Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Wind Loads on Monopoles

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I have applied a Cq=1.4 to the attachments.

The building official won't buy Cq=0.8 for the pole (not even

The 25 psf requirement essentially negates any application of Ce, Cq, etc.
as well as any reduction for low elevation.

Bill Allen

-----Original Message-----
From: Horning, Dick/CVO [mailto:dhorning(--nospam--at)]
Sent: Tuesday, September 01, 1998 9:13 AM
To: 'seaint(--nospam--at)'
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)]
> Sent: 	Monday, August 31, 1998 4:18 PM
> To: 	seaint(--nospam--at)
> 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
> 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