Appendix B. Anchor Bolt Selection and Layout

AbstractThe purpose of this appendix is to present design concepts and a procedure that can be used in designing anchor bolts or evaluating an existing anchor bolt arrangement.

Contents Page

B1.0 Introduction B-2B1.1 Failure Modes

B1.2 Nomenclature

B2.0 Design Concepts B-6B2.1 Bolt Capacities

B2.2 High-strength Bolts

B2.3 Concrete Tensile Capacity

B2.4 Concrete Shear Capacity

B2.5 Combined Shear and TensionB2.6 Factor of SafetyB2.7 Allowable Loads

B2.8 Standard Drawing GD-Q68922B3.0 Special Design For Anchor Bolt Load Transfer to Reinforcing Steel B-19B3.1 Reinforcement For Tension Force

B3.2 Reinforcement For Shear Force

B3.3 Reinforcement For Lateral Bursting Force

B3.4 Bolt Embedment and Reinforcing Steel Development Length

B4.0 Design Procedure B-28B4.1 Basic Design Steps Where Standard Drawing Limitations Can be Met

B4.2 Design Steps Where Standard Drawing Limitations Cannot be Met

B5.0 Design Examples B-31B5.1 Design Example 1B5.2 Design Example 2B6.0 References B-39Chevron Corporation B-1 June 1997

Appendix B Civil and Structural ManualB1.0 IntroductionIn the past, embedment lengths and bolt capacities for anchor bolts in tension were based on the bond strength developed between the bolt shank and the concrete foun-dation. The bond strength was based on requirements for plain reinforcing bars and reinforced concrete members established to avoid any slippage of the steel. This steel-to-concrete bond strength was small and resulted in large embedment lengths. Anchor bolt pull-out tests have indicated that embedment lengths, based on this concept, are overly conservative.

Placing a standard bolt head at the anchor bolt end, without a plate or washer, and relying on the compression on the bolt head, is reliable and practicable. Therefore, headed bolt or stud is the preferred bolt for anchorage.

Properly detailed reinforcing steel in close proximity to the bolt can increase the reliability, reduce the bolt spacing and edge distance requirements and thus, result in a more economical foundation design. Design of foundations in petrochemical facilities often involves anchorage for tall vessels and structures which are subjected to high wind and seismic forces, resulting in large diameter anchor bolts. The required embedment length, spacing, and edge distance of these anchor bolts can sometimes become excessive, and often control the size of the foundation.

Two design concepts are presented in this appendix i.e., Cast-in-place Anchor Bolt in Plain Concrete and Cast-In-Place Anchor Bolt in Reinforced Concrete. Sections B2.3 through B2.7 provide guidance for design of anchor bolt in plain concrete which is based on the requirements of Section 1925 of Vol. II of the 1994 edition of the Uniform Building Code (UBC) [6]. The guidance also includes the design of anchor bolts in concrete with minimum reinforcement parallel or perpendicular to the bolt. However, it does not take full advantage of the reinforcing bar to reduce bolt spacing and edge distance. The standard drawing for anchor bolts, GD-Q68922 is developed using the concepts presented in these sections.Section B3.0 provides guidance for the design of Cast-In-Place Anchor Bolt in Reinforced Concrete, which is developed based on the guidelines contained in a new ASCE publication entitled Design of Anchor Bolts in Petrochemical Facili-ties [13]. This design concept take full advantages of the reinforcing bar in the concrete to reduce the required edge distance and bolt spacing without any reduc-tion in capacity or ductility of the bolt. This type of anchorage design methodology is highly suitable for structures or equipment founded on small pier or pedestal foundations where the embedment, spacing, and edge distance limitations of stan-dard drawing GD-Q68922 can not be met.

B1.1 Failure Modes

Without ReinforcingAnchoring embedded bolts in concrete is designed to prevent tension, shear, wedge splitting, and lateral bursting failure of the concrete. The desired failure mode is bolt yielding because it is more reliable and ductile. The five concrete failure modes are described briefly below:June 1997 B-2 Chevron Corporation

Civil and Structural Manual Appendix B Tension: The concrete above the anchor head pulls out in the shape of a cone which radiates towards the surface from the anchor bolt head. The cone angle increases with increasing embedment depth and has conservatively been taken to be 45 (Figure B-1).

Shear: The failure mode of concrete for an anchor bolt in shear near an edge is one half of a 45 cone. The cone extends laterally from the centerline of the bolt at the concrete surface towards the edge in the direction of the shear (Figure B-2).

Lateral Bursting: Another failure mode of concrete around an anchor bolt in tension is a 45 cone which extends laterally towards the edge of the concrete from the anchor bolt head (Figure B-3). This failure mode occurs only for bolts with small edge distances.

Wedge Splitting: The concrete cracks or splits in the direction of the nearest obstruction. This mode of failure happens most frequently when bolts are placed too close together or near an edge, and the cracking forces are not resisted by adequate reinforcement (Figure B-4).

Concrete Crushing: For an anchor bolt in shear, the concrete next to the anchor bolt near the surface crushes and allows the anchor bolt to displace and break. This failure mode occurs when edge distances are large.

With ReinforcingWhere the main reinforcement is parallel to and in close proximity to the bolt, the bolt tension is transferred to the reinforcing bars. For this to occur, the bolts and reinforcing steel must be confined by hoops, spirals, or sufficient concrete edge distance to contain the high-compressive stresses which form in the region of the bolt head. When these stresses are confined, tests have shown the failure mode to be a splitting in the concrete similar to the failure mode for deformed reinforcing bars in tension. Where minimal reinforcement exists perpendicular to the bolt, tests show that the shear cone is interrupted and ultimate shear values may be higher. The cause of failure is diagonal tension; however, the solution is beyond analysis and results are given based on empirical data. Solutions to both cases are shown in this text.

Fig. B-1 Tension Failure ConeChevron Corporation B-3 June 1997

Appendix B Civil and Structural ManualFig. B-2 Shear Failure Cone

Fig. B-3 Lateral Bursting Failure

Fig. B-4 Wedge Splitting Failure

PLANEFAILUREPOTENTIAL

TENSIONFORCEJune 1997 B-4 Chevron Corporation

Civil and Structural Manual Appendix BB1.2 Nomenclature

AB Gross area of the anchor bolt (in2)AR Root area of the anchor bolt (in2)ABT Tensile stress area of bolt = 0.7854 (d-0.9734/N)2 (in2)

Where:d = Nominal bolt diameter (in)N = Number of threads per inch

ALB Ineffective cone surface area due to inadequate bolt spacing (in2)ASFC Projected area of shear failure cone (in2)AS Sloping area of the assumed failure surface (in2)ASR Total area of reinforcing steel (in2)AT The flat bottom area of the truncated pyramid of an assumed tension

failure surface (in2)B Distance between two bolts measured from center of bolt (in)BACT Actual bolt spacing to be used in field (in)BCR Critical bolt spacing (in)E Distance to concrete edge measured from center of bolt (in)EACT Actual edge distance to be used in field (in)ECR Critical edge distance (in)FY Yield tensile stress of bolt material (33000 psi for A-307 material) or

reinforcing steel (psi)FUR Ultimate tensile stress of bolt material (60,000 psi for A-307 material),

psiL Embedment length of the bolt (in)LACT Actual embedment length to be used in field (in)LCR Critical embedment length. Minimum embedment length required for

full development of the tension failure cone based on ductile failure mode (in)

L.F. Load factor as defined by the Uniform Building Code [6]P Design tensile load on the bolt (lbs)

PA Allowable bolt tension: lesser of PB or (ductile connection ) or

(non-ductile connection) (lbs)

PB Allowable bolt capacity in tension based upon the steel properties of the bolt (lbs)

PCR2.7

---------------PCR4

---------------Chevron Corporation B-5 June 1997

Appendix B Civil and Structural ManualB2.0 Design ConceptsAnchor bolts embedded in concrete foundations should be placed and sized so that the tension capacities of an anchorage system are governed by the steel properties of the anchor bolts rather than the concrete properties of the foundation. This results in a ductile connection that prevents sudden failure since the anchor bolts will yield and gradually deform plastically before the concrete approaches its tensile capacity and fails suddenly. A ductile connection is particularly important for connections which are designed to resist earthquake loads or other dynamic loads.

