757 of this Federal
Regulation. The information contained in the Technical Digest is intended to
complement the Federal Regulation and to assist the erector in compliance with
the regulation.
Copyright © 2008
by
Steel Joist Institute
All rights reserved. This Technical Digest or any part thereof must not be
reproduced in any form without the written permission of the Steel Joist
Institute.
Printed in the United States of America
Third Edition
First Printing – March 2008
TECHNICAL DIGEST 9
HANDLING AND ERECTION OF
STEEL JOISTS AND JOIST GIRDERS
Perry S. Green, Technical Director
Steel Joist Institute
Myrtle Beach, SC
Michael Winarta
Engineering Manager, New Millennium Building Systems
Butler, IN
Greg Davis
Design Engineer, New Millennium Building Systems
Butler, IN
Steel Joist Institute
3127 Mr. Joe White Avenue
Myrtle Beach, SC 29577-6760
www.steeljoist.org
ACKNOWLEDGEMENT
The development of this and other Steel Joist Institute Technical Digests is the
result of the combined effort of numerous people and organizations. The chief
author of the first edition of Technical Digest No. 9 was E.T.E. Sprague, a former
SJI Managing Director, whose 30 years of experience in the steel joist industry
provided him with the requisite background for preparing such a publication.
The second edition of Technical Digest No. 9 was prepared by Cary Andrews,
former Engineering Manager, SOCAR, Florence, SC, the Institute’s Erection
Committee and the SJI’s Technical Director, Perry S. Green, PhD, and has been
carefully reviewed by members of the Steel Erectors Association of America.
Much of the revised information is a direct result of the changes that have been
adopted in the workplace based on the new Occupational Safety and Health
Administration safety standards issued in 2001.
This third edition of Technical Digest No. 9 has been prepared by Michael
Winarta, Engineering Manager and Greg Davis, Design Engineer, New
Millennium Building Systems, Butler, IN and Perry S. Green, PhD, Technical
Director in conjunction with SJI’s Health and Safety Committee. The main
purpose of this revision is to include information related to SJI’s newest
composite steel joist series, the CJ-Series.
The primary acknowledgement must go to the erectors themselves, those
individuals who risk their lives in order to answer a distant calling to “walk the
iron” and to experience the freedom of standing above the crowd. To them, most
respectfully, we doff our hard hats.
FOREWORD
Technical Digest No 9 concerns itself with the proper handling and erection
procedures to be employed in the field to make certain that these products are
not damaged, that they perform as specified, and above all, to ensure the safety
of the steel erectors.
This Technical Digest is another addition to the series of Steel Joist Institute
publications designed to give the reader information regarding the application
and usage of Steel Joists, Joist Girders and Composite Steel Joists. These
digests serve to highlight specific areas of design and/or application for the
benefit of architects, building inspectors, building officials, designers, engineers,
erectors, students and others.
i
TABLE OF CONTENTS
ACKNOWLEDGEMENT …………………………………………………………
i
FOREWORD …………………………………………………………………......
i
TABLE OF CONTENTS ………………………………………………………….
ii
BACKGROUND AND INTRODUCTION…………………………………………. iii
GLOSSARY ……………………………………………………………………….
v
Chapter 1
PRODUCTS ………………………………………………….…..
1
Chapter 2
PRE-ERECTION MEETING …...……….……………..….........
8
Chapter 3
LOADING AND SHIPPING ……………………………………..
9
Chapter 4
RECEIVING, UNLOADING AND STORING ………….….......
12
Chapter 5
ERECTING JOIST PRODUCTS …………..…………………...
21
Chapter 6
FIELD INSPECTION ………………………………………..…..
47
Chapter 7
PANELIZED ERECTION .……………………………………….
50
Chapter 8
BRIDGING …..……………………………………………………
60
Chapter 9
MISCELLANEOUS TOPICS – COMMON FIELD ISSUES …
68
Chapter 10
SUMMARY - DO’S AND DON’TS ……..………………………
73
REFERENCES ……………………………………………………………………
75
Appendix A
Standard Hand Signals for Controlling Crane Operations ...
77
Appendix B
Standard Specifications for Open Web Steel Joists, K-Series
79
Appendix C
Standard Specifications for Longspan Steel Joists,
LH-Series and Deep Longspan Steel Joists, DLH-Series …..
88
Appendix D
Standard Specifications for Joist Girders ….…..……………...
97
Appendix E
Standard Specifications for Composite Steel Joists,
CJ-Series …………………………………………………………
101
ii
BACKGROUND AND INTRODUCTION
The first known application of steel joist construction was in the Bank of the State
of New York building that was erected in 1855 at Williams St. and Exchange
Place in New York City. The architect, James Renwick, developed a type of floor
joist that was comprised of two 1/16 in. riveted wrought iron web plates with 4 x
1/8 in. top and bottom plates riveted to the web to form the joist. The building
was razed in 1903. During the period 1885 to 1920 various proprietary and
patented joist designs were manufactured including the O’Shea Joist in Chicago,
St. Louis Joist, Berger Joist, Truscon Steel Joist, and the National Strip Steel
Joist. All these joists had solid sheet steel for their webs and it was not until
1923 that the first “open web” steel joist appeared. The Massillon Bar Joist
consisted of five bars: Two top chord bars, two bottom chord bars and a web
bar. The web bar was bent to proper dimensions and the assembly arc welded
at panel points into a Warren truss configuration. The design of each end of the
joist gave it flexibility of span.
In June 1928, the Steel Joist Institute was formed by a group of joist
manufacturers, Concrete Steel Co., New York, NY, Gabriel Steel Co., Detroit, MI,
Kalman Steel Corporation, Bethlehem, PA, The Macomber Steel Co., Canton,
OH, and Truscon Steel Co., Youngstown, OH. The original purposes for which
the Institute was founded were to standardize the methods of design and details
of construction, to promote proper building regulations and to disseminate
information relative to the proper use of steel joists. In December of that same
year the Steel Joist Institute adopted the Standard Specification of Steel Joists,
and in August 1929 the first standard loading table applicable to the design of
joists by all member companies was approved. This loading table was later
adopted as Simplified Practice Recommendation R 94-30 of the United States
Department of Commerce. In April 1931 the first Code of Standard Practice was
adopted.
The SJI’s first Catalog, Steel Joist Construction - A Handbook for Architects
and Engineers on the Uses and Properties of Steel Joists, was published
January 1932. The catalog contained information on Open Web Steel Joists,
Standard Specifications and Code of Standard Practice of the Steel Joist
Institute, Handling and Erecting Steel Joists, Standard Steel Joist Loading Tables
and Properties of Steel Joists. That catalog, in addition to the over 40 other
catalogs that have been published subsequently by the SJI, contains information
related to the proper handling and erection of steel joists. In 1932 the SJI
provided recommendations on unloading, hauling, piling (storing), setting joists,
decking, construction loads, centering, reinforcing for the top slab, wood
sleepers, placing of concrete, and mechanical trades. Today, each of the current
Standard Specifications for Open Web Steel Joists, K-Series; for Longspan Steel
Joists, LH-Series; and Deep Longspan Joists, DLH-Series has a section on
iii
Erection Stability and Handling while the Standard Specification for Joist Girders
has a section on Handling and Erection.
Today, steel joists and Joist Girders are widely used products primarily in
commercial, industrial and institutional buildings. However, until this technical
digest was first published in 1987, no definitive handbook on their handling and
erection had been written. Since the original publication date, there have been
numerous changes and innovations in the use of steel joists. Among these
changes have been the introduction of new or expanded joist products,
innovations in building materials and systems, changes in design philosophy, and
the adoption of new building codes and federal regulations. Therefore, for these
reasons the Steel Joist Institute determined that an extensive revision to this
Technical Digest No. 9 was required.
If a joist manufacturer is asked, “How good are your products?” the answer
almost certainly would be: “only as good as their installation.” A joist
manufacturer can design and build joist products with remarkable intrinsic
strength, but whether or not these products can deliver this strength is largely
dependent on how well they are handled from the time they leave the
manufacturing facility until they are permanently installed in the field.
The purpose of this digest is to present a clear and concise guide for the safe
installation of open web steel joists and Joist Girders. Though it is not possible to
include every conceivable joist application or field condition that could be
encountered, the reader should come away with a basic knowledge of open web
steel joists and Joist Girders and a general understanding of the SJI
recommended safe practices for handling, storing and erecting these products.
One of the most important aspects of safe erection of joist products is proper
bridging. Bridging is a component of the steel joist system that braces the joists
against unanticipated horizontal movement during erection as well as during the
placing of construction loads. A lateral displacement of the joist may mean that
the construction load caused the joist to distort, roll over, or shift from its intended
position resulting in both the ironworkers and joists falling. Much attention will be
given to this critical component. Additionally, as a result of changes in code
provisions and design requirements, bridging may be an integral part of the initial
as well as final structural system.
This digest does not attempt to address all hazards that may be present in a
particular construction environment. Pre-job planning and development of sitespecific plans that identify hazards are very important. The implementation of
systems and procedures to eliminate those hazards completes this process.
Contained in the technical digest is a discussion of several different types of
systems used to protect employees, but regardless of the type selected it should
be designed by a qualified person and employees should be trained in the proper
use of the system.
iv
GLOSSARY
NOTES:
Terms in Bold and their definitions come from the AISC AND AISI STANDARD,
“Standard Definitions for Use in the Design of Steel Structures,” 2004 Edition,
First Printing - April 2005.
* These terms are usually qualified by the type of load effect, e.g., nominal tensile
strength, available compressive strength, design flexural strength.
† The definitions provided for these terms come from the OSHA Steel Erection
Standard Part §1926.757 – Open Web Steel Joists.
Accessories. Structural components related to the design, fabrication and
erection of joists and Joist Girders including, but not limited to sloped end
bearings, extended ends, ceiling extensions, bridging and bridging anchors,
headers and bottom chord lateral bracing for Joist Girders.
Anchored Bridging†. The means that the steel joist bridging is connected to a
bridging terminus point.
ASD (Allowable Strength Design).
Method of proportioning structural
components such that the allowable strength equals or exceeds the required
strength of the component under the action of the ASD load combinations.
ASD Load Combination. Load combination in the applicable building code
intended for allowable strength design (allowable stress design).
Allowable Strength*. Nominal strength divided by the safety factor, Rn/Ω.
Applicable Building Code.
designed.
Building code under which the structure is
Bay. The distance between the main structural frames or walls of a building.
Bearing. The distance that the bearing shoe or seat of a joist or Joist Girder
extends over its masonry, concrete or steel support.
Bearing Plate. The steel plate used for a joist or Joist Girder to bear on when it is
supported by masonry or concrete supports. The plate is designed by the
Specifying Professional to carry the joist or Joist Girder reaction to the supporting
structure.
v
Bottom Chord Extension (BCX). The two angle extended part of a joist bottom
chord from the first bottom chord panel point towards the end of the joist.
Bridging. In general, a member connected to a joist to brace it from lateral
movement. See also Diagonal Bridging and Horizontal Bridging
Bridging Clip†. A device that is attached to a steel joist to allow the bolting of the
bridging to the steel joist.
Bridging Terminus Point†. A wall, beam, tandem joists (with all bridging installed
and a horizontal truss in the plane of the top chord) or other element at an end or
intermediate point(s) of a line of bridging that provides an anchor point for the
steel joist bridging.
Buckling. Limit state of sudden change in the geometry of a structure or any of
its elements under a critical loading condition.
Buckling Strength. Nominal strength for buckling or instability limit states.
Bundle. The banding together of joist products, bridging, and decking into certain
sizes, weights, pieces, lengths, etc. to expedite shipping, unloading and storage,
and erection at a job site.
Buyer. The entity that has agreed to purchase material from the manufacturer
and has also agreed to the terms of sale.
Camber. An upward curvature of the chords of a joist or Joist Girder induced
during shop fabrication. Note, this is in addition to the pitch of the top chord.
Cantilever. The portion of a joist product that extends beyond its structural
support. A lateral brace may need to be provided at the end of the cantilever to
ensure it is stable during erection and under load.
Ceiling Extension. A bottom chord extension except that only one angle of the
joist bottom chord is extended from the first bottom chord panel point towards the
end of the joist.
Centering. The material placed over the joists used for cast-in-place slabs and
may be ribbed metal lath, corrugated steel sheets, paper-backed welded wire
fabric, removable centering or any other suitable material capable of supporting
the slab at the designated joist spacing. Centering shall not cause lateral
displacement to the top chord of joists during installation or damage to the joists
during removal or placing of the concrete.
vi
Choker†. A wire rope or synthetic fiber rigging assembly that is used to attach a
load to hoisting equipment or device.
Chords. The top and bottom members of a joist or Joist Girder. When a chord is
comprised of two angles there is usually a gap between the members.
Clear Span. The actual clear distance or opening between supports for a joist,
that is the distance between walls or the distance between the edges of flanges
of beams.
Collateral Load. All additional dead loads other than the weight of the building,
such as sprinklers, pipes, ceilings, and mechanical or electrical components.
Competent Person†. One who is capable of identifying existing and predictable
hazards in the surroundings or working conditions which are unsanitary,
hazardous or dangerous to employees, and who has authorization to take prompt
corrective measures to eliminate them.
Connection. Combination of structural elements and joints used to transmit
forces between two or more members. See also Splice.
Connector†. An employee who, working with hoisting equipment, is placing and
connecting structural members and/or components.
Constructability†. The ability to erect structural steel members in accordance
with Subpart R without having to alter the over-all structural design.
Construction Load†. (for joist erection only) Any load other than the weight of the
employee(s), joists and the bridging bundle (see OSHA Regulations
1926.757(d)(1), (d)(2) and (d)(3)).
Deck. A floor or roof covering made out of galvanized, painted, or unpainted
gage metal attached by welding or mechanical means to joists, beams, purlins,
or other structural members.
Design Load. Applied load determined in accordance with either LRFD load
combinations or ASD load combinations, whichever is applicable.
Design Strength*. Resistance factor multiplied by the nominal strength, φRn.
Diagonal Bridging. Two angles or other structural shapes connected from the top
chord of one joist to the bottom chord of the next joist or anchorage to form an 'X'
shape. These members are almost always connected at their point of
intersection.
vii
Diaphragm. Roof, floor or other membrane or bracing system that transfers inplane forces to the lateral force resisting system.
End Anchorage. The proper attachment of the ends of a joist product to
masonry, structural concrete or structural steel.
End Diagonal or Web. The first web member on either end of a joist or Joist
Girder which begins at the end of the top chord and ends at the first bottom chord
panel point. For an underslung joist the end diagonal begins at the seat.
End Support. The masonry, structural concrete or structural steel that supports
the ends of joist products and is capable of carrying the loads transmitted to it by
the joist products.
Erection Bridging†. The bolted diagonal bridging that is required to be installed
prior to releasing the hoisting cables from the steel joists.
Erector. The entity that is responsible for the safe and proper erection of the
materials in accordance with all applicable codes and regulations.
Extended End. The extended part of a joist top chord with the seat angles also
being extended from the end of the joist extension back into the joist and
maintaining the standard end bearing depth over the entire length of the
extension.
Fall Restraint System†. A fall protection system that prevents the user from
falling any distance. The system is comprised of either a body belt or body
harness, along with an anchorage, connectors and other necessary equipment.
The other components typically include a lanyard, and may also include a lifeline
and other devices.
Filler. The material placed between the chords and/or webs at certain intervals
to ensure that the cross-section acts as a built-up member (also spacer or batten
if placed on the outside of the chords or webs). The material may be a short
piece of angle, round bar, or other type of steel shape.
Flexural Buckling. Buckling mode in which a compression member deflects
laterally without twist or change in cross-sectional shape.
Flexural-Torsional Buckling. Buckling mode in which a compression member
bends and twists simultaneously without change in cross-sectional shape.
Girt. Horizontal structural member that supports wall panels and is primarily
subjected to bending under horizontal loads, such as wind load.
viii
Gravity Load. Load, such as that produced by dead and live loads, acting in the
downward direction.
Header. A structural member located between two joists or between a joist and a
wall which carries another joist or joists. It is usually made up of an angle,
channel, or beam with saddle angle connections on each end for bearing.
Hoisting Cable. A chain, strap or cable that is attached at each end which is
used to facilitate the moving and lifting of joist products, bridging, decking, etc.
Hoisting Equipment†. Commercially manufactured lifting equipment designed to
lift and position a load of known weight to a location at some known elevation
and horizontal distance from the equipment’s center of rotation. ‘Hoisting
equipment’ includes but is not limited to cranes, derricks, tower cranes, gin poles
and gantry hoist systems. A “come-a-long” (a mechanical device, usually
consisting of a chain or cable attached at each end, that is used to facilitate
movement of materials through leverage) is not considered ‘hoisting equipment.’
Horizontal Bridging. A continuous angle or other steel shape connected to the
top and bottom chord of a joist.
Inspector. An independent person hired to verify that the erection of a structure
is in accordance with the Site-Specific Erection Plans including the Joist
Placement Plans and the deck placement drawings.
Instability. Limit state reached in the loading of a structural component, frame or
structure in which a slight disturbance in the loads or geometry produces large
displacements.
Joint. Area where two or more ends, surfaces or edges are attached.
Categorized by type of fastener or weld used and the method of force transfer.
Joist. A structural load-carrying member with an open web system which
supports floors and roofs utilizing hot-rolled or cold-formed steel and is designed
as a simple span member. Currently, the SJI has the following joist designations:
K-Series including KCS, LH-Series and DLH-Series, and CJ-Series.
Joist Girder. A primary structural load-carrying member with an open web
system designed as a simple span usually supporting equally spaced
concentrated loads of a floor or roof system acting at the panel points of the
member and utilizing hot-rolled or cold-formed steel.
Joist Placement Plans. Drawings that are prepared depicting the interpretation of
the Contract Documents requirements for the material to be supplied by the
Seller.
These floor and/or roof plans are approved by the Specifying
Professional, Buyer or Owner for conformance with the design requirements.
ix
The Seller uses the information contained on these drawings for final material
design. A unique piece mark number is typically shown for the individual
placement of joists, Joist Girders and accessories along with sections that
describe the end bearing conditions and minimum attachment required so that
material is placed in the proper location in the field.
Joist Substitute. A structural member who’s intended use is for very short spans
(10 feet or less) where open web steel joists are impractical. They are usually
used for short spans in skewed bays, over corridors or for outriggers. It can be
made up of two or four angles to form channel sections or box sections.
Lateral Buckling. Buckling mode of a flexural member involving deflection normal
to the plane of bending.
Lateral-Torsional Buckling. Buckling mode of a flexural member involving
deflection normal to the plane of bending occurring simultaneously with twist
about the shear center of the cross section.
Limit State. Condition in which a structure or component becomes unfit for
service and is judged either to be no longer useful for its intended function
(serviceability limit state) or to have reached its ultimate load-carrying capacity
(strength limit state).
Load. Force or other action that results from the weight of building materials,
occupants and their possessions, environmental effects, differential movement,
or restrained dimensional changes.
Load Effect. Forces, stresses, and deformations produced in a structural
component by the applied loads.
Load Factor. Factor that accounts for deviations of the nominal load from the
actual load, for uncertainties in the analysis that transforms the load into a load
effect, and for the probability that more than one extreme load will occur
simultaneously.
Local Buckling**. Limit state of buckling of a compression element within a cross
section.
LRFD (Load and Resistance Factor Design). Method of proportioning
structural components such that the design strength equals or exceeds the
required strength of the component under the action of the LRFD load
combinations.
LRFD Load Combination. Load combination in the applicable building code
intended for strength design (Load and Resistance Factor Design).
x
Material. Joists, Joist Girders and accessories as provided by the Seller.
Nailers. Strips of lumber attached to the top chord of a joist so plywood or other
flooring can be nailed directly to the joist.
Nesting. The positioning of joist products so that when they are bundled together
the chords of one member fit tightly against or overlap the chords of the adjacent
member in the bundle. Once the strapping that is used to bundle the joists
together is cut the joists become de-nested.
Nominal Load. Magnitude of the load specified by the applicable building code.
Nominal Strength*.
Strength of a structure or component (without the
resistance factor or safety factor applied) to resist the load effects, as determined
in accordance with the Standard Specifications.
OSHA. The Occupational Safety and Health Administration is the federal
government agency whose purpose is to save lives, prevent injuries, and protect
the health of the workers of America.
Owner. The entity that is identified as such in the Contract Documents.
Permanent Load. Load in which variations over time are rare or of small
magnitude. All other loads are variable loads.
Personal Fall Arrest System†. A system used to arrest an employee in a fall
from a working level. A personal fall arrest system consists of an anchorage,
connectors, a body harness and may include a lanyard, deceleration device,
lifeline, or suitable combination of these. The use of a body belt for fall arrest is
prohibited.
Purlin. Horizontal structural member that supports roof deck and is primarily
subjected to bending under vertical loads such as dead, snow or wind loads.
Qualified Person†. One who, by possession of a recognized degree, certificate,
or professional standing, or who by extensive knowledge, training, and
experience, has successfully demonstrated the ability to solve or resolve
problems relating to the subject matter, the work, or the project.
Quality Assurance. System of shop and field activities and controls implemented
by the owner or his/her designated representative to provide confidence to the
owner and the building authority that quality requirements are implemented.
Quality Control. System of shop and field controls implemented by the seller and
erector to ensure that contract and company fabrication and erection
requirements are met.
xi
Required Strength*. Forces, stress, and deformations produced in a structural
component, determined by either structural analysis, for the LRFD or ASD load
combinations, as appropriate, or as specified by the Standard Specifications.
Resistance Factor, φ. Factor that accounts for deviations of the actual strength
from the nominal strength, deviations of the actual load from the nominal load,
uncertainties in the analysis that transforms the load into a load effect and for the
manner and consequences of failure.
Safety Factor, Ω. Factor that accounts for deviations of the actual strength from
the nominal strength, deviations of the actual load from the nominal load,
uncertainties in the analysis that transforms the load into a load effect and for the
manner and consequences of failure.
Seller. A company certified by the Joist Institute engaged in the manufacture and
distribution of joists, Joist Girders and accessories.
Service Load. Load under which serviceability limit states are evaluated.
Serviceability Limit State. Limiting condition affecting the ability of a structure to
preserve its appearance, maintainability, durability, or the comfort of its
occupants or function of machinery, under normal usage.
Site-Specific Erection Plan. OSHA has defined a site-specific erection plan in
§1926.752(e) as one that shall be developed by a qualified person and be
available at the work site. This site-specific erection plan is one where
employers elect, due to conditions specific to the site, to develop alternate means
and methods that provide employee protection in accordance with OSHA
§1926.753(c)(5), §1926.757(a)(4) or §1926.757(e)(4).
Span. The centerline-to-centerline distance between structural steel supports
such as a beam, column or Joist Girder or the clear span distance plus four
inches onto a masonry or concrete wall.
Specified Minimum Yield Stress. Lower limit of yield stress specified for a
material as defined by ASTM.
Specifying Professional. The licensed professional who is responsible for sealing
the building Contract Documents, which indicates that he or she has performed
or supervised the analysis, design and document preparation for the structure
and has knowledge of the load-carrying structural system.
Splice. Connection between two structural members joined at their ends by
either bolting or welding to form a single, longer member.
xii
Spreader Bar. A specially designed structural steel member attached to hoisting
equipment that may be used to lift joist, bridging, or decking bundles at two
points.
Stability. Condition reached in the loading of a structural component, frame or
structure in which a slight disturbance in the loads or geometry does not produce
large displacements.
