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Re: 97 UBC Drift: ASD vs Strength Design

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In a message dated 10/12/1999 8:34:36 PM Pacific Daylight Time, 
Byainc(--nospam--at)aol.com writes:

<< I believe the intent of the statement "Where allowable stresses....." in 
 section 1630.9.1 is to clarify that once you determine that drift 
 requirements are satisfied and you want to check the stresses in the 
 elements, you can reduce the earthquake forces by 1.4 if allowable stress 
 method is used. This does not imply that you can check drift requirements by 
 reducing the base shear by 1.4. Delta, S is always determined at strength 
 level regardless of what method you use for checking element stresses. >>
 

Sorry Ben. I have to disagree with you. That's not how I read section 
1630.9.1:

"A static, elastic analysis of the lateral force-resisting system shall be
prepared using the design seismic forces from Section 1630.2.1....  Where
Allowable Stress Design is used AND where drift is being computed, the load
combinations of Section 1612.2 (changed to 1612.3 per May '98 errata) shall
be used."

Why would the code deal with the stress check of members in the drift 
section, when it already covered it in other relevant sections?

Oshin Tosounian, S.E.