Since the steel shear failure of an anchor bolt has little ductility, ensuring a ductile shear connection is meaningless. However, it is preferable to have the shear capacity of the concrete be greater than the shear capacity of the bolt.

PBY Yield capacity of bolt (lbs)PBU Ultimate capacity of bolt (lbs)PCR Tensile capacity of the concrete cone reduced for spacing and edge inter-

ferences (lbs)PC Tensile capacity of the full concrete cone (lbs)TU Factored tensile force on the bolt (lbs)V Design shear load on the bolt (lbs)

VA Allowable bolt shear: lesser of VB or (lbs)

VB Allowable bolt capacity in shear based upon the steel properties of the bolt (lbs)

VC Shear capacity of concrete (lbs)VCR Shear capacity of the concrete shear cone reduced for bolt spacing (lbs)db Nominal diameter of the reinforcing steel (in)h Short dimension of hexagon head of bolt or bottom plate (in)fc Specified compressive strength of concrete (psi)ft Tensile strength of concrete (psi)ld Development length required for the anchor bolt reinforcing steel (in) Strength-reduction factor Bolt head lateral force coefficient

VCR1.9----------------June 1997 B-6 Chevron Corporation

Civil and Structural Manual Appendix BB2.1 Bolt CapacitiesTo design a ductile anchorage system, the anchor bolt steel and concrete capacities must be calculated and compared. The allowable capacities for anchor bolt shear and tension should be determined according to the allowable stresses specified in AISC Specification for Structural Steel Buildings (1989 Edition). The allowable capacities for tension and shear based on the steel properties of the bolt are listed in Figure B-5.

B2.2 High-strength BoltsOnly standard A-307 or A-36 type bolts with American standard hexagon heads are considered in this appendix. High- strength bolts (A-325 and A-490) are not recom-mended because the higher yield strength requires greater embedment, edge distance, and more reinforcing. High-strength anchor bolts also do not have as much ductility as A-307 bolts.

If high-strength bolts are required, they should be designed according to the princi-ples presented in this appendix.

Fig. B-5 Properties of A-307 Bolts

NominalBolt

Diameter d (in.)

Tensile Stress Area

ABT (in2)

Bolt GrossArea AB

(in2)

Bolt RootArea AR

(in2)

Bolt Head Dia. h

(in)

AllowableTensile

Capacity ofBolt PB (lbs)

AllowableShear

Capacity ofBolt VB (lbs)

1/2 .142 .196 0.129 0.750 2,800 1,290

5/8 .226 .307 0.207 0.938 4,500 2,070

3/4 .334 .442 0.309 1.125 6,700 3,090

7/8 .462 .601 0.429 1.313 9,200 4,290

1 .606 .785 0.563 1.500 12,100 5,630

1-1/8 .763 .994 0.709 1.688 15,300 7,090

1-1/4 .969 1.227 0.908 1.875 19,400 9,080

1-1/2 1.41 1.767 1.32 2.250 28,200 13,200

1-3/4 1.90 2.405 1.78 2.625 38,000 17,800

2 2.50 3.142 2.34 3.000 50,000 23,400

2-1/2 4.00 4.909 3.78 3.750 80,000 37,800

3 5.97 7.069 5.70 4.500 119,400 57,000

Notes: 1. Allowable Stress = 20 ksi tension (Based on tensile stress area)2. Allowable Stress = 10 ksi shear (Based on root area)Chevron Corporation B-7 June 1997

Appendix B Civil and Structural ManualB2.3 Concrete Tensile Capacity

Concrete with no Reinforcement or with Reinforcement Perpendicular to BoltWhere concrete is unreinforced or the main reinforcement is perpendicular to the anchor bolt, the load transferred by the bolt to the foundation must be developed by the concrete. Concrete capacities are determined by evaluating the failure cones. These develop in the concrete when applying tension to the anchor bolt. Tests have shown that as tension loads are applied, the concrete capacity can be represented by a failure cone that radiates out at a 45 angle from the bolt head and intersects the concrete surface as diagrammed in Figure B-1.

The tensile capacity of the full concrete cone, PC , can be determined by applying the tensile strength of concrete over the sloping area of an assumed failure surface, AS, and the flat bottom area of the truncated pyramid of an assumed tension failure surface, AT. Summing the stresses on the concrete failure surface in the vertical direction yields the following equation:

(Eq. B-1)where:

fc = specified compressive strength of concrete (psi).AS = the sloping area (in square inches) of an assumed failure surface.

The surface to be that of a cone or truncated pyramid radiating at a 45 slope from the bearing edge of the anchor or anchor group to the surface. For shallow concrete sections with anchor groups, the failure surface shall be assumed to follow the extension of the slope through to the far side rather than truncate as in AT.

AT = the flat bottom area (in square inches) of the truncated pyramid of an assumed tension failure surface.

= concrete strength reduction factor. It is 0.85 when reinforcing steel is placed parallel to the bolt and 0.65 when parallel rein-forcing steel is not present.

For all bolt arrangements, (except the special case listed below), the failure surface should be based upon full failure cones and reduced for interferences as needed. The sloping area of the failure surface for full failure cones can be calculated by using equations B-2 and B-3 listed below:

(for tension failure cones)(Eq. B-2)

(for tension failure cones)(Eq. B-3)

ft 4 fc=

PC fc 2.8AS 4AT+( )=

AS pi L h+( )L 2=

AT 0=June 1997 B-8 Chevron Corporation

Civil and Structural Manual Appendix BFor the special case of four or more anchors simultaneously in tension and in a rect-angular pattern which are spaced closer together than twice their embedded length, the failure surface is a single pyramid truncated at the anchor-bolt heads rather than separate cones.

Adding a Plate at the Bolt HeadThe size of the tension-failure cone can be increased by adding a plate just above the bolt head. The plate increases the failure cone dimensions; and, therefore, the concrete pull-out strength. Because the bond between the plate and the concrete below is small and cannot be assured, the concrete area above the plate should not be included in calculating the cone capacity. The concrete strength, PC , is then only a function of the surface area, AS, which projects from the edge of the plate to the concrete surface.

The plate should be thick enough to resist the compressive forces which develop on its upper side. It should also be strong enough to remain intact up to the ultimate strength of the bolt. Also, the edge distance required for lateral bursting is related to the size of the bolt head; therefore, lateral bursting may have to be reevaluated.

Anchor Bolt Interference Tension (Figure B-6)Where anchor bolts are spaced less than two times their embedment depth or placed closer to a concrete edge than their embedment depth, the capacity of the tension failure cone must be reduced.

For bolt groups with tension failure cones that have restrictive spacings, the reduc-tion of the tension failure cone capacity should be based upon overlapping tension cones.

The ineffective sloping area, ALB, of the tension failure cone due to an adjacent bolt can be determined from the following equation which is based on cone geom-etry:

(Eq. B-4)For restrictive edge distances, the concrete pullout strength should be reduced by the ratio of the edge distance over the embedment length, EACT/LACT.

For bolt groups with overlapping tension failure cones, the tensile capacity of the concrete cone reduced for edge and spacing interferences (PCR) becomes:

(Eq. B-5)The reduction for edge distance is more severe than bolt spacing because tests [12] show that the effective tensile capacity of concrete drops from to for

ALB LACT 0.5h+( )2 COS 10.5BACT

LACT 0.5h+------------------------------- 0.5BACT LACT 0.5h+( )2 0.5BACT( )2[ ]1 2/ 2=

PCR fc 2.8 AS ALB( )[ ]EACTLACT--------------=

4 fc 2 fcChevron Corporation B-9 June 1997

Appendix B Civil and Structural Manualsmall edge distances. The value of EACT/LACT can never be greater than one. Also, logically, as the edge distance goes to zero, the concrete cone strength should also go to zero, not half its original value.