Stabilizer Plate. A vertical steel plate at a column inserted between the end of a
bottom chord of a joist or Joist Girder (see OSHA Regulations 1926.757(a)(1)).
A stabilizer plate may also be provided when the structural support is at a wall.
Standard Specifications. Documents developed and maintained by the Steel
Joist Institute for the design and manufacture of open web steel joists and Joist
Girders. The term “SJI Standard Specifications” encompasses by reference the
following:
ANSI/SJI-K1.1 Standard Specifications for Open Web Steel Joists, K-Series;
ANSI/SJI-LH/DLH-1.1 Standard Specifications for Longspan Steel Joists,
LH-Series and Deep Longspan Steel Joists, DLH-Series;
ANSI/SJI-JG-1.1 Standard Specifications for Joist Girders; and
ANSI/SJI-CJ1.0 Standard Specifications for Composite Steel Joists,
CJ-Series.
Strength Limit State. Limiting condition affecting the safety of the structure, in
which the ultimate load-carrying capacity is reached.
Structural Drawings. The graphic or pictorial portions of the Contract Documents
showing the design (size or type of structural elements), location and dimensions
of the work. These documents generally include plans, elevations, sections,
details, connections, all loads, schedules, diagrams and notes.
Tagged End. The end of a joist or Joist Girder where an identification or piece
mark is shown by a metal tag. The member must be erected with this tagged
end in the same position as the tagged end noted on the placement plan.
Tie Joist. A joist that is bolted at or near a column. When the joist is bolted at a
column it may be referred to as a column joist.
Top Chord Extension (TCX). The extended part of a joist top chord. This type of
extension only has the two top chord angles extended past the joist seat.
Torsional Buckling. Buckling mode in which a compression member twists about
its shear center axis.
xiii
Unbraced Length. Distance between braced points of a member, measured
between the centers of gravity of the bracing members.
Variable Load. Load not classified as permanent load.
Webs. The vertical or diagonal members joined at the top and bottom chords of
a joist or Joist Girder to form triangular patterns.
Yield Strength. Stress at which a material exhibits a specified limiting deviation
from the proportionality of stress to strain as defined by ASTM (also referred to
as yield stress).
xiv
CHAPTER 1
PRODUCTS
There are two broad categories of open web products, Joist Girders which are
considered primary load-carrying members and joists which are considered
secondary load-carrying members (see Figure 1.1). Joists, or more correctly
Open Web Steel Joists, are also known as bar joists, shortspans, longspans or
composite joists. Joists are those structural members in a steel framing system
that are designed to carry the gravity load acting over a floor or roof being
supported and transfer that load through their end supports to structural steel
beams or Joist Girders that are directly supported by structural steel columns.
The Steel Joist Institute’s Standard Specifications Load Tables and Weight
Tables for Steel Joists and Joist Girders currently consist of four joist products:
•
•
•
•
K-Series including KCS Joists and Joist Substitutes commonly referred
to as Bar Joists or Shortspans;
LH-Series Joists commonly referred to as Longspans;
DLH-Series Joists commonly referred to as Deep Longspans; and
Joist Girders
Figure 1.1 Joist Product Identification
1
The Steel Joist Institute’s Standard Specification for Composite Steel Joists
Weight Tables and Bridging Tables currently consists of one joist product:
•
CJ-Series Composite Joists
All joists consist of the following basic elements: a top chord, bottom chord,
interior diagonal and/or vertical pieces called web members and end bearing
seats as illustrated in Figure 1.2. Today, chords using back to back angles with a
gap in between is most common while the webs can be made of continuous solid
round bar, single angles, crimped angles, double angle members, cold-formed
channels or other steel members depending on the size, length and load-carrying
requirements of the joist as well as joist manufacturer preference. In all cases
the web members are connected to the top and bottom chords by welding.
Figure 1.2 Basic Joist Elements, a) Crimped Angle Web; b) Round Bar Web
Joists are designed as either underslung or with square-ends (see Figure 1.3).
Underslung joists are supported at their ends through end bearing seats while
square-ended joists are supported at the ends of the bottom chords. For the
underslung condition the bearing seat is at the top chord while there is no typical
bearing seat at the bottom chord for the square-end condition. Additionally,
underslung and square-end joists may have their top chords pitched either one
way or two ways as shown in Figure 1.4. Joists can also be designed for a
2
sloped condition. As the slope of the joist increases from 1/4:12 to something
greater, e.g. 4:12, the joist manufacturer will build the joist with appropriately
sloped bearing seats.
Figure 1.3 Standard Joist Seats, a) Underslung Joist, b) Square End Joist
Figure 1.4 Underslung and Square End Configurations of Pitched Joists,
LH-Series, DLH-Series and Joist Girders
3
1. Standard SJI Products
The following sections provide a more in-depth description of each of the
standard SJI products.
A. Open Web Steel Joists, K-Series
Depths for Open Web Steel Joists range from 8 inches through 30 inches,
at 2-inch increments; spans range from 8 feet (or less using joist
substitutes) up to 60 feet. Although both the Open Web Steel Joists and
the Longspan joists include lengths from 21 feet to 60 feet, there are
several features that help to differentiate the two joist products.
Open Web Steel Joists are usually top bearing (or underslung) as shown
in Figure 1.2. The standard bearing depth is 2 1/2” for the Open Web
Steel Joists. The web systems shown in Figure 1.2b consist of lengths of
solid rounds bent into V’s and welded to the chords or individual web
members welded to the chords. This is a standard Warren type
configuration (no verticals). Figure 1.2a shows a modified Warren truss
type configuration that is characterized by the use of vertical and diagonal
web members, where the web members may be solid rounds, crimped
angles, single or double angles, or cold-formed steel shapes.
The top and bottom chords and web members of Open Web Steel Joists
are normally comprised of hot rolled angles or cold-formed sections.
The joints are usually connected by welding, which can vary from handheld “stick” welding (SMAW), semi-automatic gas metal arc welding
(GMAW) also called MIG, or flux core welding (FCAW), to totally
automatic resistance welding.
An example of an Open Web Steel Joist designation is: 18K7 where “18”
denotes the nominal joist depth in inches; “K” is the joist series; and “7” is
the chord number designation.
B. Longspan Joists, LH-Series
Depths for Longspan Joists range from 18 inches through 48 inches and
lengths from 21 feet to 96 feet. These joists can be underslung or square
ended; their chords can be parallel, or the top chord can be single pitched
or double pitched (see Figure 1.4). The standard bearing depth for an
underslung Longspan Joist is 5 inches.
The top and bottom chords and web members are normally comprised of
hot rolled angles or cold-formed sections. The webs consist of angles –
single, double or crimped, rounds, squares, or other steel shapes. The
most common web configurations are either Warren or modified Warren,
but other truss configurations are possible. In all cases, the joints where
4
the webs are connected to the chords are made by various recognized
welding methods as specified above.
An example of a Longspan Joist designation is: 40LH13 where “40”
denotes the nominal joist depth (at mid-span) in inches; “LH” is the joist
series; and “13” is the chord number designation. The joist depth at midspan is specified whether the joist has parallel chords, or has a single
pitched or double pitched top chord.
C. Deep Longspan Joists, DLH-Series
Deep Longspan Joists are an extension of the Longspan Joists, with
depths ranging from 52 inches through 72 inches and lengths from 61 feet
to 144 feet. The standard bearing depth for an underslung Deep
Longspan Joist is 5 inches for chord number designations 10 through 17
and 7 1/2 inches for chord number designations 18 and 19.
An example of a Deep Longspan Joist designation is: 56DLH15 where
“56” denotes the nominal joist depth in inches at mid-span; “DLH” is the
joist series; and “15” is the chord number designation.
D. Joist Girders
Joist Girders are primary structural members that have been designed as
simply-supported trusses. They usually bear on columns and support the
concentrated loading from the steel joists which run perpendicular to them.
The top and bottom chords and web members of Joist Girders are
typically comprised of hot rolled angles or cold-formed sections. The web
system configurations are typically modified Warren type, but may have
other configurations, depending on the magnitude of joist loads and
spacings. The standard bearing depth is 7 1/2 inches for underslung Joist
Girders. Joist Girder depths vary from 20 inches to 120 inches, and
lengths run from 20 feet to 120 feet. The chords can be parallel, or the top
chord can be either single pitched or double pitched.
An example of a Joist Girder designation is: 36G9N6K where “36”
denotes the nominal Joist Girder depth at mid-span in inches; “G”
indicates that it is a Joist Girder; “9N” denotes that there are 9 joist
spacings; and “6K” means that the concentrated load at each panel point
or joist location is 6 kips (unfactored) from an Allowable Strength Design.
If the designation were “9F” it would mean that the concentrated load at
each panel point or joist location is 9 kips (factored) from a Load and
Resistance Factor Design.
E. Composite Steel Joists, CJ-Series
Composite Steel Joists are similar to K-, LH- and DLH-Series joists with
depths ranging from 10 inches through 96 inches and spans through 120
feet. These joists have parallel chords with underslung or square ends.
5
Standard bearing depths are 2 ½ inches, 5 inches and 7 ½ inches. The
Composite Steel Joists are capable of supporting larger loadings due to
the attachment of the concrete slab to the top chord of the composite joist.
Shear connection between the concrete slab and steel joist is typically
made by the welding of shear studs ranging in diameter from 3/8 inch to
3/4 inch thru the steel deck to the underlying Composite Joist.
An example of a Composite Steel Joist designation is:
30CJ2188/1168/420 where “30” denotes the nominal joist depth in inches;
“CJ” is the joist series; “2188” denotes the total factored composite design
load capacity in pounds per linear foot; “1168” denotes the total factored
composite live load capacity in pounds per linear foot; and “420” denotes
the total factored composite dead load capacity in pounds per linear foot.
2. Non-Standard SJI Products
In addition to the standard SJI products described above, the member firms of
the Steel Joist Institute may produce non-standard products such as: Barrel
Joists, Bowstring Joists, Gable Joists, Scissor Joists and other special truss
configurations (see Figures 1.5 and 1.6) as well as joist products over 144
feet in length and depths greater than 72 inches. These are not “standard”
Steel Joist Institute products and should be erected in accordance with the
American Institute of Steel Construction Code of Standard Practice for Steel
Buildings and Bridges Section 7. Erection (AISC 2005) and the OSHA
Regulations 1926.756 Beams and Columns.
Figure 1.5 Non-standard SJI Barrel Joists
6
Figure 1.6 Non-standard SJI Gable Joists in a Fink Truss Configuration
7
CHAPTER 2
PRE-ERECTION MEETING
On larger projects, it may be beneficial for the contractor to hold a pre-erection
meeting. Shortly after the structural fabricator, joist supplier and erector are
selected, a meeting should be held to determine shipping schedules, site access,
storage of joist products, routing considerations for over-length joists (which may
necessitate field splicing of multi-piece joists), use of sequencing, boundaries of
sequences, and other related topics. This meeting may include an owner’s
representative, the contractor, fabricator, and erector. Other crafts such as
masonry, concrete and trades involved in underground utilities may need to be
included in the meeting.
Once the area where erection will begin is determined, several factors must be
considered. They include the capacity and reach of the cranes, their access and
movement, as well as a clean laydown area. The owner’s need to have specific
areas completed early, availability of materials and foundation schedule are also
important. Proper access roads for delivery trucks and erection equipment
should be agreed upon. The AISC Code of Standard Practice for Buildings and
Bridges (AISC 2005) and the OSHA Regulations 1926.752 speak very clearly in
regard to proper access to the construction site.
The pre-erection meeting should be where the Q.C. plan is established and the
quality requirements for welding are reviewed with the erector. Other items such
as the drawing approval schedules, number of loads per day, suggested delivery
times, field splicing of multi-piece joists, bundling and tagging, possible
panelization, and the number of “crane-days” for each sequence should be
addressed. The erector should determine how much erection time will be
required for each sequence and schedule deliveries to minimize downtime for the
crane. Effective communication of sequencing and other delivery related issues
is critical to the success of the project. This information should be relayed to the
joist manufacturer at the earliest possible date.
8
CHAPTER 3
LOADING AND SHIPPING
TAGGING AND PREPARING FOR SHIPMENT
Steel joists and Joist Girders are manufactured on production lines. After a joist
product (this term will be used throughout the Technical Digest to include joists
and Joist Girders) is manufactured, a metal tag is attached to one end. Normally,
this tag is wired to the end web member, either the diagonal member for
underslung products, or the vertical member for joists with square-ends (see
Figure 3.1). The information contained on the metal tag includes:
1) The joist manufacturer's name.
2) The joist manufacturer's job number.
3) The erection mark (such as J1 or T3). This mark allows the erector to
identify the product and to place it correctly in the structure in
accordance with the Joist Placement Plans. Some joists are not
symmetrical, consequently it is imperative that the “Tag End” of a joist
be placed as indicated on the Joist Placement Plans.
Figure 3.1 Joist Information Shown on Metal Tag
The handling of joist products begins in the joist plant immediately after the joists
have been manufactured. Depending on size and length, several joists or Joist
Girders are bundled together with metal strapping and a paper or plastic tag
listing the mark numbers contained in the bundle is usually attached to the
bundle. They are painted, when required, and moved to a covered location
where they are allowed to air dry. The standard shop paint is intended to protect
the steel for only a short period of exposure in ordinary atmospheric conditions
and shall be considered an impermanent and provisional coating.
9
When a delivery date has been set, the joist products are loaded onto flat bed
trailers. The joist bundles are chained or strapped down to the trailer once the
trailer has been loaded. Joist products are usually shipped upside down. This
provides greater stability to the bundles since the top chord is usually a heavier
member than the bottom chord; and, in the more common underslung condition,
the top chord extends the entire length of the joist or Joist Girder, while the
bottom chord is shorter in length. Also, the lowest possible center of gravity is
achieved when the joist products are loaded in this manner.
There are occasions when the joists may be shipped in a “top chord up” fashion
or bundled “one up/ one down”. These cases may be necessary due to job site
or shipping considerations.
LOADING AND SHIPPING
Since the vast majority of joists are shipped by truck, attention will be
concentrated on this means of delivery. Most shipments are made by trucks
pulling flat bed trailers. However, some shipments, particularly LTL (less than
truck load) loads, are loaded onto closed-sided trailers.
Flat Bed Trailer - Shipment of joist products on flat bed trailers is by far the most
common form of conveyance. A few of the obvious reasons are:
•
•
•
•
Loading and unloading is much simpler than by any other means of
shipment.
Far greater flexibility of loading is possible in regards to the bulk, length,
weight and height of the shipment.
Delivery is made directly to the job site.
Timing of job site arrival can be estimated with reasonable accuracy.
During the loading operation, the joist bundles are placed on the bed of the
trailer, usually filling out the complete width of the bed. Spacers (normally
wooden slats called dunnage) are usually placed on top of each layer of joists,
perpendicular to their length. Additional bundles are then placed on top of the
spacers until the load is complete. When the loading operation is complete, the
entire load is chained (or strapped) down to prevent shifting or overturning (see
Figure 3.2).
Closed Trailer - The loading of joists onto closed trailers can be difficult, since the
loading crane cannot simply lower the joists in place. Instead, the crane must
balance the joist bundles on the end of the trailer bed, then "slide" them to the
interior, hopefully without gouging the trailer bed too badly or damaging the joists.
With a small number of short, light joists, this does not present a major problem.
However, the loading of a full shipment of joists in a closed trailer is strongly
discouraged.
10
Open Top Trailer - Also known as "Rag Tops", these trailers also lend
themselves to the loading of joists for LTL shipments since the lifting crane can
simply lower the joist bundles into place once the tarpaulin top has been rolled
back. For shipping fuller loads, difficulties regarding the positioning of bundles,
the removing of lifting cables or slings, and the danger to the personnel inside the
trailer body, are all present.
Figure 3.2 Loaded Delivery Truck with Joists in Upside Down Position
11
CHAPTER 4
RECEIVING, UNLOADING AND STORING
GENERAL
The handling of joist products must be accomplished with care and expertise,
and with the aid of proper equipment.
It is impossible to list every occurrence and type of improper handling of joist
products (such as pulling joists off the back of a trailer or shoving them off the
side of a truck). Suffice it to say that care must be exercised in any type of
handling procedure regarding joist products.
Joists and Joist Girders are not monolithic products; they are not like a rolled or
extruded structural shape, such as a beam, channel, angle or solid round. Joists
and Joist Girders are manufactured products, comprised of various components
that have been cut, bent, and shaped in such a manner that when the pieces are
assembled and connected to one another the final product is created. Unlike
solid structural members, joist products have spaces, separations and openings
between their various parts. Because of this, joist products are more susceptible
to damage and it is important that they be handled with care.
RECEIVING
Delivery of joist products to job sites by trucks pulling flatbed trailers is the most
common method (see Figure 4.1). Chains or straps are used to secure the entire
load to the trailer. The chains or straps prevent the load from falling off the side
of the trailer and prevent the load from shifting during transit.
The following three procedures should be considered mandatory regardless of
the method of conveyance of the joist products from the manufacturer to the job
site.
1) Inspection of the load for indicators of possible instability such as
shifted product or broken banding.
2) Inspection of the joist products for evidence of physical damage.
3) Verification of items being delivered by comparison with the piece
count and description on the Delivery Ticket or Bill of Lading.
When a truck arrives, the load should be inspected before releasing the chains or
straps that are securing the load. Bundles may have shifted in transit and could
be in danger of falling off the truck or the banding straps may be broken causing
12
the bundle to separate or “de-nest”. Such de-nesting can produce a dangerous
situation. If these or other signs of instability are present, steps must be taken to
assure that joist products will not fall when the chains or straps are released.
Once the stability of the load is confirmed, the chains or straps may be released
and the unloading process can proceed.
Figure 4.1 Loaded Truck Arriving at Jobsite for Unloading
A general inspection for any damage to the joist products is quite simple at the
time of receipt and it is critical that someone check the shipment for damage. The
receiving party should look for any permanent bend or deformation in the chords,
web members or end bearing seats. Broken welds, displaced or bent web
members, or any other deficiency or damage should be noted on the receiving
documents and reported to job site supervision. The manufacturer will not be
responsible for damage to the product unless a notation is made on the delivery
documents. The manufacturer should be notified immediately if damaged
material is detected.
A piece count also should be made of all joists, Joist Girders and accessories at
the time of receipt. Such count should be checked against the delivery
documents to ensure that all items have been included in the shipment. A piece
count is neither difficult nor time-consuming and is invaluable in preventing job
delays later on in the event that some material is missing. As in the case of
damage, unless notation is made on the delivery documents, the manufacturer
will not be responsible for claims of missing material. Diligence in this process
13
will assure that all of the joist products and accessories listed on the delivery
documents have arrived at the job site in good condition.
UNLOADING
Joist products are typically unloaded by either crane or forklift. Whenever
possible, joist products should be unloaded by bundles. Care must be exercised
to ensure that the removal of any given bundle does not cause another bundle to
fall. The entire top layer of joist products should be unloaded first, beginning with
the outer bundles. Subsequent layers should be unloaded the same way.
Bundles should be lifted off the truck and placed down gently. They should never
be dropped. If, in the process of receiving or unloading, it is determined that any
of the joist products arrived in a damaged condition, a notation should be clearly
entered on the delivery documents and the manufacturer should be notified so
that the damage can be repaired or the product replaced as quickly as possible.
Bundles should never be lifted by their strapping. The banding material is not
designed to carry the bundle’s weight. A banding strap may hold initially, but it
can break without warning, seriously injuring workers, damaging equipment or
the joist products. Sorting hooks should never be used for unloading or erecting
joist products.
UNLOADING WITH A CRANE
Care must be taken to ensure that the capacity of the unloading crane is not
exceeded. The preferred rigging method is to use two chokers configured in a
basket hitch and two-way spreaders (see Figure 4.2). Cables or chokers should
be run through the inside of the inverted V shape in the web system, taking care
not to damage the chords or webs. The attachments should be equally spaced
from each end and should be made to the chords of the joists at or near panel
points. When lifting points are being located, it is important to remember that the
bottom chord is often “up”, because many joist products are loaded for delivery
upside down to lower the bundle’s center of gravity. In this way damage to any
of the joists or Joist Girders is reduced and the load is more stable for shipping.
14
Figure 4.2 Lifting with a Crane Using Two Chokers Configured in a
Basket Hitch and Two-way Spreaders
The use of spreader cables is preferred because it provides a “two-point”
attachment, thereby producing a stable load. A “one-point” attachment to the
bundle is less desirable because it requires precise location of the balance point
and if the hoisting cable slips the load will tilt and become unstable.
Care must be taken to not rig joist products for hoisting in any manner that may
damage chord or web members. Damage to the chords or webs can produce
twisting and distortion and may affect load carrying capacity. Any damage that
occurs should immediately be brought to the attention of supervisory personnel.
Crane operators must meet current OSHA requirements for training and
certification (see OSHA 1910.180(b) General requirements.).
UNLOADING WITH A FORK TRUCK
When joist bundles are unloaded using a fork truck (see Figures 4.3 and 4.4),
care must be taken to ensure that the capacity of the lift is not exceeded. The
fork truck operator must be sure to adjust the spacing of the forks to prevent
damage to chord or web members. The operator must be sure that the load is
balanced. Figure 4.5 shows a load that is NOT properly balanced. The operator
in this situation should lower the bundle and adjust the fork location so as to
produce a balanced load. Care must also be taken to ensure that the forks do
not damage the joists. Figure 4.6 shows a lift where one of the forks is “wedged”
between two web members. This lifting technique may be helpful in preventing
the bundle from shifting but the webs could be damaged. Figure 4.7 shows
better fork placement. All safety and procedural issues covered in the crane
15
section apply equally well to fork trucks. Forklift operators must meet current
OSHA requirements for training and certification (see OSHA 1910.178(l)(1) Safe
operation.).
Figure 4.3 Unloading a Bundle of Joist Girders with a Fork-type Lift
Typically Available on Construction Sites
Figure 4.4 Storing a Bundle of Joist Girders with a Fork Type Lift
on Proper Timbers
16
Figure 4.5 Improper Joist Handling – Load is Not Balanced on the Forks
Figure 4.6 Improper Joist Handling – Fork on the Left is Wedged Between
Two Web Members and Could Damage the Webs
17
Figure 4.7 Proper Joist Handling - Forks Have Solid Contact with the Joist
Chords and Do Not Put Unnecessary Pressure on the Web Members
ADDITIONAL UNLOADING CONSIDERATIONS
Many factors can complicate unloading activities and procedures. Poor site
conditions, lack of access to unloading zones, inadequate product lay-down
areas, equipment problems, special joist product dimensions and shipping
configuration for non-standard products are examples of the kinds of issues that
may require extra attention. Proper planning for these and similar conditions is
critical to a smooth and safe unloading process. It is not possible to discuss
every conceivable condition or situation that may arise, but several of the more
common issues are addressed below.
Bundle is too heavy – If the equipment available to unload the joist products is
not of sufficient capacity to safely lift the bundle, it may be necessary to break the
bundle on the truck. Personnel conducting the unloading operation must
exercise extreme caution in this situation to ensure that the bundle to be broken,
as well as the rest of the load, remains secure as the individual pieces are
removed from the bundle and unloaded.
Long and slender joists – A standard Deep Longspan joist may be 144 feet
long. Once the joists are installed and braced, they have great strength.
However, handled singly they can be very flexible and unpredictable.
18
Determination of lifting points and rigging techniques by a qualified person is
critically important for such products. The erector must be aware of the
possibility that the joist could “fold-up” under its own weight if not lifted and
handled properly.
