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Re: Garage Floor Design

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GRileyPE(--nospam--at) wrote:
> Maybe there is something that I've been missing but getting away with. I've
> designed several hillside homes with elevated garage floor systems here in Los
> Angeles. The construction has been very similar to the one you've described.
> If I'm not mistaken, Section 1607.3.3 "Concentrated Loads" in the UBC, states
> "...placed upon any space 2 1/2 feet square,". This does not state 2 1/2
> square feet. I've always interpreted this to mean 2 1/2 feet x 2 1/2 feet
> which would distribute the 2000 pound point load over three joists and not
> two. This reduces the load to 667 pounds per joist. At this point, a uniform
> live load of 667 pounds/2.5 feet (266 pounds/foot) would be applied to that
> area of the joist. Using this methodology, the joists might calc-out.
> I would be interested in other engineers' takes on the subject. I've never had
> a problem getting a plan checker to buy into this, and I've never had a
> performance problem with any of the floors I've designed using this.
> Greg Riley PE
Greg:   Your interpretation and application is correct, but you can
still move the 2000# on the 6.25 s.f. perpendicular to the span such
that the load is not equal on all joists.

Donn Wooldriddge  RA/SE
Phoenix, AZ