TECHNICAL CORRECTIONOctober 2006 Process Industry PracticesStructuralPIP STE05121Anchor Bolt Design GuidePURPOSE AND USE OF PROCESS INDUSTRY PRACTICESIn 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, TheUniversity of Texas at Austin, 3925 West Braker Lane (R4500), Austin,Texas 78759. PIP member companies and subscribers may copy this Practicefor their internal use. Changes, overlays, addenda, or modifications of anykind are not permitted within any PIP Practice without the express writtenauthorization of PIP.PRINTING HISTORY2003IssuedJanuaryTechnicalCorrection2003OctoberTechnicalCorrection2006OctoberNot printed with State fundsTECHNICAL CORRECTIONOctober 2006 Process Industry PracticesStructuralPIP STE05121Anchor Bolt Design GuideTable of Contents1.Introduction (3)1.1Purpose (3)1.2Scope (3)1.3Use of “Shall” and “Should” (3)1.4Dimensions (3)2.References (3)2.1Process Industry Practices (3)2.2Industry Codes and Standards (3)2.3Government Regulations (4)2.4Other References (5)3.Notation (5)4.Materials (8)4.1Anchors (8)4.2Sleeves (9)4.3.Washers (9)4.4Corrosion (10)5.Strength Design (11)5.1Loading (11)5.2Anchor Bolt Design Spreadsheet(Available to PIP Members Only) (11)5.3Anchor Design Considerations (12)5.4Shear Strength of Anchors in aRectangular Pattern (12)5.5Shear Strength of Anchors in aCircular Pattern (12)5.6Minimum Dimensions (13)6.Ductile Design (14)6.1Ductile Design Philosophy (14)6.2Critical Areas Requiring DuctileDesign (14)6.3Requirements for Ductile Design (15)6.4Means to Achieve Ductile Design..157.Reinforcing Design (16)7.1General (16)7.2Failure Surface (16)7.3Reinforcing Design to TransferTensile Forces (17)7.4Reinforcing to Transfer Shear Forces188.Frictional Resistance (18)8.1General (18)8.2Calculating Resisting Friction Force199.Shear Lug Design (19)9.1Calculating Shear Load Applied toShear Lug (20)9.2Design Procedure for Shear LugPlate (20)9.3Design Procedure for Shear Lug PipeSection (21)Process Industry Practices Page 1 of 24PIP STE05121 TECHNICAL CORRECTION Anchor Bolt Design Guide October 200610.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 AnchorPretensioning Is Not Required (24)Tables1. Minimum Anchor Dimensions.......A-12. Reinforcement Tensile Capacity andTensile Development Length........A-23. Hairpin Reinforcement Design andDetails...........................................A-34. Pretension Load and TorqueRecommendations........................A-4 FiguresA. Anchor Details..............................A-5B-1. Concrete Breakout Strength ofAnchors in Shear –Octagon “Weak” Anchors.............A-6 B-2. Concrete Breakout Strength ofAnchors 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-14E. Minimum Lateral Reinforcement –Pedestal......................................A-15F. Coefficients of Friction................A-16G. Pretensioned Anchors for Turbinesand Reciprocating Compressors.A-17H. Anchor-Tightening Sequence.....A-18 Examples1. Column Plate Connection UsingAnchor Bolt DesignSpreadsheet...............................A-192. Column Plate Connection –Supplementary TensileReinforcing.................................A-243. Shear Lug Plate Section Design.A-254. Shear Lug Pipe Section Design..A-27Page 2 of 24 Process Industry PracticesTECHNICAL CORRECTION PIP STE05121 October 2006 Anchor Bolt Design Guide 1. Introduction1.1 PurposeThis Practice provides the engineer and designer with guidelines for anchordesign for use by the process industry companies and engineering/constructionfirms.1.2 ScopeThis design guide defines the minimum requirements for the design of anchors inprocess 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 agood practice.1.4 DimensionsAt the time of issue of this Practice, a metric version of the basic reference forAnchor Bolt Design, ACI 318, had not been developed; therefore this Practicewas developed in English units only.2. ReferencesWhen 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 beused, 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 andInstallation Design2.2 Industry Codes and Standards•American Concrete Institute (ACI)– ACI 318-05 - Building Code Requirements for Reinforced Concrete andCommentary– ACI 349-01 - Code