[TowerTalk] Mast wind loading
jimlux at earthlink.net
Wed Mar 29 10:27:26 EST 2006
At 03:20 PM 3/28/2006, Doug Renwick wrote:
>You are to be commended for sharing your experiences and I
>agree with your philosophy. A lot don't share their
>experiences because they get chastised by people who throw
>around words like 'unsafe'. Have these people ever heard of
>'risk analysis'? Really...how much will your tower
>withstand can only be determined by 'product testing to
>destruction'. If your tower arrangement has survived for 25
>years then IMO you have a safe installation. Great job!
Well.. there's really two aspects to these kinds of things..
The first is your personal risk acceptance posture. If a tower or antenna
failure affects only you, you get to get decide how strong or rickety you
want to make things. In this context, all the manufacturers'
recommendations, and various and sundry engineering discussions here and
elsewhere, basically go to make you an "informed risk taker", but
ultimately, you get to make the decision.
The second aspect, and one that is sadly becoming more important, is the
increasing regulatory environment, and the assumption of the responsibility
for failure by others (e.g. a city, your insurance company, etc.) 30 years
ago, I'll bet nobody ever asked for wet stamped drawings for a amateur
tower. You went out, dug the hole, put up the tower, and were done with it.
Certainly, that's what my friends and family did. These days, though, you
have to get a building permit, and that might require engineering analyses,
etc. Granted, in some cases, this is an attempt to get rid of
aesthetically offensive towers by burying them in paperwork and attached
fees for officials to review and comment upon that paperwork. However, the
regulatory burden has increased in many, many other areas, aside from
antennas(see below). In this application, you're asking someone else to
take responsibility (i.e. the city that issues the building permit, the
engineer who signs the plans, the insurance company covering the
installation). This naturally leads to a bit more conservatism. The
question has changed from "will the antenna and tower probably stay up" to
"Can you guarantee, with your life's savings, or the city's budget, that
the antenna and tower will not fall down?" Remember also, the cost of the
increased regulation falls on YOU, the consumer, not on the insurance
company who asks for more analysis (it actually reduces their exposure),
not on the city (which is now "safer", and has even increased their budget
with user review fees), so there's a HUGE incentive to ask for analysis and
As a licensed engineer myself, I use a VERY different standard on what I do
for myself than what I use professionally, and both are different than what
I might advise my friends to do over the lunch table. And, even in my
professional life, the level of analysis and margins might depend on a risk
analysis and an acceptance of potential failure consequences.
(on regulatory burden increases) It's not all due to "blood sucking, bottom
feeding plaintiff lawyers", as much as some would like to believe it. I
think it's more due to a "tragedy of the commons" type situation, where the
lack of regulation prompts a few people to really push the limits (in the
interest of improving their financial bottom line), leading to an egregious
event, followed by calls that "something MUST be done to prevent this
horrible thing from ever happening again". I'd say it's more a function of
the emphasis on monetizing everything, and being a "good citizen" costs
money, reducing the bottom line. I'd (cynically) blame the B-schools for
encouraging analysis in terms of cost/benefit with all aspects reduced to
some dollar value, that can then be tradedoff.
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