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Re: Diaphragm Calculations

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Dennis,

If I am not mistaken, the units are mixed and do not cancel out for the 
diaphragm deflection equation since this is an imperical based equation.  
John Rose or Buddy Showalter may be able to give you a better answer, since I 
can't find my APA publication of plywood diaphragms and the equations used to 
estimate the deflection.  When developing equations to describe behavior of 
materials and systems, often the equation may be imperical, and to simplify 
the equation, then mixed units may be used which do not cancel out.

Assuming I am correct, then users of Mathcad are going to have to develop a 
work around to correct for the units.

The 0.188 is a constant that was developed when you have uniform nailing 
along the panel edge to describe nail slip.  If the nailing is not constant, 
then this factor is to be adjusted.  Since the UBC nailing schedules for 
plywood are assumed to be uniform, then the constant  to use is 0.188.   
Again for the nail slip portion of the equation you are using mixed units, 
they do not cancel out.

Dennis, I know that you have frustrations with the changes related to wood 
frame designs, as do others.  But your response to Doug seems a bit harsh.  
Both Doug and Bill are not the authors of these code changes, these changes 
were proposed by SEAOC seismology and adopted by ICBO for inclusion in the 
1997 UBC.  Doug and Bill are the ones that were asked to develop examples 
showing how to implement these code changes and what would now be involved to 
satisfy these requirements.  
 
Michael Cochran