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Re: Plwd: Rigid Diaphragm Analysis - Opinions Wanted

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Thanks Mark - I appreciate the help and think that most of us who are 
struggleing through this will also.
One thing that came up in the creation of the spreadsheet that may throw a 
few engineers who are not paying attention (I certainly was not) has to do 
with diaphragm deflection analysis. The first and second terms are 
derivitives of the typical beam deflection analysis. Some of us (I assume 
others have had this problem although I might be the only one) will 
interprete the term ' v ' in the formula:
5 v L^3 / (8 E A b)  as the shear applied across the span and may in fact 
compare this term to the load applied uniformly due to wind. The two are not 
the same and will yield incorrect comparisons.
The term ' v' used in the formula is the unit shear per depth of diaphragm - 
not per width of diaphragm. I missed this since I was thinking that the 
formula was looking at the deflection between supports rather than attempting 
to convert the unit shear through the diaphragm back into a uniform 
distributed load between the supports.

This became evident as I tried to compare wind to seismic and the ' v ' term 
increased as the span ( L ) changed.

Whoops - this is why it is very important to understand where these terms 
have been derived from. To all of you who have the spreadsheet - be alert to 
this and remember, it is only a beta version which needs you help to find the 


In a message dated 7/14/99 11:36:32 PM Pacific Daylight Time, 
mswingle(--nospam--at) writes:

<< Most of the recent responses to the original post by Dennis (on July 10) 
on the subject
 listed above have not addressed the original topic, so I suggest that we 
start a new
 thread on just the Simplified static procedure (97 UBC 1629.8.2 and 
1630.2.3).  This is
 an interesting topic by itself, so I will attempt to make some quick 
comments on previous
 points made about this topic, thereby starting the new thread.
 Also, let's not forget Dennis original questions on diaphragm analysis for 
 multi-story wood-frame buildings.  He hasn't received too many responses 
specific to his
 original question, and I think he brings up some interesting topics.  I will 
try to
 respond soon, Dennis (but not tonight....)
 Mark Swingle, SE
 Oakland, CA >>