1. 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

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

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

4. WTC – Structure Project
Design of WTC towers
36 cm
1 m
Very lightweight structure : 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

5. 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

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

7. 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

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

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

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

11. WTC – Structure Project
Group 2
WTC – Structure Project

12. 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

13. 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

14. 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

15. 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

16. 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