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Dongxiao Wu P. Eng. (Alberta, Canada)

 

Home  >> Tutorial >>  Design of Anchorage to Concrete Using ACI 318-08 & CSA A23.3-04 Code 

 

 

TABLE OF CONTENTS

 

1.0   INTRODUCTION.. 2

2.0   DESIGN EXAMPLES.. 6

Example 01: Anchor Bolt + Anchor Reinft + Tension & Shear + ACI 318-08 Code. 6

Example 02: Anchor Bolt + Anchor Reinft + Tension & Shear + CSA A23.3-04 Code. 13

Example 03: Anchor Bolt + Anchor Reinft + Tension Shear & Moment + ACI 318-08 Code. 20

Example 04: Anchor Bolt + Anchor Reinft + Tension Shear & Moment + CSA A23.3-04 Code. 28

Example 11: Anchor Bolt + No Anchor Reinft + Tension & Shear + ACI 318-08 Code. 36

Example 12: Anchor Bolt + No Anchor Reinft + Tension & Shear + CSA A23.3-04 Code. 44

Example 13: Anchor Bolt + No Anchor Reinft + Tension Shear & Moment + ACI 318-08 Code. 52

Example 14: Anchor Bolt + No Anchor Reinft + Tension Shear & Moment + CSA A23.3-04 Code. 60

Example 21: Welded Stud + Anchor Reinft + Tension & Shear + ACI 318-08 Code. 68

Example 22: Welded Stud + Anchor Reinft + Tension & Shear + CSA A23.3-04 Code. 75

Example 23: Welded Stud + Anchor Reinft + Tension Shear & Moment + ACI 318-08 Code. 82

Example 24: Welded Stud + Anchor Reinft + Tension Shear & Moment + CSA A23.3-04 Code. 90

Example 31: Welded Stud + No Anchor Reinft + Tension & Shear + ACI 318-08 Code. 98

Example 32: Welded Stud + No Anchor Reinft + Tension & Shear + CSA A23.3-04 Code. 105

Example 33: Welded Stud + No Anchor Reinft + Tension Shear & Moment + ACI 318-08 Code. 112

Example 34: Welded Stud + No Anchor Reinft + Tension Shear & Moment + CSA A23.3-04 Code. 119

Example 41: Shear Lug Design ACI 349-06 Code. 126

Example 42: Shear Lug Design ACI 349M-06 Code. 130

Example 51: Base Plate (LRFD) & Anchor Bolt (ACI 318-08) Design With Anchor Reinforcement 134

Example 52: Base Plate (S16-09) & Anchor Bolt (CSA A23.3-04) Design With Anchor Reinforcement 144

3.0        REFERENCES.. 154


1.0   INTRODUCTION

Anchorage to concrete Concrete Capacity Design (CCD) Method was first introduced in ACI 318-02 and ACI 349-01 Appendix D, followed by CSA A23.3-04 Annex D. Anchorage design provisions in ACI 318-08 and ACI 349-06 Appendix D, CSA A23.3-04 Annex D are similar except that ACI 349-06 imposes a more severe penalty on non-ductile anchor design (ACI 349-06 D3.6.3) and also ACI 349-06 provides additional provisions for shear transfer using friction and shear lugs.

 

Since ACI 318-02 the ACI has released ACI 318-05, ACI 318-08, and recently ACI 318-11. In ACI 318-08 the definition for Anchor Reinforcement is introduced, and the strength of Anchor Reinforcement used to preclude concrete breakout in tension and in shear is codified (ACI 318-08 D.5.2.9 and D.6.2.9.), guidance for detailing the Anchor Reinforcement is given in ACI 318-08 RD.5.2.9 and RD.6.2.9.  

 

Since CSA A23.3-04 CSA has released several updates to catch up ACI’s revisions on anchorage design, with the latest CSA A23.3-04 (R2010, Reaffirmed 2010) partially incorporated Anchor Reinforcement (CSA A23.3-04 R2010 D.7.2.9). It’s expected that the same Anchor Reinforcement provisions as ACI 318-08 will be amended in the next revision of CSA A23.3-04 update.

