Preliminary structural and thermal simulations of the destruction of the World Trade Center towers demonstrated to Congress last month have led to the commissioning of a detailed model of the catastrophe.

(Photo courtesy of MSC Software Corp.)

On the premise that every minute the towers stood after the planes hit saved lives, researchers will use the model to study what changes in their construction would have let them stand longer.

"Our simulation is sophisticated enough to not only show the crash events, but also simulate the explosions," says Casey Heydari, of MSC Software Corp., Santa Ana, Calif., who created a preliminary model based on generic data and will now build the second on tower specifics. Heydari also is MSC's business development and marketing manager.

MSC was given a CD on April 21 with 10,000 drawings of the towers to use for the structural model. Heydari will augment that with analysis of damage to steel members recovered from the impact areas. Modeling data for the Boeing 767s that struck the buildings still has to be acquired.

A report on the initial simulation by Abolhassan Astaneh-Asi, professor of civil and environmental engineering at the University of California, Berkeley, can be seen at The study is under the direction of the National Science Foundation and is funded by the Federal Emergency Management Administration, although MSC says it is contributing its software and services for free.

The first model was based on a generic, six-story steel structure of tubular beams and columns. Together with a stand-in Boeing 747 model, it had 61,000 elements. Heydari says the next model should be about three times more complex. "You don't need to fully model the entire 110 stories," he says. "You only need to build detail at the impact area."

The first model's 250 millisecond impact simulation took 24 hours to run on a 300 MHz, dual processor. The heat transfer and thermal mechanical analysis took an additional 20 hours, with several days of post processing.