If a bolt has multiple restricting edge distances the concrete cone strength shall be reduced accordingly. A bolt group strength shall be the weakest bolt times the number of bolts.

Critical DimensionsThe minimum embedment length, edge distance, and bolt spacing are found in Figure B-7 for values of fc = 3000 psi. These dimensions should be met at all times and are based on test results and theory.

Fig. B-6 Bolt Layout Example

Fig. B-7 Critical Dimensions (fc = 3000 PSI) (1 of 2)

Bolt Diameter (in) LCR (in)

ECR (min. reinf.) (in)

ECR (no reinf.) (in)

BCR (in)

1/2 4.0 4.0 4.0 6.0

5/8 5.0 4.0 4.0 6.0

3/4 6.0 4.0 4.0 6.0

7/8 7.0 4.0 5.0 6.0

In e ffectives lop ing area s

Ver tica lIn te rsec tio np lan e d ue toa d ja cen t b o lt

Ver tica lIn te rsectionp lane s d ue toco ncre te edg es

C o ncre teedg e r = L + 0 .5h

ConcreteedgeJune 1997 B-10 Chevron Corporation

Civil and Structural Manual Appendix B1. Critical Embedment Length

LCR=7d (for all bolt sizes)2. Critical Edge Distance

a. With minimum steel reinforcement as indicated in Standard Drawing GB-Q68922

b. Without steel reinforcement =

(Eq. B-6)This equation is based on preventing a lateral concrete failure or blowout at the anchor bolt head for a force of .25 PCR with a safety factor as defined by Equation B-15. If an anchorage system governed by the concrete properties (Equation B-16) is being used, ECR may be recalculated by substituting 1.5P for PA in Equation B-6.

3. Critical bolt spacing, BCR = 6 inches d < 2 inches

Reinforcement Parallel to BoltWhere concrete reinforcement is near the anchor bolt, as in a typical pedestal for a vertical vessel, the load transferred by the bolt to the foundation will be transferred into the reinforcement. The calculation for transfer of bolt tension to the reinforce-ment is based on tests by the University of Texas [4]. These tests showed a region

1 7.0 6.0 5.0 6.0

1-1/8 8.0 6.0 6.0 6.0

1-1/4 9.0 6.0 7.0 6.0

1-1/2 11.0 6.0 8.0 6.0

1-3/4 13.0 6.0 9.0 6.0

2 14.0 6.0 11.0 6.0

2-1/2 18.0 8.0 13.0 8.0

3 21.0 8.0 16.0 8.0

ECR = 4 inches d < 1 inchECR = 6 inches 1 inch d < 2 inchesECR = 8 inches d 2 inches

BCR = 8 inches d 2 inches

Fig. B-7 Critical Dimensions (fc = 3000 PSI) (2 of 2)

Bolt Diameter (in) LCR (in)

ECR (min. reinf.) (in)

ECR (no reinf.) (in)

BCR (in)

ECRPA

12 fc----------------

1 2/ h2---+=Chevron Corporation B-11 June 1997

Appendix B Civil and Structural Manualof very high compressive stresses, a critical stress area, in the region at the bolt head. If this region is not confined by sufficient cover and reinforcement, spalling or a lateral blowout occurs, resulting in a reduction in bolt capacity. This blowout is similar to lateral bursting. The minimum edge distances needed to satisfy lateral bursting can be found in Figure B-7.

When reinforcing steel is placed parallel to the bolt, 0.85 can be used for . When calculating PCR, however, the additional resistance provided by the reinforcing steel was conservatively not included. The required area of reinforcing steel needed for the anchor bolt load to be transferred into the concrete is found by Equation B-7 listed below:

(Eq. B-7)FY is the grade of reinforcing steel in this equation. A conservative method of satis-fying Equation B-7 when using A-307 or A-36 bolts and grade 60 reinforcing steel is to provide an area of reinforcing steel equal to the tensile stress area of the bolt. This will slightly oversatisfy Equation B-7.

The reinforcing steel should be placed within a circle having a radius equal to five bolt diameters, using the bolt as the center of the circle. As a minimum, the bolt should have two reinforcing bars within six inches of the bolt and all reinforcement should be distributed evenly. The reinforcing steel should have a minimum clear distance between the bolt head and reinforcing bars of 1 inch or the bolt diameter. Reinforcement should be developed on both sides where it intersects with the surface of the predicted tension failure cone.

Figure B-8 and Standard Drawing GD-Q68922 are developed using this approach.For major equipment, the aforementioned approach may be considered to be too conservative and an alternative design method may be used. This method allows the concrete to crack and transfers the load across the crack by the reinforcing steel. To transfer the load and develop sufficient ductility, the length of the reinforcing steel on either side of the crack should equal or exceed the recommended development length of ACI 318. A minimum edge distance and sufficient stirrups shall be provided to prevent lateral bursting and splitting of concrete caused by the high stress level at the bolt head. Consult with the CRTC Civil/Structural Technical Service Team or a Structural Engineer for this type of application.

Reinforcement Perpendicular to BoltReinforcement perpendicular to the anchor bolt should be placed when the edge distance of the bolt is less than the embedment length of the bolt. This reinforce-ment should consist of continuous spirals of a #3 bar (minimum) with a maximum pitch of six inches, or closed hoops of #4 bar (minimum) spaced at six inches starting two inches from the surface of the concrete and continuing past the bolt embedment length.

ASR1.3P L.F.( )

0.9FY--------------------------=June 1997 B-12 Chevron Corporation

Civil and Structural Manual Appendix BB2.4 Concrete Shear Capacity

Unreinforced ConcreteThe failure cone, developed as shear loads are applied to the anchor bolt in unrein-forced concrete, is illustrated in Figure B-2. This potential failure cone has an apex at the intersection of the bolt and the concrete surface. It projects to the concrete edge, the face of which is parallel to the longitudinal axis of the anchor bolt. If the embedment length is very small, the failure mode for a bolt in shear can be a tension failure cone. Therefore, sufficient embedment depth should be provided to ensure against this failure mode.

The shear capacity, VC , of unreinforced concrete is given by the following expres-sions:

(Eq. B-8)

(Eq. B-9)where:

ASFC = E2

E = distance from the anchor axis to the free edge.

= concrete strength reduction factor. It is always 0.65 except it may be 0.85 in Equation B-9 if hairpin reinforcing bars are used. See Reinforcement Parallel to the Shear Loads.

The shear capacities will change with varying bolt areas and concrete edge distances.

Reinforced ConcreteWith minimum reinforcement, tests show a different behavior for shear than for tension or shear in unreinforced concrete. The shear cone of reinforced concrete is interrupted, and the stress distributed over a wider area than the shear cone of unre-inforced concrete. A value for VC shown by tests [3] is:

(Eq. B-10)where:

fc = specified compressive strength of concrete (psi)

When loaded toward an edge greater than 10 diameters away.

When loaded toward an edge less than 10 diameters away.

VC 800ABT fc=

VC 4ASFC fc=

pi2---

VC 60 fcE=Chevron Corporation B-13 June 1997

Appendix B Civil and Structural ManualWhen the edge distance is greater than nine inches, adding perpendicular rein-forcing has little effect; however, perpendicular reinforcing is recommended for shear loads whenever the edge distance is less than 10 diameters.

Anchor Bolt Interference ShearIf anchor bolts are spaced less than two times their edge distance, the capacity of the shear cone must be reduced. The reduction should be calculated using Equation B-4 and replacing LACT + 0.5h with EACT. The reduced shear cone strength for unreinforced concrete then becomes:

(Eq. B-11)In Equation B-11, VCR can never be greater than VC as calculated by Equation B-8.

There is little information on the effect of anchor bolt spacing on the concrete shear resistance when perpendicular reinforcing is present. Therefore, in the absence of more exacting information, for one bolt interference reduce the concrete shear resis-tance given by Equation B-10 by the bolt spacing divided by two times the edge distance. Equation B-10 then becomes:

For BACT < 2 EACT(Eq. B-12)

When more than one interference exists for a particular bolt, the concrete capacity must be reduced further. This reduction should be based upon engineering judg-ment.

