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RE: Wood Moment Frame?[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Wood Moment Frame?
- From: "Dennis Wish" <dennis.wish(--nospam--at)gte.net>
- Date: Wed, 5 Dec 2001 15:59:24 -0800
George, I couldn't agree with you more. SEAOSC published a document - their plan called Vision 2000. At the time, Vision 2000 was considered a plan to revise building codes to be performance based. I interpreted this to mean that the person with the checkbook could decide how much protection he was willing to invest in. This was a dangerous scheme. If you go back through many of the SEAINT archives, you will find that I attacked Vision 2000 since before the codification of 97 UBC. I was told at the last SEAOC convention held in Santa Barbara (was that 1999 or 2000) that SEAOC had no intentions of trying to promote a code that attempted to predict the performance of a building and then what they published did exactly that. However, the published code simply took away the choice and increased performance expectations while increasing design complexity. It seems strange to me that in 2001 we are still using the 1997 UBC (have not adopted the 2000 IBC) and still do not have an appropriate tool on the market that is commercially available to design in full-compliance with the intent of the code (notice that I use Intent of code as an oxymoron). On the other end of the field is the one section of the code for Type V that acts to negate all of the intentions of the code write - a small prescriptive section (2320) called Conventional Construction. I hear groaning in the background (here he goes again!). The sad fact is that there is a dividing line between these two sections of the code (full-compliance and conventional prescriptive construction) acting like a wide parkway between two roads running in opposite directions. One wants builders stiffer and more predictable but doesn't really understand the nature of the materials. The other side wants less material, less controls and is finding that their understanding of performance needs a little bid of strengthening in regions of high risk. No matter how hard many of us have tried to make these issues public, there are enough voices to dilute the issues so that each side continues to work independent and offers no hope of compromise. I will admit that I personally am leaning at the more liberal side on this argument as those who promoted conventional construction are doing more in the form of research and development to test the performance of cost effective methods such as perforated shearwalls, proprietary shear elements, and much more. On the other side is our Seismology Committee who has yet to address with conviction, the issues that we have been questioning for the last two or three years. The answers are always the same - there is nothing anyone can do to change a code that has no future, and if you have a problem with it you should be involved and try to change it (a Catch-22). What I do see emerging is an effective prescriptive method in the form of the next IRC. This looks pretty good as long as you don't use it in the high risk zones. If you want to jump into this discussion without offending SEA on their own list, you can access the thread at: http://www.structuralist.net/cgi-local/yabb/YaBB.cgi?board=gen_tech_chat &action=display&num=1007596623&start=0 (this link should all be on one line starting with http: and ending with start=0) Dennis S. Wish, PE California Professional Engineer Administrator - The Structuralist.Net Website: http://www.structuralist.net Professional Forum: http://www.structuralist.net/cgi-local/yabb/YaBB.cgi Public Forum on Housing: http://www.structuralist.net/cgi-local/yabb2/YaBB.cgi Our older "UltraBoard" discussion forum will remain operational for the next 30 to 60 days until all information has been sucessfully transfered to our new board listed above. If you are a registered member of the old forum, please logon to our new forum noted above and re-register. You may use the same name and password. You may continue to use the old board until all information has been transfered, at which time the board will be shut down to conserve on Server space. -----Original Message----- From: George Richards P.E. [mailto:george(--nospam--at)borm.com] Sent: Wednesday, December 05, 2001 1:22 PM To: 'seaint(--nospam--at)seaint.org' Subject: RE: Wood Moment Frame? Why should the house survive undamaged after a big wind storm? I thought that is what insurance was for. It should survive after a common wind storm or earthquake for that matter but not the BIG ones. I think the codes are now chasing their own tails in the sense that now in trying to make everything stiffer, stronger, and better they have lost sight of their own intent, which I thought was life safety, not economic security. The only reason the lawyers love us so is because we do not even know what we want any more. Sorry for the rant, but living in the world of type V I see the code not through rose colored but broken glasses, (sorry John could not resist the pun.) George Richards, P. E. -----Original Message----- From: Dan Goodrich [mailto:dang(--nospam--at)karren.com] Sent: Monday, December 03, 2001 9:18 AM To: seaint(--nospam--at)seaint.org Subject: Re: Wood Moment Frame? This was my concern from the start. I got involved with the project because of an issue with a suspended concrete floor slab. As I was going through the plans, I noticed the narrow shear walls. Out of curiosity I called the EOR to find out how he justified it. Apparently, the report that John Rose mentioned is about to be published. This is the response I got from Tom Skaggs: "The information that you request has recently been finalized in APA Report T2001L-56 "Narrow Wood Portal-Frame Bracing Segments"." I don't know when it will be available though. He is going to mail me a copy. Thanks, John! I think I have talked the EOR into using a Strongwall. We'll see. He did not perform a deflection check. I doubt it would meet the code requirements. I've noticed that a few of the strongwalls have a full height metal strap at the edge. I wonder if this is to limit deflection? George Richards asked "Where is the life safety issue?" If only we had to worry about life safety. What do you tell the owner/lawyer when the garage door won't open after the big wind storm because the garage is slightly out of plumb? Thanks for all the input. Dan Goodrich, P.E. ---- Original Message ----- From: "chuckuc" <chuckuc(--nospam--at)pacbell.net> To: <seaint(--nospam--at)seaint.org> Sent: Friday, November 30, 2001 11:31 PM Subject: Re: Wood Moment Frame? > The proposed wall has an aspect ratio of 5:1 and is not UBC compliant (see > Fig. 23-II-I b)--and that should be the end of the discussion. > It is certainly possible to build such a wall so as to meet the code > required drift limits, but it is extremely difficult if the loads are large > (and you'd need lab tests to prove it). Simpson (and a few others) have > gone to great lengths to fabricate and test code compliant portal > frames--tell your guy to buy some. > The aspect ratio multiplies all the sources of deflection: construction > slop, shrinkage, tie down deflection, fastener deflection, plate crushing, > etc. 5:1 is a killer and the problem is not amenable to accurate calculation > even if you tried to control all the construction variables. (I don't even > think Simpson's tests with green headers are accurate because they didn't > allow their headers to shrink before they tested them.) > Chuck Utzman, P.E. > > ******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ******** ******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********
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