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Re: LFRS analysis programs

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It's been a couple of years now.  I looked at test data and the UBC calculation method & decided that  I'd just input an equivalently stiff plywood wall in my model. I should probably revisit the issue based on the new CUREE testing.

G Manandhar wrote:
I too developed a excel spreadsheet to do the LFRS. The spreadsheet does the distribution  based on either a rigid diaphragm or a flexible diaphragm - the wall rigidity can either be based on the wall length or on the based on relative rigidity similar to the one used for masonry and tilt ups (how good this is, I ain't sure).

While I am happy with the program output for buildings with plywood shear walls only, I am at a loss when I have a moment frame or a strong wall in the lateral system.  How do you guys that use rigid diaphragm analysis handle this (other than calculating the rigidity of the plywoood sheated walls based on the code deflection equation)?


rom: chuckuc <chuckuc(--nospam--at)>
Date: Sat, 16 Nov 2002 08:25:54 -0800
To: seaint(--nospam--at)
Subject: Re: LFRS analysis programs

A late response to Bill's(?) question regarding LFRS analysis programs 
for wood framing.  I wrote my own spreadsheet program, used Keylat, and 
now use Woodworks. As long as your walls are 6' or more in length, 
assuming that stiffness is directly proportional to length x capacity is 
pretty accurate (with the same kind of sheathing)--that's what Woodworks 
does. Keylat is almost impossible to use but Woodworks is fairly easy ( 
and no canned program I've seen handles non orthogonal walls).  The big 
advantage of  this kind of program is that you get a good look at a 
boundary solution ( although I use the rigid results almost 
exclusively).  Woodworks does allow for the input on user defined wall 
stiffness when you need to do that.

It adds a little bit of time to the analysis, and sometimes a little to 
the construction costs, but the CUREE program seems to be telling us 
that we aren't nearly as smart as we think when it comes to shearwall 
design (mainly in the reliability area). I'd rather be safe than sorry, 
and I seem to be cost competitive with engineers who just do a simple 
flexible distribution.
Chuck Utzman, P.E.

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