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[SEAOC] Re: [SEAOC] wood panel shear wall/frames[Subject Prev][Subject Next][Thread Prev][Thread Next]
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- Subject: [SEAOC] Re: [SEAOC] wood panel shear wall/frames
- From: FredT5(--nospam--at)aol.com
- Date: Mon, 8 Jul 1996 19:55:14 -0400
You might check out proposal 248 in the 1997 ICBO proposed code changes which was approved as revised this winter. It provides pictures of height to width ratio limitations for wood walls. In a nutshell, if you detail the horizontal and vertical boundary elements at the corners of the openings in the walls for the respective force and moment transfer, then the effective height of the opening can be defined as the clear height at the side of an opening. See pages 140 and 141 of the March-April 1996 ICBO Building Standards Part III monograph. You'll need to check with the SEAOC Code Committee to see if there are any significant challenges to this proposal. If successful, it will be part of the 1997 UBC. Also, the Wood Technical Subcommittee 7 of the BSSC just wrote the following: Recent testing and observations from Northridge have suggested that holddown posts experience notable displacement before significant load can be carried through the holddown connector. The result is a large deformation demand placed on the nails connecting the sheathing to the framing. This often results in the nails pulling out of the sheathing at the holddown post corner and sometimes resulting in an unzipping effect where a significant portion of the remaining sheathing nailing fails as high loads fail one nailed connection and move on to overstress the next nail. The most effective solution currently known is to limit the slip and deformation at the holddown post by using a very stiff nailed or screwed holddown. When holddown slip is less than 1/16 in or so, the assumption of wall stiffness porportional to length is fairly reasonable. For larger holddown slip values, wall stiffness will move towards being proportional to the square of the wall length; more importantly, the anchorage will start exhibiting displacement compatibility problems discussed above. The currently available deflection equations are known to not always be accurate and need to be updated. Some new deflection formulas are also proposed in TS7's Proposal 7-7 now undergoing balloting. Hope this helps. ...
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