Reinforcement Parallel to the Shear LoadsStudies [11] have shown that using 180 hairpin reinforcing bars around the bolt can increase the shear resistance of the bolt when edge distances are small. The rein-forcing steel should be designed for the required loads according to ACI 318-95. The edge distance should be greater than the critical edge distance shown in Figure B-7. The allowable shear loads should be found in equations B-17 and B-11 using 0.85 for . The value of VCR can not exceed that found by Equation B-8. When using Equation B-8, is always 0.65.The hairpin should be placed directly against the bolt and vertically as close to the concrete surface as possible considering the required concrete cover. The legs of the hairpin must be long enough to satisfy the development lengths described in ACI 31895.

VCR 4 ASFC ALB

2 2---------------- fc=

VCR 60 fcBACT

2--------------=June 1997 B-14 Chevron Corporation

Civil and Structural Manual Appendix BB2.5 Combined Shear and TensionWhen tension and shear act simultaneously, the following interaction formula shall be met:

(Eq. B-13)

B2.6 Factor of SafetyThe factors of safety must satisfy the previously stated design concepts. Factors of safety can be broken down into three groups:

Tension loads, ductile design Tension loads, non-ductile design Shear loads

Tension LoadsDuctile Design

For an anchor bolt to have a ductile performance, the bolt must yield before it is pulled out of the concrete. In design, this can be met by satisfying the following equation:

(Eq. B-14)The bolt yield capacity, PBY, should be determined for A-307 bolts by using the tensile stress area, ABT, and a yield tensile strength, FY, of 33,000 psi.

The recommended safety factor for a ductile performing bolt is 2.7 and is expressed by the following equation:

(Eq. B-15)The value of 2.7 is a calculated value based upon factors found in the UBC [6].Restrictions may exist with certain installations that limit the placement of the anchor bolts. Bolts spaced close together or placed close to the concrete edge inter-fere with the full development of the failure cones in the concrete. This limitation decreases the tension capacity of the concrete cone, and can be calculated using the principles found in Section B2.3. The loss in capacity can be compensated for by increasing the embedment length of the bolt, increasing edge distance, or increasing spacing.

PPA------- 5 3/ VVA--------

5 3/+ 1

PCRPBY

--------------- 1.2

PCRPA

--------------- 2.7Chevron Corporation B-15 June 1997

Appendix B Civil and Structural ManualNon-Ductile Design

Where ductile anchorage systems are not practical, an alternative is an anchorage system governed by concrete properties. Although it is not preferred, this anchorage system may be used for resisting both static and dynamic loads. Care should be taken to avoid using these bolts for resisting earthquake tension loads on large pieces of equipment because the bolts may not have a ductile performance. This alternate system bases the placement of the anchor bolts in the foundation on the actual applied loads rather than on the anchor bolt capacities. A factor of safety of four shall be used with this design as described by the following equations:

(Eq. B-16)The factor of safety is higher than for a ductile failure because a concrete failure is sudden, with no warning.

Shear LoadsAs stated in Section B2.0, steel shear failure has little ductility. Therefore, the required safety factor against concrete breakage can be lower for shear than for tension. The following is recommended:

(Eq. B-17)

B2.7 Allowable Loads

TensionFor a ductile connection, the allowable load of an anchor bolt is the lesser of that based on the steel properties of the bolt, PB, or that based on the tension failure cone capacity, PCR, of the concrete with a factor of safety of 2.7

PCRP

--------------- 4

VCRVA

---------------- 1.9

whichever is lessPA PB=

or,

PAPCR

2.7---------------=June 1997 B-16 Chevron Corporation

Civil and Structural Manual Appendix BPB is shown in Figure B-5. PCR should be calculated in accordance with Section B2.3.

For connections that do not meet the ductility requirement of Section B2.6, the required tension failure cone strength is based upon the applied load rather than on the anchor bolt capacity. The required factor of safety is 4.0.

ShearThe allowable shear load for a bolt is the lesser of that based on the steel properties of the bolt, VB, or that based on the concrete properties, VCR, with a safety factor of 1.9.

VB is shown in Figure B-5. VCR should be calculated according to Section B2.4.

B2.8 Standard Drawing GD-Q68922The values shown on Standard Drawing GD-Q68922 are for ASTM A-307 bolts and concrete with a specified concrete strength, fc , of 3000 psi.

Figure B-8 repeats the same information listed on the standard drawing, but has been expanded to include larger bolts.

whichever is less

PPCR

4---------------=

VA VB=

or

VAVCR

1.9----------------=

Fig. B-8 Standard Anchor Bolts (1 of 2)

BOLT DIAMETER

(IN)

TENSILESTRESS

AREA(IN2)

EMBEDMENTLENGTH (IN)

EDGEDISTANCE

(IN)

MINIMUMSPACING

(IN)

TENSIONCAPACITY

WITH PARALLELREINFORCEMENT

CASE A(LBS)

SHEARCAPACITY

WITH MINIMUMREINFORCEMENT

CASE B (LBS)

TENSIONCAPACITY WITHOUT

PARALLELREINFORCEMENT

CASE B( LBS)

d ABT L E B PA VA

1/2 0.142 6 4 7 2,800 1,300 2,800

5/8 0.226 8 4 9 4,500 2,000 3,700

3/4 0.334 9 5 10 6,700 3,000 5,200

7/8 0.462 11 6 12 9,200 4,200 7,500

1 0.606 12 6 16 12,100 5,500 9,700

1-1/8 0.763 14 7 18 15,300 6,900 12,800

1-1/4 0.969 15 8 20 19,400 8,900 16,200Chevron Corporation B-17 June 1997

Appendix B Civil and Structural ManualThe embedment length, edge distance, and bolt spacing listed on Standard Drawing GD-Q68922 are as follows:

The bolt embedment length of 12d was used because with the edge distance and bolt spacing shown on the standard drawing, PCR increases very little with embed-ment depths greater than 12d. The edge distance of 6d is from the UBC and will also meet the blowout requirements listed in Figure B-7. The bolt spacing was set to satisfy Equation B-15 for bolts with parallel reinforcement and assuming the bolt geometry shown in Figure B-9.

The tension capacities with parallel reinforcing were determined according to the AISC Specification for Structural Steel Buildings (1989 Edition), using the tensile stress area instead of the nominal area. The allowable corner bolt and tension without parallel reinforcing values are based upon a ductile failure and the safety factor of Equation B-15; and the embedment, spacing, and edge distances shown on the standard drawing. The allowable shear loads are the lesser of VB shown in Figure B-5 or that found by Equation B-17 using the geometries listed on the stan-dard drawing.

Two graphs are shown on the standard drawing. An interaction graph is given for simultaneous shear and tension loads. This graph applies in all cases with the given spacing, geometries, and allowable forces shown on the standard drawing. The other graph given is a scaling graph which adjusts for concrete with other than 3000 psi specified compressive strength. This scaling graph can be used by simply multiplying the table value by the factor corresponding to the specified design concrete compressive strength. This table applies to tension without parallel rein-forcing and corner bolt values only.

1-1/2 1.41 18 9 24 28,200 10,200 21,900

1-3/4 1.90 21 11 28 38,000 14,400 31,300

2 2.50 24 12 32 50,000 17,100 39,000

2-1/2 4.00 30 15 43 80,000 26,700 64,700

3 5.97 36 18 51 119,400 38,400 92,300

Fig. B-8 Standard Anchor Bolts (2 of 2)

BOLT DIAMETER

(IN)

TENSILESTRESS

AREA(IN2)

EMBEDMENTLENGTH (IN)

EDGEDISTANCE

(IN)

MINIMUMSPACING

(IN)

TENSIONCAPACITY

WITH PARALLELREINFORCEMENT

CASE A(LBS)

SHEARCAPACITY

WITH MINIMUMREINFORCEMENT

CASE B (LBS)

TENSIONCAPACITY WITHOUT

PARALLELREINFORCEMENT

CASE B( LBS)

d ABT L E B PA VA

L = 12dE = 6dB = 13d for d

Civil and Structural Manual Appendix BSince the allowable loads for the tension with parallel reinforcing and most of the shear values are based upon the steel strength of the bolt, these values can not be increased beyond those shown on the standard drawing. They can, however, be decreased for concrete strengths below 3000 psi.

