Click Images to Enlarge 1. Facade
at 0.37 sec
3. Damage Diagram
(from FEMA Report)
4. Facade Damage
at 0.37 sec
The WTC-1 building had an exo-skeleton, a steel structure on the exterior that partially supported the weight. The incoming plane cut into that exo-skeleton and there are contemporary photographs that show the damaged outside.
The first two images show the aircraft positioned in the simulation just before entering the building (Figure 1), and after entering fully into the building (Figure 2). The damage to the exoskeleton can be compared with diagrams in the literature, prepared from photographs, that show the actual damage of the event. The diagram in the Figure 3 is from FEMA Report 403, September 2002, "World Trade Center Building Performance Report." This report is available on the web.
Figure 4 shows the simulation result and the diagram side by side.
When a swath of the exoskeleton was cut by the plane, the core support structure of the building had to carry a heavier load. It too sustained damage, although there is uncertainty as to the extent. Figure 5 shows the damage computed by our simulation.
This work has been supported in part by NSF grant DSC-0325227, A. Sameh PI.