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Re: ASCE 7-98 and 1/3 Increase for Wind Load

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The Special Edition Section 6.5.4.4 and the note on page 60 gives some direction
on the use of the load factors.   When using the Kd factor for wind, a
reduction, the combinations in 2.3.2 and 2.4.2 are to be used.  The strength
load factor for wind is higher so it seems logical that the 1/3 increase would
NOT be used for the allowable stress design.    The statement about "rate or
duration of load" sounds like it only applies to wood design.

Ed Haninger
Fluor Daniel




"PEC - Lake City" <pec(--nospam--at)isgroup.net> on 05/17/2000 01:39:49 PM

Please respond to seaint(--nospam--at)seaint.org

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Subject:  ASCE 7-98 and 1/3 Increase for Wind Load


Section 2.4.3 of the Special Edition ASCE 7-98 (section 2.4 deals with
allowable stress design) reads in part:
"Increases in allowable stress shall not be used with these loads or load
combinations unless it can be demonstrated that such an increase is
justified by structural behavior caused by rate or duration of load."

Does wind load meet the 2.4.3 rate / duration criteria?
In more simple terms, in steel design can I use a 1/3 allowable stress
increase for a DL + W combination if I am using ASCE 7-98 wind loading?

David Finley, P.E.
PEC - Lake City