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- To: seaint(--nospam--at)seaint.org
- Subject: '97 Code Questions - Answers needed ASAP
- From: Seaintonln(--nospam--at)aol.com
- Date: Mon, 5 Jul 1999 13:59:29 EDT
- Cc: BCASE1356(--nospam--at)aol.com, BJASELA(--nospam--at)aol.com, Calse(--nospam--at)aol.com, dickandpatel(--nospam--at)earthlink.net, farzad(--nospam--at)johnmartin.com, fredschott(--nospam--at)yahoo.com, hessengineering(--nospam--at)csi.com, jbruce(--nospam--at)smtplink.dsa.ca.gov, jnairvine(--nospam--at)compuserve.com, jslaicse(--nospam--at)earthlink.net, SaifH(--nospam--at)aol.com, shafat(--nospam--at)bqe.com, cgreenlaw(--nospam--at)speedlink.com, hoh(--nospam--at)eqe.com, GRileyPE(--nospam--at)aol.com, buddy_showalter(--nospam--at)afandpa.org, SE4044(--nospam--at)aol.com
Okay, I've asked this question numerous times and am getting the strong impression that the majority of you are in the same boat as I am - simply don't have a clue. Assumptions: 1. Plywood diaphragms lie someplace between flexible and rigid 2. Can disregard gables, vaulted ceilings, hips, valley's, scissors etc. Treat all as rigid (or semi-rigid). Questionable Assumptions: 1. Since a plywood diaphragm is not entirely rigid, is it appropriate to isolate sections (for example each leg of an "L", "U" or "V" shaped structure) and analyze it separately? See next statement for justification. 2. I would assume that you can not make a rigid connection out of wood members without full embeddment and, therefore, each leg of a non-rectangular structure will exhibit some non-calcable deflection that makes it act like a hinge. If this is true, than only continuous diaphragms where the direction of framing, continuity of overlapping plywood (staggered load case I) should be considered rigid - all others considered the joint between continuous beams. Let's make some definate decisions here!!!!!!!! Suggestion 1. Buildings with diaprhagms at different elevations that transfer shear through cripple or pony walls can be broken into blocks and modeled separately. Suggestons 2. Non-rectangular wood buildings with plywood diaphragms should be considered "hinged" at the junction of each "leg" and allowed to be broken down into blocks (or provide a means to calculate the stiffness of the intersection of the legs to resist rotation and calculate the deflection of each leg). I, like most of those in practice, are trying to resolve these issues as we work through existing projects that need to be completed in a reasonable time. There is simply not enough published information to justify the intent of those who created this section of the code as to how it applies to wood framed structures. The methods are fairly consistent with masonry and concrete structures and does not represent such as major change. However, wood structures have never been modeled in this manner and offer too many creative assemblies to apply such a generic and limited code. Inasmuch has been adopted, we need to resolve these common yet creative problems in the most expedient manner. It is not reasonable for SEAOC or ICBO to make the community wait while Seismology committee or the wood committee's try and work out a solution that should have been considered a long time ago and ready by July 1, 1999. This is simply unacceptable to our clients, many of whom are paying interest on borrowed money while we sit back and debate issues that should have been resolved. I urge SEAOC and ICBO to either Rescind the compliance of this code and roll back to the standard of practice prior to this code (and don't debate the wording of the '88 and '94 code which was never used for wood construction even though it did exist in wording). Otherwise, I urge you to address the problems faced by the majority of us in real world design problems. Dennis S. Wish PE
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