Re: How does controlled demolition work?

Controlled demolition of structures, or implosion, is carried out by 
carefully destroying the key elements that hold up a building.  I remember 
watching a television program on the subject on American TV not that many 
years ago.  I think it was an NBC network show hosted by Joan London.  You 
might contact them via the internet and see if it is available as a video.

Most buildings are a series of platforms (floors) separated by columns or 
load bearing walls in between.  If you can simulateosly destroy the 
supports in between each floor, usually destroying the top ones first and 
then each floor below in succession, the building will collapse upon 
itself, leaving little damage to adjacent structures.

This is done by carefully studying how the building is constructed, and 
often by looking at the plans from which it was built.  The explosives are 
controlled by placing them around key elements, such as steel or concrete 
columns.  I think I remember them wrapping the column and explosives with 
something to make sure the blast destroyed the column but little else 
nearby.

The safe distance from a blast is probably driven more by insurance fears 
and the smaller debris of dust and dirt that leave the site.  Most people 
would need hardhat and goggle protection if nearby because of the large 
cloud of dirt that forms during the few seconds of the event.

Try contacting the organization below to see if they can answer your 
questions.  They are associated with many of the most famous implosions you 
may have seen.


http://www.cdi-uk.com/implosion.htm

Controlled Demolition Site