hate to throw water on everyone, but I wouldn’t necessarily call the old
uniform loads “sanity”. We’re debating in the ASCE wind committee right now
backing off some on the current minimum load, which is 10psf. The problem is
that on a typical low-rise (~35’ mean roof height) gable roof structure, it
takes something like a 150mph wind (if I recall correctly) to generate a 10psf
load on the vertical projection of the roof using the analytical provisions.
And the wind ends up governing over SDC C, and even SDC D level seismic
explains why all those buildings designed for 15psf, 20psf, or 25psf uniform
wind loads don’t seem to have any problems—it would take a Cat 5 or an EF4 to
take them down. Regardless of whether they’re built anywhere that could
get a wind event of that magnitude.
J. Ehrlich, PE
Program Manager, Structural Codes & Standards
Association of Home Builders (NAHB)
1201 15th Street, NW,
Washington, DC 20005
ph: 202-266-8545 or 800-368-5242
the 2009 International Builders' Show
January 20-23, 2009, Las Vegas, NV
From: Bill Allen
Sent: Thursday, December 18, 2008 6:05
Subject: RE: Wind
Waaaay back when sanity
T. William (Bill)
(949) 248-8588 •
From: HBAP(--nospam--at)aol.com [mailto:HBAP(--nospam--at)aol.com]
Sent: Thursday, December 18, 2008 2:07 PM
Subject: Wind forces
Ahhh, for the good ol'
Sec. 2307 (b):
For purposes of design the
wind pressure shall be taken upon the gross area of the vertical projection of
buildings and structures at not less than 15 psf for those portions of the
building less than sixty feet (60') above ground . . .
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