Francis Scott Key Bridge collapse: FAQs

Like many of us, I was hugely shocked by the images from Baltimore yesterday morning.

In the early hours of Tuesday 26 March, a major bridge in the US city, the Francis Scott Key Bridge, collapsed into the Patapsco River.

A vast and out of control container ship had crashed into the bridge, causing it to fall.

While the engineering issues are simple to understand for us engineers, the catastrophic nature of the incident is shocking and out of proportion for the public.

The engineering community should and will learn from this - as we always do.

Throughout the day, I worked with the media team at the ICE to try to put engineering into words that are helpful and illuminating to the wider public.

We put together the following FAQs for anyone wanting to understand more about the accident and what it means for bridge design and construction in the future.

Francis Scott Key bridge collapse FAQs

What type of bridge was this?

The Francis Scott Key Bridge, also called the Key Bridge, was a continuous truss bridge, with an arched form. It opened in 1977.

This is a bridge design that was commonly used to span large distances. It’s lightweight and efficient in its use of materials, which are primarily steel with a suspended concrete deck.

What likely led to the bridge’s collapse?

The bridge was struck by a container ship after it lost power and sent out a mayday call.

The ship hitting the bridge at one of its supporting piers will have led to the collapse.

However, investigators must examine not only the circumstances that led to the collision, but also how the general state of repair and structure of the ship impact protection on the bridge could have contributed.

What can be learned from incidents like this?

In the aftermath, the most important thing we can do is investigate any navigational issues that contributed to the accident and what, if anything, went wrong in terms of the risk management of the bridge structure and general state of repair.

Whatever we learn from this will contribute to designing and building even safer bridges.

How will this impact other bridges?

It is unlikely that this incident will have an immediate impact on the design and construction of bridges currently being built.

However, it’s important to note that ship impact is a key consideration in modern, long span bridges, especially those in busy navigational and shipping areas.

It’s also important to note that this incident will be reflected on, and bridge professionals will follow the outcome of the investigation closely.

The bridge industry is very good at sharing information, so learning from this incident will contribute to designing and building safer bridges.

What can this incident tell us about the safety of other bridges?

Each bridge is unique so it’s hard to draw conclusions from this incident.

However, it’s likely that bridge owners all over the world are noting this incident and undertaking appropriate risks assessments to see if mitigation measures are needed for bridges in their estates.

What elements of bridge design need to be considered to prevent incidents like this happening?

Ship impact is a key consideration in modern, long span bridges, especially those in busy navigational and shipping areas, and has been for some time.

That means newer bridges have been designed with potential impact incidents like this in mind.

There are also safety features like dolphins (which are effectively the equivalent of road bollards, but in the water) and energy absorbing buffers that help prevent the extreme consequences of this type of collision.

What will be investigated?/What happens next?

When something like this happens, the first priority must be the rescue and recovery operation.

Then there will need to be a clear-up process. The remains of the collapsed steel work and the remaining debris must be cleared away.

Then the investigation will begin. That’s likely to take some time.

There will be two main branches of the investigation.

First, the navigation – what navigation errors, if any, contributed to the crash? Were there issues with the ship? What caused it to lose power?

Second – there will be an investigation into the behaviour of the bridge and its general state of repair, and questions like whether there was appropriate impact protection around the pier.

Learning from the investigation is absolutely critical.

When the investigation is concluded and lessons have emerged, then designing a new bridge and rebuilding is the next phase. This will take a long time.

Building a bridge like this takes anywhere from 18 months to two years, and that will be preceded by a period of design work. This will require a team of experts who will carry out the design, and plan how the bridge will be built.

In this case, it’s likely that new foundations and an entirely new structure will be needed.

It will likely be several years before a replacement is built and open.

How much will it cost?

It’s very difficult to estimate, because it depends on the scale and the complexity of the construction process.

It’s likely to run into the hundreds of millions of dollars.