ASCE 7-16 Waiving of Vertical Seismic Load Effect 2

[StructEngineer11]

I noticed that, new in the 2016 version of ASCE 7, they allow you to take the vertical seismic load effect Ev (0.2Sds*D) as zero if you're in Seismic Design Category B. This is stated in Section 12.4.2.2, which of course deals with seismic loading on building structures.

Would this also apply to nonstructural components from Chapter 13? In 13.3, you are to apply the horizontal seismic force Fp, which is a percentage of the weight of the component with various factors applied, and 13.3.1.2 says the component shall also be designed for a concurrent vertical force of +/-0.2Sds*Wp, analogous to Ev from Ch. 12. It does not state an exception for Seismic Design Category B here, though.

Would it be safe to assume the exception from Ch. 12 would also apply in Ch. 13?

 

[r13]

Good question. I suggest post the question to ASCE to request clarification.

 

[StructEngineer11]

I looked up their Seismic Committee, and coincidentally their Chair happens to be an old graduate school professor of mine, so I have reached out to him. Curious what he says.

 

[r13]

Please do come back and let us know. Thanks.

 

[StructEngineer11]

Yeah definitely.

 

[bones206]

A lot of non-structural components In SDC B are exempted from seismic altogether. The exemptions are pretty specific and are spelled out in Ch. 13.

 

[StructEngineer11]

I see the exception for SDC B listed right at the front of Ch. 13 now. Ha, that's embarrassing. Guess that answers my question then. Thanks.

 

[StructEngineer11]

It took a little while but my professor eventually got back to me on the issue. Thought I would post his reply:

"In section 12.4.2.2, it indicates that the vertical seismic load effect can be neglected in SDC B. It does so by changing the seismic load combinations (Ev = 0 so E = rho*Qe + 0) which apply unless specified otherwise to the other Seismic Chapters (e.g. 13 and 15). Since these load combinations would apply to any seismic case, allowing you to neglect the vertical component from design for the structure would also apply to nonstructural or nonbuilding structures as well. I would say that if you have components where the vertical would be important (long cantilevers) it may be beneficial to at least check it."

Added to that: "There is a proposal for ASCE 7-22 to provide reference to the load combinations that should be used in Chapter 13 and it basically says that you should be using the specified load combinations for Chapter 13 analysis with some guidance on combined loading in orthogonal directions."

 

[r13]

Thanks for sharing.

 

[StructEngineer11]

No problem.