TECHNICAL CORRECTION
October 2006
Process Industry Practices
Structural
PIP STE05121
Anchor Bolt Design Guide
PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES
In an effort to minimize the cost of process industry facilities, this Practice has
been prepared from the technical requirements in the existing standards of major
industrial users, contractors, or standards organizations. By harmonizing these
technical requirements into a single set of Practices, administrative, application, and
engineering costs to both the purchaser and the manufacturer should be reduced. While
this Practice is expected to incorporate the majority of requirements of most users,
individual applications may involve requirements that will be appended to and take
precedence over this Practice. Determinations concerning fitness for purpose and
particular matters or application of the Practice to particular project or engineering
situations should not be made solely on information contained in these materials. The
use of trade names from time to time should not be viewed as an expression of
preference but rather recognized as normal usage in the trade. Other brands having the
same specifications are equally correct and may be substituted for those named. All
Practices or guidelines are intended to be consistent with applicable laws and
regulations including OSHA requirements. To the extent these Practices or guidelines
should conflict with OSHA or other applicable laws or regulations, such laws or
regulations must be followed. Consult an appropriate professional before applying or
acting on any material contained in or suggested by the Practice.
This Practice is subject to revision at any time.
© Process Industry Practices (PIP), Construction Industry Institute, The
University of Texas at Austin, 3925 West Braker Lane (R4500), Austin,
Texas 78759. PIP member companies and subscribers may copy this Practice
for their internal use. Changes, overlays, addenda, or modifications of any
kind are not permitted within any PIP Practice without the express written
authorization of PIP.
PRINTING HISTORY
January 2003
October 2003
October 2006
Issued
Technical Correction
Technical Correction
Not printed with State funds
TECHNICAL CORRECTION
October 2006
Process Industry Practices
Structural
PIP STE05121
Anchor Bolt Design Guide
Table of Contents
5.6 Minimum Dimensions..................... 13
1. Introduction.................................3
1.1
1.2
1.3
1.4
Purpose.............. .............................. 3
Scope.............. ................................. 3
Use of “Shall” and “Should”....... ....... 3
Dimensions ...................................... 3
2. References .................................. 3
2.1
2.2
2.3
2.4
Process Industry Practices............... 3
Industry Codes and Standards......... 3
Government Regulations ................. 4
Other References............................. 5
3. Notation.......................................5
4. Materials......................................8
4.1
4.2
4.3.
4.4
Anchors ............................................ 8
Sleeves ............................................ 9
Washers........... ................................ 9
Corrosion........................................ 10
6. Ductile Design .......................... 14
6.1 Ductile Design Philosophy ............. 14
6.2 Critical Areas Requiring Ductile
Design............ ................................ 14
6.3 Requirements for Ductile Design ... 15
6.4 Means to Achieve Ductile Design .. 15
7. Reinforcing Design .................. 16
7.1 General .......................................... 16
7.2 Failure Surface............................... 16
7.3 Reinforcing Design to Transfer
Tensile Forces ............................... 17
7.4 Reinforcing to Transfer Shear Forces18
8. Frictional Resistance ............... 18
8.1 General .......................................... 18
8.2 Calculating Resisting Friction Force19
9. Shear Lug Design.. ................... 19
5. Strength Design........................11
5.1 Loading .......................................... 11
5.2 Anchor Bolt Design Spreadsheet
(Available to PIP Members Only) ... 11
5.3 Anchor Design Considerations....... 12
5.4 Shear Strength of Anchors in a
Rectangular Pattern ....................... 12
5.5 Shear Strength of Anchors in a
Circular Pattern .............................. 12
Process Industry Practices
9.1 Calculating Shear Load Applied to
Shear Lug....................................... 20
9.2 Design Procedure for Shear Lug
Plate................ ............................... 20
9.3 Design Procedure for Shear Lug Pipe
Section ........................................... 21
Page 1 of 24
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PIP STE05121
Anchor Bolt Design Guide
10. Pretensioning............................21
10.1
10.2
10.3
10.4
10.5
10.6
10.7
10.8
10.9
Advantages.....................................22
Disadvantages................................22
When to Apply Pretensioning .........22
Concrete Failure .............................23
Stretching Length............................23
Pretensioning Methods...................23
Relaxation.......................................24
Tightening Sequence......................24
Recommended Tightening if Anchor
Pretensioning Is Not Required........24
October 2006
Examples
1.
2.
3.
4.
Column Plate Connection Using
Anchor Bolt Design
Spreadsheet ............................... A-19
Column Plate Connection –
Supplementary Tensile
Reinforcing ................................. A-24
Shear Lug Plate Section Design. A-25
Shear Lug Pipe Section Design.. A-27
Tables
1.
2.
3.
4.
Minimum Anchor Dimensions.......A-1
ReinforcementTensile Capacity and
Tensile Development Length ........ A-2
Hairpin Reinforcement Design and
Details.............. ............................. A-3
Pretension Load and Torque
Recommendations........................ A-4
Figures
A. Anchor Details .............................. A-5
B-1. Concrete Breakout Strength of
Anchors in Shear –
Octagon “W eak” Anchors............ . A-6
B-2. Concrete Breakout Strength of
Anchors in Shear –
Octagon “Strong” Anchors............A-7
C-1. Tensile Reinforcement –
Vertical Dowels ............................. A-8
C-2 Tensile Reinforcement –
Vertical Hairpin ............................. A-9
D-1. Shear Reinforcement –
Horizontal Hairpin ....................... A-10
D-2. Shear Reinforcement –
Closed Ties................................. A-11
D-3. Shear Reinforcement –
Anchored Reinforcement............ A-12
D-4. Shear Reinforcement –
Shear Angles .............................. A-13
D-5. Shear Reinforcement –
Strut-and-Tie Model........... ......... A-14
E. Minimum Lateral Reinforcement –
Pedestal........... ...........................A-15
F. Coefficients of Friction ................A-16
G. Pretensioned Anchors for Turbines
and Reciprocating Compressors.A-17
H. Anchor-Tightening Sequence ..... A-18
Page 2 of 24
Process Industry Practices
TECHNICAL CORRECTION
October 2006
1.
PIP STE05121
Anchor Bolt Design Guide
Introduction
1.1
Purpose
This Practice provides the engineer and designer with guidelines for anchor
design for use by the process industry companies and engineering/construction
firms.
1.2
Scope
This design guide defines the minimum requirements for the design of anchors in
process industry facilities at onshore U.S. sites. Included are material selection,
strength design, ductile design, reinforcing, shear lugs, and pretensioning.
1.3
Use of “Shall” and “Should”
Throughout this Practice the word “shall” is used if the item is required by code,
and the word “should” is used if the item is simply recommended or its use is a
good practice.
1.4
Dimensions
At the time of issue of this Practice, a metric version of the basic reference for
Anchor Bolt Design, ACI 318, had not been developed; therefore this Practice
was developed in English units only.
2.
References
When adopted in this Practice, the latest edition of the following applicable codes,
standards, specifications, and references in effect on the date of contract award shall be
used, except as otherwise specified. Short titles will be used herein when appropriate.
2.1
Process Industry Practices (PIP)
– PIP REIE686 – Recommended Practices for Machinery Installation and
Installation Design
2.2
Industry Codes and Standards
!
American Concrete Institute (ACI)
– ACI 318-05 - Building Code Requirements for Reinforced Concrete and
Commentary
– ACI 349-01 - Code Requirements for Nuclear Safety Related Concrete
Structures, Appendix B
– ACI 355.1R-91 - State-of-the-Art Report on Anchorage to Concrete
!
American Institute of Steel Construction (AISC)
– AISC Manual of Steel Construction - Allowable Stress Design - Ninth
Edition [Short title used herein is AISC ASD Manual.]
Process Industry Practices
Page 3 of 24
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
– AISC Manual of Steel Construction - Load and Resistance Factor Design
(LRFD) - Third Edition [Short title used herein is AISC LRFD Manual.]
– AISC Steel Design Guide Series 1- Column Base Plates, Some Practical
Aspects of Column Base Selection, David T. Ricker
!
ASTM International
– ASTM A36 - Specification for Carbon Structural Steel
– ASTM A53 - Specification for Pipe, Steel, Black and Hot-Dipped, ZincCoated, Welded, and Seamless
– ASTM A193 - Specification for Alloy-Steel and Stainless Steel Bolting
Materials for High-Temperature Service
– ASTM A307 - Specification for Carbon Steel Bolts and Studs, 60,000 psi
Tensile Strength
– ASTM A354 - Specification for Quenched and Tempered Alloy Steel
Bolts, Studs, and Other Externally Threaded Fasteners
– ASTM A449 - Specification for Quenched and Tempered Steel Bolts and
Studs
– ASTM A563 - Specification for Carbon Steel and Alloyed Steel Nuts
– ASTM F436 - Specification for Hardened Steel Washers
– ASTM F1554 - Specification for Anchor Bolts, Steel, 36, 55, and 105 Ksi
Yield Strength
!
American Society of Civil Engineers (ASCE)
– Design of Anchor Bolts for Petrochemical Facilities, Task Committee on
Anchor Bolt Design, 1997 [Short title used herein is ASCE Anchor Bolt
Report.]
– ASCE 7-2002 - Minimum Design Loads for Buildings and Other
Structures
!
American Welding Society
– AWS D1.1 - Structural Welding Code - Steel
!
International Code Council (ICC)
– International Building Code (IBC)
2.3
Government Regulations
Federal Standards and Instructions of the Occupational Safety and Health
Administration (OSHA), including any additional requirements by state or local
agencies that have jurisdiction in the state where the project is to be constructed,
shall apply.
!
U.S. Department of Labor, Occupational Safety and Health Administration
(OSHA)
– OSHA 29 CFR 1910 - Industrial Safety and Regulatory Compliance
Page 4 of 24
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TECHNICAL CORRECTION
PIP STE05121
Anchor Bolt Design Guide
October 2006
2.4
Other References
– Blodgett, Omar W., Design of Welded Structures, The James F. Lincoln
Arc Welding Foundation, 1966
3.
Notation
Note:
Ad
Force and stress units shown herein under “Notation” are lb and psi respectively.
At times, it is more convenient to show these units in the text, tables, and
examples as kips and ksi, respectively. Where this is done, the units will always
be shown.
