Could huge concrete barriers have averted the Key Bridge collapse?

When a nearly 1,000-foot-long container ship collided with the Francis Scott Key Bridge around 1:30 a.m. on Tuesday, its bow appeared to cut directly into one of the concrete supports holding up the structure, skirting above the modest protective barriers at its base.

In the aftermath of the collapse that followed, engineers identified a lack of robust protection systems, which can appear mainly in two forms: “fenders” that wrap around the support columns to protect them from damage, much like the fender of a car; and “dolphins,” independent structures typically made of concrete that are designed to stop ships from colliding with the support columns in the first place, or at least reduce the impact.

About 72 miles northeast of the bridge’s northern end in Dundalk, the authorities in charge of the Delaware Memorial Bridge are constructing a nearly $93 million “ship collision protection system” that would include eight stone-filled “dolphin cylinders,” each measuring 80 feet wide, designed to deflect the types of ships that traverse nearby.

Pictures of the Key Bridge show some sparsely placed dolphins that are placed well in front of the so-called “piers” that hold up the structure.

Abi Aghayere, a professor of structural engineering at Drexel University, said that the dolphin system at the Key Bridge appeared to leave ample room for ships to maneuver around them, unlike the proposed design for the Delaware Memorial Bridge, which crowds the piers with concrete dolphins.

Aghayere said he remained surprised by the limited protection system that appeared to be in place around the 47-year-old Key Bridge, given the massive size of the container and cruise ships that routinely passed under it. He noted that the relatively modest size of the Key Bridge’s fender system was not designed to stop ships those sizes: “maybe a small boat.”

“You really need those dolphins, those big high bollards … in order to achieve the aim of the ship not colliding with the bridge component,” Aghayere said. “You want the dolphin to be the sacrificial lamb.”

Vijaya Gopu, a professor of civil engineering at the University of Louisiana at Lafayette, said he was taken aback when he saw photos of the bridge and its limited pier protection system, which left the bulk of the support structure “totally unprotected.”

“I’m amazed that Maryland would allow that,” Gopu said. “I’m totally shocked.”

The Maryland Department of Transportation and the Maryland Transportation Authority have not responded to questions about the bridge protection system.

For many, the Key Bridge collapse has brought to mind the Sunshine Skyway Bridge in the Tampa Bay area of Florida, which collapsed in May 1980 after a 609-foot freighter ship rammed into one of its support beams, killing 35 people.

The Key Bridge had opened three years earlier, in 1977, before the Federal Highway Administration issued new standards requiring bridges being built to take certain impact considerations into account. Bridges built before then didn’t need to necessarily adapt to those new conditions, said Nur Yazdani, a University of Texas at Arlington engineering professor.

After the Florida bridge collapse, a Maryland transportation official acknowledged then that neither the Key nor Bay bridges could withstand the direct impact from a similarly sized freighter ship, The Baltimore Sun reported at the time. And in August 1980, the newspaper recently reported, the Key Bridge suffered about $500,000 in damage after a freighter that lost power chipped a partially protected bridge piling.

Safety officials provided new insight into the Key Bridge and why it collapsed so suddenly on Wednesday evening.

At a press conference Wednesday night, National Transportation Safety Board officials said the bridge is a “fracture critical bridge,” meaning if one portion sustained enough damage, the entire structure would collapse. Of the roughly 615,000 bridges in the country, about 17,000 are fracture critical.

”The preferred method for building bridges today is that there is redundancy built in,” said NTSB Chairwoman Jennifer Homendy. “This bridge did not have redundancy.”

Preben Terndrup Pedersen, a civil engineering professor in Denmark, said that as cargo ship sizes have increased and bridge safety standards have evolved, it would have benefited Maryland to consistently construct and update the Key Bridge, considering its proximity to one of the country’s largest ports.

Maintaining or adding protection systems such as fenders to a bridge is a relatively cheap endeavor compared to other aspects of bridge construction, Yazdani said.

“They are sacrificial,” Yazdani said of the fenders. “They are supposed to get damaged and be replaced.”

And in recent years, the money was likely there to do that, at least to some extent, he added.

President Joe Biden set aside more than $400 billion in infrastructure funding at the beginning of his presidency, including $2.3 billion for Maryland.

State officials were also planning to add a fiberglass jacket protection system at the water pier columns, starting in the winter of 2029, suggesting some interest in protecting the bridge’s support system. They estimated that the project would take three years to complete. It’s unclear to what extent such a fiberglass system would have altered the course of the 984-foot-long Dali.

A massive ship generating massive force

There are ships larger than the Dali, but it’s still a behemoth in its own right.

Including cargo, fuel, provision crew and the rest, the neo-Panamax ship can hold roughly 116,000 deadweight tons.

Few bridges would be designed to withstand a direct hit from such a vessel, engineers and maritime experts agreed.

“There’s no way the bridge could have survived that,” said Capt. Allan Post, executive director of Marine Education Support and Safety Operations at Texas A&M University.

At 8 knots of speed, or 9.2 miles per hour, he estimates the ship could have generated 1.2 million joules of energy — a little over a million newtons.

Despite that force, Post said there was a chance that gigantic concrete cylinders like those that will soon protect the Delaware Memorial Bridge piers may have prevented the devastating impact that took down the Key Bridge.

“If a similar system were there … it may have helped, or mitigated the impact,” Post said.

He noted that new bridges are required to have fendering systems, an offshoot of the Sunshine Skyway collapse. But beyond it just being a requirement, Post said, it a critical necessity to protect huge infrastructure investments.

“These are complex machines operated by humans,” Post said of cargo ships. “What additional mitigation could we and should we take to protect our infrastructure and therefore lives when things go wrong?”

Still, others feel that the force of the ship, given its size and weight, would overcome even the type of protection systems being built in Delaware with a direct hit.

When asked whether dolphin barriers that size would have averted a collapse in Baltimore, Khalid M. Mosalam, a structural engineer and professor of civil engineering at the University of California, Berkeley, said “probably not.”

Mosalam said he and a colleague ran calculations based on estimating the ship’s speed and weight that resulted in an impact force that would have overwhelmed those barriers.

“I’m not sure if any practical system (or even retrofit of the bridge) would have been efficient or even practical to prevent this disaster,” he said.

Baltimore Banner Reporter Lee Sanderlin contributed to this report.

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