PIP STE05121 - Anchor Bolt Design Guide

Process Industry Practices

Structural

PIP STE05121

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 Issued

October 2003 Technical Correction

October 2006 Technical Correction

Not printed with State funds

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---Process Industry Practices

Structural

PIP STE05121

Anchor Bolt Design Guide

Table of Contents

1. Introduction... 3

1.1 Purpose... 3

1.2 Scope ... 3

1.3 Use of “Shall” and “Should”... 3

1.4 Dimensions ... 3

2. References ... 3

2.1 Process Industry Practices... 3

2.2 Industry Codes and Standards... 3

2.3 Government Regulations ... 4 2.4 Other References... 5

3. Notation...5

4. Materials... 8

4.1 Anchors ... 8 4.2 Sleeves ... 9 4.3. Washers... 9 4.4 Corrosion... 10

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

5.6 Minimum Dimensions... 13

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

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

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---10. Pretensioning...21

10.1Advantages...22

10.2Disadvantages ...22

10.3When to Apply Pretensioning ...22

10.4Concrete Failure ...23

10.5Stretching Length...23

10.6Pretensioning Methods ...23

10.7Relaxation...24

10.8Tightening Sequence...24

10.9Recommended Tightening if Anchor Pretensioning Is Not Required...24

Tables

1. Minimum Anchor Dimensions... A-1 2. Reinforcement Tensile Capacity and

Tensile Development Length ... A-2 3. Hairpin Reinforcement Design and

Details... A-3 4. Pretension Load and Torque

Recommendations... A-4

Figures

A. Anchor Details ... A-5 B-1. Concrete Breakout Strength of

Anchors in Shear –

Octagon “Weak” 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

Examples

1. Column Plate Connection Using Anchor Bolt Design

Spreadsheet ... A-19 2. Column Plate Connection –

Supplementary Tensile

Reinforcing ... A-24 3. Shear Lug Plate Section Design. A-25 4. Shear Lug Pipe Section Design.. A-27

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---1. 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.]

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---– 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,

Zinc-Coated, 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

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---2.4 Other References

– Blodgett, Omar W., Design of Welded Structures, The James F. Lincoln Arc Welding Foundation, 1966

3. Notation

Note: 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.

Ad = Nominal bolt area, inches2

ANc = Projected concrete failure area of a single anchor or group of anchors, for

calculation of strength in tension, inches2 Ase = Effective cross-sectional area of anchor, inches2 Ar = Reinforcing bar area, inches2

Arb = Required total area of reinforcing bars, inches2 Areq = Required bearing area of shear lug, inches2

AVc = Projected concrete failure area of a single anchor or group of anchors, for

calculation of strength in shear, inches2

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, inches2

AC = Anchor circle diameter (Figures B-1 and B-2), inches2

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 = 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

fc’ = Specified compressive strength of concrete (shall not be taken as greater than

10,000 psi), psi

ft = 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 = Transverse reinforcement index

L = 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 = Nominal flexural strength of shear lug pipe, k-inches

n = Number of anchors

Ncb = 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

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, inches3

λ = Modification factor related to unit weight of concrete

φ = Strength reduction factor φb = Steel resistance factor for flexure

φv = Steel resistance factor for shear

ψt = Factor used to modify development length based on reinforcement location

ψe = Factor used to modify development length based on reinforcement coating

ψs = Factor used to modify development length based on reinforcement size

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---ψc,V = 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)

μ = 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 from ASTM A563. If ASTM F1554 grade 55 rods are specified, add the weldability supplement.

Properties for Recommended Anchor Materials

Anchor Material Type

fya ksi

futa

ksi Ductile?

A307 Not clearly

defined

60 Yes

A36 or F1554 grade 36 36 58 Yes

F1554 grade 55 55 75 Yes F1554 grade 105 105 125 Yes do ≤ 2.5" 105 125 Yes 2.5" < do ≤ 4" 95 115 Yes A193 grade B7 Based on bolt diameter (db)

(used for high-temperature service)

4" < do

≤ 7"

75 100 Yes

A354 grade BC 109 125 Yes

A354 grade BD 130 150 Yes

1/4" < do ≤ 1" 92 120 Yes 1" < do ≤ 1.5" 81 105 Yes A449 Based on bolt diameter (db) 1.5" < do ≤ 3" 58 90 Yes

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

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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.

