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RE: New releases of Multi-Lat Flexible Analysis

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In our jurisdiction we have added a local amendment to the code to allow flexible analysis for wood diaphragms. We based this on an SEAOC position from 2000 that said

"For small, substantially regular buildings that have a good distribution of lateral resistance and are well tied together, earthquake performance to date suggests that design using flexible diaphragm assumptions is adequate for Life-Safe Performance....The results of an elaborate [rigid] diaphragm analysis are not likely to be significantly better than that produced by the conventional "flexible" assumption."

We still require analysis using rigid diaphragm assumptions where IBC section 2305.2.5 requires it and when the buildings have irregularities that will cause torsion to become an issue. 

Matthew O. Hood, E.I.T. 
Plan Review Engineer 
Municipality of Anchorage 
-----Original Message-----
From: Stanley E Scholl [mailto:sscholl2(--nospam--at)] 
Sent: Friday, December 03, 2004 7:31 AM
To: seaint(--nospam--at)
Cc: seaint(--nospam--at)
Subject: Re: New releases of Multi-Lat Flexible Analysis

How do you suggest one argue that the use of the flexible analysis is valid when in almost every case it is not possible to show that the walls are not more flexible than the diaphragm and therefore the rigid diaphragm analysis is required by Code?
I know this has been discussed previously but I don't believe we have ever come up with an acceptable answer.
Stan Scholl, P.E.
Laguna Beach, CA
On Wed, 1 Dec 2004 13:23:33 -0800 "Dennis Wish" <dennis.wish(--nospam--at)> writes:
You can now download the latest versions of Multi-Lat(tm) flexible diaphragm spreadsheet directly from the Structuralist.Net website. There is a dedicated Multi-Lat(tm) page that contains the flexible analysis and a separate but original rigid analysis that Dave Merrick worked on. I have also started a Blog that will be set up like written documentation including creative uses of the spreadsheet.
If you are using any version of Multi-Lat(tm) flexible analysis dated earlier than November 03, 2004 then please download the latest version. Many issues for multi-story shear distribution have been fixed. This Excel spreadsheet conforms only to the 1997 UBC or similar California Building Code. It does not cover ICC codes. 
Dennis S. Wish, PE
California Professional Engineer
Structural Engineering Consultant
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