After the collapse of the Key Bridge in Baltimore, many are wondering how the entire structure came down. Engineers say it’s mainly due to the bridge type-Truss.

In Truss bridges, there are no cable supports. All of the structure you see above the deck is designed to transfer the load to the eventual supports or piers that head underwater and into foundations.

When you take down one of those piers, the shape changes and the force of the crash is attempting to span twice as far in order to reach the next pier.