Joists are loaded flat – It is not unusual for non-standard joist products to be
specified at depths that can not be loaded and transported in a vertical position.
The alternative is for the joists to be loaded and shipped in the horizontal or flat
position. Unloading personnel must be aware that the joists are particularly
vulnerable to damage in this position and should be rotated to a vertical position
for handling as soon as practical in the unloading process.
Joists are loaded right side up – Much has been said about joist products
being loaded and shipped upside down. There are occasions when safety and
efficiency considerations make it better to load and ship joists right side up. The
unloading crew should be aware of this and not turn these joists over prior to
storing or erection.
Standard bridging bundle weight – Joist manufacturers supply bridging in
bundles shipped to the job site. The maximum weight of these bundles as
required by the OSHA Regulations cannot exceed 1000 pounds (454 kg). The
compact nature of bridging bundles makes it easy to underestimate the weight of
the bundles. Lifting equipment operators should be aware of this requirement as
an aid to safe lifting and handling.
JOB SITE STORAGE OF JOIST PRODUCTS
Joist products should be stored in a location that is removed from job site traffic
routes. Joists and accessories should be set on proper timbers so that they are
free from contact with the ground. For the first layer, place the timbers under
panel points at equal distances from the ends. Turning the tags in the same
direction will aid in identifying members and make sorting easier. When joist
bundles are stacked, timbers should be placed approximately at panel points and
in line with the previously placed timbers below. Note however, it is preferable to
not stack joists unless space is limited. It is also advisable to limit the height of
the stack to assure stability.
Joists should be stored in the same position in which they are shipped. Joists
that are shipped vertically should be stored vertically and joists that are shipped
flat should be stored flat. When joists are stored horizontally, the chords are
more apt to be damaged, and sweep or distortion of the joists is more likely to
occur. Additional timbers may be required on the ground and between the joists
to help prevent this damage. If banding straps have been broken or stretched
and the joists have become de-nested, the joists should be re-secured to prevent
damage.
19
Joist products are supplied with a shop coat of paint, when specified, that
complies with the Steel Joist Institute’s Standard Specifications Load Tables &
Weight Tables. The typical shop applied paint that is used to coat steel joists
and Joist Girders is a dip applied, air dried paint. The paint is intended to be an
impermanent and provisional coating which will protect the steel for only a short
period of exposure in ordinary atmospheric conditions. In some cases joist
products are supplied unpainted. Standard shop practice is to supply Composite
Steel Joists unpainted as paint may potentially hinder the installation of field
welded shear studs to the joist top chord. The length of time any joist product is
exposed to the weather while being stored at the jobsite should be limited,
whether or not the joist products are shop painted.
20
CHAPTER 5
ERECTING JOIST PRODUCTS
The Steel Joist Institute publishes standards on various products. Because
handling and erection requirements differ from one product to another, these
products will be considered separately. It bears repeating that each of the Steel
Joist Institute’s standard products is an open web truss, designed in accordance
with the appropriate specifications, and manufactured by joining various
component members into the proper configuration; in short, pieces put together
to create a product. Because of this, these products must be handled with
greater care than a rolled structural shape such as a beam or channel. Another
common characteristic of all of these joist products is that, until they are correctly
and completely installed they are inherently unstable. Complete installation
includes attachment of joist products to supporting structural elements and the
installation and anchorage of all required bridging or other bracing.
JOIST GIRDERS
Joist Girders are primary structural members that are normally supported by
columns; they can, however, bear on steel plates on masonry or concrete
supports. They can be underslung and rest on the top or side of the columns or
be square-ended and frame into the columns. On the Joist Placement Plans,
Joist Girders are given a mark number for erection placement purposes and that
same corresponding number will be found on the tag attached to the girder itself.
Joist Girders, unless otherwise specified, are cambered in accordance with the
chart shown in Chapter 9 Miscellaneous Topics - Camber. The top chord can be
either parallel with the bottom chord; single pitched, or double pitched. In many
instances Joist Girders are not loaded symmetrically; consequently, it is
imperative that the "Tag End" of a Joist Girder be placed as indicated on the Joist
Placement Plans. Often, when Joist Girders are very long (e.g. >100 feet), they
may be shipped in two or more pieces and assembled at the job site. When this
occurs, the mates must be properly matched as marked from the joist
manufacturer; otherwise the pieces will not fit correctly. As with all joist products,
Joist Girders usually come bundled upside down. They should be stored
properly, kept off the ground and protected from the elements.
Joist Girders must be erected singly. They are to be properly hoisted with
attachments placed at top chord panel points. Both ends of the Joist Girders are
to be attached to supports immediately after the girders are set. Since Joist
Girders are not bridged, they are normally prevented from overturning by means
of a vertical stabilizer plate at the bottom chord (see OSHA 1926.757(a)(1) and
Appendix D, Section 1004.5). These plates "knife in" between the bottom chord
angles that are spaced apart (see Figure 5.1). A stabilizer plate is required to be
21
provided on each column. The stabilizer plate must be a minimum of 6 inches by
6 inches and must extend at least 3 inches below the bottom chord of the Joist
Girder. If a stabilizer plate cannot be used because of an interference or other
constructability issue, some other means of laterally stabilizing the girder must be
provided (see OSHA 1926.757(a)(2)). Do not weld the Joist Girder bottom chord
to the stabilizer plate unless called for on the joist placement plans or in the
contract documents. Any final connection of the bottom chord to the column
should be in accordance with instructions from the Specifying Professional.
Figure 5.1 Joist Girder Bearing on Column with Vertical Stabilizer Plate
Joist Girders must bear a minimum of 4 inches on steel supports and a minimum
of 6 inches on steel plates supported by masonry or concrete, (see Appendix D,
Section 1004.4). The minimum end anchorage must be either two 1/4 inch fillet
welds 2 inches long, or two 3/4 inch diameter bolts (see Appendix D, Section
1004.6). The Joist Placement Plans and the project structural drawings should
be checked for specific details or requirements.
When Joist Girders are used to provide lateral stability to the supporting member,
the final connection shall be made by welding or as designated by the Specifying
Professional.
Particular attention must be paid to the setting of square ended Joist Girders right
side up. In most cases, the first diagonal web member from the support end of
the girder runs from the top chord at the point of support down to the bottom
chord (see Figure 5.2). If doubt remains as to the proper orientation of the Joist
Girder, the Joist Placement Plans should be checked and/or the joist supplier
should be contacted.
22
Joist Girders directly support the steel joists which bear on them. Typically, joists
are placed at top chord panel points of the Joist Girder. It is important that the
joist spacing be checked prior to placing the joists on the Joist Girder. This can
be accomplished by taping “in the air” or by marking the Joist Girder on the
ground. It is usually safer and more efficient to measure on the ground. When
placing joists on a Joist Girder, the Erector should set them with care so that the
girder is neither laterally displaced nor forced out of plumb. The joists should be
attached to the girder as they are set. Since Joist Girders are not "bridged" as
are joists, some bracing is normally required for the bottom chord (the top chord
of the girder is braced by the attachment of the joists bearing on them). The Joist
Placement Plans will indicate the location of the bracing, commonly referred to as
“loose struts” or a “BCB” (Bottom Chord Brace), that will be separate pieces of
material (furnished by the joist supplier) to be attached either by bolting or field
welding from the bottom chord of the joist to the bottom chord of the Joist Girder.
Additional bracing near the first bottom chord panel points of the girder may be
required (see Appendix D, Section 1004.9). No loads are to be placed on the
Joist Girder until the joists are in place and attached to the girder (see Appendix
D, Section 1004.5). When construction loads are then placed either on the joists
or the girder, such loading must not exceed the capacity of these products (see
Appendix D, Section 1005).
Figure 5.2 Proper Orientation of Square-ended Joist Girder
When a Joist Girder is being removed from a bundle, care should be taken to
assure that the remaining girders in the bundle are still secure and stable. Hook
the cable at the midpoint of the bottom of the girder to remove it from the bundle.
The preferred method to turn a girder over is to lift it by the bottom chord, lay it
horizontally on timbers, unhook and then re-hook to the top chord for hoisting to
the Connectors. Make sure the mark number on the tag is checked before
sending it to the Connectors. Also, check the Joist Placement Plans if you're not
sure of the proper orientation of the girder. It is necessary to make sure that the
structure is stable prior to the start of Joist Girder erection (see OSHA
23
1926.757(a)(5)). Careful attention to these details will make it much easier to
erect the Joist Girders and maintain proper bay spacing.
Typically, Joist Girders are connected to columns. The first girder can be erected
with Connectors working from man lifts or ladders (see Figure 5.3) although
OSHA does permit Connectors to work directly from the structure when they will
be 30 ft. or less above a lower level (see OSHA 1926.760). Each erection
company must determine what type of fall protection to use for a given project in
accordance with current OSHA regulations. Some companies rely heavily on
man lifts while others prefer to use lanyards and lifelines. Always make sure the
identification tag end on the Joist Girder is properly oriented before making the
connection. As each girder is lowered into place, one Connector makes the first
end. Then, the other Connector makes the other end. Only after the seat at
each end is attached, and each end of the bottom chord is restrained by the
column stabilizer plate may the hoisting lines be released (see OSHA
1926.757(a)(1)).
Figure 5.3 Single Point Lift of Joist Girder Being Set on Two Columns;
Bottom Chord “Knifed-in” Between Stabilizer Plates Attached to Columns
COLUMN JOISTS
Joists located at or near column lines are referred to as OSHA Column Joists, tie
joists, strut joists or “OC” joists. The current OSHA safety standard requires that,
where columns are not framed in at least two directions with solid structural steel
members, joists at column lines shall be field bolted and the joist bottom chords
24
must be restrained by a vertical stabilizer plate (see OSHA 1926.757(a)(1)). The
bearing seats of Column Joists will always be provided with slotted holes so that
the bolts can be inserted at the time of joist placement. Where constructability
does not allow a steel joist to be installed directly at the column, the OSHA safety
standard states that an alternate means of stabilizing the tie joists shall be
installed on both sides near the column (see OSHA 1926.757(a)(2)).
It is important that the bay spacing be checked prior to erecting the Column
Joists. This can be accomplished by taping "in the air" or by verifying the
Column-to-Column dimension on the ground. It is usually safer and more
efficient to measure on the ground.
The effective date of the current OSHA Safety Standards for Steel Erection, 29
CFR Part 1926 is July 18, 2001. That standard contains Column Joist
requirements in 1926.757(a)(3) Where steel joists at or near columns span 60
feet (18.3 m) or less, the joist shall be designed with sufficient strength to allow
one employee to release the hoisting cable without the need for erection
bridging. On March 22, 2002, an “Inspection policy and procedures for OSHA’s
steel erection standards for construction” was issued and subsequent to that, on
July 18, 2003 an OSHA Notice “Extension of enforcement policy on column
joists” was issued. The effective date of that enforcement policy was originally
extended to July 18, 2004, or until a new directive was to be issued. OSHA has
now extended this policy indefinitely. The policy is as follows: “for all joists at or
near columns that span 60 feet or less, employers will be considered to be in
compliance with 1926.757(a)(3) if they erect these joists either by: (1) installing
bridging or otherwise stabilizing the joist prior to releasing the hoisting cable, or
(2) releasing the cable without having a worker on the joists.”
The SJI has conducted extensive research to develop design methods in an
effort to meet the original OSHA provision for Column Joists (Emerson 2001 and
Ziemian et al 2004). The research was to produce design procedures for SJI
member companies to use in the design of Column Joists. In attempting to
develop the design procedures, it was necessary to make assumptions regarding
field conditions that could affect the strength of Column Joists. After careful
consideration of the wide range of variability in field conditions, the SJI member
companies determined that for some joist lengths there are no existing joist
designs that would provide the necessary stability (even with the stabilizer plate).
Therefore, OSHA not withstanding, the SJI can not recommend that employees
ever be allowed on unbridged Column or tie joists. SJI member companies use
the DANGER TAG shown in Figure 5.4 to warn the erection companies not to
allow employees on Column Joists that have this tag.
25
Figure 5.4 Typical Danger Tag Attached to Every Column Joist
by the Joist Manufacturer
If the Column or tie joist spans more than 60 feet it needs to be set in tandem
with an adjacent joist with all bridging installed unless an alternative method of
erection is used that provides the same stability. This alternative method needs
to have been designed by a qualified person and be included in a site-specific
erection plan (see OSHA 1926.752(e)). A site-specific erection plan allows the
employer to develop alternative means and methods that provide employee
protection equivalent to the provisions of the federal regulations (see OSHA
1926.752(e), 1926.753(c)(5), 1926.757(a)(4) and 1926.757(e)(4)).
SHORT SPAN JOISTS – K-SERIES AND KCS
Prior to erection, the joists should have been stacked in bundles, possibly upside
down, at the job site as described in Chapter 4. The bundles should be placed
so that the joist tags discussed in Chapter 3 are accessible to the Erector. When
the Erector begins the process of placing joist products on the structure, there
are several initial safety factors to remember. Proper handling and rigging
techniques must be used as previously discussed in Chapter 4. This includes
26
never lifting joist bundles by their strapping and never lifting joists by their webs.
Always keep hands and fingers away from pinch points. Remember, joist
products are often shipped and stored upside down. If this is the case, they must
be turned "right side up" to erect.
The issue of erection stability is critically important for these products. The type
and quantity of bridging required to maintain stability during erection is defined in
the Steel Joist Institute’s Standard Load Tables. In the body of the K-Series
Load Table, RED shading is used to indicate Erection Bridging requirements as a
function of span and product designation (e.g. 26K8). Erection Bridging is
defined in the OSHA safety standard as “the bolted diagonal bridging that is
required to be installed prior to releasing the hoisting cables from the steel joists”
(see OSHA 1926.751). The preamble to the Load Table states that “where the
joist span exceeds the unshaded area of the load table, the row of bridging
nearest the mid-span shall be diagonal bridging with bolted connections at the
chords and intersections.” Each K-Series joist must be placed in accordance
with the Joist Placement Plans and held with the hoisting equipment until both
sides of the bearing seat on one end of the joist can be attached and the required
bolted diagonal erection bridging is installed. The bridging row(s) must be
anchored to prevent lateral movement of the joist (see Appendix B, Section 6).
The final attachment of the joist ends can then be made by either bolting or
welding to the support structure as shown on the contract structural drawings.
In bays where Erection Bridging is not required, it may be permissible to land the
joists in bundles. Before this can be done, joists must be sorted out on the
ground and proper numbers placed in bundles for erection. Be careful when
cutting the straps. Keep hands and feet clear. Joists may move and sometimes
fall over when the straps are cut. Typically, four to six joists will be hoisted in a
bundle, depending on the actual number required in the bay. Make sure all of
the tags are turned in the proper direction as joists are not always symmetrical.
Check that the ends are even and all the joists are in proper sequence to be
spread out on the building. Refer to the Joist Placement Plans for proper joist
spacing and length of bearing.
The spacing of joists in bays must be marked on supporting beams or Joist
Girders. This is typically done after members are erected, but with proper
planning can be done on the ground. The final locations must be in accordance
with the Joist Placement Plans.
When erecting joists in bundles, Connectors should land the bundle on the
supporting structure as close as possible to the center of the bay (see Figure
5.5). Check for proper bearing at each end before releasing the hoisting cables.
When releasing the cables, be sure to hold them until they clear the bundle or the
crane operator swings the boom away from the bundle so that they don't hang
up. After the cables are released, make sure all the joist ends are sitting flat on
their supports. If necessary, use a spud wrench to shift the joists into the flat
27
position. If the joists are not to be spread and attached promptly, the bundle
should be re-secured to prevent unintentional movement to keep them from
falling (see OSHA 1926.757(a)(6)).
Figure 5.5 Landing a Bundle of Joists Near the Center of a Bay
In the case where all of the joists in a bundle are the same length and are to be
placed in the building next to one another, the bundle may be lifted and set in
place on the building. A joist bundle should never be lifted by the strapping. If
the bundle has been stored upside down it must be turned right side up (with
care) on the ground before lifting for placement on the building. In order for this
method to be utilized, the following three conditions must apply:
1) All of the joists in the bundle are turned the same way - that is, they are
not bundled one up, one down, etc.
2) All of the joists are the same length.
3) None of the joists are staggered lengthwise in the bundle.
If the joists are being erected in bundles, the bundling straps can be broken after
the bundle has been placed on the supporting structure, prior to release of the
hoisting cables.
If the above three conditions do not apply, the joist bundles must first be turned
right side up (if stored upside down), then broken open on the ground, with care
being taken not to damage the joists as the bundling straps are broken. The
joists can then be lifted onto the building individually by attachment of hooks or
28
cables to the top chord, at top chord panel points, and placed in accordance with
the Joist Placement Plans. In certain situations it may be advantageous for joists
to be rebundled and hoisted as a group. Remember, each joist has a metal,
embossed tag that carries the erection mark number, the contract number and
the name of the joist manufacturer; the mark number on the joist tag needs to be
matched with the mark number on the Joist Placement Plans for proper
placement. In those instances where a joist is not symmetrical, the Joist
Placement Plans will indicate where the "Tag End" of the joist is to be placed.
The "Tag End" is that end of the joist to which the metal tag is attached.
If the joist end bears on a concrete or masonry support, it must rest on a steel
bearing plate, anchored to the masonry unit, for a minimum distance of 4 inches.
If the joist end is resting on a steel support, it must bear a minimum of 2 1/2
inches (see Appendix B, Section 5.3). The Joist Placement Plans should be
checked for specific end bearing details.
Immediately after each subsequent joist is set in its proper position, both sides of
the joist bearing seat at one end of the joist must be attached (see Figure 5.6).
This is one of the most important safety procedures that can be practiced in the
erection of joists. This initial attachment provides additional stability to the joist,
thus making it safer for the Erector to complete the joist installation (see OSHA
1926.757(b)(3)).
Ironworkers on each end should work closely together when spreading joists.
This is typically accomplished by sliding individual joists to their final marked
location. Great care should be taken to maintain equal bearing at the ends.
When the joists are in the correct location, both sides of one end should be
attached as soon as possible. Attachment of the K-Series joist to a Joist Girder
or other structural member may be made by either bolting or welding in
accordance with current SJI Specifications (see Appendix B, Section 5.6) and the
OSHA safety standard (see OSHA 1926.757(a)(8) and (b)(1)).
When K-Series joists are used to provide lateral stability to the supporting
member, the final connection shall be made by welding or as designated by the
Specifying Professional.
Some Erectors may choose to string, “Christmas Tree” or employ multiple lift
rigging of several individual joists. Whenever this type of joist erection is
implemented, a qualified person should do the rigging and sound practices
should always be followed. This method should not be used to hoist multiple
bundles of joists.
Bridging is a critical component of the steel joist system. Its purpose is to brace
the joists against lateral movement during erection and placing of construction
loads. For bridging to function properly, it must be anchored. This can be
accomplished by securing the bridging to a fixed object such as a wall, steel
29
beam or other stable portion of the structure. OSHA refers to this anchorage
point as a bridging terminus point (see OSHA 1926.757(a)(10)). Depending on
the type and length of the specified joists, two conditions must be met before the
hoisting cables may be released or any Erectors are allowed out on the joists:
1) Required Erection Bridging must be installed; and
2) Both sides of at least one end of the joist must be attached to the
supporting structure (see Figure 5.6).
On steel joists that do not require erection bridging as shown by the unshaded
area of the Load Table, only one employee shall be allowed on the steel joists
unless all bridging is installed and anchored.
Figure 5.6 Joist Seat Attachment to Support Structure at Least at One End
on Both Sides of the Seat Immediately Upon Final Placement
The Erection Bridging may be installed from a man lift. For the specific
requirements of the joists being erected, consult the Joist Placement Plans and
the SJI K-Series Specifications. Sometimes, center X-type bridging is bolted to
the joists on the ground. This may be more easily accomplished by laying the
joist down horizontally, attaching the X-Type bridging to the joist and then placing
a bolt through the bridging at their intersection. Then the joist can be erected.
As the crane stabilizes the joist, an Ironworker attaches the loose end of the
bridging to the previously erected joist already up on the structure. This may be
30
done by standing on a walk-board bearing on the bottom chords of previously
erected and bridged joists.
The joist nearest the end of the building should be bridged first, with the ends of
the bridging rows being properly anchored. Installation should start at one end of
the joist and progress to the other end of the joist. The joist should be
straightened laterally and aligned vertically by the Erectors as the bridging rows
are being installed. Once the joist is straight, the bridging should be welded or
bolted. The far ends of the bridging rows should also be anchored.
With respect to horizontal bridging, the amount furnished allows for a minimum
lap length of 2 inches to 4 inches, plus an additional percentage more; drops of 3
feet or more should always be used. For X-type bridging, the exact numbers of
pieces are furnished, designated with mark numbers which correspond to these
same numbers shown on the Joist Placement Plans.
In certain design applications, the joists are designed to bear on the bottom
chord. This produces a “top heavy” condition. Therefore, they must be braced
with an additional row of X-type bridging at or near the bearing support as they
are being erected as shown in Figure 5.7.
Before going out on any joist, be sure that at least one end is attached on both
sides and required Erection Bridging has been installed and anchored. Going
out on unsecured joists is unsafe. Finally, attach the other end of the joist by
welding or bolting both sides.
Figure 5.7 Required X-type Bridging at Support for Bottom Bearing Joists
31
If joists don’t fit or there is an interference with other materials, do not cut or
alter the joists. Written permission and instructions from the joist manufacturer
and the Engineer of Record must be obtained prior to making any necessary field
modifications to the joist products (see OSHA 1926.757(a)(7)).
LONGSPAN AND DEEP LONGSPAN JOISTS – LH- AND DLH-SERIES
As with K-Series and KCS Joists, Longspan (LH-Series) and Deep Longspan
(DLH-Series) Joists are usually delivered upside down and strapped in bundles.
Each joist has a metal embossed tag which carries the contract number, the
erection mark number, and the manufacturer’s name. The joists should be
stored properly off the ground and protected from the elements as described in
Chapter 4.
Once again, the issue of Erection Bridging is very important. In the body of the
LH- and DLH-Series Load Tables, shading is used to indicate Erection Bridging
requirements as a function of span and product designation (e.g. 32LH06).
Erection Bridging is the bolted diagonal bridging that is required to be installed
prior to releasing the hoisting cables. The load table shading is RED, BLUE or
GRAY. RED shading indicates a single row nearest mid-span, BLUE shading
indicates two rows nearest the third points for spans of 60 feet or more, but less
than 100 feet, and GRAY shading indicates all rows for spans of 100 feet through
144 feet. Each joist must be placed in accordance with the Joist Placement
Plans and held with the hoisting equipment until both sides of the bearing seat on
one end of the joist can be attached and the required bolted diagonal erection
bridging is installed. The bridging row(s) must be anchored to prevent lateral
movement of the joist (see Appendix C, Section 105). The final attachment of
the joist ends can then be made by either bolting or welding to the support
structure as shown on the contract structural drawings.
A quite common and effective practice of erection, when bolted diagonal bridging
is used, is for two or more joists to be bridged on the ground, and then hoisted
onto the building (using hooks and/or cables at top chord panel points) as a unit
(see Figure 5.8). Once on the structure, the joists are set and spaced correctly,
both sides of the seat on one end attached, then straightened laterally and
aligned vertically as the bolted diagonal bridging is tightened.
Another common practice is to erect the joists singly with the bolted bridging
loosely attached to one side of the joist. Once the first joist is properly set and
attached, the next joist is hoisted onto the building with bolted diagonal bridging
loosely attached to one side of it. When the second joist has been properly set
and attached to its support, the bridging from the previous joist is connected to it
(see Figure 5.9). This procedure should be continued to the end of the joist run.
