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Re: Seismic Upgrade ..... Appeal to those who created the code

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In a message dated 5/12/99 8:49:20 AM EST, ROH(--nospam--at) writes:

 As a further note, to Ali's excellent explanation below-
 The Building Seismic Safety Council's Technical Subcommittee 2 is in the
 process of reviewing an introduction into the 2000 NEHRP Provisions of a
 Simplified Design Procedure.  This will be somewhat similar to that
 contained in the 1997 UBC.  Major points are:
 1- Base shear is determined by a somewhat simpler, but a little bit more
 conservative formula.
 2- Vertical shear distribution is rectangular rather than inverse
 3- Deflections need not be checked
 4- (most of interest) Structural use panel diaphragms may be considered as
 flexible, for purposes of analysis.
 These provisions will be applicable to nearly all residential construction.
 While they will not "officially" take effect for a few years, it may help
 the "Standard of Care" issue to be able to point out that it was
 specfically included in the resource document recommended for future
 editions of the IBC. Also - the note Ali suggested on the design example,
 should help as well.

Do you anticipate that there might be a cut off point for when to analyze the 
structure for flexible or rigid depending upon the type of building. 


Single story Family Residence:  flexible, no deflection check
Two story Family Residence: flexible only, with shear wall deflection check 
of first floor walls.
Apartment buildings:  plywood floor:  flexible, shear wall deflection check
Apartment buildings:  plywood floor w/ 1-1/2" gypcrete: flexible and rigid 
checks plus shear wall deflection check.


Michael Cochran