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Re: SStud: Need opinions about residential construction andsteelstud shearwalls -Reply -Reply

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Dennis S. Wish wrote:

> Snip

> [Dennis S. Wish]  Tim, yes Table #4 in APA's Report #154 by John R. Tissell, PE which was dated May 1993 shows the mode of failure for each gauge stud and panel combination. With the exception of 14 gauge studs the mode of failure indicated was "studs buckled". The load factor (factor of safety determined by dividing the ultimate load by the target design shear) varied from 2.8 to 3.7 where the studs buckled.
> However the text contains the following paragraph on page 9:
> "Most of the walls tested failed prematurely when the end studs buckled or the bottom plate buckled at the buttress of the test fixture due to tearing of the bottom track at the anchor bolts. The tests did not provide a true indicator of the capacity of sheathing panels fastened to framing due to the weakness of the metal framing. Shear walls using metal framing require careful design of the end studs as highly loaded columns, and sufficient anchor bolts to provide for shear transfer from the bottom plate into the foundation or to the diaphragm supporting the wall."
> Tim, in all fairness, I have not completed a review of LGSRG-3-96 - Shear Wall Values for Light Weight Steel Framing as prepared by Hoang Nguyen and Georgi Hall for the Project Director Reynaud Serrette for the Light Gauge Steel Research Group, Department of civil Engineering, Santa Clara University. Professor Serrette has been leading the way in his research on steel stud shearwalls and has been very active by his research sponsor - AISI as well as his association with the Light Gauge Steel Engineering Association. I suspect that it is this document which lead to the 1997 UBC provisions.

Reynaud Serrette spoke at a recent meeting of the Structural Engineers Association of Utah and it was definitely implied (and may have been stated) that his work was the basis for the most recent UBC parameters. The presentation gave some insight into his research approach which appears to recognize the past failure modes of stud buckling and racking and looks toward "forcing" it into the plywood sheathing itself. One concern mentioned by him was the brittle fastener problem for which he appears to be developing recommendations. His talk included hysterisis (?) graphing for various
combinations of materials under dynamic loading (the apparent new wave) which pointed to some of the upper limits which were established. Unfortunately, the meeting ran long and the opportunity to get beyond the basics was limited.

I'm of the opinion that the new research will be valuable in helping place better confidence in the use of plywood sheathed shear walls. Perhaps Professor Serrette could be persuaded to join this discussion.

Barry H. Welliver
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