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Re: Precast Double Tees Diaphragm

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Michael Valley wrote:

>>This interpretation is further supported by the last paragraph of Section 
6.12.1 of FEMA 273 which says, "Untopped precast concrete diaphragms have 
been limited to lower seismic zones by recent versions of the Uniform 
Building Code.  This limitation has been imposed because of the brittleness 
of connections and lack of test data concerning the various precast 
systems." <<

In addition to this, I would like to add that I believe that the 1964 Alaska 
earthquake (Prince William Sound EQ) exposed some dramatic failures of 
precast T's that were constructed without topping.  IIRC (I will have to look 
in the book tomorrow), the transverse ties (flange-to-flange weldments) 
simply pulled out of the flanges.  (IOW, they were no damned good as 
diaphragms!)

A. Roger Turk, P.E.(Structural)
Tucson, Arizona