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RE: IBC 2007 Wind calcs.

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I want to say that this method is more or less based off the simplified method that Washington has produce and has been mentioned by others.
 
Personally, while I find there to be some complexities that I don't feel are necessarily needed in the current ASCE 7 wind provisions, I don't find them that difficult to use...including Method 1.  I find that I can pump out wind pressures in method 1 in very short order.  It does take more time to use those pressures to analyze stuff in MWFRS since they now have corner pressures and such...but you don't really gain that much compared to older more "uniform" pressures except for some buildings that might be rather succeptible to torsional effects.  But it does help that I have been using the ASCE 7 methods for a LONG time, while engineers in CA are more used to only using the simplified methods that were in the UBC.
 
I would be the first to agree that ASCE 7 has gone of the deep end to some degree in "sharpening the pencil" for wind provisions, but I am not sure that I would liken them to a doctoral thesis (unless you are talking about the wind provisions for signs or flexible structures or dynamically sensitive structures and have to start calculating gust coefficients).
 
Regards,
 
Scott
Adrian, MI
-----Original Message-----
From: Matthew [mailto:sandman21(--nospam--at)gmail.com]
Sent: Thursday, February 14, 2008 12:48 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: IBC 2007 Wind calcs.

You can also try using http://www.documents.dgs.ca.gov/dsa/pubs/IR-16-7_WindLoad_12-18-07.pdf
 
Matthew

On Thu, Feb 14, 2008 at 9:34 AM, Paul Feather <PFeather(--nospam--at)se-solutions.net> wrote:
Stan,

First off, the simplified method is anything but simple.  We use the
general method (method 2) for everything and get more consistent results
easier.  The simplified method is derived from metal building
manufacturer methods, and for anything but a metal building results in a
complete book keeping atrocity.

You are looking at 25 degrees area B.  The way the simplified method
works this is just one small area that cannot be applied in the same
thinking as the UBC horizontal projected area.  You have to add the area
B to the Area E uplift, basically all areas A through H get applied
simultaneously as one load case.  Then you rotate the building reference
corner and apply the whole thing again for all four reference corners.

Get away from the simplified methods and you will simplify your life,
while getting something closer to what you are used to.  I don't believe
the ASCE wind provisions could be any more convoluted and difficult to
apply to real world engineering if we tried.  The UBC methods were
derived as a conservative simplification of the ASCE provisions years
ago, and we desperately need to achieve something similar again.
Spending three days on a doctoral thesis to develop simple wind
pressures as opposed to working on load path and quality engineering is
counter-productive, and saving 1.4 psf in wind pressure only matters to
mass produced square boxes trying to be paper thin.

Paul Feather PE, SE
pfeather(--nospam--at)SE-Solutions.net
www.SE-Solutions.net

-----Original Message-----
From: sscholl2(--nospam--at)juno.com [mailto:sscholl2(--nospam--at)juno.com]
Sent: Thursday, February 14, 2008 9:09 AM
To: seaint(--nospam--at)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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