Los Angeles Section

I have a general question on the seismic design approach of a non building structure, ASCE 7-22 chapter 15. The example is a 8 foot tall CMU ground supported CMU wall. Seismic Parameters are S1=0.77> 0.6, Sds=1.65, Sd1=1.18, TL=8. In the past ASCE 7-16 and earlier, we used equation 13.3-1, as that formulation has been used for years spanning back to UBC.

In ASCE 7-22, 13.1.1 item 2, now states that chapter 13 does not apply to non building structures within the scope of chapter 15. Table 15.4-2 in both 7-16 and 7-22 have both had values for a ground supported wall. My first interpretation is that chapter 13 does not apply, and I must use chapter 15. Going to both sections 15.4 (2) and 15.6.8, they apply ground supported walls. So reading 15.4(2) this is basically the same as 7-16, I see the minimum Cs=0.044SdsI and not less than 0.3, and the minimum for S1>0.6., But why does it refer to EQ 12.8-5? That is the long period point of the spectrum. For my example, the wall T is much less than TL, so should 15.4(2) really just reference section 12.8 as a whole, and wherever the period applies, then equations 12.8-2 thru 5 would apply? 

Sorry for the long winded question, but for comparison I get the following ballpark results.

(7-16) EQ 13.3-1 Fp=0.528

(7-22) EQ 13.3-1 Fp=0.566

Using chapter 15 approach, using I=1, R=1.25, for T<Ts Eq 12.8-3 Cs=1.320 and Csmin for S1>.6=0.493, so V=CSW= 1.32W.

I am confused on the correct seismic approach to a simple block fence, where is my error, as there is no way that I am justifying the wall for 1.32W.

Thank you

Hi @James Lascola, 

ASCE has a forum that focuses on standards questions. You may want to post your question here: https://collaborate.asce.org/standards-exchange/home

I hope you receive some helpful feedback. 

I have a general question on the seismic design approach of a non building structure, ASCE 7-22 chapter 15. The example is a 8 foot tall CMU ground supported CMU wall. Seismic Parameters are S1=0.77> 0.6, Sds=1.65, Sd1=1.18, TL=8. In the past ASCE 7-16 and earlier, we used equation 13.3-1, as that formulation has been used for years spanning back to UBC.

In ASCE 7-22, 13.1.1 item 2, now states that chapter 13 does not apply to non building structures within the scope of chapter 15. Table 15.4-2 in both 7-16 and 7-22 have both had values for a ground supported wall. My first interpretation is that chapter 13 does not apply, and I must use chapter 15. Going to both sections 15.4 (2) and 15.6.8, they apply ground supported walls. So reading 15.4(2) this is basically the same as 7-16, I see the minimum Cs=0.044SdsI and not less than 0.3, and the minimum for S1>0.6., But why does it refer to EQ 12.8-5? That is the long period point of the spectrum. For my example, the wall T is much less than TL, so should 15.4(2) really just reference section 12.8 as a whole, and wherever the period applies, then equations 12.8-2 thru 5 would apply? 

Sorry for the long winded question, but for comparison I get the following ballpark results.

(7-16) EQ 13.3-1 Fp=0.528

(7-22) EQ 13.3-1 Fp=0.566

Using chapter 15 approach, using I=1, R=1.25, for T<Ts Eq 12.8-3 Cs=1.320 and Csmin for S1>.6=0.493, so V=CSW= 1.32W.

I am confused on the correct seismic approach to a simple block fence, where is my error, as there is no way that I am justifying the wall for 1.32W.

Thank you