An engineer's take on the Baltimore bridge collapse after it was hit by a cargo ship

Transcript

DEBBIE ELLIOTT, HOST:

The collapse of Baltimore's Francis Scott Key Bridge looked like a scene from a disaster movie, but it was real, and now six people are presumed dead and one person is seriously injured. The Key Bridge was the world's third longest bridge of its kind - a continuous truss bridge - and nearly 50 years old.

We wanted to get the perspective of an engineer to help us pinpoint what went wrong when a massive cargo ship crashed into the bridge early yesterday morning, so we've called up Ben Schafer. He's a professor of civil and systems engineering at Johns Hopkins University in Baltimore. Good morning.

BEN SCHAFER: Good morning.

ELLIOTT: So give us the play-by-play from your expert eye. What happened as the container ship struck the bridge?

SCHAFER: Yes, of course. It ends up being a little bit simple. There's a ship that's as big as the bridge itself, loses power and actually strikes one of the two bridge support piers that support the structure, essentially obliterates it. And rather than seeing some slow propagation of failure, due to some, you know, unique physics, there's a complete loss of support, and you just see the bridge vertically go down, and then just seconds later, all of it into the water.

ELLIOTT: Now, this massive ship hit at a very critical point on the bridge. Could there have been, like, protective barriers or something in the way that was built to protect it and maybe prevent something like this from happening?

SCHAFER: Yeah, so the answer's a bit of a yes and no. Certainly, there's been a lot of discussion about bridge protection systems, and we know that this bridge had some bridge protection, but it doesn't have a significant system right at the bridge pier. It's not at all clear that a boat of that size - so it's not a little boat hitting a big bridge. The boat is as long as the bridge was long. The boat is as wide as the bridge was tall. So it's a massive amount of energy. And it's not clear that any bridge protection system we currently use could've taken a direct strike right at the bridge pier, as happened, you know, the other night.

ELLIOTT: So let's back up a little bit and just have you describe the Francis Scott Key Bridge to us. When was it built, and how had it performed until now?

SCHAFER: Yeah, so it was built in the 1970s, opened up in 1977. If you were sort of having a dinner at the Inner Harbor in Baltimore, you could see it off in the distance with its sort of twinkling lights. It's a metal truss arch bridge, sort of very light filigree structure that would jump over the harbor - the other crossing points are actually tunnels - so sort of the major bridge that you would see in Baltimore. It was designed and under use and to good success for, you know, almost 50 years, in regular use by the citizens of Baltimore and even by myself.

ELLIOTT: So let's think about what's going to happen next as this bridge is rebuilt. What is that going to look like, and how long might that take?

SCHAFER: Right. So the bridge is - you know, ultimately, it's part of a huge infrastructure system for Baltimore. And so the - there's rebuilding the bridge, and then there's reopening the Port of Baltimore. These are the two sort of major tasks. The - reopening the port seems like something that we can do relatively quickly. We're going to have to remove the wreckage from the water and open - reopen the shipping channel, and then we'll be back to a major infrastructure project to rebuild the bridge. It took five years to build it the first time. There was a major collapse not so dissimilar from this in Tampa in 1980. It took them seven years. We've all lived infrastructure projects. It could take a while.

ELLIOTT: And just - we have just a few seconds left. Should this raise concerns about America's infrastructure?

SCHAFER: You know, I think there's plenty for us to think about. And we always want to be improving. But this was a pretty unique event.

ELLIOTT: That's Ben Schafer, professor of civil and systems engineering at Johns Hopkins University in Baltimore. Thanks so much for joining us.

SCHAFER: Thank you. Transcript provided by NPR, Copyright NPR.