 

This technical writing includes a series of design examples covering mainly the anchorage design of grouped anchors and studs, in both ACI 318-08 and CSA A23.3-04 R2010 code. The design examples are categorized in Anchor Bolt and Anchor Stud, with Anchor Reinforcement and without Anchor Reinforcement, with moment presence and without moment presence.

 

Anchor Bolt and Anchor Stud

The main difference between anchor bolt and anchor stud is the way how they attach to the base plate. For anchor bolt normally the anchor bolt holes on base plate are much bigger than anchor bolt diameter due to cast-in anchor bolt construction tolerance, while the anchor stud is rigidly welded to the base plate. This different approach of attachment will cause the difference on shear transfer mechanism during anchorage design (ACI 318-08 RD.6.2.1(b)).

  

Anchor Reinforcement and Supplementary Reinforcement

In all concrete failure modes, the tensile and shear concrete breakout strengths are most of the time the lowest strengths among all concrete failure modes. The concrete breakout strength limits the anchor design strength and make anchor bolt design not practical in many applications such as concrete pedestal, which has limited edge distances surrounding anchor bolts.

 

In ACI 318-08 the definition for Anchor Reinforcement is introduced, and the strength of Anchor Reinforcement used to preclude concrete breakout in tension and in shear is codified (ACI 318-08 D.5.2.9 and D.6.2.9.), guidance for detailing the Anchor Reinforcement is given in ACI 318-08 RD.5.2.9 and RD.6.2.9. The use of Anchor Reinforcement in many times is the only choice to make a practical anchor bolt design in applications such as concrete pedestal.


 

Anchor Reinforcement for Tension ACI 318-08 RD.5.2.9

Anchor Reinforcement for Shear ACI 318-08 RD.6.2.9

 

 

The use of supplementary reinforcement is similar to the anchor reinforcement, but it isn't specifically designed to transfer loads. If supplementary reinforcement is used, the concrete strength reduction factor f is increase 7% from 0.70 to 0.75, which is not that significant in terms of increasing concrete breakout strength.


 

Supplementary Reinforcement        ACI 318-08            Condition B

 

 

 

 

Supplementary Reinforcement        ACI 318-08            Condition A

 

 

 

Anchor Ductility

When an anchor’s overall design strength, for both tension and shear, is equal to the design strength of anchor rod steel element, and all potential concrete failure modes have design strengths greater than the anchor rod steel element design strength, this anchor design is considered as ductile anchor design.

 

Anchor’s ductility is its own characteristic related to anchor rod material, embedment depth, anchor bolt spacing and edge distances etc, and has nothing to do with the applied loadings. If high strength anchor rod material is used, it would be more difficult to achieve the ductile design as deeper embedment depth, larger edge distances are required for concrete failure modes design strengths to surpass anchor rod material design strength. The high strength anchor bolt material shall only be used when it’s necessary, such as for anchorages required pre-tensioned or subjected to dynamic impact load in cold temperature environment (A320 Grade L7). In most cases the anchorage design won’t benefit from the high strength bolt material as the concrete failure modes will govern, and the use of high strength bolt will make the anchor ductile design almost impossible.

 

 

 

For anchorage design in moderate to high seismic zone (ACI 318-08 SDC>=C and CSA A23.3-04 R2010  IEFaSa(0.2)>=0.35) ductile anchor design is mandatory as specified in ACI 318-08 D.3.3.4 and CSA A23.3-04 R2010 D.4.3.6.

 

For anchorage design in low seismic zone (ACI 318-08 SDC<C and CSA A23.3-04 R2010  IEFaSa(0.2)<0.35), the non-ductile anchor design is permitted, but when calculating anchor bolt force distribution, the plastic analysis approach is not permitted for non-ductile anchor as specified in ACI 318-08 D.3.1 and CSA A23.3-04 R2010 D.4.1.