2
= Nominal bolt area, inches
ANc
= Projected concrete failure area of a single anchor or group of anchors, for
2
calculation of strength in tension, inches
Ase
= Effective cross-sectional area of anchor, inches
Ar
= Reinforcing bar area, inches
Arb
= Required total area of reinforcing bars, inches
2
Areq = Required bearing area of shear lug, inches
AVc
2
2
2
= Projected concrete failure area of a single anchor or group of anchors, for
2
calculation of strength in shear, inches
AVco = Projected concrete failure area of a single anchor, for calculation of strength in
shear, if not limited by corner influences, spacing, or member thickness,
2
inches
2
AC = Anchor circle diameter (Figures B-1 and B-2), inches
C
= Clear distance from top of reinforcing bar to finished surface (concrete cover),
inches
ca
= Distance from center of an anchor shaft to the edge of concrete, inches
ca,max =
Maximum distance from center of an anchor shaft to the edge of concrete,
inches
Ca,min = Minimum distance from center of an anchor shaft to the edge of concrete,
inches
ca1
= Distance from the center of an anchor shaft to the edge of concrete in one
direction, inches. If shear is applied to anchor, ca1 is taken in the direction of the
applied shear. If the tension is applied to the anchor, ca1 is the minimum edge
distance.
ca2
= Distance from center of an anchor shaft to the edge of concrete in the direction
perpendicular to ca1, inches
cb
= Smaller of (a) the distance from center of a bar or wire to nearest concrete
surface, and (b) one-half the center-to-center spacing of bars or wires being
developed, inches
D
= Octagonal pedestal “diameter” (flat to flat), inches
Process Industry Practices
Page 5 of 24
PIP STE05121
Anchor Bolt Design Guide
D
TECHNICAL CORRECTION
October 2006
= Outside diameter of shear lug pipe section, inches
db
= Nominal diameter of bar, wire, or prestressing strand, inches
do
= Outside diameter of anchor or shaft diameter of headed stud, headed bolt, or
hooked bolt, inches
ds
= Anchor sleeve diameter, inches
E
= Elastic modulus of bolt, psi
f c’
= Specified compressive strength of concrete (shall not be taken as greater than
ft
10,000 psi), psi
= Desired tensile stress, psi
futa
= Specified tensile strength of anchor steel, psi
fy
= Specified yield strength of reinforcement, psi
fya
= Specified yield strength of anchor steel, psi
G
= Grout thickness, inches
H
= Height of shear lug plate or pipe, inches
Hb
= Overall length of anchor under the head or above the base nut (Figure A),
inches
he ’
= Length of anchor below the sleeve (Figure A), inches
hef
= Effective embedment depth of anchor (Figure A), inches
hs
= Length of anchor sleeve (Figure A), inches
Ktr
L
= Transverse reinforcement index
= Length of shear lug plate or pipe, inches
l
= Bolt stretch length (the distance between the top and bottom nuts on the bolt),
inches
la, lb = Portions of standard hook development length (Table 3), inches
ld
= Development length of reinforcing bar, inches
ldh
= Actual development length of standard hook in tension, inches
lhb
= Basic development length of standard hook in tension, inches
Mu
= Ultimate moment on shear lug plate or pipe, k-inches or k-inches/inches
Mn
n
Ncb
= Nominal flexural strength of shear lug pipe, k-inches
= Number of anchors
= Nominal concrete breakout strength in tension of a single anchor, lb
Ncbg
= Nominal concrete breakout strength in tension of a group of anchors, lb
Npn
= Nominal pullout strength in tension of a single anchor, lb
Page 6 of 24
Process Industry Practices
TECHNICAL CORRECTION
PIP STE05121
Anchor Bolt Design Guide
October 2006
Nsa
= Nominal strength of a single anchor in tension as governed by the steel strength,
lb
Nsb
= Side-face blowout strength of a single anchor, lb
Nsbg = Side-face blowout strength of a group of anchors, lb
P
= Normal compression force beneficial to resisting friction force, lb
P
= Anchor projection from top of concrete (Figure A), inches
P1
= Anchor projection below bottom nut for Type 2 anchors (Figure A), inches
s
= Anchor spacing, center to center, inches
S
= Section modulus of shear lug pipe, inches
t
= Thickness of the shear lug plate or pipe wall, inches
T
= Tensile rebar capacity, lb
Tlc
= Bolt threads per unit length
Vapp = Applied shear load on shear lug, kip
Vcb
= Nominal concrete breakout strength in shear of a single anchor or shear lug, lb
Vcbg = Nominal concrete breakout strength in shear of a group of anchors, lb
Vcp
= Nominal concrete pryout strength of a single anchor, lb
Vf
= Resisting friction force at base plate, lb
Vn
= Nominal shear strength, lb
Vsa
= Nominal strength in shear of a single anchor or group of anchors as governed by
the steel strength, lb
Vua
= Factored shear force applied to a single anchor or groups of anchors, lb
W
= Width of shear lug plate perpendicular to shear force, inches
Wh
= Width of anchor head or nut, inches
X
= Clear distance between anchor nut and reinforcing bar, inches
Z
= Plastic modulus of shear lug pipe, inches
!
= Modification factor related to unit weight of concrete
3
= Strength reduction factor
b
= Steel resistance factor for flexure
v
= Steel resistance factor for shear
t
e
s
= Factor used to modify development length based on reinforcement location
= Factor used to modify development length based on reinforcement coating
= Factor used to modify development length based on reinforcement size
Process Industry Practices
Page 7 of 24
TECHNICAL CORRECTION
PIP STE05121
Anchor Bolt Design Guide
c,V
October 2006
= Factor used to modify shear strength of anchors based on presence or absence
of cracks in concrete and presence or absence of supplementary reinforcement
for anchors in shear (see ACI 318-05 D.6.2.7)
= Coefficient of friction
4.
Materials
4.1
Anchors
Refer to the ASCE Anchor Bolt Report, chapter 2, for a description of and
specifications for common materials for anchors. Unless a special corrosive
environment exists, the following should be specified:
a. For low- to moderate-strength requirements: ASTM A307 headed bolts,
ASTM A36 rods, or ASTM F1554 grade 36 rods
b. For higher strength requirements: ASTM A193 grade B7, ASTM F1554
grade 55 or grade 105, or ASTM A354 grade BC or grade BD
The following table provides properties for the recommended anchor materials.
Suitable nuts by grade may be obtained fromASTM A563. If ASTM F1554
grade 55 rods are specified, add the weldability supplement.
Properties for Recommended Anchor Materials
Anchor Material Type
A307
A36 or F1554 grade 36
F1554 grade 55
F1554 grade 105
fya
ksi
Not clearly
defined
36
55
futa
ksi
60
Ductile?
Yes
58
75
Yes
Yes
105
125
Yes
do % 2.5"
105
125
Yes
2.5" & do
% 4"
95
115
Yes
4" & do
% 7"
75
100
Yes
A354 grade BC
109
125
Yes
A354 grade BD
130
150
Yes
92
120
Yes
81
105
Yes
58
90
Yes
A193 grade B7
Based on bolt
diameter (d b)
(used for hightemperature
service)
A449
Based on bolt
diameter (d b)
1/4" < do
1"
1" < do
% 1.5"
1.5" < do
%
%
3"
Bolts made from ASTM F1554 grade 105, ASTM A193 grade B7, and
ASTM A354 materials should not be welded as part of the bolt fabrication
process. Therefore, tack welding of anchor nut as shown in Figure A, Type 2,
should be avoided for these bolt materials. Alternatively, two anchor nuts
Page 8 of 24
Process Industry Practices
TECHNICAL CORRECTION
October 2006
PIP STE05121
Anchor Bolt Design Guide
jammed together or a plate jammed between two nuts could be provided in place
of the tack-welded nut.
4.2
Sleeves
Anchors should be installed with sleeves when small movement of the bolt is
desired after the bolt is set in concrete. The two most common examples follow:
a. When precise alignment of anchors is required during installation of
structural columns or equipment. In this situation, the sleeve should be
filled with grout after installation is complete. Use of sleeves for alignment
of large diameter bolts should be discussed in contructability reviews to
determine if they provide construction advantages (large bolts do not bend
easily). Use of templates may be a better approach to address tolerance
issues for some equipment.
b. When anchors will be pretensioned to maintain the bolt under continuous
tensile stresses during load reversal. Pretensioning requires the bolt surface
to be free; therefore, the top of these sleeves should be sealed or the sleeve
should be filled with elastomeric material to prevent grout or water from
filling the sleeve.
Two types of sleeves are commonly used with anchors. A partial sleeve is
primarily used for alignment requirements, whereas the full sleeve is used for
alignment as well as for pretensioning. Sleeves do not affect the design of a
headed anchor for tensile loading because the tension in the anchor is transferred
to the concrete through the head, not the anchor–concrete bond. Sleeved anchors
can resist shear forces only when the sleeve is filled with grout.
Refer to PIP REIE686 for use of sleeves with anchor bolts in machinery
foundations.
For concrete cover requirements, refer to section 5.6.4 of this Practice.
4.3.
Washers
Washers are required for all anchor bolts. Hardened washers conforming to
ASTM F436 are required if the anchors are to be pretensioned (refer to
section 10) and are preferred for snug-tight anchors. In special cases if the design
calls for washers to be welded to the base plate, plain washers or steel plates may
be necessary to produce a good weld. In such cases, the hole in the washer
should be equal to the bolt diameter plus 1/16 inch. The following table shows
the PIP-recommended base plate hole diameters.
Process Industry Practices
Page 9 of 24
TECHNICAL CORRECTION
PIP STE05121
Anchor Bolt Design Guide
October 2006
Recommended Base Plate Hole and Washer Size
Anchor Bolt
Dia.
(Inches)
PIP-Recommended
Base Plate Hole
Diameter*
1/2
13/16
5/8
15/16
3/4
1-1/16
7/8
1-3/16
1
1-1/4
1-1/2
1-3/4
1-1/2
2
1-3/4
2-1/4
2
2-3/4
2-1/4
3
2-1/2
3-1/2
2-3/4
3-3/4
3
4
* Base plate hole size recommendations are based on
AISC ASD Manual, ninth edition, adjusted such that
standard F436 washers will cover the base plate hole.
Hole size recommendations in the current AISC LRFD
Manual, third edition, have been revised and are larger.
4.4
Corrosion
Corrosion of an anchor can seriously affect the strength and design life of the
anchor. When deciding which anchor material to use or what precaution to take
against corrosion, consider the following:
a. Is the anchor encased in concrete or exposed to the elements?
b. What elements will the anchor contact?
c.
!
Chemical compounds
!
Saltwater
!
Ground water
!
Caustic gases
What limitations are present, affecting anchor size, length, and material,
fabrication options, availability, and cost?
Galvanizing is a common option forASTM A307 bolts and for ASTM A36 and
ASTM F1554 grade 36 threaded rods. ASTM F1554 grades 55 and 105,
ASTM A193 grade B7, ASTM A354 grades BC and BD, andASTM A449 bolts
may also be galvanized if appropriate safeguards are in place. Where loss of
ductility is an issue, ASTM A143 provides guidance concerning safeguarding hotdip galvanized steel against embrittlement. Stainless steel anchors are a costly
Page 10 of 24
Process Industry Practices
TECHNICAL CORRECTION
October 2006
PIP STE05121
Anchor Bolt Design Guide
option but may be required in some environments. Painting or coating the anchor
will protect the anchor, but more maintenance may be required.
To reduce the amount of contact with corrosive substances, pier design and
anchor arrangement should consider water collection and anchor environment.
If the engineer determines that prolonged contact with a corrosive substance is
unavoidable, a metallurgist should be consulted to determine alternate anchor
materials or protective options.
5.
Strength Design
Strength design, which utilizes factored loads, shall be in accordance with Appendix D
of ACI 318-05. In this Practice, strength design will apply to headed bolts and headed
stud anchors, solidly cast in concrete. In accordance with ASCE 7-2002,
section A.9.9.1.7, the exclusion for bolts more than 2 inches in diameter or embedded
more than 25 inches (shown in ACI 318-05, D.2.2) may be ignored; however only
equation D-7 (not equation D-8) shall be used for checking the breakout strength in
cracked concrete.
