Interpretation of ASCE 7-10 Chapter-13 design forces

[jochav52802]

Good Day,

A few questions regarding Chapter-13 of ASCE 7-10, which is titled, "SEISMIC DESIGN REQUIREMENTS FOR NONSTRUCTURAL COMPONENTS"

1) Are the seismic forces derived therein intended to be just for the nonstructural component and it's attachment or is it also intended to be the seismic force that it's supporting structure needs to resist as well?

2) Section 13.1.1 titled, "Scope" specifies, "This chapter establishes minimum design criteria for nonstructural components that are permanently attached to structures and for their supports and attachments." Does their use of the word "supports" signify that the supporting structure needs to resist the loads derived in this chapter or is that word meant to reference the element that anchors the nonstructural component to the supporting structure? It's my understanding that the supporting structure must be designed based on the seismic response coefficient (Cs), derived in Chapter-12.8.

3) While designing a pipe support structure, I noticed that the Cs-value derived for the supporting structure was much higher than the Fp-value for the component itself; why does the standard require us to design components and their supports for a lower force than the support structure itself? This would seem to point out that designing the support structure for the Fp loads would result in an unconservative and code-violating design, correct?

I'd appreciate any clarity you can provide!

Thank you for your help!

jochav5280

 

[JoshPlumSE]

1) That's a good question. I've always interpreted it as the attachment forces. That need to be carried back to the main lateral load path. So, if it's attached to a beam, I want to make sure the connection to the beam can take it. But, also that the beam can handle it until the force gets into the main moment frames or braces of the lateral force resisting system.

2) Let's say you have a small frame that supports the equipment. The frame is then bolted into the main structure. You'd have to design the small equipment frame for the chapter 13 forces as well.

3) No, if you get a lower force from Fp, then you would want to design to your higher lateral resistance forces. Note: I'm not sure how this would occur. Maybe if your attachment points were very low in the structure and are using an R value of less than 3 for the pipe rack?