 

 

 


2.0   DESIGN EXAMPLES

 

Example 01: Anchor Bolt + Anchor Reinft + Tension & Shear + ACI 318-08 Code

 

 

 

 

Nu= 20 kips ( Tension )                      Vu = 25 kips

Concrete               fc’= 4 ksi                 Rebar     fy = 60 ksi

Pedestal size       16” x 16”

Anchor bolt            F1554 Grade 36  1.0” dia                 Hex Head              hef = 55”                  ha =60”

Seismic design category >= C

Anchor reinforcement                         Tension à 8-No 8 ver. bar

                                                                Shear à 2-layer, 4-leg No 4 hor. bar

 

Provide built-up grout pad


 


Example 02: Anchor Bolt + Anchor Reinft + Tension & Shear + CSA A23.3-04 Code

 

 

 

Nu= 89 kN ( Tension )                         Vu = 111.2 kN

Concrete               fc’= 27.6 MPa                        Rebar     fy = 414 MPa

Pedestal size       406mm x 406mm

Anchor bolt            F1554 Grade 36  1.0” dia                 Hex Head              hef = 1397mm       ha =1524mm

Seismic design IE FaSa(0.2) >= 0.35

Anchor reinforcement                         Tension à 8-25M ver. bar

                                                                Shear à 2-layer, 4-leg 15M hor. bar

 

Provide built-up grout pad


 


Example 03: Anchor Bolt + Anchor Reinft + Tension Shear & Moment + ACI 318-08 Code

 

 

 

 

Mu = 35 kip-ft         Nu= 10 kips (Compression)                              Vu = 25 kips

Concrete               fc’= 4 ksi                 Rebar     fy = 60 ksi

Pedestal size       26” x 26”

Anchor bolt            F1554 Grade 36  1.25” dia                Hex Head              hef = 55”                  ha =60”

Seismic design category < C

Anchor reinforcement                         Tension à 2-No 8 ver. bar

                                                                Shear à 2-layer, 2-leg No 4 hor. bar

 

Provide built-up grout pad



 


Example 04: Anchor Bolt + Anchor Reinft + Tension Shear & Moment + CSA A23.3-04 Code

 

 

 

 

 

Mu = 47.4 kNm      Nu= -44.5 kN (Compression)            Vu = 111.2 kN

Concrete               fc’= 27.6 MPa                        Rebar     fy = 414 MPa

Pedestal size       660mm x 660mm

Anchor bolt            F1554 Grade 36  1.25” dia                Hex Head              hef = 1397mm       ha =1524mm

Seismic design IE FaSa(0.2) < 0.35

Anchor reinforcement                         Tension à 2-25M ver. bar

                                                                Shear à 2-layer, 2-leg 15M hor. bar

 

Provide built-up grout pad








Example 11: Anchor Bolt + No Anchor Reinft + Tension & Shear + ACI 318-08 Code

 

This example taken from Example 8 on page 71 of ACI 355.3R-11 Guide for Design of Anchorage to Concrete: Examples Using ACI 318 Appendix D

 

 

Nu = 12 kips (tension),        Vu=4 kips,              fc’ = 3 ksi               

Anchor bolt da=3/4 in ASTM F1554 Grade 55                 hef =12 in               ha=24 in                 Anchor head à Hex

Supplementary reinforcement          Tension à Condition B                      Shear à Condition A   Yc,V =1.2

Provide built-up grout pad                 Seismic is not a consideration

Field welded plate washers to base plate at each anchor

 

 

Example 12: Anchor Bolt + No Anchor Reinft + Tension & Shear + CSA A23.3-04 Code

 

This example taken from Example 8 on page 71 of ACI 355.3R-11 Guide for Design of Anchorage to Concrete: Examples Using ACI 318 Appendix D

 

 

Nu = 53.4 kN (tension),       Vu=17.8 kN,           fc’ = 20.7 MPa      

Anchor bolt da=3/4 in ASTM F1554 Grade 55                 hef =305mm          ha=610mm            Anchor head à Hex

