> OK, I agree with what you said. But why can't a major manufacturer
> like UST provide these calcs when required and smaller guys like
> Tashjian Towers and Heights Towers can?
>
> Jim Lux wrote:
> > 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
>>And why does a major tower manufacturer stick to outdated UBC-97 50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.
A possible reason would be that IBC-2000 might be a stricter spec,
and the tower is not engineered to meet that spec, at least with
a usable antenna area on top. Does anyone know if IBC-2000 is a
tighter spec, or just a different calculation algorithm?
Rick N6RK
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