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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 1-1/2 1-1/4 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?

• Chemical compounds • Saltwater

• Ground water • Caustic gases

c. What limitations are present, affecting anchor size, length, and material, fabrication options, availability, and cost?

Galvanizing is a common option for ASTM 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, and ASTM 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 hot-dip galvanized steel against embrittlement. Stainless steel anchors are a costly

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, ψc,V, shall

be equal to 1.4. The tops of pedestals are normally outside cracked regions; therefore ψc,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 for the factored load combinations in accordance with

ACI 318-05, section 9.2 or Appendix C. Care shall be taken to assure that the

proper strength reduction factor for reinforcing, φ, is used. That is, if the load combinations in section 9.2 are used, then use the φ’s from section 9.3; if the load combinations from Appendix C are used, then use the φ’s from Appendix C. Strength reduction factor, φ, 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.

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---5.3 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 load from the base plate to the bolt without slippage is incorporated (such as welding washers in place). If 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. 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.

5.5 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:

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

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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 than required to resist the load, then ACI 318 allows the following edge distances and anchor spacing to be reduced. Refer to ACI 318-05, section 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 of 4do 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. The ASCE 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.

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---c. 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.

5.6.5 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 or by tensile failure of the anchor itself. The former is a brittle failure and the latter is a ductile failure. A brittle failure 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 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

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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, then the anchor need only be ductile for tensile loads. (The reverse would also be true but would not normally be applicable to design.) The first step is to select the anchor size considering only the steel failure modes, that is by using 0.75φNsa and 0.75φVsa. 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:

φNcb or φNcbg > φNsa,φNpn > φNsa, and φNsb or φNsbg > φNsa

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:

φVcb or φVcbg > φVsa and φVcp > φVsa

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)

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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 φNcb or

φNcbg < φ Nsa or φVcb or φVcbg < φVsa, 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

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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 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, originating 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.)

7.3 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 in accordance with ACI 318-05, section 12.2.5, and cannot be applied in areas of moderate or high seismic risk.

7.3.2 Direct tensile loads can be transferred effectively by the use of “hairpin” reinforcement or vertical dowels according to the following guidelines:

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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.)

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.

8. 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

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 base plate from slipping before the anchors can resist the load (such as welding the washer to the base plate).

Note: 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.

8.2 Calculating Resisting Friction Force

The resisting friction force, Vf, may be computed as follows: Vf = μP

P = normal compression force

μ = 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.)

a. μ = 0.90 for concrete placed against as-rolled steel with the contact plane a full plate thickness below the concrete surface.

b. μ = 0.70 for concrete or grout placed against as-rolled steel with the contact plate coincidental with the concrete surface.

c. μ = 0.55 for grouted conditions with the contact plane between grout and as-rolled steel above the concrete surface.

9.

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 plate) allows for complete transfer of the force through the shear lug, thus taking the shear load off of the anchors. The bearing on the shear lug is applied only on the 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.

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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 * φ * fc’) φ = 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 * Mu)/(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*φ*[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.

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 /(0.85φfc’) φ = 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 end moment 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–

φv Vn ≥ Vapp

where φv = 0.9 and Vn = 0.6 fyaπ(D2 – (D-2t)2)/4

Moment check–

φb Mn ≥ Mu

where φb = 0.9 and Mn = the lesser of:

= S * [{600/(D/t)} + fya] (local buckling moment)

and

= Z * fya (plastic moment)

e. Design weld between pipe stub section and base plate. f. Check the breakout shear as shown in section 9.2(f).

10. 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

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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.

10.4 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 concrete failure pyramid, the stresses induced by external uplift on the concrete are offset by the clamping force and the gravity loads. For 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:

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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 originally 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.

