Gina's tower

Spike Jones (
Mon, 19 Jul 1999 23:28:23 -0700

> 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