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Re: Open Walled "Shed"

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     At zero degrees the uplift may be zero,resulting in flutter, but as the
angle (by even 1/10's of a degree) APROACHES zero the uplift graph is
straight vertical and the magnitude is a function of the wind velocity so
the lateral deflection of the supports IS a critical factor to design for.

Greg
-----Original Message-----
From: Roger Turk <73527.1356(--nospam--at)compuserve.com>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Friday, September 24, 1999 11:49 AM
Subject: Re: Open Walled "Shed"


>Thor,
>
>Once again, I recommend referring to the report:  "Wind Forces on
>Structures,"
>published in ASCE Transactions, Vol. 126, Part II, 1961, page 1124.  Table
4
>on page 1160-1161 covers open shed roofs, such as may be used at railroad
>stations and includes the possibility of trains or stored material
>obstructing the wind.  Two roof slopes are considered; 10 deg and 30 deg.
>
>A. Roger Turk, P.E.(Structural)
>Tucson, Arizona
>
>Thor Tandy wrote:
>
>>>A peer has sought my opinion on the lateral wind loads to a structure
that
>is essentially a non-walled structure.  I.e. just a roof on a braced post
and
>beam assembly.
>
>My opinion was that he should use the the exterior vector coefficients in
the
>code for the roof using the internal pressure coefficients for a building
that
>would have large openings open during high winds.  If the eave boards or
beams
>are deep enough they could also contribute?
>
>That analysis provides a resultant vector addition according to the roof
slope
>(here 15 degrees) which would I believe be the main resultant lateral load
to
>the roof structure (together with some serious uplift).
>
>He felt that the load calculated that way was too small, even using
>corner/cladding coefficients.  I suggested using an elevated billboard of
same
>projected dimensions as an upper limit, but that gave a much higher number,
>too high to be reasonable for what is essentially an aerofoil on stilts.
>
>I think the simple vector addition of resultant roof pressures is
sufficient.
>
>What does the group think?<<
>