World Trade Center Investigators Call for Skyscraper Design Changes

World Trade Center Investigators Call for Skyscraper Design Changes
US experts said they will call for major changes to the way skyscrapers are built and managed after an exhaustive inquiry into why the World Trade Center towers collapsed in the September 11 attacks in 2001.

The experts said the two towers were felled by the way the hijacked jets dislodged key supporting columns, stripped away fireproofing and set ablaze masses of office material that burned long after the jet fuel had been consumed by fire.

The Commerce Department's National Institute of Standards and Technology (NIST) said its report was "the most detailed examination of a building failure ever conducted."

The NIST said it had found a number of safety practices and technologies that could have saved lives on September 11 and would be included in the agency's full report to be released in June.

It said it would recommend improvements in the way people design, construct, maintain and use buildings, especially high-rises. It said this would range from the design of elevators to the way office workers are trained.

"While the buildings were able to withstand the initial impact of the aircraft, the resulting fires that spread through the towers weakened support columns and floors that had fireproofing dislodged by the impacts. This eventually led to collapse as the perimeter columns were pulled inward by the saggi