What were the structural causes of the fall of the Twin Towers

According to the BBC Mundo, scientists from Massachusetts Institute of Technology (MIT), which investigated the structural causes of the collapses, concluded that they were due to the severe structural damage caused by plane crashes in every building and the chain of fires that spread over several floors .

These studies coincided with those commissioned by the United States government National Institute of Standards and Technology (NIST) and which were published in 2008.

“If there had been no fire, the buildings would not have collapsed and if there had been only fire, without the structural damage, they would not have collapsed either,” he said. the civil engineer told the BBC. Eduardo Kausel, Professor Emeritus in the Department of Civil and Environmental Engineering at the Massachusetts Institute of Technology (MIT).

According to the NIST report, the impact “severely damaged” the columns and dislodged the fire insulation that covered the framing of the steel beams and columns. “The vibration of the shock caused the flame retardant coating of the steel to break, leaving the beams more exposed to the fire,” Kausel explains.

Thus, structural damage gave way to flames, which in turn caused more structural damage. While this was happening, the temperatures, which rose to 1000 ° C, caused the window panes to swell and break, bringing in air that fed the fire. “The fire fed on air and that’s why it spread,” Kausel explains.

The intense heat stretched the beams and slabs on each floor, causing them to separate. In addition, the expansion of the beams also pushed the columns outward.

Later, the flames began to melt the steel of the beams, making them malleable. This caused what were previously rigid structures now to resemble ropes which, when arched, began to push inward the columns to which they were attached. This combination was fatal and precipitated the collapse.