Sunder noted that the collapse resembled a controlled demolition because, as the thermal expansion caused the failure of three critical internal columns, the collapse started internally and progressed to the exterior, just as in a controlled demolition.
This phenomenon of thermal expansion has not previously caused buildings to collapse. It reveals a potential fire-safety issue for other similar high-rise buildings.
Sunder notes that the problem arises because structural engineers have a job of making sure structural loads are adequate for dealing with conditions such as wind, while architects have the job of making sure fire proofing is specified. What is missing is the connection between these disciplines. No one actually evaluates the response of the structural system during a fire, he says. – sm
Bull feathers. Watch this:
The company doing the clean up of the WTC buildings was “Controlled Demolitions Incorporated.”