1. World Trade Centre Collapse Group 2

2. Introduction History Design Failure What was learnt/future prevention

3. 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

4. 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

5. Failure Fireproofing stripped Steel exposed Steel softened Floors began sagging External columns pulled inwards External columns began to bow Columns snapped Building collapsed

6. Other reasons for failure Structural Issues Sprinkler system Alarm system

7. Future prevention Structural issues Evacuation –Stairwells –Communication