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Re: Q: Lateral Resistance Capacity of Joist Seats

[Subject Prev][Subject Next][Thread Prev][Thread Next] Call me tommorrow at work Bill. (210-490-4506) I believe I have the information you are looking for. Remember reading a design example on the subject. Probably can fax it to you. A fellow San Antonio Texan.

I also attended a Vulcraft luncheon and brought up the subject and the person did not understand what I was asking. But another of Vucraft's staff who was the one who first made me realize that this needs to be considered. I had an employer who was using joist ends to resist lateral basement loads and also transfer shear loads through the seats to the walls. Not a great ides for either, as the trusses are not designed for the axial load. The load path takes the load into the trusses through the puddle welds and into the diaphragm. The other shear load case simply causes the entire slab to move and roll the joist seat over.

Easy fix is to use some tube steel between joists to take out the shear and also attach the slab directly to the basement wall. This is what we did.


From: "Bill Polhemus" <bill(--nospam--at)polhemus.cc>
Reply-To: seaint(--nospam--at)seaint.org
To: "SEAINT" <seaint(--nospam--at)seaint.org>
Subject: Q: Lateral Resistance Capacity of Joist Seats
Date: Mon, 18 Jun 2001 11:04:36 -0500

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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