Image:  The new One World Trade Center building, made with high-performance concrete. John D. Morris, CC BY-SA

When buildings collapse killing hundreds – or thousands – of people, it’s a tragedy. It’s also an important engineering problem. The 1995 collapse of the Alfred P. Murrah Federal Building in Oklahoma City and the World Trade Center towers in 2001 spawned many vows to never let anything like those events happen again. For structural engineers like me, that meant figuring out what happened, and doing extensive research on how to improve buildings’ ability to withstand a terrorist attack.

The attack on the Murrah building taught us that a building could experience what is called “progressive collapse,” even if only a few columns are damaged. The…

Read more