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RE: wood panel wall aspect ratios: shear transfer around openings

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Title: wood panel wall aspect ratios: shear transfer around openings
Scott
 
The intent of placing that Figure in the 97 UBC, as I recall, was to provide an alternate way of meeting the aspect ratio, since the limits on the ratio were reduced in that edition. I remember this well since I was on the ICBO Lateral Design Committee that year. Kelly Cobeen, representing SEAOC, was the originator of the idea. And there was much discussion on whether we should place a figure in the code, since much of the code is prescriptive language. But finally it was decided that the best way to convey the idea was by inserting a figure in the code.
 
At no time was there any discussion of altering how you place the holdowns in the wall. Everything else remains unchanged. The Perforated shear wall concept is intended to address the alternative to this, which is allowing the wall as a whole to be analyzed for overturning. But that is a completely different method of design and has nothing to do with Figure 23-II-1.
 
In regard to satisfying statics in the spandrels above and below the openings, I think it's a waist of time. If you are designing the piers to take all the load, what is the point of analyzing the shear flow in the spandrels? The worst that could happen is that you could have a few nails pop in the spandrel and the force getting redistributed to the pier, which were designed to take the load in the first place.
 
Then again that's my opinion and you may not agree with it!
 
Ben Yousefi, SE
San Jose, CA
-----Original Message-----
From: Haan Scott M DPW CIVIL ENGR(n) [mailto:scott.haan(--nospam--at)richardson.army.mil]
Sent: Monday, November 25, 2002 3:07 PM
To: seaint(--nospam--at)seaint.org
Subject: wood panel wall aspect ratios: shear transfer around openings

Hello:

97 UBC Figure 23-II-1 says that you can reduce shear wall height to width ratios if you detail force transfer around openings.   Design guide examples I have seen do not use interior anchors and so have alot more involved design of the filler panels and "panel zones".   It seems to meet the intent of the code when uplift anchors are used next to openings [with full height nailing based unit shears from horizontal pier lengths] and when only horizontal shear transfer has to be detailed above and below openings.  It seems conservative and to meet the intent of the code, to use  horizontal drag struts in the wall above and below wall openings and to design overturning restraint the traditional way ignoring filler panels [nail the whole animal based on the peir unit shear]. 

It also seems pointless, with the previously mentioned method, to assume filler point inflection points if the filler panels are not going to loaded vertically because of holdowns each side of openings especially if you edge nail vertical edges, horizontal edges, holdown posts, and horizontally at reinforcement above and below openings based on peir lengths.

How are other places handling this? Is everyone just using 2:1 full height walls? Are there any good convincing published design examples floating around out there for people that are dim like me? Thanks.


Respectfully,

Scott M. Haan P.E.
Civil Engineer
Public Works, Engineering Department
Fort Richardson, Alaska
phone: 907-384-3161
e-mail: scott.haan(--nospam--at)richardson.army.mil