Editor's Window

1 Aug, 2007 By: Amy Stankiewicz

A powerful visualization

About a month ago, as I was surfing the Internet for interesting applications of CAD and visualization technologies, I came across something that astounded me. I stumbled on an article about a group of Purdue University computer science professors and the countless hours they've spent creating a computerized simulation and animated visualization of how the North Tower of the World Trade Center collapsed on September 11, 2001.

Amy Stankiewicz
Amy Stankiewicz

Both the animation and the simulation aim to help civil engineers understand exactly how — and why — the building collapsed, said Christoph Hoffmann, a professor of computer science and director of Purdue's Rosen Center for Advanced Computing.

The fact that visualization and related technologies can help engineers and scientists better understand how structures withstand the impact of such disastrous events is truly remarkable. And, as is the case with this particular project, the results that stem from such efforts can be both impressive and beneficial.

According to the professors on the project team, the simulation — which required more than 80 hours of high-performance computing — found that the 10,000 pounds of fuel in the plane acted like a flood of flaming liquid, knocking out structural columns and removing fireproofing from support structures.

"It is the weight, the kinetic energy of the fuel that causes much of the damage in these events," Hoffmann was quoted as saying in a Purdue University news story. "If it weren't for the subsequent fire, the structural damage might be almost the same if the planes had been filled with water instead of fuel."

The professors used both SAP and LS-DYNA nonlinear finite-element-analysis technologies to prepare meshed models of the aircraft and the North Tower for the simulation, Hoffmann said. The aircraft was modeled with its structure, including ribs, spars, stringers, internal flooring, landing gear, engine, and fuel (the team used a smoothed-particle-hydrodynamics formulation of the fuel).

For the animated visualization, Voicu Popescu, an assistant professor of computer science at Purdue, developed a translator that created a link between the simulation and the visualization system, automatically translating simulation data into Autodesk's 3D Studio Max.

The animation was completed in April of this year and announced by Purdue University in June. "Since then, [the project] has generated a lot of interest both here and abroad," Hoffmann said, "both from serious news organizations and individuals, as well as from people advocating that malfeasance by the government is to blame for the collapse of the towers."

To view the completed simulation, visit To view the animated visualization, visit

And please be sure to check out Kenneth Wong's "Tech Trends" column in the September issue of Cadalyst, where Kenneth will go into more detail about the professors' simulation and visualization efforts and what the project may mean to civil and structural engineers trying to plan for future terrorist attacks and other disastrous events.

Amy Stankiewicz
Editor-In-Chief, Cadalyst

About the Author: Amy Stankiewicz

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