Since the tension without parallel reinforcing and the corner bolt values are limited by the concrete strength, these values can be increased when edges greater than those listed on the standard drawing are used. For the corner bolt values, the new allowable load is found by multiplying the value listed on the standard drawing by (EACT / E)2. The value of E in this case is shown on Standard Drawing GD-Q68922. For the tension without parallel reinforcing values, the new allowable load is found by multiplying the listed value by (EACT /E). The new allowable loads can never exceed the tension with parallel reinforcing values. At some edge distance then, the tension capacity with parallel reinforcement values can be used without including the parallel reinforcement. A simple way for omitting the parallel rein-forcement when using these values is to increase the edge distance listed on the standard drawing by 1/3.

B3.0 Special Design For Anchor Bolt Load Transfer to Reinforcing Steel

Unlike the previous sections, this design concept utilizes the full strength of the reinforcing bar rather than the concrete shear cone to resist the anchor bolt forces. It is assumed that the anchor bolt tension and shear forces are transferred to the piers vertical reinforcement and ties, respectively. The critical edge distances (with or without minimum reinforcement) and critical bolt spacing shown in

Fig. B-9 Anchor Bolt Arrangement Assumed on the Standard DrawingChevron Corporation B-19 June 1997

Appendix B Civil and Structural ManualFigure B-7 can be used without any capacity reduction if all detailing requirements presented in this section are fully adhered.

The method for load transfer is as follows:

The procedure to determine the required size of anchor bolts in reinforced concrete is basically the same as that for anchor bolt in plain concrete described in Section B2.1 and B2.5 which is based on the bolts allowable load shown in Figure B-5 and satisfying the shear-tension interaction ratio per Equation B-13.

B3.1 Reinforcement For Tension ForceA recommended arrangement of reinforcement for resisting concrete tensile stress in pier foundation of square, rectangular, and octagonal cross-section is shown in Figures B-10 and B-11. Vertical pier reinforcement intercepts potential crack planes adjacent to the bolt head. The reinforcement should be developed on both sides of the potential crack plane. To be considered effective, the distance of the reinforcement from the anchor bolt head should not exceed the lesser of one-third of ld or 6 inches as required by ACI 349. In order to minimize the embedment length of a bolt, a larger number of smaller-size bars is preferred over fewer, larger-size bars. In larger foundations, such as an octagon, two concentric layers of vertical reinforcement may be provided (as shown on Figure B-11) if required.The arrangement of reinforcement should take into consideration the minimum clearance for placing and vibrating of concrete, minimum bar spacing required by ACI 318, and the need for adequate room below the bolt head or nut to ensure there is sufficiently compacted concrete.

The required area of reinforcing steel needed to resist the tension force transferred from the anchor bolt is found by Equation B-18:

(Eq. B-18)

- Tension force: Transfer tension through vertical pier reinforcement, i.e., no additional bar or hairpin is needed.

- Shear force: Transfer shear through ties in the pier.- Lateral bursting force: Provide side cover which is sufficient to prevent side

bursting, i.e.,ECR (w/o reinforcement) in Figure B-7. Alternatively, provide ties at bolt head and provide minimum side cover ECR (w/ min. reinforcement) in Figure B-7.

ASRTU

Fy----------=June 1997 B-20 Chevron Corporation

Civil and Structural Manual Appendix Bwhere:ASR = the area of vertical pier reinforcement per bolt, in2.

TU = factored tensile load per bolt, kips (ACI 318-95, Chapter 9)Fy = minimum specified yield strength of reinforcement steel, ksi

= 0.90, strength reduction factor (ACI 318-95, Chapter 9). Chevron Corporation B-21 June 1997

Appendix B Civil and Structural ManualFig. B-10 Reinforcement for Resisting Bolt Tension in Square and Rectangular PedestalsJune 1997 B-22 Chevron Corporation

Civil and Structural Manual Appendix BFig. B-11 Reinforcement for Resisting Bolt Tension in Octagons Chevron Corporation B-23 June 1997

Appendix B Civil and Structural ManualFor ductile performance, the bolt must yield prior to yielding the reinforcing bar. To achieve this condition, the factored load TU in Equation B-18 should be set equal to or larger than the nominal tension capacity of the bolt i.e., TU = 0.75 FUB ABT. When using A307 or A36 bolts and grade 60 reinforcing steel, (FUB = 60 ksi and Fy = 60 ksi.) Equation B-18 becomes:

ASR = 0.883 ABT(Eq. B-19)

where:ABT = tensile stress area of bolt.

A conservative method of satisfying Equation B-18 when using A307 or A36 bolts and grade 60 steel is to provide an area of reinforcing steel equal to the tensile stress areas of the bolt.

The area of vertical pier reinforcement calculated using Equation B-18 is not to be considered as additive to the reinforcement required strictly for resisting the moment and tension in sections of the pier. The anchor bolt tension load should have already been included in the loads used in determining the required vertical reinforcement in the pier. Therefore, calculated area of steel required for resisting the external loads applied to the pier should be compared with the area of steel required for resisting the tension force in the anchor bolts. The area of vertical pier steel provided should equal or exceed the area of steel required for resisting the anchor bolt tension.

B3.2 Reinforcement For Shear ForceFigure B-2 illustrates a shear failure cone in unreinforced concrete resulting from a shear force applied to an anchor bolt toward an edge of the concrete. This type of failure is generally caused by inadequate edge distance. To reinforce the concrete in the failure plane, 2 sets of ties at 3 inch spacing are provided at the top of the piers. The first set of ties should be located at 2 inches from the top of pier.

Figure B-12 illustrates the arrangement of tie reinforcement to resist shear force in typical square and rectangular piers. To be considered effective, the ties should be placed such that they intercepts the potential crack plane. Equation B-20 is used to calculate the required area of steel to resist the shear force.

(Eq. B-20)where:

ASV = area of reinforcement (one leg of tie) required, in2.VU = factored shear force resisted by the bolt, kips (ACI 318-95,

Chapter 9)

ASVVU

Fyn--------------=June 1997 B-24 Chevron Corporation

Civil and Structural Manual Appendix BFy = minimum specified yield strength of reinforcement steel, ksi

n = number of legs in the top 2 sets of ties resisting the shear force. In Figure B-12, the failure plane only intersects the top tie, thus n = 1 for section A and n = 2 for section B.

= 0.85, strength reduction factor (ACI 318-95, Chapter 9)As an alternative to tie reinforcement, an equivalent spiral reinforcement may be used.

For large shear forces, it is more economical and reliable to use steel shear lugs to transfer the load to the concrete pier. In order to uniformly distribute the shear force on the top of the pier, the shear lug should be oriented perpendicular to the direction of the shear force.

B3.3 Reinforcement For Lateral Bursting ForceFigure B-3 illustrates lateral bursting failure in unreinforced concrete resulting from the bolt tension forces. This type of failure is generally caused by inadequate edge distance or confinement at the bolt head. The minimum edge distance required for preventing lateral bursting at the bolt head of concrete with no reinforcement calcu-lated using the ACI 349 criteria, for ASTM A 307 or A36 bolts, is about 5 times bolt diameter, and is shown in Figure B-5 as ECR (w/ no reinf.). A smaller edge distance is allowed, such as ECR (w/ min reinf.) shown in Figure B-7, if transverse reinforcement (ties) or hairpins at the bolt head are provided. Figures B-10, B-11, and B-12 illustrate typical arrangements of ties and hairpins for confinement at the bolt head. The required area of reinforcing steel to resist the lateral bursting force can be calculated using Equation B-21 as follows:

(Eq. B-21)where:

ASB = area of reinforcement (one leg of tie) required, in2. = 0.25, lateral force coefficient (ACI 349)

TU = factored tensile load per bolt, kips

Fy = minimum specified yield strength of reinforcement steel, ksi

n = number of legs of the 2 sets of ties at the bolts head. In Figure B-12, the failure plane only intersects the top tie, thus n = 1 for section A and n = 2 for section B. In Figure B-11, n = 4 for 2 sets hairpin.

