[TowerTalk] [Bulk] VOA tower demolition in HD

[Grant Saviers]

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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