ASCE 7-10 Code Interpretation 1

[OC_eit]

Hi all,

I recently got a comment from a plan checker that I must use 4 PSF minimum for the dead load of any ceilings on my project, irregardless of the actual ceiling weight, for both gravity and lateral design. He cites ASCE 7-10, Section 13.5.6.1, specifically where it mentions that "W[sub]p[/sub] shall not be taken as not less than 4 psf...". My issue with his comment is that I, as well as other engineers in my office, interpret this 4 psf minimum as only applying to the F[sub]p[/sub] force one would use to design the bracing and anchorage of the ceiling, not to the load we use for the overall gravity and lateral design of the building. So my question to you all is what would be the most correct interpretation of this code section?

Thanks for the help.

 

[MrHershey]

I would tend to disagree with the reviewer. That section is specifically for calculating the seismic force for sway bracing. I don't think the intent is to apply it to building lateral and certainly don't think intent is for that to be a hard minimum on ceiling weight to consider for gravity design (if it was, it needs to be in chapter 3, what if I'm SDC A/B and this section doesn't apply?)

That said, were I in your position I don't know that it's worth the argument. If you've got a suspended ceiling your actual weight is what, like 2-3 psf? I don't know that 1-2 psf is worth fighting for. Can always sharpen pencil somewhere else if I'm really that tight.

 

[OC_eit]

Thanks for the reply. I agree with the chapter 3 part, especially because it states to use the actual weights of materials for the purpose of design. I also agree that it seems not worth fighting for that 1-2 extra psf in our design loads, but the main reason I'm fighting for it is that this is a reviewer who we've had in the past and he'll always make this comment, and no one ever really pushes back on it, so I'm trying to draw a line in the sand on what's the right way to interpret this section.

 

[Mjkkb2]

Completely agree with the above. Plan reviewer is misunderstanding the code provision. However, if he’s the authority having jurisdiction then he just essentially amended the code for you. The model codes give very broad powers to local AHJ. If they say something is required you don’t have much choice but to comply.

 

[azcats]

I would argue. Despite his position, the reviewer is incorrect and needs to be educated or at least forced to give this a second thought. Especially when this could set a precedent. Even more especially with this complete mis-application of a code section. I know there are plenty of areas in the code that are open to interpretation and opinions, but this case doesn't appear that way to me. However, my argument would likely be limited to a well reasoned passage in my plan check response letter as to why he's wrong. If he held fast and bounced it out again, I'd grudgingly fold like a cheap tent while my disdain for the AHJ grows. At least I got my argument on file.

But perhaps I'm particularly jaded right now as I just received a 28 item plan check list on a design that has been approved w/o comment in this same municipality (and others) dozens (hundreds?) of times.