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Re: wind loads

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Bill Allen

P. Rajendran wrote:

> In some posts, such as this one, "word wrapping" is absent.  It
> becomes
> somewhat cumbersome to read the post.  Is there something I can do to
> introduce "word wrap" in the document, or can something be done by the
>
> author so that the document is contained within the screen width?
>
> Rajendran
>
> Harold Sprague wrote:
> >
> > Mark,
> >
> > Be careful to establish whether this is a "fastest mile" wind, a "3
> second gust" wind, a "sustained wind", or a wind reported by the
> weather service that has not been normalized.  It will make a very
> large difference.  The ASCE 7-93 dealt with "fastest mile" winds as
> does the UBC.  The ASCE 7-95 deals with "3 second gust" winds.  If it
> is not normalized, call a wind engineering expert like CPP in Fort
> Collins, CO.
> >
> > This being reported as a hurricane wind suggests a "one minute" wind
> or "sustained" wind, which is the standard of hurricane guys.  They
> will spout things like the Saffir-Simpson scale Category 5 which will
> give a range of sustained winds.  If it is a sustained wind, convert
> it to a 3 second gust using the Krayer-Marshall curve that is in the
> appendix of ASCE 7-95.  Then use the ASCE 7-95 to determine the wind
> pressures on your structure.  The conversion is not straight forward.
> >
> > If you chose to convert to a "fastest mile" wind to use ASEC 7-93,
> be careful.  Using the curves becomes an iterative process in which
> you close on a time of duration.  It takes about 3 or 4 iterations and
> is not for the uninitiated.  You can reference Emil Simu's book on
> wind design for good commentary and examples.  There is a paper
> floating around that does not use the iterative technique.  It is
> wrong.
> >
> > Also be careful in how you use the wind pressures.  You will
> obviously use them to establish loads for your primary frame.  But
> lateral drift for building performance is up to the engineer.  The
> codes will not hold your hand on this one.  Currently the trend is to
> use a 1 year wind for human perceptibility due to lateral acceleration
> issues and a 10 year wind for deformation compatibility issues.  (Yes
> deformation compatibility is an issue in other than seismic design.)
> >
> > Regards,
> > Harold Sprague
> > Krawinkler, Luth & Assoc.
> > 4412 W. Eisenhower Blvd.
> > Loveland, CO 80537
> > Voice: 970 667-2426
> > Fax: 970 667-2493
> > Email: hsprague(--nospam--at)klaalov.com