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---Appendix

TABLE 1: Minimum Anchor Dimensions

(Refer to Figure A.)

hef P1 do + 1/2" (in.) (in.) 1/2 1.00 1.00 6.0 4.5 4.5 2.0 2 5 6 5/8 1.25 1.13 7.5 4.5 4.5 2.5 2 7 6 3/4 1.44 1.25 9.0 4.5 4.5 3.0 2 7 6 7/8 1.69 1.38 10.5 4.5 5.3 3.5 2 7 6 1 1.88 1.50 12.0 4.5 6.0 4.0 3 10 6 1-1/8 2.06 1.63 13.5 4.5 6.8 4.5 3 10 7 1-1/4 2.31 1.75 15.0 5.0 7.5 5.0 3 10 8 1-3/8 2.50 1.88 16.5 5.5 8.3 5.5 4 15 8 1-1/2 2.75 2.00 18.0 6.0 9.0 6.0 4 15 9 1-3/4 3.19 2.25 21.0 7.0 10.5 7.0 4 15 11 2 3.63 2.50 24.0 8.0 12.0 8.0 4 18 12 2-1/4 4.06 2.75 27.0 9.0 13.5 9.0 4 18 14 2-1/2 4.50 3.00 30.0 10.0 15.0 10.0 6 24 15 2-3/4 4.94 3.25 33.0 11.0 16.5 11.0 6 24 17 3 5.31 3.50 36.0 12.0 18.0 12.0 6 24 18

1_{IF SLEEVES ARE USED,}

EMBEDMENT SHALL BE THE LARGER OF 12door (hs+ he')

INCREASE EDGE DISTANCE BY 0.5(ds- do)

INCREASE SPACING BY (ds - do)

2_{FOR MACHINERY FOUNDATIONS PIP REIE686 REQUIRES A MINIMUM EDGE DISTANCE OF 6 INCHES.} 6do ≥ 6" Height hs ANCHOR DIA. do SHELL SIZE 4do A307/A36 F1554 Grade 36 HIGH-STRENGTH OR TORQUED BOLTS

(in.) (in.) (in.) (in.) (in.)

12do WIDTH Wh 6do ≥ 4.5" 4do ≥ 4.5" he' Diameter ds

(in.) (in.) (in.)

HEAVY HEX HEAD/

NUT

ASCE ANCHOR BOLT REPORT MINIMUM DIMENSIONS (Refer to Section 5.6)1

SLEEVES EDGE DISTANCE ca12 SPACING

ANCH. TYPE 2

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---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, φ = 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, λ = 1.0 (Normal Weight Concrete) Transverse Reinforcement Index, Ktr = 0 (Design Simplification)

ACI 318-05, Section 12.2.3 - Tension Development Length:

ld = db (3/40) [fy/(fc')1/2] (ψtψeψsλ)/[(cb + Ktr)/db] [(cb + Ktr)/db ≤ 2.5] (12-1) 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 AREA BAR CAPACITY Ar φ*Ar*(fy)

TOP OTHER TOP OTHER

(sq. in.) (Kips) (in.) (in.) (in.) (in.) (in.) (in.)

#3 0.11 5.94 ≥ 1:5/16 13 12 ≥ 2:13/16 13 12 #4 0.20 10.80 ≥ 1:1/4 17 13 ≥ 2:3/4 17 13 #5 0.31 16.74 ≥ 1:3/16 22 17 ≥ 2:11/16 22 17 #6 0.44 23.76 ≥ 1:1/8 32 25 ≥ 2:5/8 26 20 #7 0.60 32.40 ≥ 1:1/16 55 42 ≥ 2:9/16 38 29 #8 0.79 42.66 ≥ 1 71 55 ≥ 2:1/2 43 33 #9 1.00 54.00 ≥ 15/16 91 70 ≥ 2:7/16 48 37 #10 1.27 68.58 ≥ 7/8 115 89 ≥ 2:3/8 58 44 #11 1.56 84.24 ≥ 13/16 142 109 ≥ 2:5/16 71 55 #3 ≥ 5:13/16 13 12 #4 ≥ 5:3/4 17 13 #5 ≥ 5:11/16 22 17 #6 ≥ 5:5/8 26 20 #7 ≥ 5:9/16 38 29 #8 ≥ 5:1/2 43 33 #9 ≥ 5:7/16 48 37 #10 ≥ 5:3/8 55 42 #11 ≥ 5:5/16 61 47

SPACING ≥ 3.0 in. cb = 1.5 in. SPACING ≥ 6.0 in. cb = 3.0 in.

REQUIRED COVER

TENSION DEVELOPMENT LENGTH, ld

SPACING ≥ 12.0 in. cb = 6.0 in.

FACTORS FOR DIFFERENT VALUES OF fc'

(Note: ld shall not be less than 12 inches.)

