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Re: Hardy Frame, shear walls[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc(--nospam--at)seaoc.org
- Subject: Re: Hardy Frame, shear walls
- From: ErnieNSE <ErnieNSE(--nospam--at)aol.com>
- Date: Sun, 29 Mar 1998 11:13:50 EST
Dennis, The Z-wall was the other one I was talking about that I checked out in their website(hawaii50.com/zwall) a few months back with complete details and calculations in it. I don't know it it has ICBO or L.A. City approval. Even then, when I saw it, I didn't pay much attention to it because of my concerns in my previous post. But now that we might have the 2:1 h/d limit on plywood shear walls, I might consider using this under cerain conditions and more research on its performance. I'm sure a lot of similar products are out there and there will be more new ones coming out taking advantage of this new restriction. I think it should be tested not by ICBO or any private testing agency only but by schools(engineering students with faculty supervision), steel agencies(AISI/AISC,etc), and engineering asssociations(LGSEA, SEAOC, Etc.). Then, depending on test results, it might gain wider acceptance or there will be improvements in design and restrictions in its application including possible classification of this type of shear wall system in the Code. Just like the tests on tilt-up and slender masonry walls conducted by joint engineers, contractors and manufacturers where they found out that these wall can deflect so far and still not fail. It also removed the H/t Code limit on slender walls. In certain situations(like the ones you're in), I would consider using it but with a seismic factor for braced frame along the wall line only and not in combination with other shear walls in the same wall line. I will also check and double check to make sure the buckling and welded connection failure of light gauge subjected to seismic force in a rigid braced frame configuration is really tested and researched thoroughly. I suggest that while LGSEA or other groups are testing plywood shear walls on light gauge metal studs, they consider these types of framng configuration on narrow shear walls as part of their test. Right now I still use a cantilevered steel column fixed at the base with concrete grade beam, using a seimic factor with Rw=3, and not in combination with any other type of shear wall on the same wall line. On two story houses where the narrow walls do not stack, I use rigid a steel frame with bolted connections or a shop welded connection if the frame is small enough knowing how most framers dislike field weling. I like its flexibilty and therefore more capacity to absorb and dissipate seismic forces(the same concept I see in comparing plywood shear walls with nails on wood studs with the same plywood screwed to metal studs). I also add a separate wood post, if there is extra space, to carry all vertical loads if the steel column is under a beam, to partially satisfy concerns in the SEAOC Blue Book about the cantilevered isolated column type of shear resisting system. But I still have to look closer at the shrinkage and deflection compatibility of the two columns. Ernie Natividad
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