Requirements for Nuclear Safety Related ConcreteStructures, 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 - NinthEdition [Short title used herein is AISC ASD Manual.]Process Industry Practices Page 3 of 24PIP STE05121TECHNICAL CORRECTIONAnchor Bolt Design GuideOctober 2006Page 4 of 24 Process Industry Practices– 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 RegulationsFederal Standards and Instructions of the Occupational Safety and HealthAdministration (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 ComplianceTECHNICAL CORRECTIONPIP STE05121October 2006 Anchor Bolt Design GuideProcess Industry PracticesPage 5 of 242.4 Other References– Blodgett, Omar W., Design of Welded Structures , The James F. LincolnArc Welding Foundation, 19663. NotationNote : 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, andexamples as kips and ksi, respectively. Where this is done, the units will always be shown. A d= Nominal bolt area, inches 2A Nc = Projected concrete failure area of a single anchor or group of anchors, forcalculation of strength in tension, inches 2 A se = Effective cross-sectional area of anchor, inches 2 A r= Reinforcing bar area, inches 2A rb = Required total area of reinforcing bars, inches 2 A req = Required bearing area of shear lug, inches 2A Vc = Projected concrete failure area of a single anchor or group of anchors, forcalculation of strength in shear, inches 2 A Vco = Projected concrete failure area of a single anchor, for calculation of strength inshear, if not limited by corner influences, spacing, or member thickness, inches 2 AC = Anchor circle diameter (Figures B-1 and B-2), inches 2 C = Clear distance from top of reinforcing bar to finished surface (concrete cover), inches c a= Distance from center of an anchor shaft to the edge of concrete, inchesc a,max = Maximum distance from center of an anchor shaft to the edge of concrete,inches C a,min = Minimum distance from center of an anchor shaft to the edge of concrete,inches c a1= Distance from the center of an anchor shaft to the edge of concrete in onedirection, inches. If shear is applied to anchor, c a1 is taken in the direction of the applied shear. If the tension is applied to the anchor, c a1 is the minimum edge distance. c a2= Distance from center of an anchor shaft to the edge of concrete in the direction perpendicular to c a1, inchesc b =Smaller of (a) the distance from center of a bar or wire to nearest concretesurface, and (b) one-half the center-to-center spacing of bars or wires being developed, inches D= Octagonal pedestal “diameter” (flat to flat), inchesPIP STE05121TECHNICAL CORRECTIONAnchor Bolt Design GuideOctober 2006Page 6 of 24 Process Industry PracticesD = Outside diameter of shear lug pipe section, inchesd b = Nominal diameter of bar, wire, or prestressing strand, inchesd o = Outside diameter of anchor or shaft diameter of headed stud, headed bolt, or hooked bolt, inches d s = Anchor sleeve diameter, inchesE = Elastic modulus of bolt, psif c ’= Specified compressive strength of concrete (shall not be taken as greater than10,000 psi), psi f t = Desired tensile stress, psi f uta = Specified tensile strength of anchor steel, psif y = Specified yield strength of reinforcement, psi f ya = Specified yield strength of anchor steel, psi G = Grout thickness, inchesH= Height of shear lug plate or pipe, inchesH b = Overall length of anchor under the head or above the base nut (Figure A), inches h e ’ = Length of anchor below the sleeve (Figure A), inches h ef = Effective embedment depth of anchor (Figure A), inches h s = Length of anchor sleeve (Figure A), inches K tr =Transverse reinforcement indexL = Length of shear lug plate or pipe, inchesl= Bolt stretch length (the distance between the top and bottom nuts on the bolt), inches l a , l b = Portions of standard hook development length (Table 3), inches l d = Development length of reinforcing bar, inchesl dh = Actual development length of standard hook in tension, inches l hb= Basic development length of standard hook in tension, inches M u = Ultimate moment on shear lug plate or pipe, k-inches or k-inches/inches M n = Nominal flexural strength of shear lug