World Trade
Centre Collapse
Group 2
Introduction
• History
• Design
• Failure
• What was learnt/future prevention
History
• Completed in 1970
• 2 of 7 seven towers built on 16 acre WTC
site
• 110 stories standing at 417m(tower1),
413m(tower2)
• Length and breadth 63.4m
• Each tower had 3.8 million sq ft of office
space
Design
• Inner core and outer structure
• Inner core took all gravity loading
• Outer structure took lateral loading
• Dampers added to prevent wind sway
• Inner core housed lift shafts and stairwells
• Fireproofing
Failure
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Fireproofing stripped
Steel exposed
Steel softened
Floors began sagging
External columns pulled inwards
External columns began to bow
Columns snapped
Building collapsed
Other reasons for failure
• Structural Issues
• Sprinkler system
• Alarm system
Future prevention
• Structural issues
• Evacuation
– Stairwells
– Communication