I remember having to deal with ASCE seismic requirements once and they
might as well have been in Greek or Chinese.
Gary
Scott Maxwell wrote:
> Gary,
>
> The issue is that what was in the UBC for wind was rather straight forward.
> It was simple calculation of P = Ce*Cq*qs*Iw, where:
>
> P is the design pressure
> Ce is a factor to take into account exposure type (i.e. rural with no
> obstructions, urban with similar obstructions, etc), gust effects and
> height
> Cq is a pressure cofficient for the structure or the portion of the
> structure under cosideration qs is a basic wind pressure that is a function
> of the wind speed (basically 0.00256 * (wind velocity)^2) Iw is an
> importance factor
>
> It was a very simple, straight forward process.
>
> ASCE 7 has always been a little more complicated historically. It has been
> rather similar for MWFRS pressures, but had a separate method for Components
> & Cladding (C&C) that took into accound the tributary area of the element.
> Over all, that has been a major difference between the UBC implementation
> and ASCE 7...effects of the "wind sail size" for what ever element that is
> under consideration. Personally, this is where I think the UBC has always
> been weak. Generally, speaking, however, the older ASCE 7 versions were
> only a little more complex than what was in the UBC (it tended to look a lot
> more complex due to the nomenclature...the "variables" appear more "complex"
> or "bigger", but in reality it is not that much differnet).
>
> The more current versions of ASCE 7 have mucked things up quite a bit.
> There is now a Kzt factor which takes into account topographic effects (i.e.
> hills, enscarpments, etc and how they speed up wind, etc). They have added
> in a method for flexible buildings which literally feels like rocket science
> to me. They have move to more variances in pressures for MWFRS over
> different part of the structure surface. In general, the methods have
> gotten more complex and require more calculations and thought...more
> variables in the formula...more coefficients to look up in a wider array of
> tables and figures. Not to mention the organization of ASCE 7 leaves a lot
> to be desired at times.
>
> Regards,
>
> Scott
> Adrian, MI
>
> -----Original Message-----
> From: Gary L. Hodgson and Assoc. [mailto:ghodgson@bellnet.ca]
> Sent: Friday, February 15, 2008 8:03 AM
> To: seaint@seaint.org
> Subject: Re: IBC 2007 Wind calcs.
>
>
> List,
> I have been sort of following this wind discussion and wonder if you
> could enlighten me. Since we don't use your codes, I am wondering what
> it is about these new ASCE provisions that has got all your knickers in
> a knot. Can you send an example or copy of the particular section. If
> it is too big, don't bother. I am just curious.
> Gary
>
>
>
>
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