Phil,
Oh, I am definitely not arguing (I am an EE myself and the structural stuff
is definately somebody else's ballywick) - just wondering what the purpose
of increasing the base size was - and I think soil condition was
mentioned. So if that is the case I am assuming that the idea that the
base should support the tower and windload without tipping over even if the
base is above ground is a myth and the ground surrounding the tower is an
integral part of the specifications provided by the mfg.
Thanks for the reply,
Rick
W2RDS
At 05:53 PM 11/18/02 +0000, kb9cry@attbi.com wrote:
>Rick, being a chemical engineer myself, I will and always have, left the
>details to the structural guys, but the engineer probably is increasing the
>base size due to his knowledge of the local soil conditions. You'd need a
>larger base if the soil can't support the lateral forces to prevent the tip
>over event. Also, when an licensed engineer stamps a drawing/design, they
>are
>taking full responsibility (and possible liability) for it's design and
>use. I
>wouldn't argue with an extra yard of concrete; whatever it'll take to get the
>permit. Gd luck, Phil KB9CRY
> > All,
> >
> > Have a couple of questions that I was hoping one of the many learned
> people
> > on this reflector could help me with, for my own understanding.
> >
> > 1. I have a ham buddy who is putting up a 72' freestanding tower and as
> > part of the permit process had to have the drawings reviewed and approved
> > by a New Jersey PE. One of the things the PE said was that the size of
> the
> > base had to be increased from the 4x4x7 (or whatever the exact dimensions
> > were per the mfg) to 5x5x8 (essentially one foot larger in each
> > dimension). So my question is, what does that do for the strength of the
> > tower? It seems to me that all it does is make it more difficult for the
> > entire tower (including the base - intact) to tip over, which seems like a
> > pretty unlikely failure anyway?
> >
> > 2. I have heard that the size of the base is such that it would support
> the
> > tower and rated load, at the rated wind speed, even if the base was not in
> > the ground (i.e. sitting on top of the ground). Is that true - always,
> > sometimes, never?
> >
> > 3. Does anyone know of a reference source that talks about the windload
> > ratings of a crank up tower as a function of the height it is raised
> > to? In other words, if my tower is rated at 50mph winds with 9 sq feet of
> > load, at its full height of 67', what is the rating if it is extended to
> > half that height? I believe the rating increases as the tower is lowered
> > but I have not found anything authoratitive (or semi-authoritative) that
> > discusses this - even at a generic level.
> >
> > Thanks in advance,
> > Rick
> > W2RDS
> >
> >
> > _______________________________________________
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> >
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