Report says fires caused collapse of WTC towers
A report says the World Trade Centre's twin towers were brought down by fires caused by fuel from the hijacked airliners which crashed into them.
The federal report says the buildings coped surprisingly well with the impact of the planes. But the towers couldn't withstand the fires that generated heat equivalent to the output of a nuclear power plant.
The findings of the report, commissioned by the Federal Emergency Management Agency and the American Society of Civil Engineers, are reported by The New York Times.
The report, which the newspaper said will be officially released in late April or early May, offers a detailed description of the sequence of events that brought the twin towers down.
The planes damaged support columns when they rammed into the towers, but the buildings successfully redistributed loads to other supports, the report says. It adds that without the devastating fires, the towers probably would have remained standing indefinitely unless they were hit by an earthquake or a windstorm.
According to the report, the fireballs that erupted when the planes hit the towers burned perhaps a third of each plane's fuel.
That initial explosion did little structural damage, but the fires from the remaining fuel brought the towers down.
Fire suppression systems in high-rise buildings are designed to allow fires to burn themselves out before a collapse can take place, but those systems failed in the trade centre across the board, the report concludes.
The report says the extraordinary circumstances surrounding the attack make it difficult to draw conclusions about the effectiveness of fire suppression systems in other buildings. The report says debris sent flying by the impact of the planes almost certainly sliced through pipes that supplied water for fire hoses and sprinklers.
