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RE: wind pressures[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: wind pressures
- From: "Gordon Goodell" <GordonGoodell(--nospam--at)harmonydesigninc.com>
- Date: Thu, 20 Aug 2009 11:49:41 -0600
Title: wind pressures
h = 21.5’, 3/12 shed roof
H = 1100’
Lh = 2100’
Dist from crest, x = 100’
Height above crest, z= 0 (top of roof roughly even w/ top of ridge)
Bldg is downwind (typically) of the ridge.
If I use the tabulated values for x/Lh and z/Lh in Fig 6-4. I get much lower (and realistic sounding) K values, but I don’t understand those tabulated values, where they come from, or what they mean. how could they be tabulated without knowing x or z? Maybe they were intended to be max values, which would be nice, but it doesn’t say that anywhere.
Can you provide some more details on the topography and siting of the house? While I’m not an expert on topographic effects by any stretch of the imagination, something seems way off. I have access to some unpublished tables of Kzt factors (work in progress for the next edition of AF&PA’s WFCM). The maximum Kzt for a 2D-ridge is 1.77--for a 25% upper half of slope, 1000-foot high ridge, and the house right at the crest.
J. Ehrlich, PE
Attend the 2010 International Builders' Show
I’m working on a house just below the crest of a very big ridge (2D)...a very windy site in a not unusually windy location. Accounting for topographic effects, I get Kzt = 2.83, almost tripling my wind pressures. End zone wall pressure for MWFRS is 38psf! Just for comparison, what kind of pressures do those of you in hurricane country deal with?
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