= 0.85, strength reduction factor (ACI 318-95, Chapter 9)

ASBTUFyn--------------=Chevron Corporation B-25 June 1997

Appendix B Civil and Structural ManualFig. B-12 Reinforcement for Resisting Bolt Shear in Square and Rectangular PedestalsJune 1997 B-26 Chevron Corporation

Civil and Structural Manual Appendix BFor ductile performance, TU should be set equal to or larger than the ultimate capacity of the bolt i.e., TU = FUB. ABT. When using A307 or A36 bolts and grade 60 reinforcing steel, i.e., FUB = 60 ksi and Fy = 60 ksi., Equation B-21 becomes:

ASB = 0.29 ABT(Eq. B-22)

As an alternative to tie reinforcement, an equivalent spiral reinforcement may be used.

B3.4 Bolt Embedment and Reinforcing Steel Development LengthFigures B-10, B-11, and B-12 illustrate the anchor bolt and reinforcing steel arrangement and requirement to ensure a reliable of load transfer from bolt to rein-forcing bar, and ductility of the anchor bolt system. From these figures, it can be seen that the required bolt embedment length (L) may be controlled by the develop-ment length of the reinforcing bar, which can be determined as follows:

L = ld + 2 inches (Top clear cover) + (L/3 or 6 inches max)Using the 6 inch max spacing between bolts head and the parallel bar, this equation can be reduced as follows:

L= ld + 8 inches

ld is the development length of the reinforcing steel determined in accordance with ACI 318-95. It should be noted that the reinforcing steel must be developed on both sides of the failure cone. For straight bars, Gr. 60, concrete strength of 3000 psi, and minimum clear cover of 2.5 inches, the development length is as follows:

Figure B-13 shows the bolts embedment length required for various reinforcing bar combinations. The critical edge distance and bolt spacing from Figure B-7 are also included in the table.

Shorter development lengths than are shown above can be used if the reinforcing bar is terminated in a standard hook. The required development length for rein-forcement terminating in a standard hook should also be determined in accordance with ACI 318-95. When the reinforcing bar inside the failure cone (i.e., above the bolt head) is terminated in a standard hook, it should be bent toward the anchor bolt.

for # 3 through #6 bars ld = 27 db L = 27 db + 8 inchesfor # 7 through #10 bars ld = 33 db L = 33 db + 8 inchesfor #11 and larger bars ld = 55 db L = 55 db + 8 inchesChevron Corporation B-27 June 1997

Appendix B Civil and Structural ManualB4.0 Design ProcedureThe design concepts presented in the previous sections are outlined below to assist in placing standard A-307 anchor bolts in concrete foundations. This general proce-dure addresses alternatives and special conditions for different embedment lengths, bolt spacings, and edge distances. In general, Standard Drawing GD-Q68922 will cover most cases. Determining design loads is not covered; however, these loads can be computed from other design practices and computer programs depending on the type of structure or equipment that is being investigated.

B4.1 Basic Design Steps Where Standard Drawing Limitations Can be MetDesign should begin by calculating the design loads on the anchor bolts and deter-mining their physical placement limitations. If the main loads are due to wind or earthquake, the allowable loads given on the standard anchor bolt drawing (GD-Q68922) may be increased by one third. An anchor bolt size should be selected from the standard drawing so that its capacity is greater than the loads placed on it. Shear/tension interaction should be checked in accordance with the interaction graph.

If any spacing, edge distance, or embedment requirements cannot be met by increasing the size of the foundation, an additional design is required.

Where design for reinforcement parallel to the bolt is required, it must be devel-oped as described in Section B2.3.

A more detailed procedure for anchor bolts that meet the limitations of the standard drawing can be found in subsection 241 of this manual.

Fig. B-13 Critical Dimension and Size of Reinforcing Steel (fc = 3000 psi and Fy = 60,000 psi)

BOLT TENSILE MINIMUM MINIMUM MINIMUM MINIMUM PARALLEL REBARS AND BOLT EMBEDMENT LENGTHDIAMETER STRESS EDGE EDGE C. TO C. REBAR SIZE EMBEDMENT REBAR SIZE EMBEDMENT REBAR SIZE EMBEDMENT

(IN) AREA DISTANCE DISTANCE SPACING LENGTH LENGTH LENGTH(with min. reinf.) (with no .reinf)

d ABT Ecr Ecr Bcr db L db L db L(IN2) (IN) (IN) (IN) (1 bar) (IN) (2 bars) (IN) (4 bars) (IN)

1/2 0.142 4 4 6 #4 22 2 - #3 19 - -5/8 0.226 4 4 6 #4 22 2 - # 3 19 - -3/4 0.334 4 4 6 #5 25 2 - #4 22 4 - #3 197/8 0.462 4 5 6 #6 28 2 - #4 22 4 - #3 191 0.606 6 5 6 # 7 37 2 - #5 25 4 - #4 22

11/8 0.763 6 6 6 # 8 41 2 - #5 25 4 - #4 2211/4 0.969 6 7 6 #8 41 2 - #6 28 4 - #4 2211/2 1.41 6 8 6 #10 50 2 - #7 37 4 - #5 2513/4 1.9 6 9 6 #11 84 2 - #8 41 4 - #6 282 2.5 6 11 6 - - 2 - #10 50 4 - #7 37

21/2 4 8 13 8 - - - - 4 - #9 463 5.97 8 16 8 - - - - 4 - #10 50June 1997 B-28 Chevron Corporation

Civil and Structural Manual Appendix BB4.2 Design Steps Where Standard Drawing Limitations Cannot be Met

Step 1. Basic Design Steps

Follow the basic design steps listed in Sub-section 241 of this manual to get a preliminary solution.

Step 2. Check Critical Spacing, Edge Distance, and Embedment Length

Check the geometric limitations given (edge distance, etc.) against the values found in Figure B-7. If the values cannot be met, one of the following alternatives may be used:

1. Increase foundation size.

2. Revise anchor bolt configuration using:

smaller bolts for restrictive edge distances, or larger bolts for restrictive bolt spacing.

3. Increase concrete strength.

Step 3. Options where Interference Exists

For cases where the dimensions listed on Standard Drawing GD-Q68922 cannot be met, due to interference from adjacent bolts and/or edge distance, the tension and shear strength of the concrete should be checked using the following procedure:

1. Check the tension failure cone

This procedure is valid only if the critical dimensions listed in Figure B-7 can be met. If they cannot, see alternatives recommended in Step 2.

a. Lay out bolt arrangement, and define the tensile failure planes. Find the tensile failure cone capacity reduced for bolt interference and edge distance (PCR) described in Section B2.3, assuming no parallel rein-forcing steel is present ( = 0.65).

b. If PCR >1.2 PBY, the connection is ductile. Proceed to step c.If PCR < 1.2 PBY, the following options exist:1. Increase edge distance.

2. Increase bolt spacing.

3. Increase embedment length.

4. Add reinforcing steel parallel to bolt ( = 0.85).5. Increase concrete strength.Chevron Corporation B-29 June 1997

Appendix B Civil and Structural Manual6. Design for concrete failure using Equation B-16. (Not recommended for earthquake loads).

If one of the options 1 through 5 is chosen, PCR is recalculated and this step is repeated.

c. If PCR > 2.7 PA, the full allowable anchor bolt load, PB, listed in Figure B-5 can be used.If PCR < 2.7 PA, the following options exist:1. Increase edge distance.

