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RE: Wind Loads on Monopoles

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At this point maybe you're better off to bite the bullet than continue
wrangling with the Bldg Official (disallowing the 2/3 factor for a
cylindrical pole seems unreasonable, though, basic aerodynamics would
indicate a lower drag coefficient for a circular section).  If, on the other
hand, you want to pursue it further with him, a good resource would be John
Loscheider, SEAW member and a key player in their Wind Commentaries on the
UBC .  I don't have a number for him, but he's probably in the Seattle
yellow pages under Loscheider Engineering Co.
> ----------
> From: 	Bill Allen, S.E.[SMTP:bill(--nospam--at)allendesigns.com]
> Sent: 	Tuesday, September 01, 1998 9:33 AM
> To: 	seaint(--nospam--at)seaint.org
> Subject: 	RE: Wind Loads on Monopoles
> 
> I have applied a Cq=1.4 to the attachments.
> 
> The building official won't buy Cq=0.8 for the pole (not even
> Cq=0.93=1.4*2/3).
> 
> The 25 psf requirement essentially negates any application of Ce, Cq, etc.
> as well as any reduction for low elevation.
> 
> Regards,
> Bill Allen
> 
> -----Original Message-----
> From: Horning, Dick/CVO [mailto:dhorning(--nospam--at)CH2M.com]
> Sent: Tuesday, September 01, 1998 9:13 AM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: RE: Wind Loads on Monopoles
> 
> 
> Here's a possibility -
> You're using a wind speed of 70 mph.  A number of special-purpose codes
> (such as AWWA D100 for steel reservoirs) assume 100 mph wind speed.  Using
> a
> stagnation pressure of 25.6 psf, it wouldn't require more than a 15' pole
> in
> Exposure C to get up to 25 psf.
> Having suggested that, if the pole is essentially clean of attachments or
> projecting elements, I would use Cq = 0.8 as you did.
> 
> > ----------
> > From: 	Bill Allen, S.E.[SMTP:bill(--nospam--at)allendesigns.com]
> > Sent: 	Monday, August 31, 1998 4:18 PM
> > To: 	seaint(--nospam--at)seaint.org
> > Subject: 	Wind Loads on Monopoles
> >
> > I have received some plan check comments on a foundation design I have
> > prepared. This foundation supports a monopole, 30 inches in diameter and
> > 100
> > ft. tall. The foundation is 5 ft. diameter and 15 feet deep. I used the
> > UBC
> > flagpole formula for the design (non-constrained).
> >
> > For the design, I used a Cq of 0.8 for the pole (based on "Chimneys,
> tanks
> > and solid towers" in UBC table 16-H). The plan checker wants me to
> > consider
> > the monopole as "Signs, flagpoles, lightpoles and minor structures" and
> a
> > Cq
> > of 1.4 with a 2/3 reduction for cylindrical elements. The kicker is
> (this
> > is
> > a DSA project) that, in the CA UBC, there is an additional footnote to
> the
> > table which reads "Minimum wind design pressure for flagpoles and
> > lightpoles
> > shall be 25 pounds per square foot." This equates to a wind pressure for
> a
> > structure 350 feet tall w/o reductions (Ce=2.12, Cq=2/3*1.4, qs=12.6).
> > This
> > footnote does not appear in the regular version of the UBC.
> >
> > I am interested if anyone has a reference for this code requirement and
> > what
> > kind of structure the authors of this provision was this provision
> > intended.
> >
> > Regards,
> > Bill Allen
> >
> >
> >
> 
>