Roof Diaphragm Design

[SteelPE]

I have a warehouse that I am looking at that is single story with a tilt up bearing walls around the perimeter. The building has an expansion joint running down the middle. The building is pretty repetitive and I would like to make sure I produce an economical design. The building is designed using ASCE7-05 and IBC 2009.

In accordance with ASCE7 12.10.1.1 I need to design the roof diaphragm for the same load I would design the LFRS for (Lateral Force Resisting System). When it comes to checking the diaphragm I assume I would use 0.7E to convert the strength level seismic loads to comply the allowable diaphragm loads found in the table I have from the deck mfr. Is this correct? This seems to make sense, although I have never done this before and I imagine I have been conservative.

 

[PittEng88]

Hi SteelPE,

I just finished up a similar project dealing with roof diaphragms. Yes, you are correct that you would use 0.7E to convert the strength seismic loads to allowable loads. Just be aware that certain manufacturers might have different safety factors attached their allowable design loads.

Also, as a side note, don't forget to check your minimum and maximum diaphragm forces as per ASCE 7-05 Section 12.10.1.1.

Hope this helps!

 

[MacGruber22]

I imagine your diaphragm connections don't qualify for over-strength?

http://cenews.com/article/8454/clearing-confusion-on-asce-7-05-sections-12-3-3-4-and-12-10-2-1

"It is imperative Cunth doesn't get his hands on those codes."