pipe, k-inches n= Number of anchorsN cb = Nominal concrete breakout strength in tension of a single anchor, lb N cbg = Nominal concrete breakout strength in tension of a group of anchors, lb N pn = Nominal pullout strength in tension of a single anchor, lbTECHNICAL CORRECTIONPIP STE05121October 2006 Anchor Bolt Design GuideProcess Industry Practices Page 7 of 24N sa = Nominal strength of a single anchor in tension as governed by the steel strength,lb N sb = Side-face blowout strength of a single anchor, lbN sbg = 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), inchesP 1 = 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, inchest = Thickness of the shear lug plate or pipe wall, inches T= Tensile rebar capacity, lbT lc = Bolt threads per unit length V app = Applied shear load on shear lug, kipV cb = Nominal concrete breakout strength in shear of a single anchor or shear lug, lb V cbg = Nominal concrete breakout strength in shear of a group of anchors, lb V cp = Nominal concrete pryout strength of a single anchor, lb V f = Resisting friction force at base plate, lb V n= Nominal shear strength, lbV sa = Nominal strength in shear of a single anchor or group of anchors as governed bythe steel strength, lb V ua = Factored shear force applied to a single anchor or groups of anchors, lb W = Width of shear lug plate perpendicular to shear force, inches W h = 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 3λ = 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 sizePIP STE05121TECHNICAL CORRECTIONAnchor Bolt Design GuideOctober 2006Page 8 of 24 Process Industry Practicesψc,V = Factor used to modify shear strength of anchors based on presence or absenceof 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 friction4. Materials4.1 AnchorsRefer 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 F1554grade 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 MaterialsAnchor Material Typef yaksi f uta ksi Ductile? A307 Not clearly defined60 YesA36 or F1554 grade 36 36 58 Yes F1554 grade 55 55 75 Yes F1554 grade 105 105 125 Yes d o ≤ 2.5" 105 125 Yes 2.5" < d o ≤ 4" 95 115 Yes A193 grade B7 Based on bolt diameter (d b )(used for high-temperatureservice) 4" < d o ≤ 7" 75 100 Yes A354 grade BC 109 125 Yes A354 grade BD 130150Yes1/4" < d o ≤ 1" 92 120 Yes 1" < d o ≤ 1.5" 81 105 Yes A449Based on bolt diameter (d b)1.5" < d o ≤ 3"58 90 YesBolts made from ASTM F1554 grade 105, ASTM A193 grade B7, andASTM 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 nutsjammed together or a plate jammed between two nuts could be provided in place of the tack-welded nut.4.2 SleevesAnchors should be installed with sleeves when small movement of the bolt isdesired after the bolt is set in concrete. The two most common examples follow:a. When precise alignment of anchors is required during installation ofstructural columns or equipment. In this situation, the sleeve should befilled with grout after installation is complete. Use of sleeves for alignmentof large diameter bolts should be discussed in contructability reviews todetermine if they provide construction advantages (large bolts do not bendeasily). Use of templates may be a better approach to address toleranceissues for some equipment.b. When anchors will be pretensioned to maintain the bolt under continuoustensile stresses during load reversal. Pretensioning requires the bolt surfaceto be free; therefore, the top of these sleeves should be sealed or the sleeveshould be filled with elastomeric material to prevent grout or water fromfilling the sleeve.Two types of sleeves are commonly used with anchors. A partial sleeve isprimarily used for alignment requirements, whereas the full sleeve is used foralignment as well as for pretensioning. Sleeves do not affect the design of aheaded 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 machineryfoundations.For concrete cover requirements, refer to section 5.6.4 of this Practice.4.3. WashersWashers are required for all anchor bolts. Hardened washers conforming toASTM F436 are required if the anchors are to be pretensioned (refer tosection 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 washershould be equal to the