TENSION DEVELOPMENT LENGTH, ld

REQUIRED COVER

f

c

'

_{LENGTH FACTOR}DEVELOPMENT 3,000 5,000 6,000 1.00 0.87 0.77 0.71 4,000

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---TABLE 3: Hairpin Reinforcement Design and Details

Reinforcement Yield Strength, fy = 60 ksi

Compressive Strength of Concrete, fc' = 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, λ = 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), φ = 0.90

#3 8.2 5.94 6.0 2.0 4.0 2.3 12 6.91 13 6.84 #4 11.0 10.80 7.7 3.2 4.5 3.0 13 13.40 17 12.80 #5 13.7 16.74 9.6 4.6 5.0 3.8 17 21.22 22 20.19 #6 16.4 23.76 11.5 5.5 6.0 4.5 25 29.06 32 27.84 #7 19.2 32.40 13.4 6.4 7.0 5.3 42 37.36 55 36.22 #8 21.9 42.66 15.3 7.3 8.0 6.0 55 48.37 71 47.06 #9 24.7 54.00 17.3 7.1 10.2 9.5 70 59.54 91 58.26 #10 27.8 68.58 19.5 8.0 11.4 10.8 89 74.83 115 73.39 #11 30.9 84.24 21.6 8.9 12.7 12.0 109 91.15 142 89.56 (a)

lbremains the same.

ldh= ldh*(D)

HAIRPIN CAPACITY: 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 laportion

(4) Hairpin capacity = bar capacity X (1 + la/ld) where ld= bar development length [ld> la]

5,000 6,000 0.77 0.71 3,000 4,000 1.00 0.87 0.7*ldh la lb T (hairpin ) = T (hook) x (1+la/ld) (kips) ACI 12.5.1 & Fig. R12.5.1 (ACI/ _CRSI) ldh REINFO RCEMENT BAR SIZE 180 DEG HOOK DEVELOPMENT LENGTH ldh = (0.02ψeλfy/(fc')0.5)d b (ACI 12.5.2 )

HAIRPIN AND HOOK DIMENSIONS (in.) REINFORCING BAR CAPACITY f*Ar*(fy) CAPACITY SEE NO T E ( 4)

(in.) (in.) (in.) (in.) (in.) (kips) INSIDE HOOK OTHER BARS ld(a) (ACI 12.2.3) VALUES OF fc':

f

c

'

_{Length Factor (D)}Development VERTICAL AND HORIZONTAL

HAIRPINS TOP BARS

ld (a)

(ACI

12.2.3) CAPACITY SEE NOTE (4)

(in.) (kips)

FACTORS FOR DIFFERENT

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---TABLE 4: Pretension Load and Torque Recommendations*

1/2 13 30 3,780 5/8 11 60 6,060 3/4 10 100 9,060 7/8 9 160 12,570 1 8 245 16,530 1-1/8 8 355 21,840 1-1/4 8 500 27,870 1-1/2 8 800 42,150 1-3/4 8 1,500 59,400 2 8 2,200 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 3 8 7,720 189,720

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.

*From PIP REIE686, Recommended Practices for Machinery Installation and Installation Design,

Appendix A.

Note 3: Based upon 30-ksi internal bolt stress

Nominal Bolt Diameter (inches) Number of Threads (per inch) Torque (foot-pounds) Pretension Load (pounds)

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---FIGURE A: Anchor Details

P

1

NOTE: DISTANCE BETWEEN BOTTOM OF SLEEVE AND ANCHOR BEARING

TYPE 2

SURFACE, h ' , SHALL NOT BE LESS THAN 6d NOR 6-IN. TACK NUT WELD DIST. P R O JE C T IO N o

TYPE 1

s T.O. CONC. T.O. CONC. a e f P R O JE C T IO N DIST. EDGE P s e EDGE h h C h h ' d d C h a e f h d s d o h P s h ' e o REFER TO TABLE 1 FOR MINIMUM DIMENSIONS

e

c

a

h

b

h

b

Octagon "Weak Anchors"

Do= π

Pythagorean theorem: Failure planes overlap each other to go clear across pedestal. ca22 + (AC/2)2 = (Do/2)2 AVc = 1.5ca1D (Max. AVc = nAVco = n4.5ca12)

n = Total number of bolts = 12

Calculate Do so that equivalent circle has same area as

octagon.