ACI 318-05, D.6.2.7, states that for anchors located in a region of a concrete member
where analysis indicates no cracking at service loads, the modification factor, c,V, shall
be equal to 1.4. The tops of pedestals are normally outside cracked regions; therefore
c,V should be 1.4 for most pedestals. For anchors at beams and slabs, follow the
guidelines of ACI 318-05, section D.6.2.7.
5.1
Loading
Anchors
shall
be designed
the factored
load
combinations
accordance
ACI
318-05
, section
9.2 or for
Appendix
C. Care
shall
be taken toin
assure
that thewith
proper strength reduction factor for reinforcing, , is used. That is, if the load
combinations in section 9.2 are used, then use the ’s from section 9.3; if the
load combinations from Appendix C are used, then use the ’s from Appendix C.
Strength reduction factor, for anchors is shown in ACI 318-05 Appendix D.
5.2
Anchor Bolt Design Spreadsheet (Available to PIP Members Only)
The Anchor Bolt Design Spreadsheet has been developed utilizing Appendix D
of ACI 318-05 and this Practice. (The spreadsheet, which is available to PIP
Member Companies only, not to PIP Subscribers, can be accessed via
http://www.pip.org/members/irc/index.asp under “Implementation Resource
Center” - “Tools.”) The spreadsheet gives shear and tensile capacities of an
anchor or anchor group and the concrete around it. The spreadsheet also lets the
user know whether or not the anchor configuration is ductile (refer to section 6,
this Practice). The user needs to use the spreadsheet in combination with
Appendix D of ACI 318-05 and this Practice. The spreadsheet merely saves the
user time in laborious calculations but is no substitute for the engineer’s
knowledge and expertise. See Appendix Example 1 (this Practice) for an
illustration of the use of the Anchor Bolt Design Spreadsheet.
Process Industry Practices
Page 11 of 24
TECHNICAL CORRECTION
PIP STE05121
Anchor Bolt Design Guide
5.3
October 2006
Anchor Design Considerations
To accommodate reasonable misalignment in setting the anchor bolts, base
plates are usually provided with oversized holes. If the factored shear loads
exceed the values that can be resisted by friction between the base plate and the
grout (see sections 8 and 9), a suitable means must be provided to transfer the
shear from the base plate to the foundation. This can be accomplished by the
following:
a. Either shear lugs are used, or
b. A
mechanism
to transfer(such
load from
the base
plate to
bolt If
without
slippage
is incorporated
as welding
washers
inthe
place).
washers are
to be welded in place, plain washers or steel plate (rather than hardened
washers) must be specified to ensure that a good weld can be produced.
Galvanized or painted surfaces must be prepared appropriately before
welding. Welded elements may need to be painted or the galvanizing may
need to be repaired.
If no tensile force is applied to the anchors, the anchors need not be designed for
tension. Where the tensile force is adequately transferred to properly designed
rebar, there is no requirement to check for concrete breakout strength of the
anchor or anchors in tension (Ncb or Ncbg). Refer to section 7.3.
5.4
Shear Strength of Anchors in a Rectangular Pattern
In accordance with ACI 318, the concrete design shear strength of a group of
anchors in a rectangular pattern shall be taken as the greater of the following:
a. The design strength of the row of anchors closest to the edge perpendicular
to the direction of force on the anchors
b. The design strength of the row of anchors furthest from the edge if the
anchors are welded to the attachment so as to distribute the force to all
anchors. See also section 5.3 b.
c.
5.5
Although not specifically accepted in ACI 318, the design strength of the
furthest row, if closed shear ties or other mechanisms transfer the load to
the row of anchors furthest from the edge. Refer to Figure D-2.
Shear Strength of Anchors in a Circular Pattern
Anchor bolts for tall, vertical vessels are frequently not required to resist shear.
The shear is resisted by friction created by the large compressive forces
attributable to overturning. However anchor bolts for shorter horizontal vessels
may be required to resist shear. Following are two alternative methods for
designing the anchors to resist shear:
Page 12 of 24
5.5.1
The design shear strength of an anchor group in a circular pattern can be
determined by multiplying the strength of the weakest anchor by the
total number of anchors in the circle. Refer to Figure B-1.
5.5.2
Alternatively, where closed shear ties or other mechanisms transfer the
load from the weak to the strong anchors, the design shear strength of an
Process Industry Practices
TECHNICAL CORRECTION
PIP STE05121
Anchor Bolt Design Guide
October 2006
anchor group in a circular pattern can be determined by calculating the
shear capacity of the strong anchors. Refer to Figure B-2.
5.6
Minimum Dimensions
Minimum edge distance and anchor spacing shall be in accordance with ACI 318
and should be in accordance with ASCE recommendations. Minimum
embedment should be in accordance with the recommendations of the ASCE
Anchor Bolt Report. Refer to Table 1 and Figure A of this Practice. (If
supplementary reinforcement is added to control splitting or the anchor size is
larger
thanand
required
resist the
load,
then ACI
318toallows
the following
distances
anchortospacing
to be
reduced.
Refer
ACI 318-05
, sectionedge
D.8.
5.6.1
Edge Distance
a. ACI 318 requires cast-in headed anchors that will be torqued to
have minimum edge distances of 6do. Otherwise, the only
requirement for edge distance is that at least the same cover be
present as required for (1) reinforcement cover (normally 2 inches)
and (2) to prevent side-face blowout or concrete shear failure.
b. For constructability reasons, the ASCE Anchor Bolt Report
recommends a minimum edge distance of4do but not less than
4.5 inches for ASTM A307 or ASTM A36 bolts or their equivalent
and 6do but not less than 4.5 inches for high-strength bolts.
c. According to PIP REIE686, the recommended edge distance for
anchor bolts in machinery foundations is 4do, 6 inches minimum.
5.6.2
Embedment Depth
No minimum embedment depth is specified in ACI 318 as long as the
effective embedment depth is enough to resist uplift forces. If ductility is
required, greater embedment may be necessary. TheASCE Anchor Bolt
Report recommends a minimum embedment depth of 12 diameters.
hef = 12do
5.6.3
Spacing between Anchors
ACI 318 requires the minimum spacing between anchors to be at least
4do for untorqued cast-in anchors and 6do for torqued anchors.
5.6.4
Modification for Sleeves
Where anchor sleeves are used, the preceding minimum dimensions
should be modified as follows:
a.
Edge distance should be increased by an amount equal to half the
sleeve diameter minus half the anchor diameter, 0.5(ds – do).
b. Embedment length for anchors equal to or greater than 1 inch
should not be less than the larger of 12 anchor diameters (12do) or
the sleeve length plus 6 anchor diameters (sleeve length + 6do).
For anchors less than 1 inch in diameter, the embedment length
should not be less than the sleeve length plus 6 inches.
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October 2006
c.
5.6.5
Spacing between anchors should be increased by an amount equal
to the difference between the sleeve diameter and the anchor
diameter: s 4do + (ds – do) for A307/A36 anchors or their
equivalent.
Modification for Anchor Bottom Plate
If a plate is used at the bottom of the anchor, similar to that shown in
Figure G, the edge distance should be increased by half of the plate
width or diameter minus 1/2 Wh, and the spacing should be increased by
the plate width or diameter minus Wh.
5.6.6
Anchor Projection
Anchor bolts should project a minimum of two threads above the fully
engaged nut(s).
6.
Ductile Design
6.1
Ductile Design Philosophy
A ductile anchorage design can be defined as one in which the yielding of the
anchor (or the reinforcement or the attachment to which the anchor attaches)
controls the failure of the anchorage system. This will result in large deflections,
in redistribution of loads, and in absorption of energy before any sudden loss of
capacity of the system resulting from a brittle failure of the concrete (ASCE
Anchor Bolt Report).
Anchors embedded in concrete and pulled to failure fail either by pullout of the
concrete
cone
by tensile
failure
of theAanchor
former
is a brittle
failure
and
theor
latter
is a ductile
failure.
brittleitself.
failureThe
occurs
suddenly
and
without warning, possibly causing catastrophic tragedies. In contrast, a ductile
failure will cause the steel to yield, elongate gradually, and absorb a significant
amount of energy, often preventing structures from collapsing. Consequently,
when the design of a structure is based upon ductility or energy absorption, one
of the following mechanisms for ductility shall be used.
6.1.1
Anchors shall be designed to be governed by tensile or shear strength of
the steel, and the steel shall be a ductile material (refer to section 4.1,
this Practice).
6.1.2
In lieu of the guideline in section 6.1.1, the attachment connected by the
anchor to the structure shall be designed so that the attachment will
undergo ductile yielding at a load level no greater than 75 percent of the
minimum anchor design strength.
This ductile design philosophy is consistent with that of ACI 318.
6.2
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Critical Areas Requiring Ductile Design
Anchors designed to resist critical loads, where magnitudes cannot be precisely
quantified (e.g., where design is based upon energy absorption), shall be
designed using the requirements for ductile design. Examples are anchors in
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Anchor Bolt Design Guide
October 2006
areas of intermediate or high seismicity and anchors used for blast load
resistance.
6.3
Requirements for Ductile Design
If the mechanism described in section 6.1.1 is used, the ductile design is
achieved when the anchoring capacity of the concrete is greater than that of the
anchor in tension, in shear, or in a combination of both. This is a strength
requirement and is independent of the magnitudes of the applied loads. If it can
be shown that failure that is due to tensile loads will occur before failure that is
due
to shear
loads,
thebut
anchor
need
be ductile
for tensile
(The
reverse
would
also then
be true
would
notonly
normally
be applicable
toloads.
design.)
The first step is to select the anchor size considering only the steel failure modes,
that is by using 0.75 Nsa and 0.75 Vsa. In addition, make sure that the steel
chosen is ductile steel as listed in section 4.1. The engineer will need to do the
following calculations manually, using Appendix D of ACI 318-05.
Comment: For PIP Member Companies, the loads and size can then be
entered into the Anchor Bolt Design Spreadsheet, described in
section 5.2, to check the second and third steps (next two
paragraphs).
The second step is to ensure that the concrete pullout capacities (concrete
breakout strength in tension, pullout strength of anchor in tension, and concrete
side-face blowout strength) are greater than the tensile steel capacity of the
anchor:
Ncb or Ncbg > Nsa, Npn > Nsa, and Nsb or Nsbg > Nsa
The third step is to ensure that the concrete shear capacities (concrete breakout
strength in shear and concrete pryout strength in shear) are greater than the steel
shear capacity of the anchor:
Vcb or Vcbg > Vsa and Vcp > Vsa
In lieu of the preceding requirements, the attachment to the structure that is
connected by the anchor to the foundation may be designed so that the
attachment will undergo ductile yielding at a load level no greater than
75 percent of the minimum anchor design strength.
6.4
Means to Achieve Ductile Design
If conditions as specified in section 6.3 cannot be met, the concrete capacity can
be increased to achieve a ductile design using the following:
6.4.1
Increased Concrete Tensile Capacity
Concrete tensile capacity can be increased by the following:
a. Increasing concrete strength
b. Increasing embedment depth
c. Increasing edge distance (for near edge cases)
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October 2006
d. Increasing anchor spacing (for closely spaced anchor group)
In situations for which space is limited, such as anchors embedded in
pedestals, the preceding methods may not be practical. For these cases,
reinforcing bars can be placed close to the anchor to transfer the load.
