The collapse of the World Trade Center WTC – Structure Project 4A6 (1) Structure Design Dermot O’dwyer The collapse of the World Trade Center 11 september 2001 Elodie Dutertre Romain Figueras Caoimhe Fitzpatrick Dolores Murphy Group 2 WTC – Structure Project

WTC – Structure Project Summary Design of World Trade Center Towers What happened Failure mode Prevention Group 2 WTC – Structure Project

WTC – Structure Project The WTC Towers The Twin Towers : 417 m and 415 m 110 storeys 64 m * 64 m Owners : Port Authority of New York and New Jersey Architect : Minoru Yamasaki, Emery Roth and Sons consulting Ground Breaking : August 5, 1966 Opened : 1970-73; April 4, 1973 ribbon cutting Group 2 WTC – Structure Project

WTC – Structure Project Design of WTC towers 36 cm 1 m Very lightweight structure : 500 000 t, resists 225km/h hurricane Rigid "hollow tube" of closely spaced steel columns with floor trusses extending across to a central core Core shaft : 27x42 m housing 3 exit stairways, 99 lifts, 16 escalators Group 2 WTC – Structure Project

WTC – Structure Project The central core is designed to carry part of the vertical loads Floor trusses are supported between the perimeter columns and the central core The dosely spaced tubular perimeter columns act like a hollow tube supporting part of the vertical loads and all the horizontal loads 42 m 27 m Design of WTC towers Group 2 WTC – Structure Project

WTC – Structure Project Design of WTC towers Outer perimeter box column Floor joints Angle clip clips Inner core Group 2 WTC – Structure Project

WTC – Structure Project What happened Several storeys of exterior columns were destroyed by aircraft impact Load from the damaged sections were redistributed to other parts of the structure Development of an inferno : increase in temperature of structural members Weakened and stressed the structure Group 2 WTC – Structure Project

WTC – Structure Project Building load from above Group 2 WTC – Structure Project

WTC – Structure Project Building load from above Group 2 WTC – Structure Project

WTC – Structure Project Building load from above Group 2 WTC – Structure Project

WTC – Structure Project Group 2 WTC – Structure Project

Factors that enhanced building structural performance Dense spacing of perimeter columns Redistribution of loads to adjacent intact columns Robustness of the perimeter frame-tube system Withstanding of the aircraft impact Hat truss resisted the significant weakening of the core (due to aircraft impact ) Redistribution of loads to the perimeter walls Group 2 WTC – Structure Project

Factors that could have improved building structural performance Perimeter columns and floor framing with greater mass Enhance thermal and buckling performance Other passive and active fire protection features (e.g : compartmentation) Retard spread of building fires Steels with improved high-temperature properties Enhance thermal performance Group 2 WTC – Structure Project

Factors that could have improved life safety Improved performance to delay or prevent building collapse Improved stairwell integrity Better communications to occupants Better evacuation training Group 2 WTC – Structure Project

The collapse of the World Trade Center WTC – Structure Project 4A6 (1) Structure Design Dermot O’dwyer The collapse of the World Trade Center 11 september 2001 Elodie Dutertre Romain Figueras Caoihme Fitzpatrick Dolores Murphy Group 2 WTC – Structure Project

WTC – Structure Project Central core Exterior tube frame Well above impact area hangs in tension and remaining frame acts to distribute loads to other elements Well above impact area Perimeter columns resist 40% of building weight equally distributed Core columns Core columns resist 60% of building weight Perimeter and core columns near impact zone carry more load BEFORE AIRCRAFT IMPACT AFTER AIRCRAFT IMPACT Outrigger System Group 2 WTC – Structure Project