Weight and wind load.
Those are the single largest items they have to deal with in towers that tall.
The more weight, the more they have to build up the lower structures, which increases wind load... higher wind load means larger guy wires. Larger guy wires means more pressure on the lower structures pulling down... which means larger structures... which means more wind load... which means larger guys wires... etc.
Heck, it is wasn't for that... they'd all have elevators in them all the way... at least a cable lift up there.
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greg@gregfolkert.net
PGP key 1024D/B524687C 2003-08-05
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Edited by
folkert
Jan. 28, 2013, 09:28:56 AM EST