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Re: Wind Loads on Monopoles

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Bill Allen wrote:;

<<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.>>

All the monopoles that I have been involved with (as a reviewer) have been 
designed in accordance with ANSI/TIA/EIA-222, the latest revision is "F", 
approved March 29, 1996.  This document fully defines wind loadings on 
poles, towers, antennae, dishes, etc.  This document also defines foundation 
requirements, including equations similar to the UBC "Pole" formulae.

Copies of this ANSI standard can be obtained from Global Engineering 
Documents, 800-854-7179 at a price of $80.00 each.  (Who knows, maybe you 
can find it cheaper at amazon.com.)  Hopefully, the DSA will accept 
calculations in accordance with an ANSI standard.

Rick Drake, SE
Fluor Daniel, Irvine