World Trade Center-7 Progressive Collapse Analyses

World Trade Center Collapse Analysis


ARA, in collaboration with NIST (National Institute of Standards and Technology), performed progressive collapse analyses to determine the location and cause of the initiating event (the first component(s) that failed in WTC 7) and the subsequent progression of component and subsystem failures that led to global collapse.


A modeling system called LS-DYNA was utilized to evaluate the progressive failures and collapse of the WTC 7 structures. Multiple initiating events were simulated and the resulting calculated collapse responses were compared to the observed collapse behavior.

The methods developed, along with the collaborative relationship between ARA and NIST teams, contributed to the success of this effort.

  • refine the model only in regions where damage occurs
  • develop reduced models and components that capture the behavior of the refined models


ARA developed the WTC 7 models to accurately capture the progressive failure models and investigate a variety of collapse hypotheses within the project schedule.

ARA conducted similar work in collaboration with NIST to evaluate the performance of the aircraft impacts into the World Trade Center towers.

Test and Evaluation

Weapons Development, Testing, and Effects

From penetration and detonation underground, to air-blast, to a nuclear attack against U.S. satellites in space, ARA scientists and engineers... more