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RE: Old Seismic Values

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I don't place any more faith in polls than I do in political polls. I
personally believe that our historic data is not sufficient to be this
accurate yet, this does not mean that I don't believe the necessity to
improve the product. This is one of my main complaints with Conventional
Construction provisions since this is based upon a 180-year old (give or
take) history of the first use of platform and balloon framing west of the
Rocky Mountains when the railroad was finished and shipped out timber saws
to the area. The method of tying wood structures together using spikes
rather than simply locking wood together historically (as far as our records
go) seems to work compared to other forms of construction in high risk zones
such as Adobe.
Still, it seems ludicrous that beyond life safety, our society continues to
place such high value on owned land and property but does little to protect
the performance and ultimate out-of-pocket cost that the homeowner needs to
invest to repair or replace the structure. 
I am not debating engineering at this point - I have enough issues here.
What I am focusing on is the lack of our ability as the authority of
materials and physics of the performance of the materials to be recognized
as such and to set limits where 180-year old methods or alternative
construction can be used rather than caving into the politics of skewed and
spun statistics (the NAHB-RC Guidelines for performance of post Northridge
light-framing). I don't recall the exact name of the document and would need
some time to dig it out of my archives, but I read it and laughed through
all of my debates with NAHB-RC on the accuracy of such an obviously skewed
document that choose to ignore damaged buildings and look at undamaged
buildings randomly chosen to draw conclusions on that buildings performed as
expected and as they should.


Dennis S. Wish, PE


California Professional Engineer

Structural Engineering Consultant

dennis.wish(--nospam--at)verizon.net

http://www.structuralist.net

 


-----Original Message-----
From: Christopher Wright [mailto:chrisw(--nospam--at)skypoint.com] 
Sent: Wednesday, August 11, 2004 10:31 AM
To: SEAOC Newsletter
Subject: Re: Old Seismic Values

>The
>current codes use a 2% probability of exceedence (98% confidence) in 50
yrs.
Just for my own curiosity, when does the 50 year period begin? I'd feel a 
lot better if I could be sure it started last week rather than in, say 
1953. I'd be grateful if someone could shed some light on this as I'll be 
visiting San Francisco in October, and I'd rather be there at the 
beginning of one of those 50 year periods instead of the end.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw



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