It depends on the strength of the tower. A classic brick chimney almost
always breaks into two or more parts. The reason is the top has to
accelerate faster than the bottom for the chimney/tower to stay
straight, i.e. for all parts contact the ground at the same time since
the top has more distance to cover. Since gravity is a uniform
acceleration force, the tower/chimney bends instead as the top lags
behind. For brick chimneys there is little strength in tension and they
come apart. For a steel tower and perhaps reinforced concrete chimneys,
they may be strong enough to only bend or kink. I saw first hand the
result of a 100' steel pipe flagpole failure at its base, and it did
break before hitting the ground. I missed the actual fall by 5 minutes,
which was mighty good luck. It bounced off the ground and meat
cleavered two cars almost in half lengthwise.
A different kind of failure is a pancake collapse, which is what
happened in the World Trade Center terrorist attack. If a middle or
bottom floor support fails, the now kinetic energy of the structure
above pancake collapses the entire structure more or less straight
down. So if demolition charges take out say 20' of tower legs, the
whole thing might pancake on itself, since the compression strength of
the tower legs are exceeded by the momentum of the structure above.
Grant KZ1W
On 4/6/2016 16:58 PM, Kathy Bookmiller via TowerTalk wrote:
Probably many of you have already seen this, but this is a HD version with more
views of the tower demolition.
I have one question. I've always heard that when a really tall tower comes
down, it basically collapses onto itself and doesn't fall as one solid unit
extending out the height of the tower. Watching this, I see many of the towers
didn't collapse into one small area but went down as a full unit.
Kathy
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