Francis Scott Key Bridge: What Happens Now

In March 2024, a bridge that most people around the world had never heard of made global headlines. In the US city of Baltimore, a major bridge has collapsed into the water after being struck by a cargo ship. It was an incident that sadly ended in tragedy, with several fatalities and the loss of a critical piece of American infrastructure. Since then, the pressure's been mounting to rebuild the Francis Scott Key Bridge as quickly and as safely as possible. But how's that being done in a country where thousands of other bridges have similar flaws? Is this a wake-up call for the US? And if so, how can this vital structure be replaced in a way that ensures this kind of disaster never happens again? This is Baltimore in Maryland, a city known for its seafood, historic harbour and national aquarium. Basically all things to do with the water. And when you look at where it is, you can kind of see why. Located between Washington and Philadelphia on the US east coast, Baltimore sits at the mouth of the Patapsco River and feeds Chesapeake Bay, the largest estuary in the country. In other words, a lot of water flows through here, which explains why multiple bridges and tunnels have been built across this river over time. Construction of the biggest crossing by far, the now-infamous Francis Scott Key Bridge, began in 1972 and took five years. Designed with a total length of 2.6 kilometres, it became the world's third-longest continuous truss bridge. What do we mean by that? Well, it's where the truss, that is the load-bearing superstructure, extends across three or more supports without any hinges or joints. It was very much of its time. An economic solution, a 66-metre main span. It was a pretty stretchy span at the time, in the 1970s. Ian Firth is a bridge designer and structural engineer whose past projects include the Tsingtao Bridge in Hong Kong and Copenhagen's Inner Harbour Bridge. Nobody could envisage at that point the kinds of ships we now have travelling around the planet. So, you know, given the size of the ships, the size of the port and everything else, it was an appropriate solution. By 2020, the Key Bridge was carrying around 11.5 million vehicles every year as part of Interstate 695. That was until the early hours of March 26th, four years later, when disaster struck. A huge container ship called the Dali, which weighed 116,000 tonnes, had just left port when it suddenly lost power. With the crew unable to control it, the vessel careered into one of the bridge's supports, causing a huge section to immediately collapse. The consequences were devastating. Six construction workers repairing the road on top of the bridge were killed and the shipping channel was shut down for 11 weeks. As a result, the port of Baltimore had to close, which led to massive supply chain issues and huge amounts of goods having to be diverted elsewhere. And we're not talking about small stuff here. It's ranked number one in the whole of the US for importing and exporting vehicles. In 2023, almost 850,000 cars and trucks float through here. Then, just one year later, this major trading hub was at a standstill. Due to the scale of its impact, one thing became clear. This catastrophe, which unfolded in a matter of seconds, required an equally fast response. We're going to move heaven and earth to rebuild this bridge as rapidly as humanly possible. And we're going to do so with union labour and American steel. So, what was the plan? Before any work could start on this new bridge, a major job had to be completed first. Disposing of the old one. That was no simple task. Around 50,000 tonnes of wreckage had to be pulled from the river as part of the clean-up. Specialised cranes were brought in to remove the biggest pieces. But for the bits that were too much even for these machines, controlled explosives were used to break them up. One piece that had to be dealt with that way was a large truss section that had fallen onto the ship itself. After that was cleared away, the vessel was refloated. And then attention turned to what would fill the gap left behind. But before we dive deeper into that, have you ever thought about becoming a structural engineer yourself? Because it might not be as hard as it sounds. That's right. If designing and building bridges is something you aspire to, then this week's video sponsor Brilliant has just the thing to get you on the right path. Brilliant helps build critical thinking skills through problem solving, not memorising. It offers thousands of interactive lessons in subjects like data analysis, probability, programming and coding. Their measurement course in particular is what every budding bridge builder needs. It'll teach you the essentials of geometry, from understanding relationships between shapes to mastering the Pythagorean theorem. And it doesn't have to swallow up all your time either. You can put in just a few minutes a day, if you like, and hone your skills whenever you feel like it. To try everything Brilliant has to offer for free for a full 30 days, scan the QR code on screen now, visit brilliant.org forward slash the B1M or click the link in the description. You'll also get 20% off an annual Premium subscription. Now, let's get back to Baltimore. So, what will the new bridge look like? Well, we don't know for sure yet, but some ideas have already been put forward. Webuild, the Italian design and construction firm, teamed up with architect Carlo Ratti and structure engineer Michel Verlager on a concept for the new bridge. Their suggestion was to make it a cable-stayed bridge, with a much greater height and wider span than the previous one. That would create extra space for ships to pass through, and the supports, also known as piers, would go in shallower water where boats can't reach. A design like this would make the new bridge far better suited to the needs of today, as vessels are now a lot larger than they were in the 1970s. That explains why the protection that was in place around the supports did so little to stop