Refer to section 7.3.
6.4.2
Increased Concrete Shear Capacity
Concrete shear capacity can be increased by the following:
a. Increasing concrete strength
b. Increasing edge distance (for near edge cases)
c. Increasing anchor spacing (for closely spaced anchor group)
If the preceding methods are impractical because of space limitations,
reinforcing hairpins looped around the anchors can be designed to carry
the entire shear. If this method is used, do not consider any contribution
from concrete shear strength. Refer to section 7.4.
Another alternative is the use of a shear lug. Refer to section 9. If this
alternative is chosen, either the following item a or item b must be
adhered:
a. The shear lug needs to be designed to undergo ductile yielding
before failure of the concrete.
b. The attachment that the shear lug connects to must undergo ductile
yielding at a load level no greater that 75 percent of the minimum
shear lug design strength.
7.
Reinforcing Design
7.1
General
When anchor embedment or edge distances are not sufficient to prevent concrete
failure that is due to factored loads, or for a “ductile type” connection, if Ncb or
Ncbg < Nsa or Vcb or Vcbg < Vsa, then reinforcing steel may be used to
prevent concrete failure.
The reinforcing needed to develop the required anchor strength shall be designed
in accordance with ACI 318 and the following.
7.2
Failure Surface
Reinforcement shall be fully developed for the required load on both sides of the
failure surfaces resulting from tensile or shear forces. Development lengths and
reinforcement covers shall be in accordance with ACI 318.
7.2.1
The failure surface resulting from the applied tension load shall be one
of the following:
a. For a single bolt, the failure surface is that of a pyramid, with the
depth equal to the embedded depth of the anchor (hef) and the base
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October 2006
being a square with each side equal to three times the embedded
depth (3hef). (Refer to Figure RD.5.2.1(a) of ACI 318-05.)
b. For a group of bolts where the bolts are closer together than 3hef,
the failure surface is that of a truncated pyramid. This pyramid is
formed by a line radiating at a 1.5-to-1 slope from the bearing edge
of the anchor group, edge of nuts, toward the surface from which
the anchors protrude. (Refer to Figure RD.5.2.1(b) of ACI 318-05.)
7.2.2
7.3
The failure surface resulting from the applied shear load is defined as a
half pyramid radiating at a 1.5-to-1 slope in all directions, srcinating at
the top of the concrete where the anchor protrudes and ending at the free
surface in the direction of the shear. (Refer to Figure RD.6.2.1(a) of
ACI 318-05.) For multiple anchors closer together than three times the
edge distance, ca1, the failure surface is from the outermost anchors.
(Refer to Figure RD.6.2.1(b) of ACI 318-05.)
Reinforcing Design to Transfer Tensile Forces
(Refer to Figures C-1 and C-2 and Tables 2 and 3.)
7.3.1
The required area of reinforcing bars, Arb, per anchor is as follows:
Arb = Nsa /fy
Obtain hef, the embedment depth of the anchor as follows: (Refer to
Figure C-1.)
hef = ld + C + (X + db/2)/1.5
a. Calculate ld, the development length of the reinforcing bars
resisting the load, using ACI 318. Note that the number of bars can
be increased and the size of the reinforcing bars can be decreased to
reduce the development length when required.
b. Add C, the concrete cover over the top of reinforcing bars to the
finished surface.
c. Add X, the clear distance from the anchor nut to the reinforcing
bars.
d. Add db/2, half the diameter of the reinforcing bars.
Note that the reinforcing bars were probably sized during pedestal
design. If more reinforcement is required by the pedestal design than
required by the anchor load transfer, the reinforcing bar development
length may be reduced by multiplying by the ratio of the reinforcing bar
area required to the reinforcing bar area provided:
ld required = ld x [(Arb) required / (Arb) provided]
This reduction
is ininaccordance
with ACI
, section
12.2.5, and
cannot
be applied
areas of moderate
or 318-05
high seismic
risk.
7.3.2
Process Industry Practices
Direct tensile loads can be transferred effectively by the use of “hairpin”
reinforcement or vertical dowels according to the following guidelines:
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a. “Hairpin” legs and vertical dowels shall be located within hef/3
from the edge of the anchor head.
b. “Hairpin” legs and dowels shall extend a minimum of ld, beyond
the potential failure plane, or additional rebar area shall be
provided to reduce the required embedment length (see
section 7.3.1).
c. Where tension reinforcement is designed, it should be designed to
carry the entire tension force, excluding any contribution from the
concrete.
d. For an example design calculation using hairpins, see Appendix
Example 2 (this Practice).
7.4
Reinforcing to Transfer Shear Forces
7.4.1
Several shear reinforcement configurations or assemblies can be
considered effective to prevent failure of the concrete. Depending on the
particular situation, one of the following types of shear reinforcement
can be used:
a. “Hairpins” wrapped around the anchors (Figure D-1)
b. “Closed ties” transferring load to the stronger anchors (Figure D-2)
c. “Anchored” reinforcing intercepting the failure plane (Figure D-3)
d. “Shear angles” welded to anchors (Figure D-4)
e. “Strut-and-tie model” (Refer to Appendix A of ACI 318-05 and
Figure D-5 of this Practice.)
8.
7.4.2
Shear reinforcing shall extend a minimum of ld, beyond the potential
failure plane. Where excess rebar is provided, ld, may be reduced by the
ratio of the reinforcing bar area required divided by the reinforcing bar
area provided. See section 7.3.1.
7.4.3
Where shear reinforcing is designed, it should be designed to carry the
entire shear load, excluding any contribution from the concrete.
7.4.4
For pedestals, a minimum of two No. 4 ties or three No. 3 ties is required
within 6 inches of the top of concrete of each pedestal. Refer to Figure
E. Use of three ties is recommended near the top of each pedestal if
shear lugs are used or if the pedestals are located in areas of moderate or
high seismic risk.
Frictional Resistance
8.1
General
Where allowed by code, anchors need not be designed for shear if it can be
shown that the factored shear loads are transmitted through friction developed
between the bottom of the base plate and the top of the concrete foundation. If
there is moment on a base plate, the moment may produce a downward load that
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PIP STE05121
Anchor Bolt Design Guide
will develop friction even when the column or vertical vessel is in uplift. This
downward load can be considered in calculating frictional resistance. Care shall
be taken to assure that the downward load that produces frictional resistance
occurs simultaneously with the shear load. In resisting horizontal loads, the
friction resistance attributable to downward force from overturning moment may
be used.
The frictional resistance can also be used in combination with shear lugs to resist
the factored shear load. The frictional resistance should not be used in
combination with the shear resistance of anchors unless a mechanism exists to
keep
the the
basewasher
plate from
before the anchors can resist the load (such as
welding
to theslipping
base plate).
Note:
8.2
If the design requires welding the washer to the base plate, plain
washers or steel plate (rather than hardened washers) must be
specified to ensure that a good weld can be produced.
Calculating Resisting Friction Force
The resisting friction force, Vf, may be computed as follows:
Vf =
P
P = normal compression force
= coefficient of friction
The materials used and the embedment depth of the base plate determine the
value of the coefficient of friction. (Refer to Figure F for a pictorial
representation.)
9.
a.
= 0.90 for concrete placed against as-rolled steel with the contact plane a
full plate thickness below the concrete surface.
b.
= 0.70 for concrete or grout placed against as-rolled steel with the
contact plate coincidental with the concrete surface.
c.
= 0.55 for grouted conditions with the contact plane between grout and
as-rolled steel above the concrete surface.
Shear Lug Design
Normally, friction and the shear capacity of the anchors used in a foundation adequately
resist column base shear forces. In some cases, however, the engineer may find the shear
force too great and may be required to transfer the excess shear force to the foundation
by another means. If the total factored shear loads are transmitted through shear lugs or
friction, the anchor bolts need not be designed for shear.
A shear lug (a plate or pipe stub section, welded perpendicularly to the bottom of the
base
allows
foranchors.
complete
transfer
of on
thethe
force
through
shearonly
lug, on
thus
the
shearplate)
load off
of the
The
bearing
shear
lug is the
applied
thetaking
portion
of the lug adjacent to the concrete. Therefore, the engineer should disregard the portion
of the lug immersed in the top layer of grout and uniformly distribute the bearing load
through the remaining height.
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The shear lug should be designed for the applied shear portion not resisted by friction
between the base plate and concrete foundation. Grout must completely surround the lug
plate or pipe section and must entirely fill the slot created in the concrete. When using a
pipe section, a hole approximately 2 inches in diameter should be drilled through the
base plate into the pipe section to allow grout placement and inspection to assure that
grout is filling the entire pipe section.
9.1
Calculating Shear Load Applied to Shear Lug
The applied shear load, Vapp, used to design the shear lug should be computed as
follows:
Vapp = Vua - Vf
9.2
Design Procedure for Shear Lug Plate
Design of a shear lug plate follows (for an example calculation, see Appendix
Example 3, this Practice):
a. Calculate the required bearing area for the shear lug:
Areq = Vapp
/ (0.85 *
* fc’)
= 0.65
b. Determine the shear lug dimensions, assuming that bearing occurs only on
the portion of the lug below the grout level. Assume a value of W, the lug
width, on the basis of the known base plate size to find H, the total height
of the lug, including the grout thickness, G:
H = (Areq /W) + G
c.
Calculate the factored cantilever end moment acting on a unit length of the
shear lug:
Mu = (Vapp/W) * (G + (H-G)/2)
d. With the value for the moment, the lug thickness can be found. The shear
lug should not be thicker than the base plate:
t = [(4 * M u)/(0.9*fya)]
0.5
e. Design weld between plate section and base plate.
f.
Calculate the breakout strength of the shear lug in shear. The method
shown as follows is from ACI 349-01, Appendix B, section B.11:
Vcb = AVc*4* *[fc’]
0.5
where
AVc = the projected area of the failure half-truncated pyramid defined
by projecting a 45-degree plane from the bearing edges of the
shear lug to the free edge. The bearing area of the shear lug
shall be excluded from the projected area.
= concrete strength reduction factor = 0.85
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9.3
Design Procedure for Shear Lug Pipe Section
Design of a shear lug pipe section follows (for an example calculation, see
Appendix Example 4, this Practice):
a.
Calculate the required bearing area for the shear lug:
Areq = Vapp /(0.85 fc’)
= 0.60
b. Determine the shear lug dimensions, assuming that bearing occurs only on
the portion of the lug below the grout level. Assume the D, diameter of the
pipe section, based on the known base plate size to find H, the total height
of the pipe, including the grout thickness, G:
H = (Areq/D) + G
c.
Calculate the factored cantilever endmoment acting on the shear lug pipe:
Mu = Vapp * (G + (H-G)/2)
d. Check the applied shear force and the bending moment for pipe section
failure (AISC LRFD Manual, pages 16.1-31 and 16.1-100).
Shear check–
v Vn (
where
Vapp
2
v
2
= 0.9 and Vn = 0.6 fya (D – (D-2t) )/4
Moment check–
b
where
10.
b
Mn ( Mu
= 0.9 and Mn = the lesser of:
e.
= S * [{600/(D/t)} + fya] (local buckling moment)
and
= Z * f ya (plastic moment)
Design weld between pipe stub section and base plate.
f.
Check the breakout shear as shown in section 9.2(f).