Once the entire run is set and straightened, the bridging bolts need to be
tightened.
32
Figure 5.8 Tandem Joists with X -type Bridging Being Hoisted Together
Figure 5.9 Single Joist Being Hoisted with Loose X -type Bridging Attached
33
In regards to the setting of Longspan and Deep Longspan Joists, greater
attention to correct placement must be exercised than in the case of Shortspan
Joists (K-Series and KCS Joists) because:
•
There is more likelihood that these joists are not symmetrical; and
•
The X-type bridging rows are fixed. When the joists are not
symmetrical, the Joist Placement Plans will indicate where the "Tag
End" of the joist is to be placed.
Longspan and Deep Longspan Joists bearing on concrete or masonry supports
in the building must bear on steel plates, anchored to the masonry unit for a
minimum distance of 6 inches (unless special conditions exist); if resting on steel
supports, a minimum bearing length of 4 inches is required (see Appendix C,
Section 104.4). The Joist Placement Plans and the project structural drawings
should be checked for specific details.
Under no circumstances are construction loads of any description to be placed
on unbridged joists. In addition, Erectors are cautioned that many joists are
laterally unstable until properly bridged. Extreme care should be exercised until
the joists are properly bridged and the bridging and the joists are properly
anchored.
As with Shortspan Joists (K-Series and KCS Joists), both sides of the Longspan
or Deep Longspan Joist bearing seat on one end of the joist must be attached as
soon as possible after the joist is in the correct location on the structure (see
Figure 5.6). This is one of the most important procedures in the erection of joists.
It provides greater stability to the joist and prevents the joist from being
accidentally bumped or blown off the building.
When LH- or DLH-Series joist are used to provide lateral stability to the
supporting member, the final connection shall be made by welding or as
designated by the Specifying Professional.
The joists should be completely bridged immediately after final placement and
end attachment is completed in accordance with OSHA and SJI requirements.
The Joist Placement Plans indicate the number of rows of bridging required. For
bolted diagonal bridging, the location of the bridging rows is usually fixed by the
bridging clips that are welded to the joists.
For Longspan and Deep Longspan Joists, bridging is specified as follows (see
Appendix C, Section 104.5):
For spans up through 60 feet (18288 mm), welded horizontal bridging may be
used except where the row of bridging nearest the mid-span is required to be
bolted diagonal bridging as indicated by the RED SHADED area in the Load
34
Table. For spans over 60 feet (18288 mm) bolted diagonal bridging shall be
used as indicated by the BLUE and GRAY SHADED areas of the Load Table.
Hoisting cables shall not be released until the following bolted diagonal bridging
is properly installed:
Span
33 feet up through 60 feet
Bolted Diagonal Bridging
As indicated by RED shading in the Load Table;
One row nearest mid-span
Over 60 feet up through As indicated by BLUE shading in the Load Table;
100 feet
Two lines nearest the third points
Over 100 feet
As indicated by GRAY shading in the Load Table;
All lines
(see Appendix C, Section 105)
The joist nearest the end of the building should be bridged first, with the ends of
the bridging rows being properly anchored. Installation should start at one end of
the joist and progress to the other end of the joist. The joist should be
straightened laterally and aligned vertically by the Erectors as the bridging rows
are being installed. Once the joist is straight, the bridging should be welded or
bolted. The far ends of the bridging rows should also be anchored.
With respect to horizontal bridging, the amount furnished allows for a minimum
lap length of 2 inches to 4 inches, plus an additional percentage more; drops of 3
feet or more should always be used.
For X-type bridging, the exact numbers of pieces are furnished, designated with
mark numbers which correspond to these same numbers shown on the Joist
Placement Plans. Each bridging connection to the joist must be able to resist the
horizontal bracing force shown in Appendix C, Section 104.5, Table 104.5-1.
Where two attachment points to the joist are utilized, each attachment must be
able to resist one-half of the bracing force given in the table.
After the bridging is installed, the final connections are made on the joist seats.
These shall be a minimum of two 1/4 inch fillet welds 2 inches long, or two 3/4
inch diameter bolts or equivalent (see OSHA 1926.757(b)(2)).
Bottom bearing joists must be erected right side up in order to perform properly.
The first diagonal web member at the support usually runs from the top chord
down to the bottom chord as shown in Figure 5.10. Also, the camber in the joist
will "bow up" the center of the joist (see Figure 5.10). If there is any doubt
regarding which is the top and bottom of the joist, the Joist Placement Plans
should be checked and/or the joist supplier should be contacted.
35
Figure 5.10 Profile View of Bottom Bearing Joist with Camber
For bottom bearing joists, the hoisting cables shall not be released until the ends
are restrained laterally and the bridging is installed (see Appendix C, Section
105). Normally a row of diagonal bridging at the ends of the joists is specified in
order to provide stability. Where a bottom bearing joist is extended beyond its
support to form a cantilevered end, a row of diagonal bridging near the support
should first be installed. In addition, the project structural drawings may indicate
a row of diagonal bridging in the cantilevered portion to provide stability. Care
should be exercised in installing this bridging since the cantilever is supported at
only one end.
If the joists have bottom chords extended over and connected to a column,
beam, wall, or other structure, the connection should be made in accordance with
the project structural drawings and/or instructions from the Specifying
Professional.
When uplift forces are a design consideration, a row of bottom chord bridging is
required near each end of the joists (see Appendix C, Section 104.12).
Longspan and Deep Longspan Joists, LH- and DLH-Series may have a single
sloped or a double sloped top chord. In the case of a single sloped top chord,
the Erector must be sure to set the joist "right-end-to" (the Joist Placement Plans
will show where the "Tag End" is to be placed) and to place the bridging pieces in
the correct location for easy erection. All field-welding of the joists and bridging
must be done with considerable care. In general, the component members of the
joists and, in particular the bridging pieces are relatively thin; careless or heavyhanded welding can easily damage these members.
36
COMPOSITE STEEL JOISTS – CJ-SERIES
Composite Joists are usually delivered right-side up and strapped in bundles.
Each joist has a metal embossed tag which carries the contract number, the
erection mark number, and the manufacturer’s name. The joists should be
stored properly off the ground and protected from the elements as described in
Chapter 4.
Once again, the issue of Erection Bridging is very important. Erection Bridging is
the bolted diagonal bridging that is required to be installed prior to releasing the
hoisting cables. For spans up through 60 feet refer to joist manufacturer’s joist
placement plans for Erection Bridging requirements. For spans over 60 feet, but
less than 100 feet two rows of Erection Bridging are required nearest the third
points. For spans over 100 feet all rows are to be Erection Bridging. Each joist
must be placed in accordance with the Joist Placement Plans and held with the
hoisting equipment until both sides of the bearing seat on one end of the joist can
be attached and the required bolted diagonal erection bridging is installed. The
bridging row(s) must be anchored to prevent lateral movement of the joist (see
Appendix E, Section 105). The final attachment of the joist ends can then be
made by either bolting or welding to the support structure as shown on the
contract structural drawings.
In bays where Erection Bridging is not required, it may be permissible to land the
joists in bundles. Before this can be done, joists must be sorted out on the
ground and proper numbers placed in bundles for erection. Be careful when
cutting the straps. Keep hands and feet clear. Joists may move and sometimes
fall over when the straps are cut. Typically, four to six joists will be hoisted in a
bundle, depending on the actual number required in the bay. Make sure all of
the tags are turned in the proper direction. Check that the ends are even and all
the joists are in proper sequence to be spread out on the building. Refer to the
Joist Placement Plans for proper joist spacing and length of bearing.
The spacing of joists in bays must be marked on supporting beams or Joist
Girders. This is typically done after members are erected, but with proper
planning can be done on the ground. The final locations must be in accordance
with the Joist Placement Plans.
When erecting joists in bundles, Connectors should land the bundle on the
supporting structure as close as possible to the center of the bay. Check for
proper bearing at each end before releasing the hoisting cables. When releasing
the cables, be sure to hold them until they clear the bundle or the crane operator
swings the boom away from the bundle so that they don't hang up. After the
cables are released, make sure all the joist ends are sitting flat on their supports.
If necessary, use a spud wrench to shift the joists into the flat position. If the
joists are not to be spread and attached promptly, the bundle should be re-
37
secured to prevent unintentional movement to keep them from falling (see OSHA
1926.757(a)(6)).
In the case where all of the joists in a bundle are the same length and are to be
placed in the building next to one another, the bundle may be lifted and set in
place on the building. A joist bundle should never be lifted by the strapping. If
the bundle has been stored upside down it must be turned right side up (with
care) on the ground before lifting for placement on the building. In order for this
method to be utilized, the following three conditions must apply:
1) All of the joists in the bundle are turned the same way - that is, they are
not bundled one up, one down, etc.
2) All of the joists are the same length.
3) None of the joists are staggered lengthwise in the bundle.
If the joists are being erected in bundles, the bundling straps can be broken after
the bundle has been placed on the supporting structure, prior to release of the
hoisting cables.
If the above three conditions do not apply, the joist bundles must first be turned
right side up (if stored upside down), then broken open on the ground, with care
being taken not to damage the joists as the bundling straps are broken. The
joists can then be lifted onto the building individually by attachment of hooks or
cables to the top chord, at top chord panel points, and placed in accordance with
the Joist Placement Plans. In certain situations it may be advantageous for joists
to be rebundled and hoisted as a group. Remember, each joist has a metal,
embossed tag that carries the erection mark number, the contract number and
the name of the joist manufacturer; the mark number on the joist tag needs to be
matched with the mark number on the Joist Placement Plans for proper
placement. In those instances where a joist is not symmetrical, the Joist
Placement Plans will indicate where the "Tag End" of the joist is to be placed.
The "Tag End" is that end of the joist to which the metal tag is attached.
If the joist end bears on a masonry or concrete support, it must rest on a steel
bearing plate, anchored to the masonry unit or concrete, for a minimum distance
of 4 inches at seat depths less than 5 inches and 6 inches at seat depths of 5
inches and greater, over the masonry or concrete support (see Appendix E,
Section 104.4(a)). If the joist end is resting on a steel support, it must bear a
minimum of 2 1/2 inches at seat depths less than 5 inches and 4 inches at seat
depths of 5 inches and greater (see Appendix E, Section 104.4(b)). The Joist
Placement Plans should be checked for specific end bearing details.
Immediately after each subsequent joist is set in its proper position, both sides of
the joist bearing seat at one end of the joist must be attached. This is one of the
most important safety procedures that can be practiced in the erection of joists.
38
This initial attachment provides additional stability to the joist, thus making it safer
for the Erector to complete the joist installation (see OSHA 1926.757(b)(3)).
Ironworkers on each end should work closely together when spreading joists.
This is typically accomplished by sliding individual joists to their final marked
location. Great care should be taken to maintain equal bearing at the ends.
When the joists are in the correct location, both sides of one end should be
attached as soon as possible. Attachment of the CJ-Series joist to a Joist Girder
or other structural member may be made by either bolting or welding in
accordance with current SJI Specifications (see Appendix E, Section 104.7) and
the OSHA safety standard (see OSHA 1926.757(a)(8)).
When CJ-Series joists are used to provide lateral stability to the supporting
member, the final connection shall be made by welding or as designated by the
Specifying Professional.
Bridging is a critical component of the steel joist system. Its purpose is to brace
the joists against lateral movement during erection and placing of construction
loads. For bridging to function properly, it must be anchored. This can be
accomplished by securing the bridging to a fixed object such as a wall, steel
beam or other stable portion of the structure. OSHA refers to this anchorage
point as a bridging terminus point (see OSHA 1926.757(a)(10)). Depending on
the type and length of the specified joists, two conditions must be met before the
hoisting cables may be released or any Erectors are allowed out on the joists:
1) Required Erection Bridging must be installed; and
2) Both sides of at least one end of the joist must be attached to the
supporting structure.
On steel joists that do not require erection bridging only one employee shall be
allowed on the steel joists unless all bridging is installed and anchored.
The Erection Bridging may be installed from a man lift. For the specific
requirements of the joists being erected, consult the Joist Placement Plans and
the SJI CJ-Series Specifications. Sometimes, center X-type bridging is bolted to
the joists on the ground. This may be more easily accomplished by laying the
joist down horizontally, attaching the X-Type bridging to the joist and then placing
a bolt through the bridging at their intersection. Then the joist can be erected.
As the crane stabilizes the joist, an Ironworker attaches the loose end of the
bridging to the previously erected joist already up on the structure. This may be
done by standing on a walk-board bearing on the bottom chords of previously
erected and bridged joists.
The joist nearest the end of the building should be bridged first, with the ends of
the bridging rows being properly anchored. Installation should start at one end of
the joist and progress to the other end of the joist. The joist should be
39
straightened laterally and aligned vertically by the Erectors as the bridging rows
are being installed. Once the joist is straight, the bridging should be welded or
bolted. The far ends of the bridging rows should also be anchored.
With respect to horizontal bridging, the amount furnished allows for a minimum
lap length of 2 inches to 4 inches, plus an additional percentage more; drops of 3
feet or more should always be used. For X-type bridging, the exact numbers of
pieces are furnished, designated with mark numbers which correspond to these
same numbers shown on the Joist Placement Plans.
In certain design applications, the joists are designed to bear on the bottom
chord. This produces a “top heavy” condition. Therefore, they must be braced
with an additional row of X-type bridging at or near the bearing support as they
are being erected.
Before going out on any joist, be sure that at least one end is attached on both
sides and required Erection Bridging has been installed and anchored. Going
out on unsecured joists is unsafe. Finally, attach the other end of the joist by
welding or bolting both sides.
If joists don’t fit or there is an interference with other materials, do not cut or
alter the joists. Written permission and instructions from the joist manufacturer
and the Engineer of Record must be obtained prior to making any necessary field
modifications to the joist products (see OSHA 1926.757(a)(7)).
ERECTION BRIDGING
The SJI K-Series and LH- and DLH-Series Load Tables show the total safe
uniformly distributed loads for standard products at various spans. As the span
increases for a particular joist designation, the uniformly distributed load-carrying
capacities decrease. The Load Tables also indicate when the span becomes too
great for a particular joist designation to be erected without Erection Bridging.
These spans are indicated by the RED SHADED area in the K-Series Load
Table, the RED or BLUE SHADED areas in the LH-Series Load Table and the
BLUE or GRAY SHADED areas in the DLH-Series Load Table. For any of these
spans, the Erector must install bolted X-type bridging (bolted diagonal bridging),
called Erection Bridging as each joist is erected. The quantity and location of
the required Erection Bridging will be defined for each joist series.
The Erection Bridging requirements for standard K-Series joists are indicated by
the RED SHADED area in the Load Table and are found in the OSHA safety
standard 1926.757 Table A - Erection Bridging for Short Span Joists. This table
gives the minimum span for each short span joist designation that indicates when
Erection Bridging must be installed (see OSHA 1926.757(c) and (d)(1)). If Table
A indicates that Erection Bridging is Not Mandatory (NM), the joists can be
40
spaced out, attached, and then bridged in accordance with the SJI K-Series
Specifications (see Appendix B Section 6).
If Erection Bridging is required, each short span joist must be set in its proper
position and held with the hoisting equipment until both sides of one end of the
joist are attached and the Erection Bridging is installed. The required Erection
Bridging must be installed as the row of bridging nearest the mid-span of the
joist. The Erection Bridging must also be anchored to prevent lateral movement
of the joist (see OSHA 1926.757(a)(10) and (d)(1)) prior to the hoisting cables
being released. Both ends of the joist must then be permanently fastened down.
The Erection Bridging requirements for standard LH-Series joists are indicated
by the RED or BLUE SHADED areas in the Load Table and are also found in the
OSHA safety standard 1926.757 Table B - Erection Bridging for Long Span
Joists. This table gives the minimum span for each long span joist designation
that indicates when Erection Bridging must be installed (see OSHA 1926.757(c),
(d)(1) and (d)(2)). If Table B indicates that Erection Bridging is Not Mandatory
(NM), the joists can be spaced out, attached, and then bridged in accordance
with the SJI LH-Series Specifications (see Appendix C Section 105).
If Erection Bridging is required, each long span joist must be set in its proper
position and held with the hoisting equipment until both sides of one end of the
joist are attached and the Erection Bridging is installed. Where the span of the
steel joist is less than 60 feet, the Erection Bridging must be installed as the row
of bridging nearest the mid-span of the joist. Where the span of the steel joist is
over 60 feet through 100 feet, the required Erection Bridging must be installed as
the two rows of bridging nearest the third points of the joist. The hoisting cables
are not to be released until the bolted diagonal Erection Bridging is installed and
anchored to prevent lateral movement of the joist (see OSHA 1926.757(d)(2)).
Both ends of the joist must then be permanently fastened down.
The Erection Bridging requirements for standard DLH-Series joists are indicated
by the BLUE or GRAY SHADED areas in the Load Table. Erection Bridging is
required for all Deep Long Span Joists. Each DLH-Series joist must be set in its
proper position and held with the hoisting equipment until both sides of one end
of the joist is attached and the Erection Bridging is installed. Where the span of
the steel joist is over 60 feet through 100 feet, the required Erection Bridging
must be installed as the two rows of bridging nearest the third points of the joist.
Where the span of the steel joist is over 100 feet through 144 feet, all rows of
bridging are considered Erection Bridging and must be completely installed. The
hoisting cables are not to be released until the bolted diagonal Erection Bridging
is installed and anchored to prevent lateral movement of the joist (see OSHA
1926.757(c) and (d)(3)). Both ends of the joist must then be permanently
fastened down.
41
The Erection Bridging requirements for CJ-Series joists are as indicated in
Appendix E, Section 104.5 (c). If Erection Bridging is not required, the joists can
be spaced out, attached, and then bridged in accordance with the SJI CJ-Series
Specifications (see Appendix E Section 105).
If Erection Bridging is required, each composite steel joist must be set in its
proper position and held with the hoisting equipment until both sides of one end
of the joist are attached and the Erection Bridging is installed. Where the span of
the steel joist is 60 feet or less, the Erection Bridging must be installed as the row
of bridging nearest the mid-span of the joist. Where the span of the steel joist is
over 60 feet through 100 feet, the required Erection Bridging must be installed as
the two rows of bridging nearest the third points of the joist. Where the span of
the steel joist is over 100 feet all rows are to be Erection Bridging. The hoisting
cables are not to be released until the bolted diagonal Erection Bridging is
installed and anchored to prevent lateral movement of the joist (see OSHA
1926.757(d)(2)). Both ends of the joist must then be permanently fastened
down.
The mark numbers of the bolted bridging are shown on the Joist Placement
Plans where they occur. Where the bundles of bridging are marked, but not the
individual bridging pieces, it is incumbent upon the Erector to identify each
bridging mark number after the bundles have been broken. This can be
accomplished by comparing the lengths of the pieces to the appropriate bridging
Bill of Material. In some instances, the joist manufacturer may place a tag on the
diagonal bridging itself so that it can be placed more easily in the correct location
on the structure.
Following the attachment of one end of the joists, the bridging is installed as
indicated on the Joist Placement Plans. If Erection Bridging is required, it must
be installed as the joists are erected and before the hoisting cables are released.
It is the Erector's responsibility to ensure that the joist is straight lengthwise, and
that it is vertically plumb. As bridging is installed, sweep in the joist should be
removed (see Figure 5.11), and vertical misalignment should be corrected (see
Figure 5.12).
•
At no time is more than one employee allowed on short span joists (see
OSHA 1926.757 (d)(1) and Table A) until all other bridging is installed and
anchored.
•
At no time are more than two employees allowed on long span joists
greater than 60 feet, but less than or equal to 100 feet (see OSHA
1926.757(d)(2) and Table B) until all other bridging is installed and
anchored.
42
•
At no time are more than two employees allowed on long span joists
greater than 100 feet, but less than or equal to 144 feet (see OSHA
1926.757(d)(3)) until all bridging is installed and anchored.
Figure 5.11 Plan View of Joist with Sweep (Prior to Bridging)
Figure 5.12 Cross-section View of Joist Leaning Out-of-Plane
(Prior to Bridging)
After installation of any required Erection Bridging, a row of bridging nearest one
end of the joist is installed next. Bridging installation progresses from one row of
bridging to the adjacent row until all rows have been installed and anchored
properly. Each row of bridging must be properly anchored in order to provide the
restraint required to stabilize the joists during erection.
Bolted bridging allows adjustment in joist alignment by means of slots in the
bridging itself. In some instances, bridging clips with slots are welded to the
joists, in which case the bridging may be punched with either holes or slots. The
joists must be straightened before the bolted connections are tightened. Both
ends of each row of bridging must be anchored securely.
The vast majority of bridging is welded, horizontal type. This bridging is typically
furnished as an angle shape in standard 20 foot lengths. A sufficient amount is
shipped to the jobsite to provide two inch to four inch laps, plus a percentage
43
more to allow for short drops; however, drops of three feet or more should be
used.
The horizontal bridging is welded to the top and bottom chords of the joists as
they are properly aligned. Care must be exercised in welding the bridging
because the materials being welded (both the bridging and the joist chords) may
be quite thin; carelessness can result in the burning away of a portion of either
the joist chord or the bridging. Therefore, field welding shall be performed in
such a manner that no damage to the joists or bridging results. Heavy-handed
welding can easily "blow-out" a portion of the joist chord or the bridging. The SJI
K-Series Specification requires that each welded bridging connection resist a
horizontal force of not less than 700 pounds (see Appendix B, Section 5.4).
After all of the bridging is installed, the final field welds are made on the bearing
seats of the joists. A minimum of two 1/8 inch fillet welds one inch long are
required at each end if the final attachment is to be welded. Otherwise, if the
final attachment of the bearing seats are to be bolted, two 1/2 inch diameter bolts
at each end or equivalent are required. For joists at column lines, bolting of the
joist ends is required as described in the previous section.
For bottom bearing joists, their ends must be restrained laterally in accordance
with the SJI K-Series Specifications (see Appendix B, Section 5.4d), SJI LH- and
DLH-Series Specifications (see Appendix C, Section 104.5f) or SJI CJ-Series
Specifications (see Appendix E, Section 104.5g). This is accomplished by
means of a row of diagonal bridging placed at the ends of the joists. In those
instances where the entire bottom bearing joist is extended over its support to
form a cantilevered end, a row of diagonal bridging over the support (as
previously mentioned) should first be installed (see Figure 5.13). In addition, the
Specifying Professional (Engineer of Record) may also require a row of diagonal
bridging in the cantilevered portion of the joist to provide stability. This bridging
should be installed only after the diagonal bridging over the support is installed.
Care should be exercised in installing the bridging in the cantilever since the joist
is only laterally supported at one end.
In erecting bottom bearing (or square ended) joists, it is imperative that they be
erected right side up. The first diagonal web member at the support end of the
joist usually extends from the top chord, immediately above the point of support,
down to the bottom chord as previously shown in Figure 5.10. When the joist is
erected properly, and if the joist possesses camber, the joist will "bow up" at midspan (again, see Figure 5.10). If the joist is erected upside down, the load
carrying capacity will be reduced significantly. If there is any doubt regarding
which is the correct vertical orientation of the joist product, the Joist Placement
Plans should be checked and/or the joist supplier should be contacted.
When uplift forces are a design consideration, a row of bottom chord bridging is
required near each end of the joists in accordance with the SJI K-Series
44
Specifications (see Appendix B, Sections 5.6 and 5.11).
For additional
information on Uplift and uplift bridging requirements the reader is referred to
SJI’s Technical Digest No. 6, “Structural Design of Steel Joists Roofs to Resist
Uplift Loads”.