the Dali. They weren't designed to stop ships that simply didn't exist back then. So, one of the big problems with the old bridge was that its narrow span, 366 metres, was just not long enough, and it meant that the piers were in water that was deep enough for the ship to get to it. So, there's no doubt that the replacement bridge would have a longer span. It would also be higher because the navigation clearance in the old bridge, only 56 metres, is nothing like high enough now for modern-day vessels we would be designing for 65 or 70. Okay, but why make it cable-stayed? Well, because this is one of the best ways to build a bridge with a long span in today's world. Instead of trusses and supports that run all the way across, it requires just two towers to be constructed for the middle section. These are then attached to a series of cables. Their job is to take the tension of the deck while the towers bear the actual load. Cable-stayed bridges can also be built quicker and often cheaper than other options like suspension bridges. The cable-stayed bridge of something like 700 metres, it's very much in the middle of what the range of cable-stayed bridges can easily do. It's an economic kind of use of that type of bridge, seems to me to be the right sort of solution. The key thing being getting the supports out of the danger zone. Moving those supports as far away from these ships as possible sounds very sensible, but what about strengthening the protection around them? Well, the quay bridge was obviously vulnerable to large collisions, so surely its replacement is going to be better defended. Well, that is the idea. Shortly after the collapse, officials from the Maryland Department of Transportation said the new one is said to have significantly more pier protection. Well, to get a feel for what that might actually mean, we asked Ian what safeguards are typically found on bridges that were built more recently. Even having got the span long, you're still going to have to deal with the unlikely but possible scenario of a ship, for whatever reason, going outside the channel. And hitting a bridge structure. And so, yes, we provide some kind of vessel impact protection. Whether that be an island around the pier. You have a beach so that a ship will ground on the beach before it hits the pier. Or what we call dolphins. It's basically a structure in the water which is sacrificial. The point is, it's that, not the bridge. And that is standard practice now. Now, the quay bridge did already have four of these, but they either weren't strong enough or there needed to be more of them. Now, we should reiterate that these are only theories of what the new bridge will offer and how it could provide better protection. The actual design is still yet to be revealed. But most of the other big questions have already been answered. We know the estimated cost is USD $1.7BN. It'll need to be completed by October 2028 at the latest, and the company in charge of making it happen has now been chosen. Omaha-based Kiewit Infrastructure was awarded a $73M contract for Phase 1 of the project in August. Now, Phase 1 covers the design of the new bridge, while Phase 2, which Kiewit also has exclusive negotiating rights for, involves the actual building of it. Renderings of a preliminary design are expected later in 2024. It's also hoped the whole thing is going to be federally funded, another pledge made by the president during the aftermath. Usually, the federal government only pays 90% when interstate highways and bridges have to be rebuilt following a disaster, the state picking up the rest of the bill. In a way, that's another sign of just how important replacing the Francis Scott Key Bridge has become to the United States. And yet, what it's also done is raise fears about other bridges around the country. Could there be more out there with similar vulnerabilities? There are 17,468 fracture-critical bridges in the United States out of 615,000 bridges total. Fracture-critical is where a bridge is built without structural redundancy in place. It means that if just one key piece of the structure is taken out, it could lead to a partial or full collapse. Most of those bridges were built between the 1950s and 70s during the construction of the interstate highway system. So, how much of a red flag is this for the US and could we soon see a programme of bridge upgrades to bolster these older structures? I believe it's pretty well known that the US infrastructure is in fairly poor shape in many places. There are an awful lot of bridges which need a lot of attention. And so when something like this comes along, which clearly becomes a priority for whatever funds are available, if they start spending money on this, it means that probably they're not going to spend money elsewhere and it is a big problem, it's a big challenge. The reality is that it won't be as straightforward as just making every bridge indestructible straight away. And it's important to add that fracture critical doesn't necessarily mean unsafe. But the Key Bridge tragedy has certainly caused a scare among the people who make those decisions and lessons will have definitely been learned. It may have had its flaws, but there are several reasons why the destruction of this one bridge made shocking news. Not only were lives tragically lost in this terrible accident and we should point out that an FBI investigation remains ongoing, but it was also something that most people never expected to happen here, despite the risks sitting there in plain sight. Hopefully, some good can emerge from this disaster. A bigger, better bridge for Baltimore, but also a much-needed warning for the entire nation and its infrastructure. This video was sponsored by Brilliant. You can learn more about that at the link below. Don't forget that we're inspiring the next generation of builders through our investment into BrickBorrow, a fantastic LEGO subscription service. You can learn more and get started today over at brickborrow.com. 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