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m Structures

Terry Weatherby wrote:

<        It would seem the allowable stress increases could be used , at
<least for wood structures. For example, a structure with a life span of
<three months duration could be designed with a 115% stress increase (similar
<to snow loads in the UBC). A structure with a lifespan of seven days could
<be designed for a 125% stress increase (roof live load in the UBC). A
<structure that would be up for only an hour could be designed for a 160%
<stress increase (like for wind in the newer 1994 UBC)!
<       Personally, I have always designed short term structures normally
<knowing that I would have a higher factor of safety on them. 

It would be overly conservative to apply the duration of load factors
provided in the NDS because these factors are based on the structural member
being fully loaded for that duration of time.  A temporary structure will not
always be fully loaded.

Rich Lewis, P.E.
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