[TowerTalk] Comparing Structural Standards

[Kurt Andress]

Hi All,
This is a followup to the "Formula" thread.

Dave Leeson, (W6NL ex W6QHS) sent me a paper he prepared quite some time
back titled Comparison of Wind Force Structural Standards. It is a very
informative look at the differences, or lack thereof, between them. 
To boil the whole thing down I'll just cite a summary chart from the paper:
Wind pressure in Lb/SqFt @ 70 Mph fastest mile basic wind speed.

Standard	Height = 33'	Height=100'

EIA 222-C	20		20
EIA 222-D/E	19		24
UBC		17		21
CP3		22		24
ASCE		17		20

The differences are not particularly dramatic. We can still use the simple
..004V^2 from EIA 222-C and use a safety factor of 1.2 if we want to get
closer to C at 100 Feet. Most of us don't know exactly what the fastest
mile of wind is at our qth, we are usually designing for approximations and
comparing against other designs we know that have survived.

73, Kurt

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