For input into PIP STE05121 Anchor Bolt

Design Spreadsheet, available to PIP

Members only.

AVc = 1.5ca1D

ca2, ca4 = [(1.03D/2)2-(AC/2)2]1/2

= 1.03D

Note: Area of octagon = 0.828D2

π Do2 = 0.828D2(4)

ca2 =[(1.03D/2)2 - (AC/2)2] 1/2

0.828D2₍₄₎

FIGURE B-1: Concrete Breakout Strength of Anchors in Shear -

Approximate solution AVc (max) = n 4.5ca12 ca1= Do /2 - AC/2 π Do2/4 = 0.828D2 ca1 =1.03D/2 - AC/2

c

a1

1.5c

a

c

a1

c

a2

shall be used for resisting shear.

n = 6

ca1 (ALT) =As shown above

ca2 (ALT) = (D-Cos(45 ο )AC)/2 AVc = 1.5ca1(ALT) D A_Vc(max) = n 4.5(c_a1(ALT))2 n = 4 AVc = 1.5ca1 D A_Vc (max) = n 4.5c_a12

FIGURE B2: Concrete Breakout Strength of Anchors in Shear

Octagon "Strong" Anchors

ca1 will vary with the number of anchors considred. Only anchors with

an edge distance, c_a1, greater than or equal to the c_a1for the chosen bolt

For the case shown above, if the dimension marked c_a1is chosen, n = 6 bolts. If the dimension marked ca1 (ALT) is chosen, n = 4 bolts.

ca1 =As shown above

c_a2 = (D-AC)/2

For input into PIP STE05121 Anchor Bolt Design

Spreadsheet , available to PIP Members only. Alternate

c

a2

c

a2

c

a1

_c

a1

c

a1

FIGURE C-1: Tensile Reinforcement - Vertical Dowels

NOTE: Refer to Section 7.3

SECTION

(h /3 max.)

a

e

f

T.O. CONC.

1.5

s

h

X

o

1

b

(m

in

.)

TO MAT

DOWEL

(m

in

.)

d

C

X

PLAN

(Centerline of Anchor Bolt to Centerline of Dowel = (W /2 + X + (d /2))

e

f

VERTICAL DOWELS

EDGE

DIST.

(h

/3

M

ax

.)

c or c

_{1 2}

h

rb

d

h

h

l

dl

d

d

W

ef

Required Anchor Embedment, h = l + C + (X + d /2) /1.5

b

d

Refer to Table 3 for ld

ef

c

a1

or c

a2

h

b

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---FIGURE C-2: Tensile Reinforcement - Vertical Hairpin

SECTION

REINFORCEMENT HAIRPIN (h /3 max.) T.O. CONC. ef (h /3 max.) h X o REINFORCEMENT HAIRPIN

PLAN

X (m in .) d h (m in .) d 1.5 1 ef h d W l l ef

Refer to Table 3 for l and l ._{dh d}

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---FIGURE D-1: Shear Reinforcement - Horizontal Hairpin HAIRPIN

SECTION

REINFORCEMENT EDGE DISTANCE EDGE DISTANCE SHEAR DIRECTION CONCRETE FACE OF 5 d (min.) ANCHOR REINFORCEMENT HAIRPIN

PLAN

ANCHOR M IN IM U M C O V E R d H O O K D IM E N S IO N 18 0 D E G . S T D . l d l 5 d (min.)

Refer to Table 3 for l ._d o o

--`,,`````,``,`,,``,```,,,`,`,,-`-`,,`,,`,`,,`---FIGURE D-2: Shear Reinforcement - Closed Ties

PLAN

SHEAR DIRECTION

SECTION

REINFORCEMENT CLOSED TIE

PLAN

EDGE DISTANCE ANCHOR EDGE DISTANCE FACE OF CONCRETE EDGE DISTANCE FACE OF CONCRETE 5 d (min.) ANCHOR WEAK S T D . H O O K D IM E N S IO N 1 80 D E G . ANCHOR WEAK 18 0 D E G . D IM E N S IO N S T D . H O O K ANCHOR M IN IM U M REINFORCEMENT

CLOSED TIE ANCHOR STRONG REINFORCEMENT HAIRPIN STRONG ANCHOR o 5 d (min.)_o 5 d (min.)_o