Probably because most building departments don't require IBC-2000 yet. Codes
get revised every few years, but municipalities don't have to adopt them,
and sometimes prefer to stay with the older code, since everyone is used to
it. For instance, Thousand Oaks, where I live, uses the California Building
code, 2001 Edition, which is based on UBC97. I would assume that most of
California is the same. One should also bear in mind that folks doing a LOT
of construction, or who have significant development plans might agitate for
a change in codes in a locality to make their life easier. Since you're in
the Las Vegas area, where there's a lot of new residential development, and
some pretty significant resort/hotel development as well, maybe one of the
developers likes the particular provisions of the other code, for what
they're spending their millions of dollars on, and is willing to convince
the city to go along.
It would probably cost a fair amount for the mfr (several thousand $,
perhaps) to update all the calculations, etc., and unless a majority of
their customers want it, they're not going to invest the dollars. How many
towers does the mfr sell in a year? How many of a particular model (because
the calculations are model specific)? Say they sell one tower of a given
type a week (50 a year) at $2000 a crack, retail. They actually only
probably get $1500 or so wholesale for the tower, so they're making around
$150 profit on each one. Call it $7500 total profit on that model for a
year. Say it takes an engineer a week to do all the calculations. That's
about $3000-$4000 (by the time you count the benefits, burden, taxes, etc.).
It's just not worth it for the company to blow half their profit margin on a
set of calculations that a small fraction of the customers need. They'll
figure that those folks who really need it will fork out the bucks needed to
persuade their local building department. As far as the retailer being able
to get data where you can't, I would think it unlikely. If the mfr has it,
they'll supply it. If they don't, the retailer's probably not going to do
any better than you, unless they can convince the mfr that they've got
customers lined up to buy towers, if only the mfr had the calcs.
So, in summary, it's just the economics of the situation. When it comes to
building regulations, hams are an anomaly, with little incentive on
anybody's part to make life easier (at least not for free).
Jim, W6RMK
----- Original Message -----
From: "Alan C. Zack" <k7acz@cox.net>
To: <WarrenWolff@aol.com>; <towertalk@contesting.com>
Sent: Monday, September 13, 2004 7:53 PM
Subject: Re: [TowerTalk] Calculations
> And why does a major tower manufacturer stick to outdated UBC-97 50
> and 70 MPH wind calcs rather than the newer IBC-2000 specs. UST did
> send me a nice set of drawings based on UBC-97 that my Bldg Dept said
> were great IF they were based on IBC-2000 instead. I suppose some
> hams will order and install the towers without a Bldg Permit or some
> Bldg Depts still accept the UBC-97 specs, but why can't they provide
> what the Bldg Dept requires?
> Even my local AES store tried to get the IBC-2000 specs for me and
> were also unsuccessful.
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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