bolt diameter plus 1/16 inch. The following table showsthe PIP-recommended base plate hole diameters.Recommended Base Plate Hole and Washer SizeAnchor BoltDia. (Inches) PIP-Recommended Base Plate HoleDiameter*1/2 13/165/8 15/163/4 1-1/167/8 1-3/161 1-1/21-1/4 1-3/41-1/2 21-3/4 2-1/42 2-3/42-1/4 32-1/2 3-1/22-3/4 3-3/43 4* Base plate hole size recommendations are based onAISC ASD Manual, ninth edition, adjusted such thatstandard F436 washers will cover the base plate hole.Hole size recommendations in the current AISC LRFDManual, third edition, have been revised and are larger.4.4 CorrosionCorrosion of an anchor can seriously affect the strength and design life of theanchor. When deciding which anchor material to use or what precaution to takeagainst 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 gasesc. 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 andASTM F1554 grade 36 threaded rods. ASTM F1554 grades 55 and 105,ASTM A193 grade B7, ASTM A354 grades BC and BD, and ASTM A449 boltsmay also be galvanized if appropriate safeguards are in place. Where loss ofductility is an issue, ASTM A143 provides guidance concerning safeguarding hot-dip galvanized steel against embrittlement. Stainless steel anchors are a costlyoption but may be required in some environments. Painting or coating the anchorwill protect the anchor, but more maintenance may be required.To reduce the amount of contact with corrosive substances, pier design andanchor arrangement should consider water collection and anchor environment.If the engineer determines that prolonged contact with a corrosive substance isunavoidable, a metallurgist should be consulted to determine alternate anchormaterials or protective options.Design5. StrengthStrength design, which utilizes factored loads, shall be in accordance with Appendix Dof ACI 318-05. In this Practice, strength design will apply to headed bolts and headedstud 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 embeddedmore than 25 inches (shown in ACI 318-05, D.2.2) may be ignored; however onlyequation D-7 (not equation D-8) shall be used for checking the breakout strength incracked concrete.ACI 318-05,D.6.2.7, states that for anchors located in a region of a concrete memberwhere 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; thereforeψc,V should be 1.4 for most pedestals. For anchors at beams and slabs, follow theguidelines of ACI 318-05, section D.6.2.7.5.1 LoadingAnchors shall be designed for the factored load combinations in accordance withACI 318-05, section 9.2 or Appendix C. Care shall be taken to assure that theproper strength reduction factor for reinforcing, φ, is used. That is, if the loadcombinations in section 9.2 are used, then use the φ’s from section 9.3; if theload 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 Dof ACI 318-05 and this Practice. (The spreadsheet, which is available to PIPMember Companies only, not to PIP Subscribers, can be accessed via/members/irc/index.asp under “Implementation ResourceCenter” - “Tools.”) The spreadsheet gives shear and tensile capacities of ananchor or anchor group and the concrete around it. The spreadsheet also lets theuser know whether or not the anchor configuration is ductile (refer to section 6,this Practice). The user needs to use the spreadsheet in combination withAppendix D of ACI 318-05 and this Practice. The spreadsheet merely saves theuser time in laborious calculations but is no substitute for the engineer’sknowledge and expertise. See Appendix Example 1 (this Practice) for anillustration of the use of the Anchor Bolt Design Spreadsheet.5.3 Anchor Design ConsiderationsTo accommodate reasonable misalignment in setting the anchor bolts, baseplates are usually provided with oversized holes. If the factored shear loadsexceed the values that can be resisted by friction between the base plate and thegrout (see sections 8 and 9), a suitable means must be provided to transfer theshear from the base plate to the foundation. This can be accomplished by thefollowing:a. Either shear lugs are used, orb. A mechanism to transfer load from the base plate to the bolt withoutslippage is incorporated (such as welding washers