A group of experts, including structural engineers Weildlinger Associates and Arup Fire, produced the report. Gene Cawley, the expert who led the original investigation into the collapse of the towers, has also put his name to the findings.
The report says that computer simulations reveal that damage caused by the planes’ impact was so severe that the south tower ought to have collapsed immediately.
The floors are thought to have survived the initial impact and the fires that followed and to have been in place when the columns failed. The report notes that the fires that occurred after impact further weakened the structure, leading to its eventual collapse. A spokesperson for Arup said it was unable to comment because the report has yet to be published officially. The findings are based on analysis of structural drawings, thousands of photographs and many videos.