Supplementary reinforcement          Tension à Condition B                      Shear à Condition A   Yc,V =1.2

Provide built-up grout pad                 Seismic is not a consideration

Field welded plate washers to base plate at each anchor


 


Example 13: Anchor Bolt + No Anchor Reinft + Tension Shear & Moment + ACI 318-08 Code

 

 

 

 

Mu = 25 kip-ft         Nu= 10 kips (Compression)                              Vu = 10 kips

Concrete               fc’= 5 ksi

Anchor bolt            F1554 Grade 36  1.25” dia                Heavy Hex Head                  hef = 16”                  ha =20”

Oversized holes in base plate

Seismic design category < C

Supplementary reinforcement          Tension à Condition A

                                                                Shear à Condition A          Yc,V  = 1.2

Provide built-up grout pad









Example 14: Anchor Bolt + No Anchor Reinft + Tension Shear & Moment + CSA A23.3-04 Code

 

 

 

 

Mu = 33.9 kNm      Nu= 44.5 kN (Compression)                             Vu = 44.5 kN

Concrete               fc’= 34.5 MPa

Anchor bolt            F1554 Grade 36  1.25” dia                Heavy Hex Head                  hef = 406mm         ha =508mm

Oversized holes in base plate

Seismic design IE FaSa(0.2) < 0.35

Supplementary reinforcement          Tension à Condition A

                                                                Shear à Condition A          Yc,V  = 1.2

Provide built-up grout pad

 



Example 21: Welded Stud + Anchor Reinft + Tension & Shear + ACI 318-08 Code

 

 

 

 

Nu= 20 kips ( Tension )                      Vu = 25 kips

Concrete               fc’= 4 ksi                 Rebar     fy = 60 ksi

Pedestal size       16” x 16”

Anchor stud          AWS D1.1 Grade B              1.0” dia                  hef = 55”                  ha =60”

Seismic design category >= C

Anchor reinforcement                         Tension à 8-No 8 ver. bar

                                                                Shear à 2-layer, 4-leg No 4 hor. bar

 

No built-up grout pad for embedded plate.

 

Note: The stud length used in this example may not be commercially available and it’s for illustration purpose only.

          Deep anchor stud embedment hef is required for anchor reinforcement to develop resistance on both sides of the

          failure plane.








Example 22: Welded Stud + Anchor Reinft + Tension & Shear + CSA A23.3-04 Code

 

 

Nu= 89 kN ( Tension )                         Vu = 111.2 kN

Concrete               fc’= 27.6 MPa                        Rebar     fy = 414 MPa

Pedestal size       406mm x 406mm

Anchor stud          AWS D1.1 Grade B              1.0” dia                  hef = 1397mm       ha =1524mm

Seismic design IE FaSa(0.2) >= 0.35

Anchor reinforcement                         Tension à 8-25M ver. bar

                                                                Shear à 2-layer, 4-leg 15M hor. bar

 

No built-up grout pad for embedded plate.

 

Note: The stud length used in this example may not be commercially available and it’s for illustration purpose only.

          Deep anchor stud embedment hef is required for anchor reinforcement to develop resistance on both sides of the

          failure plane.








Example 23: Welded Stud + Anchor Reinft + Tension Shear & Moment + ACI 318-08 Code

 

 

 

Mu = 35 kip-ft         Nu= 10 kips (Compression)                              Vu = 25 kips

Concrete               fc’= 4 ksi                 Rebar     fy = 60 ksi

Pedestal size       26” x 26”

Anchor stud          AWS D1.1 Grade B              1.0” dia                  hef = 55”                  ha =60”

Seismic design category < C

Anchor reinforcement                         Tension à 2-No 8 ver. bar

                                                                Shear à 2-layer, 2-leg No 4 hor. bar

 

No built-up grout pad for embedded plate.

 

Note: The stud length used in this example may not be commercially available and it’s for illustration purpose only.

          Deep anchor stud embedment hef is required for anchor reinforcement to develop resistance on both sides of the

          failure plane.