Pretensioning
Pretensioning induces preset tensile stresses to anchor bolts before actual loads are
applied. When properly performed, pretensioning can reduce deflection, avoid stress
reversal, and minimize vibration amplitude of dynamic machinery. Pretensioning may be
considered for the following:
a.
Towers more than 150 feet tall
b.
Towers with height-to-width ratios of more than 10
c. Dynamic machinery such as compressors (PIP REIE686)
However, pretensioning adds cost, and the stress level is difficult to maintain because of
creep and relaxation of the bolt material. AISC does not recommend pretensioning
anchors. The AISC LRFD Manual paragraph C-A3.4 states, “The designer should be
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October 2006
aware that pretensioning anchor bolts is not recommended due to relaxation and stress
corrosion after pretensioning.” AISC Steel Design Guide Series 1, anchor bolt section
states, “Because of long-term relaxation of concrete, prestressing of anchor bolts is
unreliable and hardly ever justified.”
In practical applications, the engineer should decide whether to pretension the anchor
bolt by considering the following advantages and disadvantages:
10.1
Advantages
The advantages of pretensioning are as follows:
a. Can prevent stress reversals on anchors susceptible to fatigue weakening
b. May increase dampening for pulsating or vibrating equipment
c. Will decrease, to some extent, the drift for process towers under wind or
seismic load
d. Will increase the frictional shear resistance for process towers and other
equipment
10.2
Disadvantages
The disadvantages of pretensioning are as follows:
a.
Can be a costly process to install accurately
b. No recognized code authority that gives guidance on the design and
installation of pretensioned anchors. There is little research in this area.
c. Questionable nature about the long-term load on the anchor from creep of
concrete under the pretension load
d. Possible stress corrosion of the anchors after pretensioning
e.
Typically, no bearing resistance to shear on the anchor. This is because
during pretensioning, the sleeve around the anchor typically is not filled
with grout.
f.
Little assurance that the anchor is properly installed and pretensioned in
the field
g. Possible direct damage from pretensioning. The pretensioning itself can
damage the concrete if not properly designed or if the pretension load is
not properly regulated.
10.3
When to Apply Pretensioning
Pretensioning should be considered for vertical vessels that are more than
150 feet tall or for those with height-to-width ratios of more than 10 and if
recommended by the equipment manufacturer; pretensioning is required if
required for warrantee. When not otherwise specified, anchors for turbines and
reciprocating compressors should be torqued to the values shown in Table 4.
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10.4
PIP STE05121
Anchor Bolt Design Guide
Concrete Failure
In certain situations, the use of high-strength anchors in concrete with high
pretension forces may exceed the ultimate capacity of the concrete by
prematurely breaking out the concrete in the typical failure pyramid. Whether
this situation can occur depends on the depth of the anchor and on other factors,
such as edge conditions and arrangement of the base plate. To ensure that
premature concrete failure does not occur, pretensioned anchors shall be
designed so that the breakout strength of the anchor in tension is greater than the
maximum pretension force applied to the anchor. In the case of a stiff base plate
covering
the are
concrete
stresses
induced
external
on
the concrete
offsetfailure
by the pyramid,
clampingthe
force
and the
gravitybyloads.
For uplift
this case,
the breakout strength needs only to be designed for the amount that the external
uplift exceeds the gravity plus pretensioning force loads.
10.5
Stretching Length
Prestressing should be implemented only when the stretching (spring) length of
the anchor extends down near the anchor head of the anchor. On a typical anchor
embedment, where there is no provision for a stretching length, if a prestressing
load is applied to the anchor, the anchor starts to shed its load to the concrete
through its bond on the anchor. At that time, a high bond stress exists in the first
few inches of embedment. This bond will relieve itself over time and thereby
reduce the prestress load on the anchor. Therefore it is important to prevent
bonding between the anchor and concrete for pretensioned anchors. Refer to
Figure G for a suggested detail.
10.6
Pretensioning Methods
Methods used to apply preload are as follows:
10.6.1 Hydraulic jacking: Hydraulic jacking is the most accurate method and is
recommended if the pretension load is essential to the integrity of the
design. The anchor design should accommodate any physical clearance
and anchor projections required for the hydraulic equipment.
10.6.2 Torque wrench: Torque wrench pretensioning provides only a rough
measure of actual pretension load but can be the method of choice if the
amount of pretension load is not critical. Torque values are shown in
Table 4.
10.6.3 Turn-of-nut: This method is the easiest to apply, but there are questions
as to the accuracy of the pretension load. The pretension load from
stretching the anchor can be closely determined, but accounting for the
compression of the concrete between the base plate and the nut at the
bottom of the anchor is difficult. Per the ASCE Anchor Bolt Report, the
required amount of nut rotation from the “snug tight” condition to
produce
a desired
tensile stress in the bolt (ft) can be determined using
the
following
formula.
Nut rotation in degrees = (360 l Ase ft Tlc) / (E Ad)
where:
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October 2006
l
=
bolt stretch length (the distance between the top and bottom
nuts on the bolt)
Ase
=
effective cross-sectional area of anchor
ft
=
desired tensile stress
Tlc
=
bolt threads per unit length
E
=
elastic modulus of bolt
Ad
=
nominal bolt area
If the bolt is to be retightened to compensate for any loss of pre-load,
this method requires that nuts be loosened, brought to a “snug tight”
condition, and then turned the number of degrees srcinally specified.
10.6.4 Load indicator washers: This method is good if the amount of pretension
desired is as much as the required load in slip-critical structural steel
connections. These loads are typically very high and not normally
required for anchors.
10.7
Relaxation
According to ACI 355.1 R, section 3.2.2, “If headed anchors are pretensioned,
the initial force induced in the anchor is reduced with time due to creep of the
highly stressed concrete under the anchor head. The final value of the tension
force in the anchor depends primarily on the value of bearing stresses under the
head, the concrete deformation, and the anchorage depth. In typical cases the
value of that final force will approach 40 to 80 percent of the initial preload
(40 percent for short anchors, 80 percent for long anchors).” Retensioning the
anchors about 1 week after the initial tensioning can reduce the loss of preload.
According to ACI 355.1R, the reduction of the initial preload can be reduced by
about 30 percent by retensioning.
10.8
Tightening Sequence
Pretensioned anchors should be tightened in two stages:
a. First stage should apply 50 percent of the full pretension load to all
anchors.
b. Second stage should apply full pretension load to all anchors.
Anchors should be tightened in a crisscross pattern. (Refer to Figure H.)
10.9
Recommended Tightening if Anchor Pretensioning Is Not Required
Anchors should be brought to a snug, tight condition. This is defined as the
tightness that exists after a few impacts from an impact wrench or the full effort
of a man using a spud wrench. At this point all surfaces should be in full contact.
Page 24 of 24
Process Industry Practices
Appendix
Figures, Tables, and Examples
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
TABLE 1: Minimum Anchor Dimensions
(Refer to Figure A.)
HEAVY
HEX
HEAD/
NUT
ASCE ANCHOR BOLT REPORT MINIMUM
ANCH.
TYPE 2
DIMENSIONS (Refer to Section 5.6)
hef
A307/A36
F1554
P1
ANCHOR
WIDTH
DIA.
Wh
do
12do
do + 1/2"
(in.)
1/2
5/8
3/4
7/8
1
1-1/8
1-1/4
1-3/8
1-1/2
1-3/4
2
2-1/4
2-1/2
2-3/4
3
2
EDGE DISTANCE ca1
1
SLEEVES
SPACING
HIGHSTRENGTH
OR
Grade 36
TORQUED
BOLTS
4do ≥ 4.5"
6do ≥ 4.5"
'
SHELL SIZE
he
4do
Diameter
ds
Height
6do ≥ 6"
hs
(in.)
1.00
1.25
1.44
1.69
1.88
2.06
2.31
2.50
2.75
3.19
3.63
4.06
(in.)
1.00
1.13
1.25
1.38
1.50
1.63
1.75
1.88
2.00
2.25
2.50
2.75
(in.)
6.0
7.5
9.0
10.5
12.0
13.5
15.0
16.5
18.0
21.0
24.0
27.0
(in.)
4.5
4.5
4.5
4.5
4.5
4.5
5.0
5.5
6.0
7.0
8.0
9.0
(in.)
4.5
4.5
4.5
5.3
6.0
6.8
7.5
8.3
9.0
10.5
12.0
13.5
(in.)
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
7.0
8.0
9.0
(in.)
2
2
2
2
3
3
3
4
4
4
4
4
(in.)
5
7
7
7
10
10
10
15
15
15
18
18
4.50
4.94
5.31
3.00
3.25
3.50
30.0
33.0
36.0
10.0
11.0
12.0
15.0
16.5
18.0
10.0
11.0
12.0
6
6
24
24
24
6
(in.)
6
6
6
6
6
7
8
8
9
11
12
14
15
17
18
IF SLEEVES ARE USED,
EMBEDMENT SHALL BE THE LARGER OF 12do or (hs + he')
INCREASE EDGE DISTANCE BY 0.5(ds - do)
INCREASE SPACING BY (ds - d o)
FOR MACHINERY FOUNDATIONS PIP REIE686 REQUIRES A MINIMUM EDGE DISTANCE OF 6 INCHES.
Process
Industry
Practices
Page
A-1
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
TABLE 2: Reinforcement Tensile Capacity and Tensile Development Length
Reinforcement Yield Strength, fy = 60 ksi
Compressive Strength of Concrete, fc' = 3,000 psi
Design Tensile Strength Reduction Factor, = 0.90 (ACI 318-05, Section 9.3)
Reinforcement Location Factor, ψt = 1.3 (Top Reinforcement), 1.0 (Other Reinforcement)
Coating Factor, ψe = 1.0 (Uncoated Reinforcement)
Reinforcement Size Factor, ψs = 0.8 (≤ #6 bar), 1.0 (> #6 bar)
Lightweight Aggregate Concrete Factor,
= 1.0 (Normal Weight Concrete)
Transverse Reinforcement Index, Ktr = 0 (Design Simplification)
ACI 318-05 , Section 12.2.3 - Tension Development Length:
1/2
ld = db (3/40) [fy/(fc') ] (ψtψeψs )/[(c b + Ktr)/d b]
(12-1)
[(cb + Ktr)/db ≤ 2.5]
where cb is the smaller of either the distance from the center of the bar to the
nearest concrete surface or one-half the center-to-center spacing of the bars
BAR
SIZE
BAR
BAR
AREA CAPACITY
Ar
(sqi.n.)
#3
#4
#5
#6
#7
#8
#9
#10
#11
*Ar*(fy)
(Kips)
0.11
0.20
0.31
0.44
0.60
0.79
1.00
1.27
1.56
SPACING ≥3.0 in.
REQUIRED
COVER
(in.)
:5/16
:1/4
:3/16
:1/8
:1/16
1.5in.
SPACING ≥6.0 in.
5/ 16
/8
3/ 16
(in.)
13
17
22
32
55
71
91
115
142
FACTORS FOR DIFFERENT VALUES OF fc'
(Note: ld shall not be less than 12 inches.)
fc'
DEVELOPMENT
LENGTH FACTOR
3,000
4,000
5,000
6,000
1.00
0.87
0.77
0.71
Process
Industry
Practices
b=
c
b
= 3.0 in.
