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RE: Wind on Small Signs

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> Fellow Engineers,
> I have a client that wants me to check the wind loading on small
> signs (no parking, handicap, 18" x 12" type) and how high these
> signs can be placed on the pole.  They are placed in a precast
> pyramid type base.  I initially used ASCE 7-02 for solid signs
> and a 90mph wind, and followed the steps for these signs in ASCE
> 7-02.  These signs are used in large parking lots that are totally
> open. Is this the correct path or is this too conservative?

Technically, this is the correct path.  If you design everything exactly per
code then theoretically those signs should be completely stable in
everything but an F2 or higher tornado.  If you're in a hurricane zone it's
even more stringent.

BUT, ASCE 7-02 loads are intended mostly for life-safety and prevention of
damage to structures.  If these signs are blown over, will it cause damage
to the signs or base?  Will anyone get hurt if a "no-parking" sign falls
over in a thunderstorm?  If the answer to either of these is "YES", then you
need to use full ASCE 7 loads. 

Otherwise, I'd allow the client to make the decision as to the level of
design, as long as my professional ethics are preserved.  Maybe use the full
design loads but without the 1.5 factor of safety vs. overturning; or keep
the 1.5 factor of safety with lower wind loads.

The lesser loads should result in smaller sign bases or higher (or multiple)
signs on a standard base.  The down side is that the ultimate owner might
have to pick them back up when they fall over every couple of years in a
thunderstorm.

HTH,

---
Jason Kilgore
Leigh & O'Kane, LLC
Kansas City, Missouri



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