Thursday, February 14, 2008

RE: IBC 2007 Wind calcs.

What is your roof angle? And which zone are you looking at?

If you take a fairly typical roof pitch (say 6:12), then the horizontal ps30
pressures will be about:

Zone Horizontal Pressure
A 14.4 psf (End zone of wall - is a distance 2*a wide)
B 2.3 psf (End zone of roof - a distance of 2*a wide)
C 10.4 psf (Interior zone of wall)
D 2.4 psf (Interior zone of roof)

This basically means that you have a lateral MWFRS pressure of about
somewhere between about 10.4 to 14.4 psf acting laterally on the wall
surfaces for a mean height of 30 ft, Exposure B, Kzt=1 and I=1.

Regards,

Scott
Adrian, MI

-----Original Message-----
From: sscholl2@juno.com [mailto:sscholl2@juno.com]
Sent: Thursday, February 14, 2008 12:09 PM
To: seaint@seaint.org
Subject: IBC 2007 Wind calcs.

After 40 yrs. of doing UBC calcs. I am attempting to do my first IBC calcs.
and need help, even after attending a seminar, which seemed to cover lots of
things but not this.

For a simple house, using 6.4 Method 1 Simplified Procedure, I cannot get a
reasonable wind pressure of something between 15 psf and 25 psf.

>From 6.4.2.1, I get p s= 1.0 (1.0) 1.0 (2.3) = 2.3 psf which is
>unrealistic. This is using Fig. 6-2, exposure B, h=30 ft., Kzt =1
and I=1

Can someone point out my omissions/errors?

Stan Scholl, P.E.
Laguna Beach, CA
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