TENSION DEVELOPMENT
TENSION DEVELOPMENT
REQUIRED
LENGTH, ld
LENGTH, ld
COVER
T OP
OTHER
T OP
OT H E R
(in.)
5.94 1≥
10.80 1 ≥
16.74 1≥
23.76 1 ≥
32.40 1≥
42.661
≥
54.00 1≥
68.58 7 ≥
84.24
1≥
c
(in.)
12
13
17
25
42
2
≥
2≥
2
≥
2≥
2≥
55 2≥
70
2≥
89
2≥
109
2≥
(in.)
(in.)
:13/16
13
:3/4
17
:11/16
22
:5/8
26
:9/16
38
:1/2
43
:7/16
48
:3/8
58
:5/16
71
SPACING ≥12.0 in. c
12
13
17
20
29
33
37
44
55
b = 6.0 in.
#3
#4
#5
#6
#7
#8
#9
5
≥
5≥
5
≥
5≥
5≥
5≥
5≥
:13/16
:3/4
:11/16
:5/8
:9/16
:1/2
:7/16
13
17
22
26
38
43
48
12
13
17
20
29
33
37
#10
5≥
:3/8
55
42
#11
5≥
:5/16
61
47
Page
A-2
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
TABLE 3: Hairpin Reinforcement Design and Details
Reinforcement Yield Strength, fy = 60 ksi
Compressive Strength of Concrete, f c' = 3,000 psi
Minimum Reinforcement Cover = 2.5 in.
Minimum Reinforcing Spacing = 3.0 in.
Coating Factor, ψe = 1.0 (Uncoated Reinforcement)
Lightweight Aggregate Concrete Factor,
= 1.0 (Normal Weight Concrete)
Development Length Reduction Factor (ACI 318-05 , Paragraph 12.5.3a) = 0.70
Design Tensile Strength Reduction (ACI 318-05, Paragraph 9.3.2.1),
T
N
E
M
E
C
R
O
F
N
I
E
R
180 DEG HOOK
DEVELOPMENT
LENGTH
E
IZ
ldh =
S
R (0.02ψeλfy/(f c')0.5)d
A
B
b
(ACI 12.5.2 )
HAIRPIN AND HOOK
DIMENSIONS
G
Y
IN
IT
C
R R C
O A A
F B P
A
N
I
C
E
R
ldh
f*Ar*(fy)
0.7*ldh
VERTICAL AND HORIZONTAL
HAIRPINS
/I
C
A
(
ACI 12.5.1 &
Fig. R12.5.1
la
lb
= 0.90
I)
S
R
C
OTHER
BARS
ld (a)
(ACI
INSIDE
HOOK 12.2.3)
Y
T
I
C
A
P
A
C
)
4
(
E
T
O
N
E
E
S
TOP
BARS
ld (a)
(ACI
12.2.3)
Y
T
I
C
A
P
A
C
)
(4
E
T
O
N
E
E
S
#3
#4
#5
#6
#7
#8
(in.)
8.2
11.0
13.7
16.4
19.2
21.9
(kips)
5.94
10.80
16.74
23.76
32.40
42.66
(in.)
6.0
7.7
9.6
11.5
13.4
15.3
(in.)
2.0
3.2
4.6
5.5
6.4
7.3
(in.)
4.0
4.5
5.0
6.0
7.0
8.0
(in.)
2.3
3.0
3.8
4.5
5.3
6.0
(in.)
12
13
17
25
42
55
(kips)
6.91
13.40
21.22
29.06
37.36
48.37
(in.)
13
17
22
32
55
71
(kips)
6.84
12.80
20.19
27.84
36.22
47.06
#9
#10
#11
24.7
27.8
30.9
54.00
68.58
84.24
17.3
19.5
21.6
7.1
8.0
8.9
10.2
11.4
12.7
9.5
10.8
12.0
70
89
109
59.54
74.83
91.15
91
115
142
58.26
73.39
89.56
(a)
FACTORS FOR DIFFERENT
VALUES OF fc':
fc'
Development
Length Factor (D)
3,000
4,000
5,000
6,000
lb remains the same.
T (hairpin ) = T (hook) x (1+l a/ld)
HAIRPIN CAPACITY:
1.00
0.87
0.77
0.71
ldh = ldh*(D)
la = ldh-lb
(1) Standard 180 hook capacity = capacity of straight bar
(2) Capacity of la portion of hook = bar capacity X (la/ld)
[ld > la]
(3) Capacity of lb portion of hook = bar capacity - capacity of la portion
(4) Hairpin capacity = bar capacity X (1 + la/ld) where ld = bar development length [ld > la]
Process
Industry
Practices
Page
A-3
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
TABLE 4: Pretension Load and Torque Recommendations*
Nominal Bolt
Diameter (inches)
Number of Threads
(per inch)
Torque
(foot-pounds)
Pretension Load
(pounds)
1/2
13
30
3,780
5/8
3/4
7/8
11
10
9
60
100
160
6,060
9,060
12,570
1-1/8
1-1/4
1-1/2
1-3/4
2
8
8
8
8
8
355
500
800
1,500
2,200
21,840
27,870
42,150
59,400
79,560
2-1/4
8
3,180
102,690
2-1/2
8
4,400
128,760
2-3/4
8
5,920
157,770
8
7,720
189,720
1
8
3
245
16,530
Note 1: All torque values are based on anchor bolts with threads well lubricated with oil.
Note 2: In all cases, the elongation of the bolt will indicate the load on the bolt.
Note 3: Based upon 30-ksi internal bolt stress
* From PIP REIE686, Recommended Practices for Machinery Installation and Installation Design,
Appendix A.
Process
Industry
Practices
Page
A-4
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE A: Anchor Details
ca
T.O. CONC.
C
T
EDGE
DIST.
E
P
P
h
b
hh
ds
h
do
h
TYPE 1
c
T
a
C
EDGE
DIST.
T.O. CONC.
E
P
P
h
b
hh
h
ds
do
h
P
TACK
WELD
NUT
TYPE 2
NOTE: DISTANCE BETWEEN BOTTOM OF SLEEVE AND ANCHOR BEARING
SURFACE, h e' , SHALL NOT BE LESS THAN 6d o NOR 6-IN.
REFER TO TABLE 1 FOR MINIMUM DIMENSIONS
Process
Industry
Practices
Page
A-5
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE B-1: Concrete Breakout Strength of Anchors in Shear Octagon "Weak Anchors"
ca1
1.5ca
ca2
ca1
Approximate solution
ca1= Do /2 - AC/2
Calculate D o so that equivalent circle has same area as
octagon.
Note: Area of octagon = 0.828D
2
π Do /4 = 0.828D
π
2
Do
2
2
2
2 1/2
AVc = 1.5ca1D
2
0.828D (4)
π
AVc (max) = n 4.5c a1
= 1.03D
2
n = Total number of bolts = 12
Failure planes overlap each other to go clear across pedestal.
AVc = 1.5ca1D
(Max. AVc = nAVco = n4.5ca1 )
Pythagorean theorem:
ca2 + (A C/2) = (D o/2)
2
ca1 =1.03D/2 - AC/2
ca2, ca4 = [(1.03D/2) -(AC/2) ]
2
= 0.828D (4)
Do =
For input into PIP STE05121 Anchor Bolt
Design Spreadsheet, available to PIP
Members only.
2 1/2
ca2 =[(1.03D/2) - (AC/2) ]
Process
Industry
Practices
Page
A-6
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE B-2: Concrete Breakout Strength of Anchors in Shear Octagon "Strong" Anchors
ca2
ca2
ca1
1
a
c
1
a
c
1.5ca1
ca1 will vary with the number of anchors considred. Only anchors wit
an edge distance, c a1, greater than or equal to the c a1 for the chosen bolt
shall be used for resisting shear.
For the case shown above, if the dimension marked ca1 is chosen, n = 6 bolts.
If the dimension marked ca1 (ALT) is chosen, n = 4 bolts.
For input into PIP STE05121 Anchor Bolt Design
Spreadsheet , available to PIP Members only.
ca1 =As shown above
ca2 = (D-AC)/2
AVc = 1.5c a1 D
AVc (max) = n 4.5c a1
n=6
Process
Industry
Practices
Alternate
ca1 (ALT) =As shown above
ο
ca2 (ALT) = (D-Cos(45 )AC)/2
AVc = 1.5c a1(ALT) D
AVc (max) = n 4.5(c a1(ALT))
n=4
Page
A-7
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE C-1: Tensile Reinforcement - Vertical Dowels
/3
f
e
(h
.)
ax
M
X
ca1
or ca2
1
2
VERTICAL DOWELS
EDGE
DIST.
(Centerline of Anchor Bolt to Centerline of Dowel = (W /2 + X + (d /2))
rb
h
PLAN
db
T.O. CONC.
b
h
ds
do
1.5
1
Wh
X
(hef /3 max.)
NOTE: Refer to Section 7.3
DOWEL
TO MAT
SECTION
Required Anchor Embedme nt, h = l + C + (X + d /2) /1.5
ef
d
b
Refer to Table 3 for l d
Process
Industry
Practices
Page
A-8
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE C-2: Tensile Reinforcement - Vertical Hairpin
HAIRPIN
REINFORCEMENT
X
(hef /3 max.)
PLAN
T.O. CONC.
1.5
1
do
Wh
X
(hef /3 max.)
HAIRPIN
REINFORCEMENT
SECTION
Refer to Table 3 for l dhand l d.
Process
Industry
Practices
Page
A-9
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE D-1: Shear Reinforcement - Horizontal Hairpin
D
T
ld
EDGE DISTANCE
5 do (min.)
FACE OF
CONCRETE
E
D
E
D
ANCHOR
HAIRPIN
REINFORCEMENT
PLAN
SHEAR DIRECTION
EDGE DISTANCE
5 do (min.)
ld
ANCHOR
E
V
R
HAIRPIN
REINFORCEMENT
SECTION
Refer to Table 3 for l d .
Process
Industry
Practices
Page
A-10
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE D-2: Shear Reinforcement - Closed Ties
K
EDGE DISTANCE
5 d o (min.)
FACE OF
CONCRETE
E
D
H
D
T
N
N
E
M
D
WEAK
ANCHOR
HAIRPIN
PLAN
K
EDGE DISTANCE
5 d o (min.)
FACE OF
CONCRETE
E
D
H
D
T
STRONG
ANCHOR
REINFORCEMENT
N
N
E
M
D
WEAK
ANCHOR
STRONG
ANCHOR
CLOSED TIE
REINFORCEMENT
PLAN
EDGE DISTANCE
5 d o (min.)
M
SHEAR DIRECTION
ANCHOR
ANCHOR
M
N
M
CLOSED TIE
REINFORCEMENT
SECTION
Process
Industry
Practices
Page
A-11
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE D-3: Shear Reinforcement - Anchored Reinforcement
SHEAR DIRECTION
SHEAR DIRECTION
ANCHOR
ANCHOR
ld
ld
ANCHOR
ANGLE
ANCHOR
PLATE
dl
Z
1.5
1.5
ANCHORED
REINFORCEMENT
1
1
LINE AT SURFACE OF
HALF-PYRAMID INTERSECTING
HAIRPIN
SECTION
EDGE
DIST.