Figure 5.13 X type Bridging Installed at Wall Bearing of Bottom
Bearing Joists with Cantilevered End
CONSTRUCTION LOADS
THE OSHA SAFETY STANDARD STRICTLY PROHIBITS
IMPORTANT!
PLACING CONSTRUCTION LOADS ON UNBRIDGED JOISTS.
CONSTRUCTION LOADS ARE DEFINED IN THE OSHA SAFETY STANDARD
AS “ANY LOAD OTHER THAN THE EMPLOYEE(S), THE JOISTS AND THE
BRIDGING BUNDLES.”
THE PROPER PROCEDURE FOR LANDING
BRIDGING BUNDLES ON UNBRIDGED JOISTS IS GIVEN IN THE CODE OF
FEDERAL REGULATIONS 29 CFR PART 1926 SAFETY STANDARDS FOR
STEEL ERECTION AND SPECIFICALLY OSHA 1926.757(e)(1), (2) AND (3).
LANDING OF BRIDGING BUNDLES SHALL BE IN STRICT ACCORDANCE
WITH THESE PROVISIONS.
45
ANY ERECTOR WHO ALLOWS CONSTRUCTION LOADS TO BE PLACED ON
UNBRIDGED JOISTS IS IN DIRECT VIOLATION OF THIS FEDERAL
REGULATION AS WELL AS THE STEEL JOIST INSTITUTE’S K-SERIES
SPECIFICATIONS (SEE APPENDIX B, SECTION 6), LH- AND DLH-SERIES
SPECIFICATIONS (SEE APPENDIX C, SECTION 105) AND CJ-SERIES
SPECIFICATIONS (SEE APPENDIX E, SECTION 105 AND MAY BE HELD
LIABLE FOR ANY INJURIES SUSTAINED.
46
CHAPTER 6
FIELD INSPECTION
Field inspection of steel joists can be performed properly only by personnel who
have experience with and knowledge of these products.
A thorough
understanding of the job specifications and a working knowledge of the Steel
Joist Institute’s Standard Specifications are mandatory for any Inspector before
beginning a job site inspection. Particular emphasis should be placed on the SJI
Standard Specifications regarding: End Supports, End Anchorage, Bridging,
Installation of Bridging, and Floor and Roof Decks.
INSPECTION OF JOIST PRODUCTS PRIOR TO ERECTION
It is strongly recommended that the joist products be inspected prior to erection.
When this is done, any questions that may arise can be answered expeditiously
without affecting jobsite progress.
The Inspector should be looking for any damage that may have occurred to the
joists in the process of storing them or moving them around the site. If damage is
discovered, it should be reported to the project superintendent immediately. If
repair is necessary, see Chapter 9, Job Site Repair of Joist Products. During
this inspection, it should be noted whether the joists are being stored in a proper
manner.
INSPECTION OF JOIST PRODUCTS AFTER ERECTION
An inspection of the erected joists prior to placement of the deck is strongly
recommended in order to determine whether a proper job of erection has been
done. A sample Q.C. Field Joist Welding Checklist is shown in Figure 6.1.
First and foremost, inspect the bridging as follows:
1. Have all lines of bridging been properly anchored?
2. Is the bridging properly spaced?
3. Are the specified number of bridging rows installed? (see OSHA
Regulations, SJI Specifications, Project Contract Drawings, and Joist
Placement Plans)
4. Has the horizontal bridging been properly welded in accordance with AWS
D1.1 or D1.3?
At all laps?
To the joist chords?
47
To the bridging terminus points? (see OSHA, Illustrations of Bridging
Terminus Points: Non-mandatory. Guidelines for complying with
1926.757(a)(10) and 1926.757(c)(5))
5. Has the diagonal bridging been properly bolted or welded?
To the joists?
To the bridging terminus points? (see OSHA, Illustrations of Bridging
Terminus Points: Non-mandatory. Guidelines for complying with
1926.757(a)(10) and 1926.757(c)(5))
Proceeding from the bridging, inspect for the following:
1. Are the joists spaced correctly? (see Joist Placement Plans)
2. Are the joists properly anchored down? (see OSHA Regulations, SJI
Specifications and Joist Placement Plans)
a. If the joist seats are bolted, have the bolts been properly tightened? At
a minimum the bolts should be in a snug-tight condition unless
otherwise indicated by the Specifying Professional.
b. If the joist seats are welded, are the welds in accordance with AWS?
All field welding should be in accordance with AWS D1.1 or D1.3.
3. Is there sufficient joist bearing on the structural steel beams, or the
masonry or concrete? (see OSHA Regulations, SJI Specifications and
Joist Placement Plans)
4. Are bottom chord struts attached?
specifications)
Should they be? (Check project
5. Have any joists been damaged during erection?
6. If concentrated loads are present, are they located in accordance with the
Joist Placement Plan?
7. Are the joists laterally straight? (Is there any sweep in the joist?)
8. Are the joists aligned vertically? (Are the joists plumb?)
48
Q.C. Joist Field Welding Checklist
Item
Description
1
Low-hydrogen electrodes are to be used for all welding
2
Electrode storage will conform to AWS D1.1
3
All bearing seat fillet welds are to be cleaned, i.e. remove all slag and
wire brush
4
Fillet welds are to conform to AWS D1.1 or AWS D1.3 profile
requirements (see Figure 5.4)
5
Cracks, incomplete fusion or overlap is unacceptable
6
A sum diameter of 3/8 inch or more porosity per 1 inch of weld is
unacceptable
7
Tack welds for bridging connections are unacceptable
8
When joist bearing seats are to be welded, preheat base metal within 6
inches of joint to 70°F when base metal temperature is less than 70°F
and air temperature is less than 32°F
9
No welding is to be permitted in rain or snow
10
No welding is permitted when the ambient air temperature is less than
10°F
11
Personnel welding Joist Girder seats shall be qualified for the process
being used under the AWS D1.1 Welding Code
12
Personnel welding bridging shall be qualified for the process being
used under any AWS, API or ASME Code
13
The steel erector shall submit a written quality control (Q.C.) plan
before any work is to start
14
The steel erector’s designated Q.C. representative is required to
inspect at least 20% of welds at joist bearing seats and 5% of bridging
welds
15
All Q.C. inspections shall be documented in writing
Figure 6.1 Sample Q.C. Joist Field Welding Checklist
49
Yes/No
CHAPTER 7
PANELIZED ERECTION
Today, a growing number of erectors are panelizing joists on the ground prior to
erection. This is done in full or part bays, depending on the total weight of the lift
and the available crane capacity. This method of erection can be safer and more
productive with proper planning. It should be noted that panelized erection may
not be viable for a given job site because of site size, site access, or other
limitations.
The following steps provide the basic means for panelization:
1. Create a work platform on the ground to simulate actual supporting members.
This can be done with "dummy" beams or Joist Girders spaced to match the
actual bay size. Be sure these members are adequately braced to prevent
overturning. It’s critical that the support frame must be square.
2. Mark the joist spacing. If several typical spaced bays are to be assembled,
clamp a plate or angle to the support frame to mark each location.
3. Place the joists on the supports, either individually or in a bundle, depending
on the size of the joists. Check the spacing and bearing of each joist. You
may want to tack weld or clamp a piece of angle to the support frame as a
bearing control.
4. Before any bridging is attached, the joists should be checked for sweep. You
may have to use a “come-a-long” or other approved method to remove any
observed sweep in the joists. If bolted diagonal bridging is required as shown
on the Joist Placement Plans, spacing and alignment of the joists need to be
checked prior to installing and tightening the bridging bolts. Any required
horizontal bridging shown on the Joist Placement Plans should then be
installed and welded in place. Be sure to locate the bridging for proper lap at
splice points of any adjoining panels.
5. If touch-up painting is required, it is probably easier to do it while the joists are
on the ground rather than after erection.
6. In certain cases, you can install roof opening frames prior to erection. Careful
measurements must be made to assure proper location of the frame.
50
7. A variety of lifting frames or beams have been used for panelized erection as
can be seen in Figures 7.1 thru 7.3. The lifting device should be designed to
lift each joist panel, be properly balanced, lightweight and easily released with
minimum fall exposure to the connector personnel. It's important not to warp
the joist panel during hoisting.
8. When landing the joist panel, check for proper bearing. If the panel includes
a tie joist, all of its bolts must be installed prior to releasing the crane.
Figure 7.1 Panelized Erection of Joists with Top and Bottom Rows
of Bridging Installed
51
Figure 7.2 Panelized Erection of Joists with Bridging and Decking Installed
Figure 7.3 Panelized Erection of Joists and Joist Girders with Top and
Bottom Rows of Bridging Installed
52
There are numerous methods of panelization. Some erectors prefer to assemble
full bays, including the tie joist. Others install the tie joist prior to erecting the filler
panel. Still others panelize in 20 foot widths to accommodate standard bridging
lengths. Most joist suppliers will work with erectors, for special length bridging,
as long as it can be cut from standard stock lengths. Clear communication
between the erector and joist supplier will usually result in minimizing field cutting
and splicing. Additional benefits come from less material waste and reduced
labor time.
Current OSHA regulations allow for joists to be erected in panels without
supporting members being punched for bolting. An exception is made at tie
joists, which must be punched and bolted (see OSHA 1926.757(a)(8)).
The following erection sequence (see Figures 7.4 thru 7.8) illustrates a panelized
project with steel deck attached prior to the panels being lifted into place. The
bridging is all bolted cross-bridging (in place of horizontal bridging) and is placed
only where required to stabilize the panel and meet the bottom chord
slenderness requirements.
Figure 7.4 Metal Decking Being Secured to Joists Making Up Panel
Assembly; Cross-bridging Already Installed (not shown)
53
Figure 7.5 Gradall Lift Positioning Tines to Raise Joist Panel Assembly
Figure 7.6 Moving Joist Panel Assembly to Area Being Constructed;
Joist Cross-bridging Now Visible
54
Figure 7.7 Raising Joist Panel Assembly into Final Position on Roof
Figure 7.8 Lowering Joist Panel Assembly into Final Position on Roof
55
WOOD PANELIZED ROOF SYSTEM
This panelized roof system joins open web steel joists and Joist Girders with a
APA Rated Sheathing. In so doing, it utilizes the economy and strength of the
steel products and the low insulation costs, high diaphragm capacities and
unique erection method of the panelized wood roof. Figure 7.9 shows a
simplified schematic diagram of the open web steel joist and Joist Girder
panelized wood roof system.
Figure 7.9 Open Web Steel Joist and Joist Girder Panelized
Wood Roof System
WOOD PANELIZED ROOF SYSTEM ERECTION
The erection procedure is critical to the system. A panelized wood roof system is
one where the sub-purlins, erection stability braces and roof decking is
connected to the steel joist with its pre-attached wood nailer while all
components are on the ground. This entire unit, comprised of the steel joist,
wood nailer, sub-purlins, erection stability braces and wood decking is then lifted
into its proper place on the roof. The free edge of the decking is positioned and
nailed to the previously placed steel joist and the ends of the joist are attached to
the support structure securing the panel assembly before the hoisting equipment
is released. This is done before any load is applied to the joist and before the
next joist is placed. As with any panelized system, the Erector is responsible for
the proper and safe handling and erection of the panels so constructed. Figures
7.10 thru 7.15 show the sequence of constructing and erecting a wood panelized
roof system.
56
Figure 7.10 Constructing a Wood Panelized Joist Assembly; Nailing
Sub-purlins to Wood Nailers Connected to Joists
Figure 7.11 Installing Wood Sheathing to Complete Panelized System
57
Figure 7.12 Raising Panelized Assembly into Position using Forklift Truck
Figure 7.13 Lowering Panelized Assembly into Position onto Tilt-up Walls
and Joist Girder. This is a Doubler Panel (with two joists) to Start a Bay
58
Figure 7.14 Subsequent Wood Panelized Assemblies Being Placed in a
Bay. Each Panel Now Only has One Joist Attached
Figure 7.15 Welder Connecting Wood Panelized Joist Assembly
to Joist Girder
59
CHAPTER 8
BRIDGING
Bridging is a component of the steel joist system that braces the joists against
lateral displacement during erection (see OSHA 1926.757(d) Erection bridging)
and placing of construction loads (see OSHA 1926.757(e) Landing and placing
loads).
The number of rows of bridging is dependent on the span of the joist, as well as
the size of the top and bottom chords. With lighter, shorter joists, fewer rows of
bridging are required to stabilize the top and the bottom chords. Without
bridging, joists can easily roll over and fall which could possibly result in a serious
injury to workers on site. Joists can still fall even when they are attached to the
supporting members. When a load is applied to a joist that is not properly
restrained, the joist will tend to roll over and may collapse. Properly installed
bridging solves this problem.
Today, the most common bridging material is angle. Typical angle sizes range
from 1” x 1” up to 2 1/2” x 2 1/2”. In special applications, even larger sizes may
be used. It's important to understand that the steel joist system will not function
to support the construction loads without bridging being in place.
The Steel Joist Institute has specifications for the type, spacing, size and number
of rows of bridging required based on the type, depth, chord number and span of
a joist. There are some joists spanning less than 30 feet that require Erection
Bridging be installed prior to releasing the crane hoisting lines while there are
other joists spanning greater than 50 feet that do not require Erection Bridging.
As an Erector, you should be aware that until all the Erection Bridging is installed,
the joists will not safely support you. Therefore, the Erection Bridging must be
installed prior to the installation of the balance of the bridging. Only after all the
bridging is installed and anchored can additional loads be placed on the joists.
When joists span over 60 feet up through 100 feet, all rows of bridging must be
bolted diagonal bridging. At least two rows of bolted diagonal bridging must be
installed as Erection Bridging nearest the third points of the steel joist prior to
releasing the hoisting lines. The hoisting lines shall not be released until this
bolted diagonal Erection Bridging is installed and anchored; and even then, no
more than two employees shall be allowed on these spans until all other bridging
is installed and anchored (see OSHA 1926.757(d)(2)).
When the span of the joist is over 100 feet, then all the rows of bolted diagonal
bridging must be installed and anchored prior to releasing the hoisting lines of the
crane. No more than two employees shall be allowed on these spans until all
bridging is installed and anchored (see OSHA 1926.757(d)(3)). For steel joists
60
spanning over 144 feet, the erection methods used shall be in accordance with
OSHA Regulations §1926.756 Beams and columns and not §1926.757 Open
web steel joists (see OSHA 1926.757(d)(4)).
In general, bridging is either classified as horizontal or diagonal. Horizontal
bridging consists of continuous horizontal steel members attached to the top
chord and the bottom chord of each joist. Connections to the joists are made by
welding or bolting. Diagonal bridging consists of cross-bracing connected to the
top and bottom chords of adjacent joists. For the diagonal bridging to function as
designed, it is essential that they are properly connected at their intersection.
Connections are made by welding or bolting. Typical bridging details for the
installation of horizontal bridging and welded or bolted diagonal bridging are
shown in Figures 8.1 and 8.2. Each horizontal bridging attachment to the joist
chords must be capable of resisting a horizontal force not less than that specified
in SJI’s K-Series Specification Section 5.4, LH- and DLH-Series Specification
Section 104.5 or CJ-Series Specification Section 104.5. Tables 8-1, 8-2, 8-3,
and 8-4 show the minimum required welds required for K-Series, LH- and DLHSeries, and CJ-Series joist bridging attachment, calculated in accordance with
the latest AISC Specification for Structural Steel Buildings (AISC 2005) that meet
this criteria. Values shown in brackets [ ] are recommended weld leg sizes and
lengths, respectively.
If the steel joists being erected are bottom chord bearing joists, special attention
needs to be taken as these joists have an even greater tendency to roll over and
collapse than the more typical top chord bearing joists. In addition to the typical
number of rows of bridging, a row of diagonal bridging is to be provided near the
supports. This bridging is to be bolted diagonal bridging and shall be installed
and anchored before the hoisting lines are released for all joists governed by
OSHA 1926.757(d)(5).
The employer needs to be aware that when bolted diagonal erection bridging is
required to be installed, the following shall apply (see OSHA 1926.757(d)(6):
•
•
•
•
•
The bridging shall be indicated on the Joist Placement Plans;
The Joist Placement Plans shall be the exclusive indicator of the proper
placement of this bridging;
Shop installed bridging clips, or functional equivalents, shall be used
where the bridging bolts to the steel joists;
When two pieces of bridging are attached to the steel joist by a common
bolt, the nut that secures the first piece of bridging shall not be removed
from the bolt for the attachment of the second; and
Bridging attachments shall not protrude above the top chord of the steel
joist.
61
Table 8-1 Weld to Provide Minimum 700 lb Nominal Strength for K-Series
Joists
Weld Type
Weld Leg Size (in.)
Minimum Weld Length (in.)
Fillet
7/64 [1/8]
7/16
Fillet
1/8
[1/8]
3/8
Fillet
5/32
[3/16]
5/16 [ 5/8 ]
[1]
[ 3/4 ]
Table 8-2* Weld to Provide Minimum 1000 lb Nominal Strength for LH- and
DLH-Series Joists, Section Numbers 02 through 12, and CJ-Series Joists
Weld Type
Weld Leg Size (in.)
Minimum Weld Length (in.)
Fillet
7/64 [1/8]
5/8 [ 1 1/4 ]
Fillet
1/8
[1/8]
9/16
Fillet
5/32
[3/16]
5/8 [ 3/4 ]
[1]
Table 8-3* Weld to Provide Minimum 2000 lb Nominal Strength for LH- and
DLH-Series Joists, Section Numbers 13 through 19, and CJ-Series Joists
Weld Type
Weld Leg Size (in.)
Fillet
7/64 [1/8]
Fillet
1/8
[1/8]
Fillet
5/32
[3/16]
Minimum Weld Length (in.)
1 1/4
1 1/8
[2]
[ 1 1/2 ]
7/8 [ 1 1/4 ]
Table 8-4* Weld to Provide Minimum 3500 lb Nominal Strength for
CJ-Series Joists
Weld Type
Weld Leg Size (in.)
Minimum Weld Length (in.)
Fillet
7/64 [1/8]
2 1/4
[ 2 1/2 ]
Fillet
1/8
[1/8]
1 7/8
[ 2 1/4 ]
Fillet
5/32
[3/16]
1 1/2 [ 2 ]
*Tables 8-2, 8-3 and 8-4 have been created to assist the erector in determining
the length of the bridging weld needed for the joist. Different combinations of
nominal force and weld length are possible depending on the joist series
requirements. Contact the joist manufacturer for different weld combination
possibilities.
62
K-SERIES BRIDGING DETAILS
Figure 8.1 K-Series Bridging Details
63
CJ-, LH-, AND DLH-SERIES BRIDGING DETAILS
Figure 8.2 CJ-, LH- and DLH-Series Bridging Details
64
During the construction period, the employer placing a load on steel joists shall
ensure that the load is distributed so as not to exceed the carrying capacity of
any steel joist (see OSHA 1926.757(e)(1)). Before bridging can be installed, it
must be landed up on the structure. No construction loads are allowed on the
steel joists until all bridging is installed and anchored and all joist bearing ends
are attached (see OSHA 1926.757(e)(2)). OSHA requires that a bundle of
bridging not exceed a total of 1,000 pounds (see Figure 8.3). In addition, the
bundle should be placed on a minimum of three joists and within one foot of a
secured end as shown in Figure 8.4 (see OSHA 1926.757(e)(3)).
Figure 8.3 Bridging Bundles Prior to Being Landed on a Building
Before any construction loads other than a bundle of decking are landed, all the
joists must be safely and completely erected in a bay or area. This means all the
bridging is in place and anchored, and all joist bearing ends are attached (see
OSHA 1926.757(e)(2)). One exception to this is when a construction load that
65
consists of metal decking is being placed on steel joists. This can occur when all
of the following conditions are met:
1) The employer has first determined from a qualified person and
documented in a site-specific erection plan that the structure is capable
of supporting the load;
2) The bundle of decking is placed on a minimum of three joists;
3) The joists supporting the bundle of decking are attached at both ends;
4) At least one row of bridging is installed and anchored; and
5) The total weight of the bundle of decking does not exceed 4,000
pounds 91816 kg). Placement of the bundle of decking shall be placed
within 1 foot (0.30 m) of the bearing surface of the joist end (see OSHA
1926.757(e)(4) and OSHA 1926.757(e)(5)).
Do not stack bundles of metal decking.
Figure 8.4 Bridging Bundle Being Placed Across Three Joists
Near Their Ends on a Building
66
In some situations, it is not practical to bridge the entire bay and/or project prior
to “spotting” or landing metal deck bundles on the joists. When this is the case,
the Steel Erector must determine, using a qualified person, that the structure is
capable of supporting a load of decking. This is done through a Site Specific
Erection Plan (see OSHA 1926.752(e)). At the very least, the joists that are
supporting the bundle of decking should have the load distributed over a
minimum of three joists. In addition, both ends of the joists must be attached in
accordance with the Joist Placement Plans, as well as at least one row of
bridging installed and anchored.
Joists must be fully installed and bridged prior to placing construction
loads other than deck bundles.
67
CHAPTER 9
MISCELLANEOUS TOPICS
COMMON FIELD ISSUES
CAMBER
Camber is defined as an arching or curvature. In joists it is exactly this - an
upward arching of the chords. The approximate camber for K-, LH- and DLHSeries joists and Joist Girders is in accordance with the following table:
Length
(ft.)
20
30
40
50
60
Approximate
Camber
(in.)
1/4
3/8
5/8
1
1 1/2
Length
(ft.)
70
80
90
100
110
Approximate
Camber
(in.)
2
2 3/4
3 1/2
4 1/4
5
Length
(ft.)
120
130
140
144
Approximate
Camber
(in.)
6
7
8
8 1/2
This is mentioned here to alert the erector to the fact that the weight of the joist
and deck seldom, if ever, removes all of this camber. If the first joist is in close
proximity to the end of the structure, i.e. a non-cambered element such as a wall,
the connection of the deck to the building wall or perimeter beam may pose a
problem unless prior means have been provided to resolve this matter. This
situation can make deck installation extremely difficult.
The joist manufacturer is able to provide joists with special camber upon request.
Composite Steel Joists, CJ-Series, are cambered during manufacturing. The
approximate camber is based on the deflection associated with 100% of the noncomposite, unfactored dead load plus any additional loads defined by the
Specifying Professional.
This amount of approximate camber will be
substantially removed during construction with the application of the dead loads
from the joists, bridging, steel deck, and concrete slab.
CONCENTRATED LOADS
In many instances, concentrated loads from HVAC (heating, ventilating, and air
conditioning) equipment on the roof cannot be located accurately until after the
joists are manufactured and delivered to the job site. Frequently, the exact
location of these roof top units (RTUs) is not known until after the joists have
been erected. A concerted attempt should be made to locate these concentrated
68
loads at top chord panel points on the joists. In those cases where this is not
possible, additional web members running from the point of load down to the
nearest bottom chord panel point may have to be added. The connecting of
these web members to the joist should be done in strict accordance with
instructions from the Specifying Professional, and with extreme care, ensuring
that the joist components are not damaged.
For loads hung from the bottom chords of the joists, a similar procedure should
be followed, except that any added web members should run from the point of
load up to the nearest top chord panel point. In any event, the rated capacity of a
given joist must not be exceeded by the addition of a concentrated load.
CONSTRUCTION LOADS
Once the joists have been set, bridged, and welded down properly, THEN AND
ONLY THEN can construction loads be placed on the joists. Even then, these
loads should be placed near the ends of the joists, preferably over a beam or a
wall. Also, the loads must be such that they do not cause an overloading of the
joist (See Appendix B, Section 6). Furthermore, the top chord of a joist is not
designed to resist concentrated loads, so care must be taken not to cause
bending or other damage to this member.
