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Q: Lateral Resistance Capacity of Joist Seats

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Last week sometime, we were having a discussion about non-standard joist
bearing seat heights. Someone mentioned the need to "check" that the bearing
seat heights won't lead to the danger of "rollover."

I have never actually considered the use of joist bearing seats to transfer
lateral load from the roof diaphragm before, and in most cases I don't think
it would be wise in areas like the Texas Gulf Coast where substantial
lateral forces might occur.

However, I have a small building that is long and narrow, and the
per-unit-foot diaphragm force in the long direction, even though the basic
wind speed is 110 mph, is actually pretty small. So this might lend itself
to relying upon the joist seats to transfer the lateral force.

Trouble is, I'm not sure how to determine the joist seat capacity for
resistance of lateral forces. I can't find it in the joist manufacturer's
literature--and I don't have a copy of the now-out-of-print "Steel Joist
Design Manual," which MIGHT address this information.

Has anyone got any information they might share with me?

William L. Polhemus, Jr., P.E.
Polhemus Engineering Company
Katy, Texas
Phone 281-492-2251
Fax 281-492-8203

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