ANCHOR
ld
ANCHORED
REINFORCEMENT
Z
ANCHORED
REINFORCEMENT
ANCHORED
REINFORCEMENT
(ALTERNATE)
LINE AT SURFACE OF
HALF-PYRAMID INTERSECTING
HAIRPIN
SECTION
ld = development length of reinforcement
z = vertical hairpin concrete cover + 0.5d b
FAILURE HALF-PYRAMID
1.5
1
LINE AT SURFACE OF
HALF-PYRAMID INTERSECTING HAIRPIN
PLAN
Note:
1. See Table 2 for rebar capacities.
2. Anchor plate or anchor angle must be designed for load from anchor.
3. Taking l d from centerline of bolt is conservative.
Process
Industry
Practices
Page
A-12
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE D-4: Shear Reinforcement - Shear Angles
EDGE DISTANCE
5d (min.)
o
ANCHOR
FACE OF
CONCRETE
1
FAILURE
HALF-TRUNCATED
PYRAMID
1
PLAN
SHEAR DIRECTION
EDGE DISTANCE
5d (min.)
o
ANCHOR
TACK WELD
FAILURE
HALF-TRUNCATED
PYRAMID
SECTION
NOTE:
OF THE BEARING
OF
SHEAR DEDUCT
ANGLE INAREA
CALCULATING
A p (THESURFACE
PROJECTION
OF THE FAILURE HALF-TRUNCATED PYRAMID).
Process
Industry
Practices
Page
A-13
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE D-5: Shear Reinforcement - Strut-and-Tie Model
VERTICAL
REBAR
TIE
T2
C1
ANCHOR
BOLT
T1
25°
M I N.
T1
C1
25°
M I N.
T3
NOTES:
1. C 1 AND C2 ARE COMPRESSION
FORCES.
2. T1 , T2, AND T3 ARE TENSION
FORCES.
3. ACTUAL FORCES WILL VARY
WITH GEOMETRY.
Process
Industry
Practices
Page
A-14
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE E: Minimum Lateral Reinforcement - Pedestal
PROVIDE THIS
TIE
PROVIDE
THISADDITIONAL
ADDITIONAL
IN
MODERATE
OR
HIGHTIE IN HIGH-SEISMIC AREAS
SEISMIC
AREAS
OR IS
IF USED
SHEAR
OR
IF SHEAR
LUG
LUGS OR NO. 3 TIES ARE USED.
Process
Industry
Practices
Page
A-15
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE F: Coefficients of Friction
CONCRETE
SURFACE
GROUT
= 0.90
CONCRETE
SURFACE
GROUT
= 0.70
GROUT
CONCRETE
SURFACE
= 0.55
Process
Industry
Practices
Page
A-16
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE G: Pretensioned Anchors for Turbines and Reciprocating Compressors
Notes:
T0P OF DUCT TAPE
1. Materials:
BOTTOM OF GROUT
GROUT
Anchor plate: ASTM A36
TOP
NUT
WASHER
Anchor rod: ASTM A36 or F1554 GR 36.
Nuts: ASTM A563 Grade A heavy hex
DUCT TAPE
Washer: ASTM F436
BOTTOM OF DUCT TAPE
ANCHOR ROD
FILL WITH ELASTOMERIC
PIPE SLEEVE
MOLDABLE NON-HARDENING
MATERIAL
d
o
FDN.
Pipe sleeve: ASTM A53 SCH 40
2. Weld shall be inaccordance with AWS D1.1 .
3. Fabrication Sequence:
ANCHOR
NUT 1
PLATE
NUT 2
T
A. Position anchor rod to obtain the specified
projection above the anchor plate.
B. Holding nut 1, tighten nut 2 to a snug tight
condition.
C. Hold nut 2, tighten nut 3 to a snug tigh t condition.
T
d
o
NUT 3
D. Position and weld the pipe sleeve.
DIMENSIONS ARE IN INCHES
ANCHOR
ROD
ANCHOR PLATE
DIMENSIONS
NOMINAL
PIPE SLEEVE
(in.)
(in.)
(in.)
3/4
1-1/2
2 1/2 x 2 1/2
7/8
ANCHOR PLATE
THICKNESS (T)
(in.)
5/8
3x3
2
7/8
2
3x3
7/8
1-1/8
2-1/2
3 1/2 x 3 1/2
1
1-1/4
2-1/2
3 1/2 x 3 1/2
1
1-1/2
1-3/4
4 1/2 x 4 1/2
3
5x5
3-1/2
2
4
1
1/4
1
1/2 1
5 1/2 x 5 1/2
3/4
2
2-1/4
5
6 1/2 x 6 1/2
2-1/2
5
7x7
1/4
2
2-3/4
5
7x7
1/4
2
3
6
Process
Industry
Practices
8x8
1/2
Page
A-17
1
2
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
FIGURE H: Anchor-Tightening Sequence
1
12
5
9
8
4
3
7
10
TIGHTENING
SEQUENCE
EQUIPMENT
6
11
2
EQUIPMENT
Process
Industry
Practices
Page
A-18
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
EXAMPLE 1 - Column Plate Connection Using An ch or Bo lt Desi gn Spr eads heet
Base Plate Connection Data
W12 x 45 column
Four anchors on 8" x 16" spacing
Base plate 1 1/2" x 14" x 1'-10" with vertical stiffener plates
Factored base loads (gravity plus wind - maximum uplift condition)
Shear (V ua) = 17 kips
Moment (M
u)
Tension (N
= 146 kip-feet
) = 17 kips
ua
Low-seismic area (ductility not required)
fc' = 3000 psi, A36 anchor material
Σ MP = 0
Nu
Mu
T = (146 k-ft x 12 + 17 k x 8.625")/(11 + 8 - 2.67)
ANCHO R BOL T
TOP OF PED.
Vu
T = 116 k for 2 bolts
P = 116 - 17 = 99 kips
Resisting friction load (Vf) = m P
8"
11"
T
x
P
m = 0.55 ( PIP STE05121 - Figure F)
Vf = 0.55 x 99 = 54 kips > 17 kips
Therefore, anchors are not required to
resist shear.
X = 2.67
(Refer to Blodgett - Design of Welded Structures - Figure 17 [Similar].)
Note: Other theorys for determining "X" are equally valid.
By trial and error using theAnchor Bolt Design Spreadsheet , available to PIP Member
Com anies onl , the followin is determined. This takes onl a few minutes.
Nom. Anchor Diameter = 1 3/4" Anchor Embedment = 21" (12 anchor diameters)
Pedestal Size = 6' 4" x 5' 4" (c a1 = 30", ca2 = 28", ca3 = 46", ca4 = 28", s2 = 8", s1 = 0")
(Because only two bolts resist tension, s1 must be input as 0".)
The Anchor Bolt Design Spreadsheet input and output sheets are attached for this condition.
This is a very large pedestal. If a smaller pedestal is required ordesired, supplementary
tensile reinforcing can beused to resist the load. See Example 2.
Process
Industry
Practices
Page
A-19
Anchor Bolt Design Spreadsheet
Revision 4, January 06
PIP STE05121
January 2003
Output
PIP
Company
1 of 1
Sheet
Project
PIP STE05121
Project
#
Example 1- Column Plate Connection using Anchor Bolt Design Spreadsheet
Subject
Date 10/4/2006
Name
Checked
by
Check
Date
BOLT PARAMETERS
Grade
Size
do
A36, Fu = 58
1 3/4 in.
1.750 in.
LOADCONDITIONS
Load Conditions
Tensile Load, Nu
ShearLoad,Vu
f ya
f uta
A se
A br g
36 ksi h ef
58 ksi n (tension)
1.900 sq. in. n (shear)
4.144 sq. in.
21.00 in.
2
4
REINFORCEMENT
Section 9.2
116.0 kips Reinfor cement NO T designed to carry tensil e load
0.0kips
Reinfor cement NO T designed to carry shear load
DESIGN CONSIDERATIONS
Ducitlity NOT req'd for tension
Ducitlity NOT req'd for shear
Low seismic risk
Eccentricities
3000 psi
1.4
Grout Pad
e'N = 0.00 in.
DESIGNFORTENSION
Nsa
Steel Strength
Concrete breakout
strength of anchor(s)
Concrete Strength, fc'
Cracking Modification Factor, Ψc,V
Ncb or Ncbg
Pullout strength of
anchors (s)
e'V = 0.00 in.
DESIGNFORSHEAR
220.4 kips Steel Strength
Concrete breakout strength of
anchor(s), Perpendicular to
168.7 kips edge
Vsa
211.6 kips
Vcb or Vcbg
111.5 kips
Vcp
337.5 kips
Concrete pryout strength of
nNpn
Concrete sideface
blowout strength of
headed anchor(s)
Nsb or Nsbg
(governing)
278.5 kips anchor(s)
NA
EDGE DISTANCES, SPACINGS,
FAILURE
AREAS
c1 s1 c3
4
c
2
s
ca1
SUMMARY OF RESULTS
TENSION
SteelCapacity
165.3kips
Tension
Shear
ConcreteCapacity
118.1kips
30.00 in.
30.00 in. Tensile ductility not required by user input.
ca2
28.00 in.
ca3
46.00 in.
ca4
28.00in.
s1
0.00in.
s2
8.00in.
28.00 in.
SHEAR
2
c
ANc or AVc
28.00in.
SteelCapacity
137.5kips
ConcreteCapacity
8.00in.
3840 sq. in.
2880 sq. in.
Calculated
Calculated
78.1kips
Shear ductilit y not required by user input
INTERACTION OF TENS
ILE A ND SHEAR FORCES
*
= φ Nn
118.1 kips
>= Nua = 116.0 kips
78.1 kips
*
*
= φ Vn
>= V ua
*
Nua/(φNn ) + Vua/(φVn ) =
= 0.0 kips
0.98 + 0<= 1.0
OK
*Multiplied by 0.75 if intermediate or high seismic area
Process Industry Practices
Anchor Bolt Design Spreadsheet
Revision 4, January 06
PIP STE05121
January 2003
Calculations
Selected Bolt :
do = 1.750 in.
1 in.
3/4
Ase = 1.900 sq. in.
hef = 21.0 in.
A36,
Fu
=
58
Abrg = 4.144 sq. in.
fya = 36 ksi
No.
of
Bolts
nt(tension) = 2
futa = 58 ksi
nv(shear) = 4
Note: Figures in parenthesis and in red refer to equations or paragraphs in ACI 318-05 , Appendix D.
Steel Strength i n Tension:
Nsa = nAsefuta (futa < 1.9fya and futa < 125 ksi) = 220.4 kip s
(D-3)
Nsa(1) = 1 x Asefuta (futa < 1.9fya and futa < 125 ksi) = 110.2 kips/bolt
1. Concrete brea kout str ength of anchor in t ension:
se ef = 20.00 in.
(D.5.2.3)
(See Supplementary Calculations below)
ANc(calc) = 3840.0 sq. in.
Use ANc = 3840.0 sq. in.
Ψec,N = [1/(1 + 2eN'/3hef) <= 1] = 1.00
ca,min = 28.0 in.
Ψed,N = 0.980
Ψc,N = 1.25
2
ANco = 9hef = 3600.0 sq. in.