COORDINATING OTHER STRUCTURAL ELEMENTS
The joists can be used as support for many items other than just decking.
Depending on what other items the joist is supporting they may require additional
reinforcing.
DECK ATTACHMENT
Following the erection of the joists and bridging, some type of deck or centering
is placed on the joists, oriented perpendicular to their length. In regards to
centering, a means must be provided to prevent lateral displacement or
deformation of the top chord of the joists. Regardless of what type of material is
placed on top of the joists, the SJI Specifications require that the attachments to
the top chord of the joists be spaced at no more than 36 inches. Each
connection of the decking must be capable of resisting forces as shown:
JOIST PRODUCT
CHORD OR
SECTION NUMBER
K-Series Joists
LH-Series and DLHSeries Joists
02 thru 04 incl.
05 thru 09 incl.
10 thru 17 incl.
18 and 19
69
NOMINAL (UNFACTORED)
RESISTING FORCE
300 lbs
120 lbs/ft.
150 lbs/ft.
200 lbs/ft.
250 lbs/ft.
CJ-Series joists will have both deck and shear connector attachment which will
work together in stabilizing the top chord of the composite steel joist. The deck
shall be attached in accordance with the Steel Deck Institute requirements prior to
placing construction loads on the composite joists. This deck attachment, together
with the shear connector placed on the composite steel joist top chord, will provide
the necessary top chord lateral support requirement for the design loading as
intended by the Specifying Professional.
FIELD WELDING THRU PAINT
In accordance with the latest SJI Specifications and Code of Standard Practice
(2005), Section 3.2 Paint it states in part, “The paint is intended to be an
impermanent and provisional coating which will protect the steel for only a short
period of exposure in ordinary atmospheric conditions.” This coating is typically
1.0 mil in thickness, but possibly could vary from as little as 0.8 mils to as much
as 2.0 mils. The minimum thickness condition comes from SSPC-Paint 15, Steel
Joist Shop Primer Section 4.4 which states, “The dry film thickness of the
primer shall be as recommended by the manufacturer. If no recommendation is
given, the dry film thickness shall be a minimum of 20 micrometers (0.8 mils)
unless indicated otherwise.” Even at the upper thickness this coating is thin as
compared to any field applied paint system that might be applied to Open Web
Steel Joists.
In AWS D1.1 Section 5.15 Welding to Base Metal, it states that one of the
exceptions allowing welding is, “Mill scale that can withstand vigorous wire
brushing, a thin rust-inhibitive coating, or antispatter compound may remain …”
This thin rust-inhibitive coating is essentially the same description that the SJI
uses in their description of the paint and should be interpreted as such.
Therefore, according to the current provisions in AWS, welding thru shop applied
joist paint is an acceptable practice by the Steel Joist Institute.
JOB SITE REPAIR OF JOIST PRODUCTS
If damage to the joists is discovered during the site inspection or occurs at the job
site, it should be reported immediately to the project superintendent who then
should immediately report it to the joist manufacturer.
Steel joists are designed to exacting standards and manufactured in a unique
manner. A joist manufacturer implicitly guarantees the performance of its
products to safely support the loads as called for in the SJI Standard
Specifications Load Tables & Weight Tables for Steel Joists and Joist Girders,
providing, of course, that the joists have been erected properly. If the products
are altered in any way, without the manufacturer’s knowledge and approval, their
guarantee is void since the product is no longer that which was contractually
manufactured.
70
Since a joist manufacturer knows its products better than anyone else, they are
in the best position to make decisions regarding the repair of a joist. For the
safety of the public, the joist manufacturer must decide whether such repair
should be made at the job site or back at the manufacturing facility or whether
replacement of the product is required.
It is strongly recommended that, if repair or alteration at the job site is approved
by the joist manufacturer, very close supervision of this work be made, as well as
subsequent inspection and verification of such repair or alteration.
JOIST PRODUCTS SHALL NOT BE REPAIRED OR ALTERED
WITHOUT PRIOR APPROVAL OF THE JOIST MANUFACTURER AND
THE ENGINEER OF RECORD.
NON STANDARD PRODUCTS
Many joist manufacturers are building joists with a bowstring, scissor or various
other configurations which require special precautions during erection. Many of
these products have a high center of gravity relative to their bearing elevation, or
in other words they are “top heavy”. These types of products have much more of
a tendency to roll over.
SECURING COMPONENTS AT THE END OF THE WORK DAY
Before leaving the job site, make sure all joists and deck have been secured to
prevent damage due to changing weather.
SHEAR STUD CONNECTORS
Shear connection between Composite Steel Joists, CJ-Series, and concrete slab
is typically made by welding shear connector studs ranging in diameter from 3/8
inch to 3/4 inch through the metal deck. See Appendix E, Section 106 and Joist
Placement Plans for installation requirements.
STANDING SEAM ROOFS
The joists that support a standing seam roof may sometimes require additional
top chord bridging to provide sufficient lateral bracing. In most instances the
bridging will be more than the standard amount from the SJI table.
TEMPORARY ANCHORAGE
In the event some type of temporary anchorage is used, it should be installed
such that no permanent damage to the joists occurs.
71
TWO-PIECE JOISTS (or MULTI-PIECE JOISTS)
When joists are of such a length that they cannot be shipped or accommodated
in one piece, they are spliced and shipped in two pieces. There may be other
design, shipping or erection considerations such as job site storage or adding
joist product in an existing building to increase the roof or floor capacity that
would necessitate a joist being manufactured in two or more pieces. Almost
without exception, the joist supplier furnishes a bolted splice, complete with high
strength bolts. In assembling the joist, the Erector must "match mates". The joist
mates will typically be marked "1A" and "1B" or "A1" and "A2" or some similar
marking to indicate mates. Two dissimilar mates may “fit” together, but if they
are not the match marked mates then proper camber or profile may not be
maintained. A suitable location at the job site must be found where the joists can
be handled safely and where the splice can be made properly on the ground.
For splices that are made on long joists, special care must be exercised in
erecting these joists to ensure that they not be allowed to bow laterally, thus
possibly damaging the splice plates. Hoisting cables must not be released until
the ends of the joists are attached and bridging is installed as required by the SJI
Specifications and OSHA Regulations. In addition, erection of two-piece steel
joists in an existing building will require the joist top chord to be laterally
stabilized in accordance with the SJI Specifications. In many cases, a field
dimension of the camber requirement to match the existing joists is required.
This in turn will allow the two-piece joist top chord to be connected to the existing
decking (see Deck Attachment).
UPLIFT
If the joist has a net uplift specified then it must have uplift bridging. This bridging
will occur at or near the first bottom chord panel point on each end of the joist.
72
CHAPTER 10
SUMMARY – DO’S AND DON’TS
DO THE FOLLOWING:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
Follow all requirements found in the Occupational Safety and Health
Administration (OSHA) Regulations 29 CFR 1926, Safety Standards for
Steel Erection and more specifically 29 CFR 1926.757, Open Web Steel
Joists.
Handle all joist products with care.
Use proper equipment for unloading, handling and erection.
Verify piece count of all joist products upon delivery.
Inspect all joist products for damage upon delivery.
Report any damage to the joist supplier and to jobsite supervisors.
Attach cables only at panel points of joists.
Store joists with top chord down and with joists in a vertical position.
Store deep joists horizontally if they were shipped on their sides.
Store joists off the ground and away from jobsite traffic.
Protect stored joists from the elements.
Erect all joist products and accessories in accordance with OSHA
Regulations and Steel Joist Institute Specifications.
Place the "tag end" of joists as shown on the Joist Placement Plans.
Ensure that square-end joists are erected right side up.
Attach both sides of one end of each joist immediately after placement in
its final position.
Insert bolts at time of placement, for joists with bolted ends.
Field weld all joist products with care.
Use low-hydrogen electrodes for all welding and store them at 250°F.
Remove slag from all welds or at least all bearing seat welds.
Straighten joists both laterally and vertically as bridging is being installed.
Restrain and stabilize the ends of all square-end joists.
Securely anchor the ends of all rows of bridging.
Permanently anchor ends of joists after all bridging has been completely
installed.
Ensure that mates are matched on spliced joists.
Place joists on Joist Girders in accordance with the Joist Placement Plans.
It should be noted that there are many instances where Joist Girders have
been properly designed with joists not being located exactly at the Joist
Girder panel points.
Install the bracing from the bottom chord of the joists to the bottom chord
of the Joist Girder in accordance with the Joist Placement Plans.
73
27.
28.
Make permanent connections of the bottom chords of Joist Girders only as
directed by the Specifying Professional (i.e. the Registered Design
Professional).
Make attachments of the steel deck to the top chord of the joists at a
spacing of not more than 36 inches apart and as directed by the deck
placement plan.
DON’T DO THESE THINGS:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Don't pull or push joists off a delivery truck, or drop them in any way.
Don’t lift bundles of joist products by their strapping.
Don’t attach cables, chains or hooks to the web members of joists.
Don’t store joists on their sides.
Don’t place construction loads on unbridged joists.
Don’t cause damage to the joists when field welding.
Don’t cut away vertical leg of bridging where bridging makes an elevation
transition; Weld separate piece of bridging at transition.
Don’t use tack welds to secure lower chord bridging.
Don’t use a burn-through technique to weld lower chord bridging.
Don’t overload joists.
Don’t place joists between panel points on Joist Girders unless specifically
shown on the Joist Placement Plans.
Don’t repair or alter joists without the approval of the Registered Design
Professional and/or the Joist Manufacturer.
74
REFERENCES
American Institute of Steel Construction (2005a), AISC 303-05, Code of Standard
Practice for Steel Buildings and Bridges, AISC, Chicago, IL.
American Institute of Steel Construction (2005b), Specification for the
Qualification of Steel Structures Inspectors, AISC, Chicago, IL.
American Institute of Steel Construction (2005c), ANSI/AISC 360-05,
Specification for Structural Steel Buildings, March 9, 2005, AISC, Chicago, IL.
American Iron and Steel Institute (AISI) (2007), North American Specification for
Design of Cold-Formed Steel Structural Members, Washington, D.C.
American Society of Civil Engineers (2005), ASCE/SEI 7-05, Minimum Design
Loads for Buildings and other Structures, Including Supplement No. 1, ASCE,
Reston, VA.
American Society of Mechanical Engineers (2004), ASME-B30.5, Mobile and
Locomotive Cranes, Fairfield, NJ.
American Welding Society (2006), ANSI/AWS D1.1/D1.1M Structural Welding
Code – Steel, AWS, Miami, FL.
Emerson, M. R. (2001), Stability of Unbraced Steel Joists Subject to Mid-Span
Loading, A Thesis Presented to the Faculty of Bucknell University in Partial
Fulfillment of the Requirements for the Degree of Master of Science in Civil
Engineering, Lewisburg, PA.
Federal Register, Department of Labor, Occupational Safety and Health
Administration (OSHA), 29 CFR Part 1910.178 Powered industrial trucks.
Washington, D.C.
Federal Register, Department of Labor, Occupational Safety and Health
Administration (OSHA), 29 CFR Part 1910.180 Crawler locomotive and truck
cranes. Washington, D.C.
Federal Register, Department of Labor, Occupational Safety and Health
Administration (OSHA) (2001), 29 CFR Part 1926 Safety Standards for Steel
Erection; Final Rule, §1926.757 Open Web Steel Joists-January 18, 2001,
Washington, D.C.
Steel Deck Institute (2006), SDI Manual of Construction with Steel Deck,
Publication No. MOC2, SDI, Fox River Grove, IL.
75
Steel Joist Institute (2005), 42nd Edition Catalog (contains Standard
Specifications, Load Tables and Weight Tables for Steel Joists and Joist
Girders: K-Series, LH- and DLH-Series, Joist Girders), SJI, Myrtle Beach,
SC.
Steel Joist Institute (2007), First Edition Catalog (contains Standard Specification
for Composite Steel Joists, CJ-Series, Weight Tables and Bridging Tables),
SJI, Myrtle Beach, SC.
Steel Joist Institute (2007), Technical Digest No. 3, Structural Design of Steel
Joist Roofs to Resist Ponding Loads, SJI, Myrtle Beach, SC.
Steel Joist Institute (1988), Technical Digest No. 5, Vibration of Steel JoistConcrete Slab Floors, SJI, Myrtle Beach, SC.
Steel Joist Institute (2008), Technical Digest No. 6, Structural Design of Steel
Joist Roofs to Resist Uplift Loads, SJI, Myrtle Beach, SC.
Steel Structures Painting Council (2000), Steel Structures Painting Manual,
Volume 2, Systems and Specifications, Paint Specification No. 15, Steel Joist
Shop Primer, SSPC, , Pittsburgh, PA, May 1, 1999.
Ziemian, R. D., Schwarz, J. E., Emerson, M. R., and Potts, D. R. (2004).
“Stability of Unbraced Steel Joists Subject to Mid-span Loading.” Structural
Stability Research Council Annual Stability Conference, Annual Technical
Session Proceedings, March 24-27, Long Beach, CA.
76
APPENDIX A
STANDARD HAND SIGNALS FOR CONTROLLING
CRANE OPERATIONS
77
Reprinted from ASME B30.5-2004, by permission of The American Society
of Mechanical Engineers. All rights reserved.
78
APPENDIX B
(Applicable sections only are reprinted below)
STANDARD SPECIFICATION
FOR OPEN WEB STEEL JOISTS, K-SERIES
Adopted by the Steel Joist Institute November 4, 1985
Revised to November 10, 2003 - Effective March 01, 2005
5.3 END SUPPORTS
(a) Masonry and Concrete
K-Series Joists supported by masonry or concrete are to bear on steel
bearing plates and shall be designed as steel bearing. Due consideration of
the end reactions and all other vertical or lateral forces shall be taken by the
Specifying Professional in the design of the steel bearing plate and the
masonry or concrete. The ends of K-Series Joists shall extend a distance of
not less than 4 inches (102 millimeters) over the masonry or concrete support
and be anchored to the steel bearing plate. The plate shall be located not
more than 1/2 inch (13 millimeters) from the face of the wall and shall be not
less than 6 inches (152 millimeters) wide perpendicular to the length of the
joist. The plate is to be designed by the specifying professional and shall be
furnished by other than the joist manufacturer.
Where it is deemed necessary to bear less than 4 inches (102 millimeters)
over the masonry or concrete support, special consideration is to be given to
the design of the steel bearing plate and the masonry or concrete by the
specifying professional. The joists must bear a minimum of 2 ½ inches (64
millimeters) on the steel bearing plate.
(b) Steel
Due consideration of the end reactions and all other vertical and lateral forces
shall be taken by the specifying professional in the design of the steel
support. The ends of K-Series Joists shall extend a distance of not less than
2 ½ inches (64 millimeters) over the steel supports.
5.4 BRIDGING
Top and bottom chord bridging is required and shall consist of one or both of
the following types.
79
(a) Horizontal
Horizontal bridging shall consist of continuous horizontal steel members.
Attachments to the joist chords shall be made by welding or mechanical
means and shall be capable of resisting a nominal (unfactored) horizontal
force of not less than 700 pounds (3114 Newtons).
The ratio of unbraced length to least radius of gyration, l/r, of the bridging
member shall not exceed 300, where l is the distance in inches (millimeters)
between attachments and r is the least radius of gyration of the bridging
member.
(b) Diagonal
Diagonal bridging shall consist of cross-bracing with a l/r ratio of not more
than 200, where l is the distance in inches (millimeters) between connections
and r is the least radius of gyration of the bracing member. Where
cross-bracing members are connected at their point of intersection, the l
distance shall be taken as the distance in inches (millimeters) between
connections at the point of intersection of the bracing members and the
connections to the chord of the joists. Connections to the chords of steel
joists shall be made by positive mechanical means or by welding.
(c) Quantity and Spacing
The number of rows of top chord bridging shall not be less than as shown in
Bridging Tables 5.4-1 and 5.4-2 and the spacing shall meet the requirements
of Section 4.4(a). The number of rows of bottom chord bridging, including
bridging required per Section 5.11, shall not be less than the number of top
chord rows. Rows of bottom chord bridging are permitted to be spaced
independently of rows of top chord bridging. The spacing of rows of bottom
chord bridging shall meet the slenderness requirement of Section 4.3 and any
specified strength requirements.
(d) Bottom Chord Bearing Joists
Where bottom chord bearing joists are utilized, a row of diagonal bridging
shall be provided near the support(s). This bridging shall be installed and
anchored before the hoisting cable(s) is released.
80
TABLE 5.4-1
U.S. CUSTOMARY UNITS
NUMBER OF ROWS OF TOP CHORD BRIDGING**
Refer to the K-Series Load Table and Specification Section 6 for required bolted diagonal bridging.
Distances are Joist Span lengths in feet – See “Definition of Span” preceding Load Tables.
*Section
One
Two
Three
Four
Five
Number
Row
Rows
Rows
Rows
Rows
#1
#2
#3
#4
#5
#6
#7
#8
#9
#10
#11
#12
Up thru 16
Up thru 17
Up thru 18
Up thru 19
Up thru 19
Up thru 19
Up thru 20
Up thru 20
Up thru 20
Up thru 20
Up thru 20
Up thru 20
Over 16 thru 24
Over 17 thru 25
Over 18 thru 28
Over 19 thru 28
Over 19 thru 29
Over 19 thru 29
Over 20 thru 33
Over 20 thru 33
Over 20 thru 33
Over 20 thru 37
Over 20 thru 38
Over 20 thru 39
Over 24 thru 28
Over 25 thru 32
Over 28 thru 38
Over 28 thru 38
Over 29 thru 39
Over 29 thru 39
Over 33 thru 45
Over 33 thru 45
Over 33 thru 46
Over 37 thru 51
Over 38 thru 53
Over 38 thru 53
Over 38 thru 40
Over 38 thru 48
Over 39 thru 50
Over 39 thru 51
Over 45 thru 58
Over 45 thru 58
Over 46 thru 59
Over 51 thru 60
Over 53 thru 60
Over 53 thru 60
Over 50 thru 52
Over 51 thru 56
Over 58 thru 60
Over 58 thru 60
Over 59 thru 60
*Last digit(s) of joist designation shown in Load Table
**See Section 5.11 for additional bridging required for uplift design.
TABLE 5.4-2
METRIC UNITS
NUMBER OF ROWS OF TOP CHORD BRIDGING**
Refer to the K-Series Load Table and Specification Section 6 for required bolted diagonal bridging.
Distances are Joist Span lengths in millimeters – See “Definition of Span” preceding Load Tables.
*Section
One
Two
Three
Four
Five
Number
Row
Rows
Rows
Rows
Rows
#1
#2
#3
#4
#5
#6
#7
#8
#9
#10
#11
#12
Up thru 4877
Up thru 5182
Up thru 5486
Up thru 5791
Up thru 5791
Up thru 5791
Up thru 6096
Up thru 6096
Up thru 6096
Up thru 6096
Up thru 6096
Up thru 6096
Over 4877 thru 7315
Over 5182 thru 7620
Over 5486 thru 8534
Over 5791 thru 8534
Over 5791 thru 8839
Over 5791 thru 8839
Over 6096 thru 10058
Over 6096 thru 10058
Over 6096 thru 10058
Over 6096 thru 11278
Over 6096 thru 11582
Over 6096 thru 11887
Over 7315 thru 8534
Over 7620 thru 9754
Over 8534 thru 11582
Over 8534 thru 11582
Over 8839 thru 11887
Over 8839 thru 11887
Over 10058 thru 13716
Over 10058 thru 13716
Over 10058 thru 14021
Over 11278 thru 15545
Over 11582 thru 16154
Over 11887 thru 16154
*Last digit(s) of joist designation shown in Load Table
**See Section 5.11 for additional bridging required for uplift design.
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Over 11582 thru 12192
Over 11582 thru 14630
Over 11887 thru 15240
Over 11887 thru 15545
Over 13716 thru 17678
Over 13716 thru 17678
Over 14021 thru 17983
Over 15545 thru 18288
Over 16154 thru 18288
Over 16154 thru 18288
Over 15240 thru 15850
Over 15545 thru 17069
Over 17678 thru 18288
Over 17678 thru 18288
Over 17983 thru 18288
5.5 INSTALLATION OF BRIDGING
Bridging shall support the top and bottom chords against lateral movement
during the construction period and shall hold the steel joists in the approximate
position as shown on the joist placement plans.
The ends of all bridging lines terminating at walls or beams shall be anchored
thereto.
5.6 END ANCHORAGE
(a) Masonry and Concrete
Ends of K-Series Joists resting on steel bearing plates on masonry or
structural concrete shall be attached thereto with a minimum of two 1/8 inch
(3millimeters) fillet welds 1 inch (25 millimeters) long, or with two 1/2 inch (13
millmeters) ASTM- A307 bolts, or the equivalent.
(b) Steel
Ends of K-Series Joists resting on steel supports shall be attached thereto
with a minimum of two 1/8 inch (3 millmeters) fillet welds 1 inch (25
millmeters) long, or with two 1/2 inch (13 millimeters) ASTM – A307 bolts, or
the equivalent. When K-Series Joists are used to provide lateral stability to
the supporting member, the final connection shall be made by welding or as
designated by the specifying professional.
(c) Uplift
Where uplift forces are a design consideration, roof joists shall be anchored to
resist such forces (Refer to Section 5.11 Uplift).
5.7 JOIST SPACING
Joists shall be spaced so that the loading on each joist does not exceed the
design load (LRFD or ASD) for the particular joist designation and span as
shown in the applicable load tables.
5.8 FLOOR AND ROOF DECKS
(a) Material
Floor and roof decks may consist of cast-in-place or pre-cast concrete or
gypsum, formed steel, wood, or other suitable material capable of supporting
the required load at the specified joist spacing.
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(b) Thickness
Cast-in-place slabs shall be not less than 2 inches (51 millimeters) thick.
(c) Centering
Centering for cast-in-place slabs may be ribbed metal lath, corrugated steel
sheets, paper-backed welded wire fabric, removable centering or any other
suitable material capable of supporting the slab at the designated joist
spacing.
Centering shall not cause lateral displacement or damage to the top chord of
joists during installation or removal of the centering or placing of the concrete.
(d) Bearing
Slabs or decks shall bear uniformly along the top chords of the joists.
(e) Attachments
The spacing for slab or deck attachments along the joist top chord shall not
exceed 36 inches (914 millimeters), and shall be capable of resisting a
nominal (unfactored) lateral force of not less than 300 pounds (1335
Newtons), i.e., 100 plf (1.46 kN/m).
(f) Wood Nailers
Where wood nailers are used, such nailers in conjunction with deck or slab
shall be attached to the top chords of the joists in conformance with Section
5.8(e).
(g) Joist With Standing Seam Roofing
The stiffness and strength of standing-seam roof clips varies from one
manufacturer to another. Therefore, some roof systems cannot be counted
on to provide lateral stability to the joists which support the roof. Sufficient
stability must be provided to brace the joists laterally under the full design
load. The compression chord must resist the chord axial design force in the
plane of the joist (i.e., x-x axis buckling) and out of the plane of the joist (i.e.,
y-y axis buckling). Out-of-plane strength may be achieved by adjusting the
bridging spacing and/or increasing the compression chord area, the joist
depth, and the y-axis radius of gyration. The effective slenderness ratio in the
y-direction equals 0.94 L/ry; where L is the bridging spacing in inches
(millimeters). The maximum bridging spacing may not exceed that specified
in Section 5.4(c).
