Design Flaws Ruled Out in WTC Structural Failures

Design flaws have been ruled out in the collapse of the World Trade Center towers.

Some have suggested that lack of fireproofing and lack of strength in the lightweight floors played critical roles in the eventual collapse of both towers after they were rammed by hijacked airliners.

A detailed report that was released yesterday points out that “the twin towers failed because the structural columns at the buildings' core, damaged by the impact of the airliners, buckled and shortened as the fires burned, gradually shifting more load to the tower's trademark exterior pinstripe columns.” Those external columns took most of the weight load of the floors above the impact areas and failed, which caused the structures to fall in on themselves.

In other words, the internal structures holding the buildings up were severed, severely damaged, or melted by the 1,000 to 2,000 degree fires that were raging in the damaged areas of the building. Eventually both buildings began to sag in the damaged areas and the weight was caught by the outside columns. You could almost see it happening when you look at video of the burning buildings.

Some of these columns were damaged by the impact as well, or were damaged also by the unbelievable heat, so failure was only a matter of time. When enough of the columns were weakened, the weight overcame the strength of the columns and the skyscrapers collapsed in a matter of seconds, killing thousands of people who were still inside the burning towers as well as people standing near the buildings who couldn’t escape the huge sections of building that came crashing down on top of them.

Here’s the New York Times story.

I don't know if any lessons can be learned from this or what can be done to strengthen existing skyscrapers against the same kind of thing happening. I don't think armoring new towers will help either. Steel and concrete have been shown to be susceptable to this new kind of terrorism. I can't see making the walls one hundred feet thick either. The weight load would be unbelievable. Could such a structure even be built and not collapse under its own weight? More questions than answers.