(D-9)
(D-10 or D-11)
Ψcp,N = 1.00
Nb = 129.1 kip s
(D-7 or D-8)
Ncb or Ncb g = (ANc/ANco)Ψec,NΨed,NΨc,NΨcp,NNb = 168.7 kip s
(D-4 or D-5)
(D.5.2.6)
2. Pullout st rength of anchor in tension (crushi ng of conc rete under he ad):
Ψc,P = 1.4
Np = Abrg8fc' = 99.5 kip s
(D.5.3.6)
For n bolts, nN pn = nΨc,PNp = 278.5 kip s
For n bolts, Nsa = 220.4 kip s
Note: φnNpn
>
(D.5.2.7)
(D-15)
(D-14)
(D-3)
φNsa
3. Concrete side-face blowou t str ength of headed a nchor i n tension:
ca1 = 30.0 in.
ca2 = 28.0 in.
Side-face blowout strength does not apply.
0.5
(D-6)
ca2/ca1 = 1.07
0.5
Nsb = 160ca1(Abrg) (f'c) = NA
Side blowout group effects do not apply.
Nsbg = (1+s/6ca1)Nsb = NA
Nsb (modified) = NA
(D-17)
(D-18)
s=
0
Nsb or Nsb g (governing) = NA
Steel Strength of Fastener in Shear:
Vsa = nAse(0.6 futa)*(0.8 if there is a grout pad) = 211.6 kip s
Process Industry Practices
Sheet 1 of 3
(D-20 & D.6.1.3)
(D.5.4.1)
Anchor Bolt Design Spreadsheet
Revision 4, January 06
1. Concrete breakout strength o
AVc(calc) = 2880.0 sq. in.
f anchor in shear:
Use AVc = 2880.0 sq. in.
AVc (max) = nA Vco = 16200.0 sq. in. (D.6.2.1)
le = min (8do and hef) = 14.0 in.
ca1 (max) = 30.00 in.
0.2
PIP STE05121
January 2003
Calculations
0.5
2
AVco = 4.5ca1 = 4050.0 sq. in.
(D.6.2.2)
Use ca1 = 30.00 in.
(D.6.2.4)
0.5
Vb = 7(le/do) (do) (f'c) (ca1)
1.5
= 126.3 kips
Ψec,V = 1/(1 + 2eV'/3ca1) <= 1 = 1
(D-24)
(D-26)
Ψed,V = [0.7+0.3(ca2/(1.5ca1) if ca2 < 1.5ca1, 1.0 if ca2 >= 1.5ca1] = 0.887
Ψc,V = 1.4
Vcb or Vcb g = (AVc/AVco)Ψec,V Ψed,VΨc,VVb = 111.5 kip s
251.5 kip s
2. Concrete pryout strength o f anchor in shear:
kcp = 2
(D.6.3.1)
Vcp = kcpNcb or Vcpg = k cpNcbg, = 337.5 kip s
(D-23)
Use min A Vc = 2880.0 sq. in.
(D-27 or D-28)
(D.6.2.7)
(D-21 or D-22)
Shear perpendicular to edge
<------- Appl ies
(D-22(c))
Shear parallel to edge, Ψ ed,V =1.0
<-------- NA
Ncb or N cbg = 168.7 kip s
(D-4 or D-5)
(D-29 or D-30)
Summary of Results:
φ for concrete = 0.70
φ for steel = 0.75
Tension:
Steel capacity = φNn[*0.75 if inter. or high seismic risk] = 165.3 kip s
(D.4.4)
(D.3.3.3)
Concrete capacity = φNn[*0.75 if inter. or high seismic risk] = 118.1 kip s
(D.3.3.3)
Governing mode of concrete failure: Concrete breakout strength of anchor in tension
Tensile ductility not required by user input.
Shear:
φ for concrete = 0.70
φ for steel = 0.65
(D.4.4)
Steel capacity = φVn[*0.75 if inter. or high seismic risk] = 137.5 kip s
Conc. capacity = φVn[*0.75 if inter. or high seismic risk] = 78.1 kip s
Ductility Req'd?
Tension: No
(D.3.3.3)
(D.3.3.3)
Shear: No
Governing mode of concrete failure: Concrete breakout strength of anchor in shear
Interaction of tensil e and shear forces:
φNn = 118.1 kips
0.2φNn = 23.6 kips
(D.4.3 & D.7)
φVn = 78.1 kips
(D.7.1)
Nua = 116.0 kips
Nua/(φNn) = 0.98
Applicable equation = (D-1)
Process Industry Practices
0.2φVn = 15.6 kips
(D.7.2)
Vua = 0.0 kips
Vua/(φVn) = 0.00
Nua/(φNn) + Vua/(φVn) = 0.98
118.12
OK
Sheet 2 of 3
Less
than
1.0
or
1.2?
(D.7.3, D-31)
<= 1.0
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
EXAMPLE 2 - Column Plate Connection - Supplementary Tensile Reinforcing
Same data as Example 1. Use supplementary tensile reinforcing toreduce pedestal size.
Shear (Vua) = 17 kips
Per Example 1:
Moment (Mu) = 146 kip-feet
T = 116 k on two bolts
Tension (Nua) = 17 kips
Friction will take shear load.
Nom. anchor diameter = 1-3/4"
Assume a 2'-0" x 2'-6" pedestal.
Assume anchors are resisted by three hairpins.
116k / 3 = 38.7 kips
Per Table 3 of PIP STE05122, one #8 hairpin resists 48.37 kips. OK.
ldh (min) = 15.3" per Table 3. Width of hairpin = 6.0" + #8 diam. = 7.0". See Table 3.
Space hairpins 3" away from each anchor.
2
2 0.5
Distance from anchor to leg of hairpin = [3 +(7.0/2) ] = 4.61"
Required h ef = C + ldh + 4.61/1.5. See Figure C-2.
Where C = concrete cover = 2"
hef = 2 + 15.3 + 4.61/1.5 = 20.4"
min. hef = 12 d0 = 12 x 1.75 = 21"
Use h
Final Design
T
ef
= 21"
1 3/4" DIA. ANCHOR
(TYP.)
A
C
ANCH OR
(TYP.)
C
h
(TYP.)
1.5
1
e
h
HAIRPIN
(TYP.)
#8 HAIRPIN
(TYP.)
o
1'-4"
2'-6"
ELEVATION
* USE l
IF HOOK IS ADDED
dh
AT BO TTOM O F HAIRP IN
Process
Industry
Practices
PLAN
(NOTE: OTHER REINF. NOT
SHOWN FOR CLARITY)
Page
A-24
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
Example 3 - Shear Lug Plate Section Design
PLAN
V u = 40 K (ULTIMATE)
SECTION
Process
Industry
Practices
Page
A-25
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
EXAMPLE 3 - S hear Lug Plate Secti on Desig n
Design a shear lug plate for a 14-in. square base plate, subject to a factored axial dead load
of 22.5 kips, factored live load of 65 kips, and a factored shear load of 40 kips. The base
plate and shear lug have f ya = 36 ksi and f c' = 3 ksi. The contact plane between the grout and
base plate is assumed to be 1 in. above the concrete. A 2-ft 0-in. square pedestal is
assumed. Ductility is not required.
Vapp = Vua – Vf = 40 – (0.55)(22.5) = 27.6 kips
2
Bearing area = A req = Vapp / (0.85 φ fc') = 27.6 kips / (0.85*0.65*3 ksi) = 16.67 in.
On the basis of base plate size, assume the plate width, W, will be 12 in.
Height of plate = H = A req/ W + G = 16.67 in. /12 in. + 1 in. = 2.39 in.
Use 3 in.
Ultimate moment = M u = (Vapp / W) * (G + (H – G)/2)
= (27.6 kips / 12 in.) * (1 in. + (3 in.-1 in.)/2) = 4.61 k-in. / in.
Thickness = t = [(4 * M u)/(φ* fya)]½ = ((4*4.61 kip-in.)/(0.9*36 ksi)) ½ = 0.754 in. Use 0.75 in.
This 12-in. x 3-in. x 0.75-in. plate will be sufficient to carry the applied shear load and resulting
moment. Design of the weld between the plate section and the base plate is left to the
en ineer.
Check concrete breakout strength of the shear lug in shear.
Distance from shear lug to edge of concrete = (24 - 0.75) / 2 = 11.63 in.
AV = 24 * (2+11.63) – (12 * 2) = 303 in.
0.5
Vcb = AVc*4*φ*[fc']
Process
Industry
Practices
2
= 303 * 4 * 0.85 * [3000]
0.5
= 56400 lb = 56.4 kips > 27.3 kips
OK
Page
A-26
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
Example 4 - Shear Lug Pipe Section Design
PLAN
V u= 40K (ULTIMATE)
SECTION
Process
Industry
Practices
Page
A-27
PIP STE05121
Anchor Bolt Design Guide
TECHNICAL CORRECTION
October 2006
EXAMPLE 4 - Shear Lug Pipe Section Design
Design a shear lug pipe section for a 14-in. square base plate, subject to a factored axial dead load of
22.5 kips, factored live load of 65 kips, and a factored shear load of 40 kips. The base plate and
shear lug have fya = 36 ksi and fc' = 3 ksi. The contact plane between the grout and base plate is
assumed to be 1 in. above the concrete. A 2-ft 0-in. square pedestal is assumed. Ductility is not
required.
Vapp = Vua – Vf = 40 – (0.55)(22.5) = 27.6 kips
Bearing area = Areq = Vapp / (0.85 φ fc') = 27.6 kips / (0.85*0.65*3 ksi) = 16.7 in.
2
Based on base plate size, assume the pipe diameter will be 8-in. nominal std. weight pipe.
3
3
D = 8.625 in., t = 0.322 in., S = 16.81 in. , Z = 22.2 in.
2
Height of pipe = H = Areq / D + G = 16.67 in. / 8.625 in. + 1 in. = 2.93 in.
Use 3.5 in.
Ultimate moment = M u = Vapp * (G + (H – G)/2)
= 27.63 kips * (1 in. + (3 .5 in. - 1 in.)/2) = 62.1 7 k-in.
Check moment:
Mn = S [600/(D/t) + f ya] = 16.81 in.3 *(600/(8.625 in./0.322 in.) + 36 ksi) = 982 k-in.
or Mn = Z * fya = 22.2 in.*336 ksi = 799 k-in
φb = 0.9
φbMn = (0.9)*(799 k-in.) = 719 k-in. > 62.17 k-in.
Use M
n
= 799 k-in
OK
Check
2
2
2
2
2
Vn = 0.6 Fy π(D – (D-2t) )/4 = 0.6* 36 ksi * π* ( 8.625 – (8.625 – 2*0.322) ) in. / 4
= 181.4 kips
φv = 0.9
φvVn = (0.9)*(181.4 kips) = 163.2 kips > 27.6 kips
OK
This 3.5-in.-long x 8-in.-diameter nominal std. weight pipe will be sufficient to carry the applied shear
load and resulting moment.
Check failure plane of pedestal:
Distance from edge of pipe to edge of concrete = (24 – 8.625) / 2 = 7.69 in.
AVc = 24*(2.5 + 7.69) – 8.62*2.5 = 223 in. 2
Vcb = AVc*4*f*[f’c]0.5 = 223 * 4 * 0.85 * [3000]0.5 = 41500 lb = 41.5 kips > 27.3 kips
Process
Industry
Practices
OK
Page
A-28