83
Horizontal bridging members attached to the compression chords and their
anchorage’s must be designed for a compressive axial force of 0.0025nP,
where n is the number of joists between end anchors and P is the chord
design force in kips (Newtons). The attachment force between the horizontal
bridging member and the compression chord is 0.005P. Horizontal bridging
attached to the tension chords shall be proportioned so that the slenderness
ratio between attachments does not exceed 300. Diagonal bridging shall be
proportioned so that the slenderness ratio between attachments does not
exceed 200.
5.9 DEFLECTION
The deflection due to the design nominal live load shall not exceed the following:
Floors:
Roofs:
1/360 of span.
1/360 of span where a plaster ceiling is attached or suspended.
1/240 of span for all other cases.
The specifying professional shall give consideration to the effects of deflection
and vibration* in the selection of joists.
* For further reference, refer to Steel Joist Institute Technical Digest #5, Vibration of Steel Joist-Concrete Slab Floors"
and the Institute's Computer Vibration Program.
5.10 PONDING*
The ponding investigation shall be performed by the specifying professional.
* For further reference, refer to Steel Joist Institute Technical Digest #3, “Structural Design of Steel Joist Roofs to
Resist Ponding Loads” and AISC Specifications.
5.11 UPLIFT
Where uplift forces due to wind are a design requirement, these forces must be
indicated on the contract drawings in terms of NET uplift in pounds per square
foot (Pascals). The contract documents shall indicate if the net uplift is based
upon LRFD or ASD. When these forces are specified, they must be considered
in the design of joists and/or bridging. A single line of bottom chord bridging
must be provided near the first bottom chord panel points whenever uplift due to
wind forces is a design consideration.*
* For further reference, refer to Steel Joist Institute Technical Digest #6, “Structural Design of Steel Joist Roofs to
Resist Uplift Loads”.
5.12 INSPECTION
Joists shall be inspected by the manufacturer before shipment to verify
compliance of materials and workmanship with the requirements of these
specifications. If the purchaser wishes an inspection of the steel joists by
84
someone other than the manufacturer's own inspectors, he may reserve the right
to do so in his "Invitation to Bid" or the accompanying "Job Specifications".
Arrangements shall be made with the manufacturer for such inspection of the
joists at the manufacturing shop by the purchaser's inspectors at purchaser's
expense.
5.13 PARALLEL CHORD SLOPED JOISTS
The Span of a parallel chord sloped joist shall be defined by the length along the
slope. Minimum depth, load-carrying capacity, and bridging requirements shall
be determined by the sloped definition of span. The Standard Load Table
capacity shall be the component normal to the joist.
SECTION 6*.
ERECTION STABILITY
AND HANDLING
When it is necessary for the erector to climb on the joists, extreme caution must
be exercised since unbridged joists may exhibit some degree of instability under
the erector's weight.
(a) Stability Requirements
1) Before an employee is allowed on the steel joist: BOTH ends of joists at
columns (or joists designated as column joists) shall be attached to its
supports. For all other joists a minimum of one end shall be attached
before the employee is allowed on the joist. The attachment shall be in
accordance with Section 5.6 – End Anchorage.
When a bolted seat connection is used for erection purposes, as a
minimum, the bolts must be snug tightened. The snug tight condition is
defined as the tightness that exists when all plies of a joint are in firm
contact. This may be attained by a few impacts of an impact wrench or
the full effort of an employee using an ordinary spud wrench.
2) On steel joists that do not require erection bridging as shown by the
unshaded area of the Load Tables, only one employee shall be allowed on
the steel joist unless all bridging is installed and anchored.
* For a thorough coverage of this topic, refer to SJI Technical Digest #9, "Handling and Erection of Steel
Joists and Joist Girders".
3) Where the span of the steel joist is within the red shaded area of the Load
Table, the following shall apply:
85
a) The row of bridging nearest the mid span of the steel joists shall be
bolted diagonal erection bridging; and
b) Hoisting cables shall not be released until this bolted diagonal erection
bridging is installed and anchored, unless an alternate method of
stabilizing the joist has been provided; and
c) No more than one employee shall be allowed on these spans until all
other bridging is installed and anchored.
4) When permanent bridging terminus points cannot be used during erection,
additional temporary bridging terminus points are required to provide
stability.
5) In the case of bottom chord bearing joists, the ends of the joist must be
restrained laterally per Section 5.4(d).
6) After the joist is straightened and plumbed, and all bridging is completely
installed and anchored, the ends of the joists shall be fully connected to
the supports in accordance with Section 5.6 End Anchorage.
(b) Landing and Placing Loads
1) Except as stated in paragraphs 6(B)(3) and 6(B)(4) of this section, no
"construction loads”(1) are allowed on the steel joists until all bridging is
installed and anchored, and all joist bearing ends are attached.
2) During the construction period, loads placed on the steel joists shall be
distributed so as not to exceed the capacity of the steel joists.
3) The weight of a bundle of joist bridging shall not exceed a total of 1000
pounds (454 kilograms). The bundle of joist bridging shall be placed on a
minimum of 3 steel joists that are secured at one end. The edge of the
bridging bundle shall be positioned within 1 foot (0.30 m) of the secured
end.
(1)
See Appendix E for definition of “construction load”. A copy of the OSHA Steel Erection Standard §1926.757,
Open Web Steel Joists, is included in Appendix E for reference purposes.
4) No bundle of deck may be placed on steel joists until all bridging has been
installed and anchored and all joist bearing ends attached, unless the
following conditions are met:
a) The contractor has first determined from a qualified person and
documented in a site-specific erection plan that the structure or portion
of the structure is capable of supporting the load;
b) The bundle of decking is placed on a minimum of 3 steel joists;
c) The joists supporting the bundle of decking are attached at both ends;
86
d) At least one row of bridging is installed and anchored;
e) The total weight of the decking does not exceed 4000 pounds (1816
kilograms); and
f) The edge of the decking shall be placed within 1 foot (0.30 meters) of
the bearing surface of the joist end.
g) The edge of the construction load shall be placed within 1 foot (.30
meters) of the bearing surface of the joist end.
(c) Field Welding
1) All field welding shall be performed in accordance with the contract
documents. Field welding shall not damage the joists.
2) On cold-formed members whose yield strength has been attained by cold
working, and whose as-formed strength is used in the design, the total
length of weld at any one point shall not exceed 50 percent of the overall
developed width of the cold-formed section.
(d) Handling
Care shall be exercised at all times to avoid damage to the joists and
accessories.
(e) Fall Arrest Systems
Steel joists shall not be used as anchorage points for a fall arrest system
unless written direction to do so is obtained from a “qualified person” (2).
(2)
See Appendix E for OSHA definition of “qualified person”.
87
APPENDIX C
(Applicable sections only are reprinted below)
STANDARD SPECIFICATION
FOR LONGSPAN STEEL JOISTS, LH-SERIES AND
DEEP LONGSPAN STEEL JOISTS, DLH-SERIES
104.4 END SUPPORTS
(a) Masonry and Concrete
LH- and DLH-Series Joists supported by masonry or concrete are to bear on
steel bearing plates and shall be designed as steel bearing.
Due
consideration of the end reactions and all other vertical and lateral forces
shall be taken by the specifying professional in the design of the steel bearing
plate and the masonry or concrete. The ends of LH- and DLH-Series Joists
shall extend a distance of not less than 6 inches (152 millimeters) over the
masonry or concrete support and be anchored to the steel bearing plate. The
plate shall be located not more than 1/2 inch (13 millimeters) from the face of
the wall and shall be not less 9 inches (229 millimeters) wide perpendicular to
the length of the joist. The plate is to be designed by the specifying
professional and shall be furnished by other than the joist manufacturer.
Where it is deemed necessary to bear less than 6 inches (152 millimeters)
over the masonry or concrete support, special consideration is to be given to
the design of the steel bearing plate and the masonry or concrete by the
specifying professional. The joists must bear a minimum 4 inches (102
millimeters) on the steel bearing plate.
(b) Steel
Due consideration of the end reactions and all other vertical and lateral forces
shall be taken by the specifying professional in the design of the steel
support.
The ends of LH- or DLH-Series Joists shall extend a distance of not less than
4 inches (102 millimeters) over the steel supports. Where it is deemed
necessary to butt opposite joists over a narrow steel support with bearing less
than that noted above, special ends must be specified, and such ends shall
have positive attachment to the support, either by bolting or welding.
88
104.5 BRIDGING
Top and bottom chord bridging is required and shall consist of one or both of the
following types.
(a) Horizontal
Horizontal bridging lines shall consist of continuous horizontal steel members.
The l/r of the bridging member shall not exceed 300, where l is the distance
in inches (millimeters) between attachments and r is the least radius of
gyration of the bridging member.
(b) Diagonal
Diagonal bridging shall consist of cross-bracing with a l/r ratio of not more
than 200, where l is the distance in inches (millimeters) between connections,
and r is the least radius of gyration of the bridging member. Where
cross-bracing members are connected at their point of intersection, the l
distance shall be taken as the distance in inches (millimeters) between
connections at the point of intersection of the bridging members and the
connections to the chord of the joists.
(c) Bridging Lines
For spans up through 60 feet (18288 mm), welded horizontal bridging may be
used except where the row of bridging nearest the center is required to be
bolted diagonal bridging as indicated by the Red shaded area in the Load
Table. For spans over 60 feet (18288 mm) bolted diagonal bridging shall be
used as indicated by the Blue and Gray shaded areas of the Load Table.
(d) Quantity and Spacing
The maximum spacing of lines of top chord bridging shall not exceed the
values in Table 104.5-1. The number of rows of bottom chord bridging,
including bridging required per Section 104.12, shall not be less than the
number of top chord rows. Rows of bottom chord bridging are permitted to be
spaced independently of rows of top chord bridging. The spacing of rows of
bottom chord bridging shall meet the slenderness requirement of Section
103.4(a) and any specified strength requirements.
89
TABLE 104.5-1
LH-,DLHSECTION
NUMBER*
MAX. SPACING OF
LINES OF TOP
CHORD BRIDGING
NOMINAL**
HORIZONTAL
BRACING FORCE
lbs
(N)
02, 03, 04
11'-0″ (3352 mm)
400
(1779)
05, 06
12'-0″ (3657 mm)
500
(2224)
07, 08
13'-0″ (3962 mm)
650
(2891)
09, 10
14'-0″ (4267 mm)
800
(3558)
11, 12
16'-0″ (4876 mm)
1000
(4448)
13, 14
16'-0″ (4876 mm)
1200
(5337)
15, 16
21'-0″ (6400 mm)
1600
(7117)
17
21'-0″ (6400 mm)
1800
(8006)
18, 19
26'-0″ (7924 mm)
2000
(8896)
Number of lines of bridging is based on joist clear span dimensions.
* Last two digits of joist designation shown in load table.
** Nominal bracing force is unfactored.
(e) Connections
Connections to the chords of the steel joists shall be made by positive
mechanical means or by welding, and capable of resisting a horizontal force
not less than that specified in Table 104.5-1.
(f) Bottom Chord Bearing Joists
Where bottom chord bearing joists are utilized, a row of diagonal bridging shall
be provided near the support(s). This bridging shall be installed and anchored
before the hoisting cable(s) is released.
104.6 INSTALLATION OF BRIDGING
Bridging shall support the top and bottom chords against lateral movement
during the construction period and shall hold the steel joists in the approximate
position as shown on the joist placement plans.
The ends of all bridging lines terminating at walls or beams shall be anchored to
resist the nominal force shown in Table 104.5-1.
104.7 END ANCHORAGE
(a) Masonry and Concrete
Ends of LH- and DLH-Series Joists resting on steel bearing plates on
masonry or structural concrete shall be attached thereto with a minimum of
90
two 1/4 inch (6 millimeters) fillet welds 2 inches (51 millimeters) long, or with
two 3/4 inch (19 millimeters) ASTM – A307 bolts (minimum), or the
equivalent.
(b) Steel
Ends of LH- and DLH-Series Joists resting on steel supports shall be
attached thereto with a minimum of two 1/4 inch (6 millimeters) fillet welds 2
inches (51 millimeters) long, or with two 3/4 inch (19 millimeters) ASTM –
A307 bolts, or the equivalent. When LH/DLH series joists are used to provide
lateral stability to the supporting member, the final connection shall be made
by welding or as designated by the specifying professional.
(c) Uplift
Where uplift forces are a design consideration, roof joists shall be anchored to
resist such forces (Refer to Section 104.12).
104.8 JOIST SPACING
Joists shall be spaced so that the loading on each joist does not exceed the
design load (LRFD or ASD) for the particular joist designation and span as
shown in the applicable load tables.
104.9 FLOOR AND ROOF DECKS
(a) Material
Floor and roof decks may consist of cast-in-place or pre-cast concrete or
gypsum, formed steel, wood, or other suitable material capable of supporting
the required load at the specified joist spacing.
(b) Thickness
Cast-in-place slabs shall be not less than 2 inches (51 millimeters) thick.
(c) Centering
Centering for structural slabs may be ribbed metal lath, corrugated steel
sheets, paper-backed welded wire fabric, removable centering or any other
suitable material capable of supporting the slab at the designated joist
spacing. Centering shall not cause lateral displacement or damage to the top
chord of joists during installation or removal of the centering or placing of the
concrete.
91
(d) Bearing
Slabs or decks shall bear uniformly along the top chords of the joists.
(e) Attachments
The spacing of attachments along the top chord shall not exceed 36 inches
(914 millimeters). Such attachments of the slab or deck to the top chords of
joists shall be capable of resisting the following forces:
TABLE 104.9-1
SECTION NUMBER*
NOMINAL** FORCE REQUIRED
02 to 04 incl.
120 lbs/ft. (1.75 kN/m)
05 to 09 incl.
150 lbs/ft. (2.19 kN/m)
10 to 17 incl.
200 lbs/ft. (2.92 kN/m)
18 and 19
250 lbs/ft. (3.65 kN/m)
* Last two digits of joist designation shown in load table.
** Nominal bracing force is unfactored.
(f) Wood Nailers
Where wood nailers are used, such nailers in conjunction with deck or slab
shall be firmly attached to the top chords of the joists in conformance with
Section 104.9(e).
(g) Joist with Standing Seam Roofing
The stiffness and strength of standing-seam roof clips varies from one
manufacturer to another. Therefore, some roof systems cannot be counted
on to provide lateral stability to the joists which support the roof. Sufficient
stability must be provided to brace the joists laterally under the full design
load. The compression chord must resist the chord axial design force in the
plane of the joist (i.e., x-x axis buckling) and out of the plane of the joist (i.e.,
y-y axis buckling). Out of plane strength may be achieved by adjusting the
bridging spacing and/or increasing the compression chord area, the joist
depth, and the y-axis radius of gyration. The effective slenderness ratio in the
y-direction equals 0.94 L/ry; where L is the bridging spacing in inches
(millimeters). The maximum bridging spacing may not exceed that specified
in Section 104.5(d).
Horizontal bridging members attached to the compression chords and their
anchorages must be designed for a compressive axial force of 0.0025nP,
where n is the number of joists between end anchors and P is the chord
design force in kips (kiloNewtons). The attachment force between the
horizontal bridging member and the compression chord is 0.005P. Horizontal
bridging attached to the tension chords shall be proportioned so that the
92
slenderness ratio between attachments does not exceed 300. Diagonal
bridging shall be proportioned so that the slenderness ratio between
attachments does not exceed 200.
104.10 DEFLECTION
The deflection due to the design live load shall not exceed the following:
Floors:
Roofs:
1/360 of span.
1/360 of span where a plaster ceiling is attached or suspended.
1/240 of span for all other cases.
The specifying professional shall give consideration to the effects of deflection
and vibration* in the selection of joists.
* For further reference, refer to Steel Joist Institute Technical Digest #5, "Vibration of Steel Joist-Concrete Slab Floors"
and the Institute's Computer Vibration Program.
104.11 PONDING *
The ponding investigation shall be performed by the specifying professional.
* For further reference, refer to Steel Joist Institute Technical Digest #3, “Structural Design of Steel Joist Roofs to
Resist Ponding Loads” and AISC Specifications.
104.12 UPLIFT
Where uplift forces due to wind are a design requirement, these forces must be
indicated on the contract drawings in terms of NET uplift in pounds per square
foot (Pascals). The contract documents shall indicate if the net uplift is based on
ASD or LRFD. When these forces are specified, they must be considered in the
design of joists and/or bridging. A single line of bottom chord bridging must be
provided near the first bottom chord panel points whenever uplift due to wind
forces is a design consideration.*
* For further reference, refer to Steel Joist Institute Technical Digest #6, “Structural Design of Steel Joist Roofs to
Resist Uplift Loads.”
104.13 INSPECTION
Joists shall be inspected by the manufacturer before shipment to verify
compliance of materials and workmanship with the requirements of these
specifications. If the purchaser wishes an inspection of the steel joists by
someone other than the manufacturer's own inspectors, he may reserve the right
to do so in his "Invitation to Bid" or the accompanying "Job Specifications".
Arrangements shall be made with the manufacturer for such shop inspection of
the joists at the manufacturing shop by the purchaser’s inspectors at purchaser’s
expense.
93
104.14 PARALLEL CHORD SLOPED JOISTS
The span of a parallel chord sloped joist shall be defined by the length along the
slope. Minimum depth, load-carrying capacity, and bridging requirements shall
be determined by the sloped definition of span. The Load Table capacity shall be
the component normal to the joist.
SECTION 105*.
ERECTION STABILITY
AND HANDLING
When it is necessary for the erector to climb on the joists, extreme caution must
be exercised since unbridged joists may exhibit some degree of instability under
the erector's weight.
(a) Stability Requirements
1) Before an employee is allowed on the steel joist: BOTH ends of joists at
columns (or joists designated as column joists) shall be attached to its
supports. For all other joists a minimum of one end shall be attached
before the employee is allowed on the joist. The attachment shall be in
accordance with Section 104.7 – End Anchorage.
When a bolted seat connection is used for erection purposes, as a
minimum, the bolts must be snug tightened. The snug tight condition is
defined as the tightness that exists when all plies of a joint are in firm
contact. This may be attained by a few impacts of an impact wrench or
the full effort of an employee using an ordinary spud wrench.
2) On steel joists that do not require erection bridging as shown by the
unshaded area of the Load Tables, only one employee shall be allowed on
the steel joist unless all bridging is installed and anchored.
* For a thorough coverage of this topic, refer to SJI Technical Digest #9, "Handling and Erection of Steel Joists
and Joist Girders".
3) Where the span of the steel joist is within the Red shaded area of the
Load Table, the following shall apply:
a) The row of bridging nearest the mid span of the steel joist shall be
bolted diagonal erection bridging; and
b) Hoisting cables shall not be released until this bolted diagonal erection
bridging is installed and anchored, unless an alternate method of
stabilizing the joist has been provided; and
c) No more than one employee shall be allowed on these spans until all
other bridging is installed and anchored.
94
4) Where the span of the steel joist is within the Blue shaded area of the
Load Table, the following shall apply:
a) All rows of bridging shall be bolted diagonal bridging; and
b) Hoisting cables shall not be released until the two rows of bolted
diagonal erection bridging nearest the third points of the steel joist are
installed and anchored; and
c) No more than two employees shall be allowed on these spans until all
other bridging is installed and anchored.
5) Where the span of the steel joist is in the Gray shaded area of the Load
Table, the following shall apply:
a) All rows of bridging shall be bolted diagonal bridging; and
b) Hoisting cables shall not be released until all bridging is installed and
anchored; and
c) No more than two employees shall be allowed on these spans until all
other bridging is installed and anchored.
6) When permanent bridging terminus points cannot be used during erection,
additional temporary bridging terminus points are required to provide
lateral stability.
7) In the case of bottom chord bearing joists, the ends of the joist must be
restrained laterally per Section 104.5(f) before releasing the hoisting
cables.
8) After the joist is straightened and plumbed, and all bridging is completely
installed and anchored, the ends of the joists shall be fully connected to
the supports in accordance with Section 104.7 - End Anchorage.
(b) Landing and Placing Loads
1) Except as stated in paragraph 105(b)(3) of this section, no "construction
loads”(1) are allowed on the steel joists until all bridging is installed and
anchored, and all joist bearing ends are attached.
2) During the construction period, loads placed on the steel joists shall be
distributed so as not to exceed the capacity of the steel joists.
3) No bundle of deck may be placed on steel joists until all bridging has been
installed and anchored and all joist bearing ends attached, unless the
following conditions are met:
a) The contractor has first determined from a “qualified person”(2) and
documented in a site-specific erection plan that the structure or portion
of the structure is capable of supporting the load;
b) The bundle of decking is placed on a minimum of 3 steel joists;
95
c) The joists supporting the bundle of decking are attached at both ends;
d) At least one row of bridging is installed and anchored;
e) The total weight of the decking does not exceed 4000 pounds (1816
kilograms);
f) The edge of the bundle of decking shall be placed within 1 foot (0.30
meters) of the bearing surface of the joist end; and
g) The edge of the construction load shall be placed within 1 foot (0.30
meters) of the bearing surface of the joist end.
(c) Field Welding
1) All field welding shall be performed in accordance with the contract
documents. Field welding shall not damage the joists.
2) On cold-formed members whose yield strength has been attained by cold
working, and whose as-formed strength is used in the design, the total
length of weld at any one point shall not exceed 50 percent of the overall
developed width of the cold-formed section.
(d) Handling
Particular attention should be paid to the erection of Longspan and Deep
Longspan Steel Joists. Care shall be exercised at all times to avoid damage
to the joists and accessories.
Each joist shall be adequately braced laterally before any loads are applied.
If lateral support is provided by bridging, the bridging lines as defined in
Section 105(a), paragraphs 2, 3, 4 and 5 must be anchored to prevent lateral
movement.
(e) Fall Arrest Systems
Steel joists shall not be used as anchorage points for a fall arrest system
unless written direction to do so is obtained from a “qualified person” (2).
(2)
See Appendix E for OSHA definition of “qualified person”.
96
APPENDIX D
(Applicable sections only are reprinted below)
STANDARD SPECIFICATION
FOR JOIST GIRDERS
Adopted by the Steel Joist Institute November 4, 1985
Revised to November 10, 2003 - Effective March 01, 2005
1004.4 END SUPPORTS
(a) Masonry and Concrete
Joist Girders supported by masonry or concrete are to bear on steel bearing
plates and shall be designed as steel bearing. Due consideration of the end
reactions and all other vertical and lateral forces shall be taken by the
specifying professional in the design of the steel bearing plate and the
masonry or concrete. The ends of Joist Girders shall extend a distance of not
less than 6 inches (152 millimeters) over the masonry or concrete support
and be anchored to the steel bearing plate. The plate shall be located not
more than 1/2 inch (13 millimeters) from the face of the wall and shall be not
less 9 inches (229 millimeters) wide perpendicular to the length of the girder.
The plate is to be designed by the specifying professional and shall be
furnished by other than the joist manufacturer.
Where it is deemed necessary to bear less than 6 inches (152 millimeters)
over the masonry or concrete support, special consideration is to be given to
the design of the steel bearing plate and the masonry or concrete by the
specifying professional. The girders must bear a minimum of 4 inches (102
millimeters) on the steel bearing plate.
(b) Steel
Due consideration of the end reactions and all other vertical and lateral forces
shall be taken by the specifying professional in the design of the steel
support. The ends of Joist Girders shall extend a distance of not less than 4
inches (102 millimeters) over the steel supports and shall have positive
attachment to the support, either by bolting or welding.
