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

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

>In Section 2.4.3 of ... ASCE 7-98 ... can I use a 1/3 allowable stress
>increase for a DL + W combination if I am using ASCE 7-98 wind loading?

I think the new language in ASCE 7-98 more strictly limits the use of the 1/3 stress increase. Note that ASCE 7 applies the 1/3 stress increase as a reciprocal 3/4 load reduction factor since they are a load code. The way I read it, ASCE 7-98 Section 2.4.3 does not permit the application of the 3/4 load reduction factor to dead load at all. Nor does it permit the application of the 3/4 load reduction factor to a transient load acting alone. Said another way, you can only apply it to the component of the total load that is due to multiple transient loads acting in the same combination.

Speaking more philosophically, the reasoning behind the 1/3 stress increase is probably one of the most debated topics around. And given the longevity of the 1/3 stress increase, its basis may now be lost in antiquity. An article in the AISC Engineering Journal by Duane Ellifritt titled "The Mysterious 1/3 Stress Increase", may give you some insight. It appeared in the 4th Quarter 1977 issue.

Charlie