2. Increase bolt spacing.

3. Increase embedment length.

4. Add reinforcing parallel to the bolt ( = 0.85).5. Use a lower allowable load PA =

6. Increase concrete strength.

2. Check the shear failure cone

Since the steel strength of the anchor bolt controls for most of the bolts listed on the standard drawing, the allowable shear load of a bolt not meeting the required place-ment dimensions may be the same. To find the allowable load, use the following procedure:

a. Calculate VCR as described in section B2.4b. Find the allowable shear load, VA, on the bolt by taking the lesser of

or VB listed in Figure B-5. If more shear resistance is

needed, use one of the following options:

1. Use a shear key.

2. Increase edge distance.

3. Increase bolt spacing.

4. Include hoop reinforcing bars for shear (see Step 4).5. Increase concrete strength.

6. Design connection so that the threads of the bolt are out of the shear plane.

Options 2 through 5 will increase the allowable bolt shear loads when the concrete properties control. When option 6 is used, the gross area instead of the root area can be used in calculating the allowable bolt shear capacity, VB. This will increase the allowable bolt shear load, VA, when the steel strength of the bolt governs.

PCR2.7

---------------

VCR1.9----------------June 1997 B-30 Chevron Corporation

Civil and Structural Manual Appendix BStep 4. Adding Reinforcement

Adding reinforcement parallel to the applied loads can increase the reliability and ductility of the anchor bolt system. Therefore, a of 0.85 instead of 0.65 can be used. The reinforcing steel must be able to resist the required loads and be fully developed on both sides of the failure cone as described in section B2.3. The following procedure is recommended:

1. Provide parallel reinforcing steel according to the following.

(Tension)

For tension, the above can be met by providing an area of reinforcing steel (60 ksi) parallel to the bolt and equal to or greater than the bolt area. The minimum number of reinforcing bars is two, and the bars should be spaced equally around the bolt within a radius as described in Section B2.3.

As mentioned earlier, 180 hairpin reinforcing bars can increase the shear resis-tance of a bolt when edge distances are small. Hairpin steel should be placed as described in Section B2.4.

Reinforcement perpendicular to the bolt should be included according to Section B2.3.

2. Develop the reinforcing steel.

Reinforcing steel must be developed on both sides of the failure cone according to ACI 318-95 with confinement steel as described in Section B2.3. Hairpin legs should be developed according to ACI 318-95. If the reinforcing bars cannot be developed, the following options exist:

a. Reconfigure the reinforcing with smaller bars.

b. Use a lower reinforcing steel yield strength.

c. Increase foundation thickness and/or bolt embedment.

d. Increase concrete compressive strength.

B5.0 Design Examples

B5.1 Design Example 1Determine the anchor bolt diameter and placement dimensions required to anchor a vertical pressure vessel to a reinforced concrete foundation. Assume the anchor bolt circle diameter and number of anchor bolts are fixed due to the vessel design.

The anchor bolt layout and foundation are shown in Figure B-14.

Given:

ASR1.3P L.F.( )

0.9FY--------------------------=Chevron Corporation B-31 June 1997

Appendix B Civil and Structural ManualEarthquake Loads (Simultaneous):P = 16,000 lbs/bolt

V = 3,200 lbs/bolt

Geometric Conditions:

Anchor bolt spacing: 13.7 inches

Edge distance: 4.5 inches

In the solution (given next), standard drawing refers to GD-Q68922.Solution:

1. Find anchor bolt diameter:

Try a 1 inch diameter bolt. From the standard drawing, PA = 12,100 lbs. Since the loads are seismic, the allowable values may be increased by 1/3.

2. Check shear:

3. Check tension:

Fig. B-14 Anchor Bolt Layout and Foundation (Design Example 1)

VA = 5,500 lbs (from standard drawing)V = 3,200 lbs < 1.33 VA = (1.33) 5,500 = 7,300 lbs OK

P = 16,000 lbs < 1.33 PA =(1.33)12,100 = 16,100 lbs OKJune 1997 B-32 Chevron Corporation

Civil and Structural Manual Appendix BCheck interaction:

Therefore: No Good

Note 1.33 VA and 1.33 PA were substituted for VA and PA in the interaction equation because the loads are seismic.

4. Choose a larger bolt. d = 1-1/8 inch

Check interaction:

Therefore: Bolt size is O.K.

5. Check spacing:

It is readily apparent that the design cannot be met using the values printed on the standard anchor bolt drawing; therefore, use the procedure detailed in this appendix. Since the bolt spacing provided is less than that shown on the stan-dard drawing but greater than the critical spacing, Step 3 (Options where Inter-ference Exists) will be required.

6. Evaluate the bolts for interference: (Step 3)Tension failure cone capacity

PA = 15,300 lbs (from standard drawing)1.33 PA = (1.33)15,300 = 20, 400 lbsVA = 6,900 lbs (from standard drawing)1.33 VA = (1.33)6,900 = 9,200 lbs

BACT = 13.7 inches (from equipment requirement)B = 18 inches (from standard drawing)BCR = 6.0 inches (From Figure B-7)6 inches < 13.7 inches < 18 inchesTherefore: No Good

V1.33VA------------------

3 200,7 300,------------- 0.44= =

P1.33PA-----------------

16 000,16 100,---------------- 0.99= =

P1.33PA----------------- 5 3/ V1.33VA------------------

5 3/+ 1.24 1.0>=

P1.33PA-----------------

16 000,20 400,---------------- 0.78 V1.33VA

------------------

3 200,9 200,------------- 0.35= = = =

P1.33PA-----------------

5 3/ V1.33VA------------------

5 3/+ 0.84 1.0

Appendix B Civil and Structural ManualBecause the bolt spacing cannot be changed and the edge distance is less than the edge distance shown on the standard drawing, the capacity of the tensile failure cone PCR will not meet our required safety factors and needs to be increased. Therefore, increase the edge distance E to that recommended on the standard drawing and check the concrete cone strength.

(Eq. B-2)From Equation B-4

(per bolt interference), ALB = 2(212) in this example

Therefore, we have a non-ductile connection. Since the loads are seismic, ductility is particularly important. Therefore, choose one of the options that will increase the concrete cone strength. Try increasing the edge distance to 9 inches.

EACT = 9 inches

Recalculating the concrete cone strength

Therefore, the connection is ductile.

EACT 7=

LACT 14=

PCR fc 2.8 AS ALB( )[ ]EACTLACT--------------=

AS pi 2 LACT h+( )LACT 976 in2= =

ALB LACT 0.5h+( )2COS 10.5BACT

LACT 0.5h+------------------------------- 0.5BACT LACT 0.5h+( )2 0.5BACT( )2[ ]1 2/ 2=

ALB 212 in2=

PCR 0.65 3 000, 2.8 976 2 212( )( )[ ]7

14------ 27 500 lbs,= =

PBY 33 000 ABT( ), 25 180 lbs,= =PCR PBY 1.09 1.2= =June 1997 B-34 Chevron Corporation

Civil and Structural Manual Appendix BTherefore, since the maximum allowable bolt load is desired, increase the concrete design strength, PCR, by adding parallel reinforcing steel, is then 0.85.

Alternatively, the edge distance could be increased to 11 inches and parallel rein-forcing would not be required.

Shear failure cone capacity

Since EACT is 9 inches, calculate the shear cone capacity assuming unreinforced concrete. From Equation B-11:

ALB for shear is:

Check if the required safety factor is met.

OK

Therefore, the full allowable shear load may be used. Note that since VCR/VB > 1.9, the full allowable shear load based on the steel properties could be used, i.e., VA = VB = 7,090 lbs.

7. Adding Reinforcement (Step 4)Parallel:

Provide ASR = ABT = 0.763 in2 within a maximum radius of five bolt diame-ters = 5.6 inches and a minimum radius of 1-1/8 inches + h/2 + db/2 = 2.22

PCRPA

---------------

35 400,15 300,---------------- 2.31 2.7= =

VCR 4 ASFCALB2 2

--------------- fc=ASFC

pi2---EACT

pi2--- 9( )2 127 in2= = =

ALB EACT( )2COS 10.5BACT

EACT---------------------- 0.5BACT EACT( )2 0.5BACT( )2[ ]1 2/ 2=

ALB 24 in2=

VCR 0.65 4( ) 127 2 24( )

2 2-------------- 3 000,=

VCR 15 670 lbs,=

VCRVA

----------------

15 670,6 900,---------------- 2.27 1.9

Appendix B Civil and Structural Manualinches (#4 bar assumed). The minimum radius satisfies the required clear distance between the bolt head and the reinforcing steel.