97
1004.5 BRACING
Joist Girders shall be proportioned such that they can be erected without bridging
(See Section 1004.9 for bracing required for uplift forces). Therefore, the
following requirements must be met:
a) The ends of the bottom chord are restrained from lateral movement to
brace the girder from overturning. For Joist Girders at columns in steel
frames, restraint shall be provided by a stabilizer plate on the column.
b) No other loads shall be placed on the Joist Girder until the steel joists
bearing on the girder are in place and welded to the girder.
1004.6 END ANCHORAGE
(a) Masonry and Concrete
Ends of Joist Girders resting on steel bearing plates on masonry or structural
concrete shall be attached thereto with a minimum of two 1/4 inch (6
millimeters) fillet welds 2 inches (51 millimeters) long, or with two 3/4 inch (19
millimeters) bolts, or the equivalent.
(b) Steel
Ends of Joist Girders resting on steel supports shall be attached thereto with
a minimum of two 1/4 inch (6 millimeters) fillet welds 2 inches (51 millimeters)
long, or with two 3/4 inch (19 millimeters) bolts, or the equivalent. In steel
frames, bearing seats for Joist Girders shall be fabricated to allow for field
bolting.
(c) Uplift
Where uplift forces are a design consideration, roof Joist Girders shall be
anchored to resist such forces (Refer to Section 104.9).
1004.7 DEFLECTION
The deflections due to the design live load shall not exceed the following:
Floors:
Roofs:
1/360 of span.
1/360 of span where a plaster ceiling is attached or suspended.
1/240 of span for all other cases.
The specifying professional shall give consideration to the effects of deflection
and vibration* in the selection of Joist Girders.
* For further reference, refer to Steel Joist Institute Technical Digest #5, "Vibration of Steel Joist-Concrete Slab Floors"
and the Institute's Computer Vibration Program.
98
1004.8 PONDING*
The ponding investigation shall be performed by the specifying professional.
* For further reference, refer to Steel Joist Institute Technical Digest #3, “Structural Design of Steel Joist Roofs to
Resist Ponding Loads" and AISC Specifications.
1004.9 UPLIFT
Where uplift forces due to wind are a design requirement, these forces must be
indicated on the contract drawings in terms of NET uplift in pounds per square
foot (Pascals). The contract drawings must indicate if the net uplift is based on
ASD or LRFD. When these forces are specified, they must be considered in the
design of Joist Girders and/or bracing. If the ends of the bottom chord are not
strutted, bracing must be provided near the first bottom chord panel points
whenever uplift due to wind forces is a design consideration.*
* For further reference, refer to Steel Joist Institute Technical Digest #6, “Structural Design of Steel Joist Roofs to resist
Uplift Loads”.
1004.10 INSPECTION
Joist Girders shall be inspected by the manufacturer before shipment to verify
compliance of materials and workmanship with the requirements of this
specification. If the purchaser wishes an inspection of the Joist Girders by
someone other than the manufacturer's own inspectors, he may reserve the right
to do so in his "Invitation to Bid" or the accompanying "Job Specifications".
Arrangements shall be made with the manufacturer for such inspection of the
Joist Girders at the manufacturing shop by the purchaser’s inspectors at
purchaser’s expense.
SECTION 1005*.
HANDLING AND
ERECTION
Particular attention should be paid to the erection of Joist Girders.
Care shall be exercised at all times to avoid damage through careless handling
during unloading, storing and erecting. Dropping of Joist Girders shall not be
permitted.
In steel framing, where Joist Girders are utilized at column lines, the Joist Girder
shall be field-bolted at the column. Before hoisting cables are released and
before an employee is allowed on the Joist Girder the following conditions must
be met:
99
a) The seat at each end of the Joist Girder is attached in accordance with
Section 1004.6.
When a bolted seat connection is used for erection purposes, as a minimum,
the bolts must be snug tightened. The snug tight condition is defined as the
tightness that exists when all plies of a joint are in firm contact. This may be
attained by a few impacts of an impact wrench or the full effort of an
employee using an ordinary spud wrench.
b) Where stabilizer plates are required the Joist Girder bottom chord must
engage the stabilizer plate.
During the construction period, the contractor shall provide means for the
adequate distribution of loads so that the carrying capacity of any Joist Girder is
not exceeded.
Joist Girders shall not be used as anchorage points for a fall arrest system
unless written direction to do so is obtained from a “qualified person”. (1)
Field welding shall not damage the Joist Girder. The total length of weld at any
one cross-section on cold formed members whose yield strength has been
attained by cold working and whose as-formed strength is used in the design,
shall not exceed 50 percent of the overall developed width of the cold-formed
section.
* For a thorough coverage of this topic, refer to SJI Technical Digest #9, "Handling and Erection of Steel Joists and
Joist Girders".
(1)
See Appendix E for OSHA definition of “qualified person”.
100
APPENDIX E
(Applicable sections only are reprinted below)
STANDARD SPECIFICATION
FOR COMPOSITE STEEL JOISTS, CJ-SERIES
Adopted by the Steel Joist Institute May 10, 2006
- Effective May 10, 2006
104.4 END SUPPORTS
(a)
Masonry and Concrete
CJ-Series Joists supported by masonry or concrete are to bear on steel
bearing plates and shall be designed as steel bearing. Due consideration of
the end reactions and all other vertical and lateral forces shall be taken by
the specifying professional in the design of the steel bearing plate and the
masonry or concrete. The ends of CJ-Series Joists shall extend over the
masonry or concrete support as shown below and be anchored to a steel
bearing plate. This steel bearing plate shall be located no more than 1/2
inch (13 millimeters) from the face of the wall. The distance over the wall
that the composite joist shall bear, width of the steel bearing plate and
anchorage of the CJ-Series Joists shall be as defined below:
For 2 1/2” ≤ Seat Depth < 5”:
•
The ends of CJ-Series Joists shall extend a distance of not
less than 4 inches (102 millimeters) over the masonry or
concrete support and be anchored to the steel bearing plate.
•
The width of the plate perpendicular to the span of the
Composite Steel Joist shall be not less than 6 inches (152
millimeters).
•
The Composite Steel Joists must bear a minimum of 2 1/2
inches (64 millimeters) on the steel bearing plate.
For Seat Depth ≥ 5”:
•
The ends of CJ-Series Joists shall extend a distance of not
less than 6 inches (152 millimeters) over the masonry or
concrete support and be anchored to the steel bearing plate.
•
The width of the plate perpendicular to the span of the
Composite Steel Joist shall be not less than 9 inches (229
millimeters).
101
•
The Composite Steel Joists must bear a minimum of 4
inches (102 millimeters) on the steel bearing plate.
The steel bearing plate is to be designed by the specifying professional and
shall be furnished by other than the joist manufacturer.
Where it is deemed necessary to bear less than the dimensions listed above
over the masonry or concrete support, special consideration is to be given
to the design of the steel bearing plate and the masonry or concrete by the
specifying professional.
The joist must meet the minimum bearing
requirement on the steel bearing plate.
(b)
Steel
Due consideration of the end reactions and all other vertical and lateral
forces shall be taken by the specifying professional in the design of the steel
support.
For 2 1/2” ≤ Seat Depth < 5”:
The ends of CJ-Series Joists shall extend a distance of not less
than 2 1/2 inches (64 millimeters) over the steel supports.
For Seat Depth ≥ 5”:
The ends of CJ-Series Joists shall extend a distance of not less
than 4 inches (102 millimeters) over the steel supports.
Where it is deemed necessary to butt opposite joists over a narrow steel
support with bearing less than that noted above, special ends must be
specified, and such ends shall have positive attachment to the support,
either by bolting or welding.
104.5 BRIDGING
Top and bottom chord bridging is required and shall consist of one or both of the
following types:
(a)
Horizontal
Horizontal bridging lines shall consist of continuous horizontal steel
members. The l/r ratio of the bridging member shall not exceed 300, where
l is the distance in inches (millimeters) between attachments and r is the
least radius of gyration of the bridging member.
(b)
Diagonal
Diagonal bridging lines shall consist of cross-bracing with a l/r ratio of not
more than 200, where l is the distance in inches (millimeters) between
connections and r is the least radius of gyration of the bracing member.
102
Where cross-bracing members are connected at their point of intersection,
the l distance shall be taken as the distance in inches (millimeters) between
connections at the point of intersection of the bridging members and the
connections to the chords of the joists.
(c)
Bridging Lines
For spans up through 60 feet (18.3 meters), welded horizontal bridging may
be used except where the row of bridging nearest the center is required to
be bolted diagonal bridging as indicated on the joist manufacturer’s joist
placement plans. When the span of the composite steel joist is over 60 feet
(18.3 meters), but not greater than 100 feet (30.5 meters), hoisting cables
shall not be released until the two rows of bridging nearest the third points
are completely installed. When the span exceeds 100 feet (30.5 meters)
hoisting cables shall not be released until all rows of bridging are completely
installed. For spans over 60 feet (18.3 meters) all rows of bridging shall be
diagonal bridging with bolted connections at the chords and intersections.
(d)
Spacing
Bridging must be properly spaced and anchored to support the decking and
the employees prior to the attachment of the deck to the top chord. The
maximum spacing of lines of bridging, lbr shall be the lesser of,
dj ⎞
⎛
l br = ⎜⎜ 100 + 0.67 d j + 40 ⎟⎟ ry , in.
L⎠
⎝
dj ⎞
⎛
l br = ⎜⎜ 100 + 0.026 d j + 0.48 ⎟⎟ ry , mm
L⎠
⎝
(104.5-1a)
(104.5-1b)
or
l br = 170 ry
(104.5-2)
Where,
dj is the steel joist depth, in. (mm)
L is the design length for the composite joist, ft. (m)
ry is the out-of-plane radius of gyration of the top chord, in. (mm)
The number of rows of bottom chord bridging shall not be less than the
number of top chord rows. Rows of bottom chord bridging are permitted to
be spaced independently of rows of top chord bridging.
(e)
Connections
Connection of bridging to the chords of the Composite Steel Joists shall be
made by positive mechanical means or by welding. Ends of all bridging
lines terminating at walls, beams, or double joists boxed by diagonal
bridging shall be anchored.
103
Connection of the horizontal and diagonal bridging to the joist chord or
bridging terminus point shall be capable of resisting the nominal top chord
horizontal force, Pbr given in Equation 104.5-3.
Pbr = 0.0025 n At Fconstruction , lbs (N)
(104.5-3)
Where,
n = 8 for horizontal bridging
n = 2 for diagonal bridging
At = cross sectional area of joist top chord, in.2 (mm2)
Fconstruction = assumed nominal stress in top chord due to construction
loads
Fconstruction
Fconstruction
⎛
⎜
⎜ π2 E
=⎜
⎜ ⎛ 0.9 l
br
⎜⎜
⎜ ⎜ ry
⎝⎝
⎛
⎜
⎜ π2 E
=⎜
⎜ ⎛ 0.9 l
br
⎜⎜
⎜ ⎜ ry
⎝⎝
⎞
⎟
⎟
⎟ ≥ 12.2 ksi
2
⎞ ⎟
⎟ ⎟
⎟ ⎟
⎠ ⎠
(104.5-4a)
⎞
⎟
⎟
⎟ ≥ 84.1 MPa
2
⎞ ⎟
⎟ ⎟
⎟ ⎟
⎠ ⎠
(104.5-4b)
Where,
E = Modulus of Elasticity of steel = 29,000 ksi (200,000
MPa)
l br
is determined from Equations 104.5-1a, 104.5-1b
ry
or 104.5-2
and
(f)
Sizing of Bridging
Horizontal joist bridging shall be designed to resist the nominal compressive
force shown in Equation 104.5-3. Diagonal bridging shall be capable of
resisting in tension the nominal horizontal force shown in Equation 104.5-3.
(g)
Bottom Chord Bearing Joists
Where bottom chord bearing joists are utilized, a row of diagonal bridging
shall be provided near the support(s). This bridging shall be installed and
anchored before the hoisting cable(s) is released.
104
104.6 INSTALLATION OF BRIDGING
Bridging shall be provided to support the top chord during installation of the
decking prior to the attachment of the deck to the top chord. All bridging and
bridging anchors shall be completely installed before construction loads are
placed on the joists. Bridging shall support the top and bottom chords against
lateral movement during the construction period and shall hold the steel joists in
the approximate position as shown on the joist placement plans.
104.7 END ANCHORAGE
(a)
Masonry and Concrete
Ends of Composite Steel Joists resting on steel bearing plates on masonry
or structural concrete shall be attached thereto as defined below:
For 2 1/2” ≤ Seat Depth < 5”:
With a minimum of two 1/8 inch (3 millimeters) fillet welds 1 inch
(25 millimeters) long, or with two 1/2 inch (13 millimeters) ASTM
A307 bolts, or with the equivalent.
For Seat Depth ≥ 5”:
With a minimum of two 1/4 inch (6 millimeters) fillet welds 2 inches
(51 millimeters) long, or with two 3/4 inch (19 millimeters) ASTM
A307 bolts or the equivalent.
(b)
Steel
Ends of Composite Steel Joists resting on steel supports shall be attached
thereto as defined below:
For 2 1/2” ≤ Seat Depth < 5”:
With a minimum of two 1/8 inch (3 millimeters) fillet welds 1 inch
(25 millimeters) long, or with two 1/2 inch (13 millimeters) ASTM
A307 bolts, or with the equivalent.
For Seat Depth ≥ 5”:
With a minimum of two 1/4 inch (6 millimeters) fillet welds 2 inches
(51 millimeters) long, or with two 3/4 inch (19 millimeters) ASTM
A307 bolts or the equivalent.
In steel frames, where columns are not framed in at least two directions with
solid structural steel members, joists at column lines shall be field bolted
and the joist bottom chords must be restrained by a vertical stabilizer plate
attached to the column providing lateral stability during construction. Where
constructability does not allow a steel joist to be installed directly at the
column, an alternate means of stabilizing the joist shall be installed on both
sides near the column (OSHA 2001). When CJ-Series Joists are used to
105
provide lateral stability to the supporting member, the final connection shall
be made by welding or as designated by the specifying professional.
(c)
Uplift
Where uplift forces are a design consideration, composite joists used in roof
applications shall be anchored to resist such forces (Refer to Section
104.12).
104.8 JOIST SPACING
Composite joists shall be spaced so that the loading on each joist does not
exceed the design load.
104.9 DECKS
(a)
Material
Floor deck shall consist of formed steel capable of supporting the required
load at the specified joist spacing.
(b)
Thickness
Cast-in-place slabs shall be not less than 2 inches (51 millimeters) thick
above the deck.
(c)
Bearing
Slabs or decks shall bear uniformly along the top chords of the joists.
(d)
Attachments of the steel deck
The deck shall be attached per Steel Deck Institute requirements prior to
placing construction loads on the composite joists. The spacing of the
attachments along the top chord shall not exceed 36 inches (914
millimeters).
104.10 DEFLECTION
The deflection due to the design live load shall not exceed the following:
Floors:
1/360 of span.
Roofs:
1/360 of span where a plaster ceiling is attached or suspended.
1/240 of span for all other cases.
The specifying professional shall give due consideration to the effects of
deflection, both short and long term, and vibration* in the selection of composite
joists. All deflection calculations should account for the inherent flexibility of the
open web configuration.
106
*For further reference, refer to Steel Joist Institute Technical Digest #5, “Vibration of Steel Joist-Concrete Slab Floors”
and the Institute’s Computer Vibration Program.
104.11 PONDING
When Composite Steel Joists are used in roofs, a ponding* investigation shall be
performed by the specifying professional.
* For further reference, refer to the Steel Joist Institute Technical Digest #3, “Structural Design of Steel Joist Roofs to
Resist Ponding Loads” and AISC Specifications.
104.12 UPLIFT
When Composite Steel Joists are used in roofs, and where uplift forces due to
wind are a design requirement, these forces must be indicated on the contract
drawings in terms of net uplift in pounds per square foot (kilopascals). When
these forces are specified, they must be considered in the design of the joists
and/or bridging. A single line of bottom chord bridging must be provided near the
first bottom chord panel points whenever uplift due to wind forces is a design
consideration.*
* For further reference, refer to Steel Joist Institute Technical Digest #6, “Structural Design of Steel Joist Roofs to
Resist Uplift Loads”.
104.13 INSPECTION
Joists shall be inspected by the manufacturer before shipment to verify
compliance of materials and workmanship with the requirements of these
specifications. If the purchaser wishes an inspection of the steel joists by
someone other than the manufacturer’s own inspectors, they may reserve the
right to do so in their “Invitation to Bid” or the accompanying “Job specifications”.
Arrangements shall be made with the manufacturer for such shop inspection of
the joists at the manufacturing shop by the purchaser’s inspectors at purchaser’s
expense.
107
SECTION 105*.
ERECTION STABILITY
AND HANDLING
When it is necessary for the erector to climb on the composite steel joists,
extreme caution must be exercised since unbridged joists may exhibit some
degree of instability under the erector’s weight.
* For a thorough coverage of this topic, refer to Steel Joist Institute Technical Digest #9, “Handling and Erection of Steel
Joists and Joist Girders”.
(a)
Erection Stability
Joist erection bridging requirements shall be determined by the joist
manufacturer and indicated on the joist placement plans.
(b)
Stability Requirements during Joist Erection
(1)
Before an employee is allowed on the composite steel joist: BOTH
ends of composite joists at columns (or composite joists designated as
column joists) shall be attached to its supports. For all other composite
joists a minimum of one end shall be attached before the employee is
allowed on the composite joist. The attachment shall be in accordance
with Section 104.7- End Anchorage.
When a bolted seat connection is used for erection purposes, as a
minimum, the bolts must be snug tightened. The snug tight condition
is defined as the tightness that exists when all plies of a joint are in firm
contact. This may be attained by a few impacts of an impact wrench or
the full effort of an employee using an ordinary spud wrench.
(2)
On composite steel joists that do not require erection bridging as
shown on the joist placement plans, only one employee shall be
allowed on the composite joist unless all bridging is installed and
anchored.
(3)
Where the span of the composite steel joist requires one line of bolted
diagonal erection bridging nearest the mid-span of the joist, as
indicated on the joist placement plans, the following shall apply:
a. Hoisting cables shall not be released until the row of bolted
diagonal erection bridging is installed and anchored, unless an
alternate method of stabilizing the composite steel joist has been
provided; and
b. No more than one employee shall be allowed on these spans until
all bridging is installed and anchored.
108
(4)
Where the span of the Composite Steel Joist requires two lines of
bolted diagonal erection bridging nearest the third points of the joist, as
indicated on the joist placement plans, the following shall apply:
a. Hoisting cables shall not be released until the two rows of bolted
diagonal erection bridging are installed and anchored; and
b. No more than two employees shall be allowed on these spans until
all other bridging is installed and anchored.
(5)
Where the span of the composite steel joist requires all lines of
bridging to be bolted diagonal erection bridging as indicated on the
joist placement plans, the following shall apply:
a. Hoisting cables shall not be released until all bridging is installed
and anchored; and
b. No more than two employees shall be allowed on these spans until
all other bridging is installed and anchored.
(c)
(6)
When permanent bridging terminus points can not be used during
erection, additional temporary bridging terminus points are required to
provide lateral stability.
(7)
In the case of bottom chord bearing joists, the ends of the composite
joist must be restrained laterally per Section 104.5(g) before releasing
the hoisting cables.
(8)
After the composite steel joist is straightened and plumbed, and all
bridging is completely installed and anchored, the ends of the joists
shall be fully connected to the supports in accordance with Section
104.7- End Anchorage.
Landing and Placing Loads
(1)
Except as stated in paragraph 105(c)(3) of this section, no
“Construction Loads” are allowed on the Composite Steel Joists until
all bridging is installed and anchored, and all joist bearing ends are
attached. “Construction Loads” (for joist erection) means any load
other than the weight of the employee(s), the joists, and the bridging
bundle(s).
(2)
During the construction period, loads placed on the Composite Steel
Joists shall be distributed so as not to exceed the non-composite
capacity of the composite steel joists.
(3)
No bundle of deck may be placed on Composite Steel Joists until all
bridging has been installed and anchored and all composite steel joist
109
bearing ends attached, unless the following conditions are met:
a. The contractor has first determined from a “qualified person” and
documented in a site specific erection plan that the structure or
portion of structure is capable of supporting the load. A “qualified
person” means one who, by possession of a recognized degree,
certificate, or professional standing, or who by extensive
knowledge,
training,
and
experience,
has
successfully
demonstrated the ability to solve or resolve problems relating to the
subject mater, the work, or the project;
b. The bundle of decking is placed on a minimum of 3 composite steel
joists;
c. The composite steel joists supporting the bundle of decking are
attached at both ends;
d. At least one row of bridging is installed and anchored;
e. The total weight of the decking does not exceed 4000 pounds
(1816 kilograms);
f. The edge of the bundle of decking shall be placed within 1 foot
(0.30 meter) of the bearing surface of the composite steel joist end.
(4)
(d)
(e)
The edge of any construction load shall be placed within 1 foot (0.30
meter) of the bearing surface of the composite steel joist end.
Field Welding
(1)
All field welding shall be performed in accordance with contract
documents. Field welding shall not damage the composite joists.
(2)
On cold-formed members whose yield strength has been attained by
cold working, and whose as-formed strength is used in the design, the
total length of weld at any one point shall not exceed 50 percent of the
overall developed width of the cold-formed section.
Handling
Particular attention should be paid to the erection of Composite Steel Joists.
Care shall be exercised at all times to avoid damage to the composite joists
and accessories.
Each Composite Steel Joist shall be adequately braced laterally before any
loads are applied. If lateral support is provided by the bridging, the bridging
lines as defined in Section 105(b), paragraphs (2), (3), (4) and (5), must be
anchored to prevent lateral movement.
(f)
Fall Arrest Systems
Composite steel joists shall not be used as anchorage points for a fall arrest
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system unless written approval to do so is obtained from a “qualified person”
as defined in paragraph 105(c)(3)(a).
SECTION 106.
SHEAR CONNECTOR
PLACEMENT AND WELDING
(a)
Shear connectors required on each side of the point of maximum
positive or negative bending moment, shall be distributed uniformly
between that point and the adjacent points of zero moment, unless
otherwise specified. However the number of shear connectors placed
between any concentrated load and the nearest point of zero moment
shall be sufficient to develop the maximum moment required at the
concentrated load point.
(b)
Studs shall be alternately placed on each chord angle section for
double angle top chords. When constructability does not allow this to
occur, stud placement shall be limited as follows:
1. No more than three studs shall be placed consecutively on any
one chord angle, and
2. No more than 60% of the total number of studs shall be placed
on any one chord angle.
Studs shall have a minimum of 1/2 inch (13 millimeters) concrete cover
over the head of each stud (see Section 103.6(d)).
(c)
The minimum center-to-center spacing of stud connectors shall be six
stud diameters along the longitudinal axis of the supporting composite
joist, except that within the ribs of formed steel decks oriented
perpendicular to the steel joists, the minimum center-to-center spacing
shall be four stud diameters in any direction.
(d)
The distance measured along the longitudinal axis of the joist from the
free edge of the concrete slab to the first stud shall not be less than the
deck height plus four stud diameters.
(e)
The spacing of stud shear connectors along the length of the
supporting joist shall not exceed eight times the slab depth or 36
inches (914 millimeters).
(f)
To resist uplift, the steel deck shall be anchored to all supporting
members at a spacing not to exceed 18 inches (460 millimeters). Such
anchorage shall be provided by stud connectors, a combination of stud
connectors and arc spot (puddle) welds, or other devices.
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