Penthouse Risk Category

[VSS Engineering]

My team is designing a grandstand, which we have done quite a few of over the years. This one in particular has a press-box at the top that is designed by a different engineer. We're having a bit of a disagreement on the risk cat. for the press-box design. The press-box EOR is dictating the press-box as a risk cat. II structure, where we believe it should be a risk cat. III structure since the support structure, the grandstand, is risk cat. III.

Has anyone dealt with a similar situation or have a code reference that provides direction as whether or not a "penthouse" risk category has to match that of the support structure?

 

[phamENG]

I agree with your stance. If an earthquake hits, where will the press box land if it falls off? Right smack into the people that are making the rest of the structure RC III.

Who is the overall EOR for the project? Their word should go unless overturned by the AHJ.

 

[kissymoose]

reference:

https://www.eng-tips.com/viewthread.cfm?qid=458198

1.5.2 ASCE 7. They're not independent structures, so make them RC III.

 

[lexpatrie]

I go to RC III, I wasn't there for a minute but then I remembered the Indiana State Fair equipment system collapsed into a high occupancy crowd.

Similar can apply when a risk category III structure exits through what's normally risk category II.