Importance Factor used in serviceablity design? 2

[joder]

If you have a builidng that requires an Importance Factor of 1.15 for wind (per ASCE-7), can this factor be waived in non-life safety situations? For example, it is neccesary to design metal stud backup of brick veneer for a deflection criteria of L/600? I don't believe this is addressed in ASCE-7. I would still design for strength because a veneer failure could be a life safety issue. But it seems reasonable to me to waive the 1.15 factor in calculating cladding deflections since no one is going to get hurt if a mortar joint happens to open up during a 3 second gust.

My situation is this: its an outdoor stadium. I = 1.15 because it holds more than 300 people. I think even the 1.15 for MWFRS of the structure is ridiculous because no one is going to occupying an outdoor stadium during a 140 mph hurricane. And I think its even more ridiculous to have to beef the studs up because of that 1.15 factor. It's already conservative enough with the L/600 criteria in my opinion. But I don't see any way out of it.

Which brings up another subject: Can my engineering judgement override the code?

 

[joder]

ASCE does not give the L/600, but it's spreading like wildfire. It started with Brick Institute Tek note 28-B. The L/600 requirement now appears in UFC 3-301-01, Structural Engineering, which is required for all military projects. It is often specifically written into the Statements of Work for military projects.

I think it should go to L/360 per the Canadian research.

 

[steellion]

ASCE doesn't really have anything in terms of deflection criteria. You are correct about the UFC.

IBC lists deflection criteria, but it is not as stringent. L/240 for exterior walls with brittle finishes. IBC allows you to consider wind for deflection as 70% C&C. It also refers in mandatory language to ACI 530. ACI 530 requires L/600 max deflection vertically under D+L load, not horizontally.

So going back to the original question, I see no compelling argument for ignoring the importance factor for deflection. But there's also nothing that requires you to design to L/600 laterally if it's not a military job. L/360 seems appropriate.