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ACI 318 Appendix D, Anchorage for Simpson Strong walls

ACI 318 Appendix D, Anchorage for Simpson Strong walls

ACI 318 Appendix D, Anchorage for Simpson Strong walls

(OP)
Hello,

I have been reading all the threads that I can regarding the ACI 318 Appendix D and the calculation for anchor bolt capacity placed in concrete.  I just recently performed a calculation based on a Simpson shearwall that is SW18x9 and is resisting a relatively minor ASD load of 420 lb, when translated to LRFD and multiplied by the 2.5 factor (assuming concrete failure) becomes about 1470 lb.  In deterimining the uplift load based on the 9 ft height and 1.5' width, the tension load on the anchor at each side becomes quite large, about 8830 lbs.

It appears that the only way to get the anchorage to work is to insure that ductile failure of either the anchor bolt or holdown occurs rather than the concrete failure.

In this case I was prepared to use a 12"x 28" deep footing because simpson suggests using the SSTB28 anchor bolt, with just under 25" of embedment.
assume
c1 = 2 inches.  
hef = 8*do (can I use the full embedment or is this the limiting factor
single anchor


It appears based on all the different failure modes, that pullout governed by 0.9f'cehdo is the lowest load based on the concrete compressive strength (2500 psi), anchor bolt diameter (7/8"), and eh which is apparently between 3 and 4.5 times the bolt diameter as well as the factor yc,p (1.4 I assumed non cracked at service loads).

By using the previous equation and taking the additional 0.75 required by the CBC20007 (D3.3.3).  I get that a 1.25" diameter anchor bolt would be required for this load.

That seems a little crazy for this situation.  can somebody tell me if I have incorrect calculations or if they have performed the calculations for simpson shear walls and were able to come up with a different answer?

Thanks for your help!

structeng13
 

RE: ACI 318 Appendix D, Anchorage for Simpson Strong walls

(OP)
After looking into more, it appears that the use of a headed bolt will be required because the ESR report for the SSTB28 isn't updated to the IBC2006 yet.  But my question still remains regarding the use of simpson strongwalls if people have calculated using the SSTB anchor bolts.   

RE: ACI 318 Appendix D, Anchorage for Simpson Strong walls

Another option is to introduce a 'fuse'.  This can be accomplished with a coupler, reducing the size of your anchor bolt once in is out of concrete.  Also, if still having trouble, contact Simpson.  They have been dealing with the problems Appendix D has created and have been helpful as they still want their products to be used.

RE: ACI 318 Appendix D, Anchorage for Simpson Strong walls

(OP)
Thanks for the responses!  I did check out the new ESR report and I will definitely take into consideration designing a 'fuse' that will not require the 2.5 multiplication factor of the factored loads

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