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RE: Apartment Building Collapse

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Actually, the statement should be interpreted that there is no absolute
minimum life of a building against natural events of a certain magnitude
(wind, seismic, etc).  For example, in the latest seismic codes, the
"design level event" has a 2% probability of exceedence in 50 years (if I
recall correctly).  While I am not that great at probability, I believe
that means that there is a 2% chance in the next 50 years that a seismic
event will exceed that level...which translates into a recurrance period
of about 2500 years (that is a seismic event of that magnitude would occur
on average ever 2500 years).  It could so happen that it is "about that
time" (ie we have reached that 2500 year average), and then low and behold
a 1 day old building is subjected to a seismic event beyond the design
level and collapses.


On Wed, 13 Dec 2000, Christopher Wright wrote:

> >I believe that the extreme loads on structures (seismic,
> >wind, snow) have a probability of non-exceedance of typically 50 years,
> I'd say that would be interpreted that the absolute minimum life is 
> considered to be 50 years. 
> As a corrolary, most of the people I know who are involved in residential 
> construction have told me they wouldn't buy a house less than 15 years 
> old anyway. Minnesota has had some pretty serious problems ranging from 
> moisture accumulation and poor air quality to fancy coped structural 
> joints that wouldn't hold for various reasons, and in houses in the 300 
> grand+ price range. These may have service lives of around 50 years--some 
> needed rehab that cost more than a new house (keeping in mind that the 
> original cost included a lot, which wasn't replaced.) 
> Christopher Wright P.E.    |"They couldn't hit an elephant from
> chrisw(--nospam--at)        | this distance"   (last words of Gen.
> ___________________________| John Sedgwick, Spotsylvania 1864)