Engineers, computer scientists and graphics technology experts
at
Purdue University have created the first publicly available
simulation that uses scientific principles to model what happened
when the Boeing 757 crashed into the Pentagon last Sept. 11. The
simulation merges a realistic-looking visualization of the airliner
approaching the building with a technical, science-based animation of
the plane crashing into the structure.
The simulation project was led by Mete
Sozen, Purdue's Kettelhut Distinguished Professor of
Structural Engineering and Christoph
M. Hoffmann, a professor in the Department of Computer
Sciences and at Purdue's Computing Research Institute. Sozen created
a mathematical model of reinforced concrete columns. The model was
then used as a starting point to produce the simulation. Hoffmann
turned Sozen's model into the simulation by representing the plane
and its mass as a mesh of hundreds of thousands of "finite
elements," or small squares containing specific physical
characteristics.
The simulation deals specifically with steel-reinforced concrete buildings, as opposed to skyscrapers like the World Trade Center's twin towers, in which structural steel provided the required strength and stiffness. Reinforced concrete is inherently fire resistant, unlike structural steel, which is vulnerable to fire and must undergo special fireproofing. The model indicates the most critical effects were from the mass moving at high velocity. The mesh of finite elements in the model require that millions of calculations be solved for every second of simulation. Creating only one-tenth of a second of simulation took about 95 hours of computation time on a supercomputer. Researchers originally worked closely with Information Technology at Purdue (ItaP) and University Information Technology Services to use IBM supercomputers at Indiana University and Purdue University.
In the simulation, the plane crashes into the building's concrete support columns, which were reinforced with steel bars. In this simulation the columns were assumed to be "spirally reinforced," a technique popular in the 1940s in which steel bars were wound around columns in a helical shape. The coiled steel provided added strength to the columns and probably is responsible for saving many lives, Sozen said.
The simulation might be especially useful for engineers who
are
trying to design reinforced concrete structures that better withstand
terrorist attacks or accidents involving aircraft crashes.
The Purdue team used commercial software that is normally used by auto manufacturers to simulate car crashes, combined with realistic-looking scientific simulation graphics.
The work was funded, in part, by a grant from the National Science Foundation. [an error occurred while processing this directive]