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Re: Point load on garage diaphragm

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Since the slab is non-structural, does ASCE even govern? In the past, APA had done some testing that justified 3/4" ply. with the 2k load (& IFRC probably 3k also). I used to distribute the load for bending but not shear, but I had to argue the point a couple of times with plan checkers & finally just said the heck with load distribution. YMMV
Chuck Utzman, P.E.

Gordon Goodell wrote:

My copy of this came through as all symbols. Did everyone else get it that way? We’ve been experiencing some email weirdness for the last week or so, since we switched to a new host/service provider.


Read the ASCE commentary on concentrated live loads, C4.3. The answer to your question is no, you are not required to design the plywood for 3000# over 4.5"x4.5"; that provision is intended to apply only to primary framing members. You don't necessarily even have to design the floor joist for it, as it is a repetitive member, and the failure of one joist would not cause a collapse.

HOWEVER, this load is designed to mimic a floor jack lifting a car, which seems likely on your floor, so aside from what you are required to do, I would design all components for this load. And I would use normal-wt concrete w/ bars to distribute this load among members (and take care of plywood concerns). Your wearing surface will be much more durable, too.


Gordon Goodell

Alta, WY

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