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

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I recall reading or hearing that an ASCE committee is
working on a Standard regarding the design of
temporary works.

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Date: Wed, 20 Mar 96 09:05:00 PST
From: "Nester, Melvin R." <mrnester(--nospam--at)>
Subject: RE: [SEAOC] Factors of Safety: Short-Term Structures

In many industries--such as aerospace--short design life is a common 
parameter.  Often the useful life of a new facility is 6-18 months.   In 
designing such, minimum  factors of safety do not change, and codes are 
still "minimum" requirements.  Design decisions for durability, maintenance 
costs, and longevity, however, may not be same as for the typical 30 year 
structure.  (According to the IRS, minimum design life of a typical 
structure is 30 years.  Anything less is "accellerated amortization".)

M. Russell Nester, SE, GE
From: billp(--nospam--at)
To: seaoc(--nospam--at)
Subject: [SEAOC] Factors of Safety: Short-Term Structures
Date: Tuesday, March 19, 1996 6:58PM

A bit of a philosophical question:

We don't often think about the fact that, when we design a structure in
steel or concrete, using the requisite building/design codes, there is a
built-in supposition that the structure is "permanent," which in
practical, human terms means a life-span of perhaps twenty years or so
(unless it is a sports stadium, which seems to be "old-fashioned" and
"out of date" within five years after completion, if you believe the
NFL/NBA owners.  But I digress...)

But what if you have a structure which, although it will have a glorious
existence, will have a necessarily brief one?  By "brief," I'm talking
in terms of just a few weeks!  Must you apply just as rigorous a regimen
of safety factors to such a structure?  And if not, HOW would one
rationally compute the "additional" allowable?

I'd love some input on this.  Thank you.

*      William L. Polhemus, Jr., P.E.         *
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