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Re: [SEAOC] Factors of Safety: Short-Term Structures

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> What about safety factors for short-term loading conditions such as during 
> construction or excavation - can safety factors be reduced for conditions 
> which may only last a few weeks or months?  For example, if portions of an 
> existing structure must resist abnormal loads during rehabilitation, is it 
> reasonable to reduce safety factors?  If so, by how much?  What about sliding 
> factor of safety for temporary excavation conditions? 
I feel that this is the best reason given so far for not permitting 
special concessions on load calculations for temporary structure.
Even if we know that the structure is temporary, and so many people
have recounted stories of "permanent" temporary structures, the 
design calculations in most case will be governed by load combinations
or load cases that have *low* probability of occurance.  For such 
cases, both the temporary as well as permanent structures will have 
the same probable maximum loads.

BTW, can anyone throw light on the actual probability calculations that
led to the load factors for different load combinations in design 
codes all over the world, including UBC.  

Ravi Sinha			email: rsinha(--nospam--at)
Assistant Professor		       rsinha(--nospam--at)
Department of Civil Engineering	       Phone: (91-22)-578-2545 Ext. 2336
IIT, Powai, Bombay - 400 076, India    Fax: (91-22)-578-3480