Skidmore, Owings and Merrill, or SOM, the architects designing the tower, have taken that imperative literally: If terrorists pilot a fully-fuelled commercial jet into their building, they believe it will stand.
"Based on the identified threats there wouldn't be a disproportionate collapse of the structure," says Carl Galioto, SOM's technical partner. "In many cases there wouldn't even be a distortion; key elements of the tower would not be deformed out of place."
"It is generally impossible to assure that a structure will not collapse as we simply cannot predict what extraordinary loads may be put onto it," says Robert Woodbury, Scientific Director of the Canadian Design Research Network and a Professor at Simon Fraser University. "What is most important is to give people sufficient time to escape before collapse, and sufficient means of egress to leave."
That's what the core is all about. All the buildings' life-safety systems will be encased here, and the core will serve as the primary escape route in the event of a crisis. The core contains extra-wide emergency stairs, pressurized to push out smoke, and a dedicated staircase for fire fighters to use so rescue efforts aren't hampered if people rush down.
There are areas of refuge on each floor where people can await rescue and enhanced elevators that function in emergencies. Photo-luminescent strips will indicate routes in the event of a power failure and all communication and sprinkler systems are contained in the core.
In addition to interconnected exits all the exit pathways lead directly out on to the surrounding streets, totally avoiding the lobby, which will serve as a base for rescue operations. In the event of an emergency, Galioto says a fully occupied building could be evacuated using both stairs and elevators in under two hours.