NEW YORK'S twin towers 'should not have collapsed so quickly and completely', Professor Wilem Frischmann, designer of London's National Westminster Tower and Centre Point, told NCE this week.
In a paper 'Obituary for the two tall towers', the Pell Frischmann Group chairman added that evacuation procedures should have enabled more people to get out before the towers collapsed.
'Technology is available for existing and proposed new tall buildings, so that even in extreme scenarios, each building should have high fire and collapse resistance with good means of escape and excellent strategies to fight a fire, ' he said.
Frischmann, who served as an expert witness in the Ronan Point progressive collapse inquiry, stressed that damage to the outside walls would not alone have triggered the classic progressive collapse witnessed.
'The sprayed fire protection should have maintained steel strength for several hours, ' he said. 'British regulations require that vital steel must remain capable of carrying its full load safely for two or four hours, and with modern materials and techniques, that requirement can be achieved.'
Designers of existing and new high rise structures would have lessons to learn about fire resistance and evacuation procedures, he said. 'There was surely time before collapse to ensure that all lower levels of the towers were evacuated.'
He also warned against building future skyscrapers in clusters, highlighting the damage to buildings around the towers.