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WE'RE ALL IN THE SAME BOAT: Sorry About That![Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: WE'RE ALL IN THE SAME BOAT: Sorry About That!
- From: sasquake <sasquake(--nospam--at)uswest.net>
- Date: Wed, 22 Sep 1999 18:58:58 -0700
- Delivered-to: fixup-seaint(--nospam--at)seaint.org@fixme
SORRY ABOUT THAT! SHIP HAPPENS! "Ron O. Hamburger" <ROH(--nospam--at)eqe.com> Date: Fri, 30 Jul 1999 14:45:57 -0700 Subject: Redundancy Factor Previously had written: A recent thread of discussion on the list server has called my attention to what I believe is an uintentional and also unfortunate problem with this factor in the 97 UBC. When the committee first developed this factor, the intent was that the rmax represent the % of the story shear carried by the most heavily loaded element. We then proceeded to define what an "element" is. For example, each brace is an element, etc. When we got to shear wall structures, the intent was that each individual wall pier across a horizontal plane cut through the building would be an "element". Then, someone on the committee noted that if you had a 100' x 100' tltup type structure, with a number of 20' wide panels, this would be considered to have high redudance (because each 20' panel would be an element). However, if you had the same structure with cast-in-place walls, then it would be non-redundant, as the whole side of the structure would be only one element. In order to solve this problem, for shear walls, we introduced the rule that when a shear wall exceeded 10' in length, each 10' segement (or part thereof) could be considered an element. The intent was as follows - If you have a wall line with 10 - 4' piers between windows, each pier would be an element. If you had a wall line with a 40' wall, you would have 4 elements. Somehow, in the word-smithing that went into the actual code language, this logic got badly messed up. Now each wall segement is multiplied by 10/lw. This has the desired effect for long walls, but has a penalty effect for short wall segments. This was, in my opinion, never intended. This has some serious negative impacts on wood frame construction. Please consider this matter, at your next Seismology Committee meeting. *************************************************************
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