Use four #4 bars in a five-inch radius circle.

Perpendicular: (from paragraph B2.3)Use hoop ties which require #4 bars in a closed hoop with a maximum spacing of six inches.

8. Developing the Reinforcement

From the standard drawing, the development length needed is 17 inches for a straight bar and eight inches for a hooked bar.

With the reinforcing bar at five inches from the bolt, the bar needs to extend:

above the bolt head without a hook

below the bolt head, assuming a hook

Since 21.1 inches > LACT = 14 inches, hook the top end of the reinforcing bar.

OK

Also, increase the foundation thickness by one inch to accommodate the rein-forcing bar.

Summary:

Use 1-1/8 inch diameter bolts with an embedment of 14 inches, given spacing of 13.7 inches and an edge distance of nine inches. Use four #4 bars spaced evenly around each bolt and hooked on both ends, and #4 closed hoop ties at two inches from the top of the pedestal and six inches below the top mat. The total foundation thickness is 21 inches.

B5.2 Design Example 2Determine the anchor bolt diameter and placement dimensions required to anchor a structural column to a reinforced concrete foundation. Assume that the anchor bolt spacing and number of anchor bolts are fixed due to the column design.

The anchor bolt layout and foundation are shown in Figure B-15

Given:Loads: (Simultaneous)

17 5 h2--- + 21=

8 5 h2--- 3.8=

8 5 h2--- + 12.1 14

Civil and Structural Manual Appendix BP = 5,000 lbs (only the two western most bolts at once)V = 1,400 lbs

Geometric Condition:

Anchor bolt spacing: 8

Edge distance: 18 inches

In the solution (given next), standard drawing refers to GD-Q68922.

Solution:1. Find anchor bolt diameter:

From the standard drawing, try 3/4-inch diameter bolt; PA= 6,700 lbs.

Since the loads are not from wind or earthquake, the allowable loads are not increased by 1/3.

PA = 6,700 lbs > P = 5,000 lbs OK

2. Check shear:

From the standard drawing VA = 3,000 lbs.

VA = 3,000 lbs > V = 1,400 lbs OK

3. Check interaction:

Fig. B-15 Anchor Bolt Layout and Foundation (Design Example 2)Chevron Corporation B-37 June 1997

Appendix B Civil and Structural Manual4. Check spacing:

The required spacing is less than given for the standard drawing. It is, however, more than critical (see Design Step 2, Section B4.2); therefore, the standard drawing limitations cannot be met. Step 3 (Options Where Interference Exists) will be required.

5. Check edge distance:

6. Find embedment:

Since the depth of the foundation is 18 inches and minimum cover is three inches, this embedment is O.K.

7. Evaluate the bolts for interference. Since only the two bolts 8 inches apart are in tension, only their interference is considered below:

Tension failure cone capacity

where:

LACT = 9 inches

EACT = 18 inches > LACT ( Use EACT = 9 inches for Equation B-5 above)

BACT = 8 inches

h = 1.125 inches

BACT = 8 inches (from column design)B = 9 inches (from standard drawing)BCR = 6 inches (from Figure B-7)

EACT = 18 inches (from column design)E = 5 inches (from standard drawing)EACT > E OK

L = 9 inches (from standard drawing)

PPA-------

5 000,6 700,------------- 0.75= =

VVA--------

1 400,3 000,------------- 0.47= =

PPA-------

5 3/ VVA--------

5 3/+ 0.75( )5 3/ 0.47( )5 3/+ 0.90 1.0 OK

Civil and Structural Manual Appendix B = 0.65 (No parallel reinforcement assumed)With these five initial numbers, the rest is determined.

AS = (9 + 1.125) 9 = 405 in2

Similarly:

ALB = 98 in2 (For the interference of the bolt 8 inches away)PCR = 30,600 lbs

PBY = 33,000 ABT = 11,020 lbs

PCR/PBY = 2.78 > 1.2Therefore, the connection is ductile.

Since PCR/PA > 2.7, the full allowable load can be used.Shear failure cone capacity

Since EACT is much greater than that listed on the standard drawing, and BACT is only slightly smaller, it is readily apparent that the concrete shear strength is OK.

8. Adding reinforcement

Parallel:

Since 0.65 was used for when calculating PCR, reinforcement parallel to the bolt is not required.

Perpendicular:

Since EACT is greater than L, and EACT > 10d, additional horizontal reinforce-ment is not required for the anchor bolts.

Summary:

Use 3/4-inch diameter anchor bolts with an embedment of 9 inches and the column bolt spacing of 8 inches. No additional reinforcement is required for the given edge distance.

B6.0 References1. Tennessee Valley Authority, Civil Design Standard DS-C6.1, Concrete

Anchorages, August 1976.

2. Prestressed Concrete Institute Design Handbook, Welded Headed Studs, Part 6.1.13, First Edition 1972.

pi 2

PCRPA

---------------

30 600,6 700,---------------- 4.57 2.7>= =Chevron Corporation B-39 June 1997

Appendix B Civil and Structural Manual3. California Department of Transportation, Lateral Resistance of Anchor Bolts Installed in Concrete, Technical Report, May 1977 (Report No. FHWA-CA-ST-4167-77-12).

4. J. E. Breen, Center for Highway Research, The University of Texas, Develop-ment Length for Anchor Bolts, Technical Report, April 1964.

5. Tennessee Valley Authority, Division of Engineering Design, Anchorage to Concrete, Technical Report, December 1975 (Report No. CEB 75-32).

6. International Conference of Building Officials, Uniform Building Code, Volume II, Section 1925, Anchorage to Concrete, 1994 Edition.

7. ACI Journal, Proposed Additions to Code Requirements for Nuclear Safety and Related Concrete Structures (ACI 349-76), Report Title Number 75-35, August 1978.

8. Concrete International, Guide to the Design of Anchor Bolts and Other Steel Embedments, Vol. 3 No. 7, July 1981.

9. The University of Texas, Tensile Capacity of Short Anchor Bolts and Welded Studs, by R. E. Klingner and J. A. Mendonca, June 1981.

10. R. E. Klingner and J. A. Mendonca Shear Capacity of Short Anchor Bolts and Welded Studs: A Literature Review, ACI Journal, September - October 1982. (pp. 339 - 349)

11. R. E. Klingner, J. A. Mendonca, J. B. Malik Effect of Reinforcing Details on the Shear Resistance of Anchor Bolts Under Reversed Cyclic Loading, ACI Journal, January-February 1982 (pp. 3-12)

12. A. F. Shaikh and W. Yi In-Place Strength of Welded Headed Studs, PCI Journal, March - April 1985. (pp. 56-81)

13. ASCE Publication, Design of Anchor Bolts in Petrochemical Facilities, 1996.June 1997 B-40 Chevron Corporation

Manual ContentsApp. B ContentsB1.0 IntroductionB1.1 Failure ModesB1.2 Nomenclature

B2.0 Design ConceptsB2.1 Bolt CapacitiesB2.2 High-strength BoltsB2.3 Concrete Tensile CapacityB2.4 Concrete Shear CapacityB2.5 Combined Shear and TensionB2.6 Factor of SafetyB2.7 Allowable LoadsB2.8 Standard Drawing GD-Q68922

B3.0 Special Design For Anchor Bolt Load Transfer ...B3.1 Reinforcement For Tension ForceB3.2 Reinforcement For Shear ForceB3.3 Reinforcement For Lateral Bursting ForceB3.4 Bolt Embedment and Reinforcing Steel Developm...

B4.0 Design ProcedureB4.1 Basic Design Steps Where Standard Drawing Lim...B4.2 Design Steps Where Standard Drawing Limitatio...

B5.0 Design ExamplesB5.1 Design Example 1B5.2 Design Example 2

B6.0 ReferencesEngineering SpecificationsStandard Drawings & Forms