Example 24: Welded Stud + Anchor Reinft + Tension Shear & Moment + CSA A23.3-04 Code

 

 

 

 

Mu = 47.4 kNm      Nu= 44.5 kN (Compression)                             Vu = 111.2 kN

Concrete               fc’= 27.6 MPa                        Rebar     fy = 414 MPa

Pedestal size       660mm x 660mm

Anchor stud          AWS D1.1 Grade B              1.0” dia                  hef = 1397mm                       ha =1524mm

Seismic design IE FaSa(0.2) < 0.35

Anchor reinforcement                         Tension à 2-25M ver. bar

                                                                Shear à 2-layer, 2-leg 15M hor. bar

 

No built-up grout pad for embedded plate.

 

Note: The stud length used in this example may not be commercially available and it’s for illustration purpose only.

          Deep anchor stud embedment hef is required for anchor reinforcement to develop resistance on both sides of the

          failure plane.



Example 31: Welded Stud + No Anchor Reinft + Tension & Shear + ACI 318-08 Code

 

 

 

Nu= 20 kips (Tension)                        Vu = 10 kips

Concrete               fc’= 4.5 ksi

Anchor stud          AWS D1.1 Grade B              1.0” dia                  hef = 12”                  ha =15”

Seismic design category < C

Supplementary reinforcement          Tension à Condition A

                                                                Shear à Condition A          Yc,V  = 1.2

 

No built-up grout pad for embedded plate.

 

Note: The stud length used in this example may not be commercially available and it’s for illustration purpose only.






Example 32: Welded Stud + No Anchor Reinft + Tension & Shear + CSA A23.3-04 Code

 

 

 

Nu= 89 kN (Tension)                           Vu = 44.5 kN

Concrete               fc’= 31 MPa

Anchor stud          AWS D1.1 Grade B              1.0” dia                  hef = 305mm                         ha =381mm

Seismic design IE FaSa(0.2) < 0.35

Supplementary reinforcement          Tension à Condition A

                                                                Shear à Condition A          Yc,V  = 1.2

 

No built-up grout pad for embedded plate.

 

Note: The stud length used in this example may not be commercially available and it’s for illustration purpose only.








Example 33: Welded Stud + No Anchor Reinft + Tension Shear & Moment + ACI 318-08 Code

 

This example taken from Example 10 on page 82 of ACI 355.3R-11 Guide for Design of Anchorage to Concrete: Examples Using ACI 318 Appendix D

 

 

Mu = 30 kip-ft         Nu = 0 kips,           Vu=20 kips,            fc’ = 4.5 ksi           

Anchor stud da=7/8 in         hef =9 in                  ha=18 in                

Supplementary reinforcement          Tension à Condition B                      Shear à Condition A   Yc,V =1.2

Provide built-up grout pad                 Seismic is not a consideration

Field welded plate washers to base plate at each anchor

 

Notes:

There are two locations in this calculation which are different from calculation in ACI 355.3R-11 Example 10

1.       Concrete tension breakout ANc = 1215 in2, different from ANc = 1519 in2 , value in ACI 355.3R-11 page 86.

We assume the moment may apply in both directions. When moment causes tensile anchors being close to the edge

side, the ANc value is consequently reduced.

2.       Concrete shear breakout ca1 reduction from 27” to 12” in ACI 355.3R-11 page 90 is not correct. It doesn't comply with both edge distances ca2,1<1.5ca1 and ca2,2<1.5ca1 . Refer to ACI 318-11 Fig. RD.6.2.4 for more details.







