[TowerTalk] Fwd: Tower Permitting Spec's
jimlux at earthlink.net
Tue May 1 14:00:52 EDT 2018
On 5/1/18 8:46 AM, Grant Saviers wrote:
> The reference about power line cable oscillations is interesting, I
> think more applicable to wire antennas rather than masts. I found this
> thesis which delves into the issues for masts and how to use FEA tools
> to analyze them (it's an MS level thesis so is at least superficially
> readable by me w/o delving into the partial differential equations, etc.)
a very interesting thesis.
BTW, he (and everyone else) cites Blevins - "Applied Fluid Dynamics
Handbook" - this is a really, really useful book because it gathers all
the useful stuff, both theoretical and empirical, into one place. It's
kind of pricey ($70) but it has simple answers for all kinds of drag
questions and useful tables for stuff. You want to know what the
formula is for a grid of X" diameter bars separated by Y", it's in there.
You want to know what the standard wind velocity and turbulence profiles
vs height are? It's in there.
There *is* some stuff that's more modern that is worth tracking down,
but for the most part, Blevins is the tome to look at first. (When
google says "Cited by 1410" - that tells you something).
I wonder if some of the cases of wind induced tower/mast vibration are a
case where the tower is actually being driven by vibrations of the guy
wires. The other thing is that the drag forces on guy wires could be
pretty substantial in a high wind, and most of the analyses you see
focus on drag on the tower and antennas.
I'll have to get my copy of Blevins out and see what the drag on a 100
foot length of 3/16" would be in a 100 mi/hr wind.
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