Interesting and Educational!
Loyd E. Eskildson | Phoenix, AZ. | 09/15/2008
(5 out of 5 stars)
""Demolition" does a good job of both portraying the range of current demolition techniques and the methods used in the past.
The program's main attractions consist of explanations of how explosives are used in demolition and seeing them in action. Viewers see linear shaped charges (developed by NASA to separate rocket stages during liftoff), "boxing" to hold in shrapnel created by the blast, and partially cut beams (top and bottom of a floor) with "kicker" charges used to knock the centerpieces out. Viewers also learn the critical importance of timing the charges as a means of tilting a building's fall - as little as .5 seconds differential is required.
Some cities (eg. New York) do not allow demolition for fear of damage to underground utilities, subways, and nearby buildings. Then monster hydraulic shears that can cut through 1.75' steel beams may be used - some of these can reach up to 160 feet. Robotically-controlled machines are also used in some instances.
Cleanup of the World Trade Center was complicated obviously by the presence of human remains, as well as red-hot steel in some areas up to two weeks afterwards, and steel compacted by the force of the fall.
Demolition firms recycle as much as economically possible - metallic debris is separated, compressed, shredded, picked over manually and with magnets.
Time-frames: A medium-sized hotel taken down as part of the film required 4 weeks for preparation, 10 seconds to actually fall down, and six weeks to clean up. Mechanized demolition can take much longer - eg. 2 years for the ConEd generating plant in New York City."
Gift
K. Myers | Alexandria, VA | 09/05/2009
(5 out of 5 stars)
"My dad asked for a video of demolitions for his birthday. This was the only one I could find, and he loved it."