Example 34: Welded Stud + No Anchor Reinft + Tension Shear & Moment + CSA A23.3-04 Code

 

This example taken from Example 10 on page 82 of ACI 355.3R-11 Guide for Design of Anchorage to Concrete: Examples Using ACI 318 Appendix D

 

 

Mu = 40.7 kNm      Nu = 0 kN,              Vu=89 kN,              fc’ = 31 MPa          

Anchor stud da=7/8 in         hef =229mm                          ha=457mm                           

Supplementary reinforcement          Tension à Condition B                      Shear à Condition A   Yc,V =1.2

Provide built-up grout pad                 Seismic is not a consideration

Field welded plate washers to base plate at each anchor

 

Notes:

There are two locations in this calculation which are different from calculation in ACI 355.3R-11 Example 10

1.       Concrete tension breakout ANc = 1215 in2, different from ANc = 1519 in2 , value in ACI 355.3R-11 page 86.

We assume the moment may apply in both directions. When moment causes tensile anchors being close to the edge

side, the ANc value is consequently reduced.

2.       Concrete shear breakout ca1 reduction from 27” to 12” in ACI 355.3R-11 page 90 is not correct. It doesn't comply with both edge distances ca2,1<1.5ca1 and ca2,2<1.5ca1 . Refer to ACI 318-11 Fig. RD.6.2.4 for more details.








Example 41: Shear Lug Design ACI 349-06 Code

 


 


 


 


Example 42: Shear Lug Design ACI 349M-06 Code

 


 


 


 


Example 51: Base Plate (LRFD) & Anchor Bolt (ACI 318-08) Design With Anchor Reinforcement


Example 52: Base Plate (S16-09) & Anchor Bolt (CSA A23.3-04) Design With Anchor Reinforcement

3.0     REFERENCES

 

1. ACI 318-08 Building Code Requirements for Structural Concrete and Commentary

2. ACI 318M-08 Metric Building Code Requirements for Structural Concrete and Commentary

3. ACI 349-06 Code Requirements for Nuclear Safety-Related Concrete Structures & Commentary              

4. ACI 349.2R-07 Guide to the Concrete Capacity Design (CCD) Method - Embedment Design Examples                  

5. ACI 355.3R-11 Guide for Design of Anchorage to Concrete: Examples Using ACI 318 Appendix D                            

6. Design of Anchor Reinforcement in Concrete Pedestals by Widianto, Chandu Patel, and Jerry Owen

7. CSA A23.3-04 (R2010) - Design of Concrete Structures

8. AISC Design Guide 1: Base Plate and Anchor Rod Design 2nd Edition            

9. PIP STE05121 Anchor Bolt Design Guide-2006                                                                                                                                     

 

                               

                                                               

 

 

 


Anchor Bolt    Anchor Reinforcement    Supplementary Reinforcement    ACI 318-08    ACI318-08 Appendix D    ACI 349-06    CSA-A23.3-04     CSA-A23.3-04 Annex D    CSA-A23.3-04 (R2010)     ACI 349.2R-07     ACI 355.3R-11    ACI318-08 D.5.2.9    ACI318-08 RD.5.2.9    ACI318-08 D.6.2.9    ACI318-08 RD.6.2.9     Anchor Bolt Blowout    Anchor Bolt Breakout    Anchor Bolt Pryout    Anchor Bolt Pullout    Anchor Bolt Shear   Anchor Bolt Moment   Anchor Bolt Tension    Anchor Bolt Tensile    

Concrete Anchorage    Anchor Rod    Anchor Bolt Ductility    Anchor Bolt Ductile    Anchor Bolt Seismic   Anchor Bolt Condition A    Anchor Bolt Condition B     Base Plate    Base Plate Large Moment    Base Plate Small Moment    Base Plate Tensile   

Base Plate Compression    AISC Design Guide 1    Base Plate and Anchor Rod Design    Anchor Bolt CCD    Anchor Bolt Sleeve    Anchor Stud    Hairpin    Anchor Ductile    Grout Pad    Ductile Steel     Anchor Bolt Strut-and-Tie    Anchor Bolt Concrete   

Anchor Bolt Concrete Anchorage    Anchor Bolt Embedment    Anchor Bolt Pretension    Anchor Bolt Edge Distance    Anchor Bolt Three Edges    Anchor Bolt Hairpin    Anchor Bolt Design    Anchor Bolt Design Software    Anchor Bolt Design Spreadsheet