From: Spike Jones (spike66@ibm.net)
Date: Tue Jul 20 1999 - 00:28:23 MDT
> Ron Kean wrote: If cost is no object, other materials which have
> a higher strength to weight ratio than steel could be used, such as
> titanium or perhaps carbon fiber composites. Doubtless much taller
> buildings could be constructed using steel than already have been...
Ron I may have misinterpreted Gina's original question. Assuming
she did not restrict herself to a *building* as we know it, but meant
*any* structure, practical or otherwise, in a 1 G field, how high could
it go? Lets ignore wind loads, since everyone would have different
assumptions on that, plus the aero drag on circular cross sections
are approximation-ey. Also, lets forget fiber composites, since they
tend to be lousy in compression, and ignore soils restrictions (assume
an infinitely rigid infinitessimally flat base).
Surprise: for this kind of application, good old common steel does
as well as titanium. The ratio of the sheer moduli (Ti/steel) is almost
the same as their density ratio (in fact steel is *slightly* better than Ti.
Steel beats aluminum and magnesium too). So assume a steel tower
and a solid round cross section since making it hollow doesnt allow you to
go any higher.
Lets assume a steel tower, minimum diameter of one meter at the
top, maximum diameter of 200 m at the base, sheer modulus of
8.3E4 MPa and a density of 7.8 g/cm^3. Come back tomorrow
with an answer, see if we get the same. spike
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