in place). If washers areto be welded in place, plain washers or steel plate (rather than hardenedwashers) must be specified to ensure that a good weld can be produced.Galvanized or painted surfaces must be prepared appropriately beforewelding. Welded elements may need to be painted or the galvanizing mayneed 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 designedrebar, there is no requirement to check for concrete breakout strength of theanchor or anchors in tension (N cb or N cbg). Refer to section 7.3.5.4 Shear Strength of Anchors in a Rectangular PatternIn accordance with ACI 318, the concrete design shear strength of a group ofanchors 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 perpendicularto the direction of force on the anchorsb. The design strength of the row of anchors furthest from the edge if theanchors are welded to the attachment so as to distribute the force to allanchors. See also section 5.3 b.c. Although not specifically accepted in ACI 318, the design strength of thefurthest row, if closed shear ties or other mechanisms transfer the load tothe row of anchors furthest from the edge. Refer to Figure D-2.5.5 Shear Strength of Anchors in a Circular PatternAnchor bolts for tall, vertical vessels are frequently not required to resist shear.The shear is resisted by friction created by the large compressive forcesattributable to overturning. However anchor bolts for shorter horizontal vesselsmay be required to resist shear. Following are two alternative methods fordesigning the anchors to resist shear:5.5.1 The design shear strength of an anchor group in a circular pattern can bedetermined by multiplying the strength of the weakest anchor by thetotal number of anchors in the circle. Refer to Figure B-1.5.5.2 Alternatively, where closed shear ties or other mechanisms transfer theload from the weak to the strong anchors, the design shear strength of ananchor group in a circular pattern can be determined by calculating theshear capacity of the strong anchors. Refer to Figure B-2.Dimensions5.6 MinimumMinimum edge distance and anchor spacing shall be in accordance with ACI 318 and should be in accordance with ASCE recommendations. Minimumembedment should be in accordance with the recommendations of the ASCEAnchor Bolt Report. Refer to Table 1 and Figure A of this Practice. (Ifsupplementary reinforcement is added to control splitting or the anchor size islarger than required to resist the load, then ACI 318 allows the following edgedistances and anchor spacing to be reduced. Refer to ACI 318-05, section D.8.5.6.1 Edge Distancea. ACI 318 requires cast-in headed anchors that will be torqued tohave minimum edge distances of 6d o. Otherwise, the onlyrequirement for edge distance is that at least the same cover bepresent 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 Reportrecommends a minimum edge distance of 4d o but not less than4.5 inches for ASTM A307 or ASTM A36 bolts or their equivalentand 6d o but not less than 4.5 inches for high-strength bolts.c. According to PIP REIE686, the recommended edge distance foranchor bolts in machinery foundations is 4d o, 6 inches minimum.5.6.2 Embedment DepthNo minimum embedment depth is specified in ACI 318 as long as theeffective embedment depth is enough to resist uplift forces. If ductility isrequired, greater embedment may be necessary. The ASCE Anchor BoltReport recommends a minimum embedment depth of 12 diameters.h ef = 12d o5.6.3 Spacing between AnchorsACI 318 requires the minimum spacing between anchors to be at least4d o for untorqued cast-in anchors and 6d o for torqued anchors.5.6.4 Modification for SleevesWhere anchor sleeves are used, the preceding minimum dimensionsshould be modified as follows:a. Edge distance should be increased by an amount equal to half thesleeve diameter minus half the anchor diameter, 0.5(d s – d o).b. Embedment length for anchors equal to or greater than 1 inchshould not be less than the larger of 12 anchor diameters (12d o) orthe sleeve length plus 6 anchor diameters (sleeve length + 6d o).For anchors less than 1 inch in diameter, the embedment lengthshould not be less than the sleeve length plus 6 inches.。
