When a 900-foot container ship struck the San Francisco-Oakland Bay Bridge in 2007, the span remained standing and no one died, either on the ship or on the highway above.
The bridge’s supports were protected by a fender system of concrete and other materials installed to absorb such shocks. And it now begs the question: Could such a system — or systems like it — have saved Baltimore’s Francis Scott Key Bridge?
Some experts say yes.
Sherif El-Tawil, an engineering professor at the University of Michigan, said there are several safety measures that “would have made a huge difference” if they had been in place Tuesday morning when a freighter plowed into the bridge and caused it to collapse.
El-Tawil said a fender system may have softened the blow of the 300-meter ship. Poles, known as dolphins, anchored into the riverbed are another measure that could have helped deflect the container ship Dali. And yet another potential protection would have been islands of rock or concrete around the bridge’s supports.
“It may seem like a very large force,” El-Tawil said of the massive cargo ship. “But I think you can design around it, either through a safety system or by designing the bridge itself to have huge towers.”
Such protective measures have become a focal point in the aftermath of the tragedy, which claimed the lives of six construction workers. Experts say the 47-year-old Key Bridge did not appear to have the protection common to newer spans.
The incident raises questions about how much money American taxpayers are willing to spend to protect themselves from these rare but deadly catastrophes. And not everyone agrees that the Key Bridge could have been saved.
“There is a lot of discussion among the engineering community about whether these characteristics could have played a role in a situation like this,” U.S. Transportation Secretary Pete Buttigieg said during a White House briefing on Wednesday.
“It’s hard to overstate the impact of this clash we’re talking about,” Buttigieg said. “It’s not just the size of a building, it’s really the size of a block: 100,000 tons are going into this pier all at once.”
Buttigieg did not directly answer a question about whether steps should be taken to protect the nation’s bridges. But the secretary noted that many bridges have been designed to better protect against collisions since a cargo ship struck Florida’s Sunshine Skyway Bridge in 1980, killing 35 people.
Baltimore’s Key Bridge opened three years before the 1977 disaster, a time when freighters were much smaller in size. In recent years, ships have grown to carry more containers to save on shipping costs. Ports in Georgia and South Carolina have dredged deeper channels to accommodate them, while part of a bridge has been raised to allow larger ships to reach ports in the New York City area.
The Tampa Skyway Bridge disaster created a paradigm shift in design in the early 1980s, says Mark Luther, an oceanography professor at the University of South Florida and director of the USF Center for Maritime and Port Studies.
The new Skyway Bridge was built with islands of rock around the main supports and large cylindrical piers on either side of those islands to make it “very difficult for a ship to hit and topple any part of the bridge,” Luther said.
“To go back and retrofit a bridge like the Key Bridge with these features would be extremely expensive,” Luther said. “And as far as I know, no one has done it. (They have) just had to accept what risk there is with the construction that was state-of-the-art in the 1970s.
Roberto Leon, a professor of engineering from Virginia Tech, said the technology exists to protect a bridge from a collision with a huge cargo ship like the Dali.
But he warned that governments will always weigh the costs and risks. And the safeguards put in place don’t always match the scale of the disaster, even when the Key Bridge was retrofitted with modern safety measures.
“This was a huge burden,” he said of the ship hitting the Key Bridge. “If the restraint system was designed for that load. I think it would have protected the bridge. But a big question is: would you design it for such a huge load? Because as the tax increases, it becomes much more expensive.”
