IT WAS THE FIRE, CAUSED THE TWIN TOWER COLLAPSE

After more than two years of intensive research, investigators uncovered what they said was an elementary shortcoming in the trade center towers.

World Trade Centre’s twin towers collapsed in large part because fireproofing was dislodged when hijacked airliners crashed into them on September 11, 2001, but better evacuation plans and communications would have saved lives, a federal study has said.

The point is; these buildings didn’t immediately collapse, they took almost an hour for Tower 2 and well over an hour for Tower 1 the North Tower to collapse. According to Ronald Hamburger a structural engineer investigating the disaster, “We have reason to believe that, without the fire, the buildings could have stood indefinitely and been repaired.�? The fire caused most of the life loss and building damage and the buildings were evidently deficient in fire protection.

The WTC towers were indeed designed to withstand the impact of a large commercial aircraft. They were not, however, designed to withstand the prolonged effect of fire resulting from a bomb in the guise of a fully fueled aircraft.

Some 60 tons or more of jet fuel could have easily caused sustained high temperatures of 1,500 F and higher. Under these conditions, structural steel looses rigidity and strength. The resulting failure of the 2-3 floor system at the site of impact sent the 30 to 25 floors above free-falling onto the 80 to 85 floor structure below. The enormous energy released by this collapse was too large to be absorbed by the structure below. That impact may have ultimately caused the explosive buckling, floor after floor, of the WTC towers.

For nearly every man and woman on the upper floors of the towers, the lack of intact staircases meant that they could not get out after the planes struck. Clustered in the centers of the buildings, those staircases were encased in lightweight drywall that was immediately destroyed. Sturdier walls around staircases that were remote from each other “might have provided greater opportunities for escape,” said the lead investigator

Experts elaborate on a series of new escape systems for high rise buildings under fire (or damaged by explosions) whose aim is to bypass impassable floors or blocked stairways. These would allow people trapped in higher elevations to escape safely to the street. He considers various types of devices, including those that can be deployed inside or on the exterior walls of the building. Finally, they discusses the effects that terrorist acts can have on the timely supply of raw materials and parts to industry, and on the need for a new strategy that blends on-time supplies with adequate strategic reserves.

The staircases in the twin towers, their number, location, and the weak walls around them, emerged as critical factors in the deaths of many of those killed in the Sept. 11 terrorist attack on the World Trade Center, according to a federal safety report released yesterday. The findings will be used to shape federal recommendations for building-code changes across the country.