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Some bridges have large concrete islands known as dolphins or bumpers placed around them for protection
The collapse of the Francis Scott Key Bridge in Baltimore on Tuesday has raised serious questions about what safety or protective mechanisms might have prevented the disaster and the loss of six lives.
It is still unclear what caused a massive 985-foot long cargo vessel to apparently lose control and strike a pier, also known as a pylon, a critical part of the structure that keeps the deck of the bridge in place.
But could the bridge have been better protected to safeguard against a large vessel striking a key part of its infrastructure?
From 1960 to 2015, there were 35 major bridge collapses worldwide due to ship or barge collisions, with a total of 342 people killed, according to a 2018 report from the World Association for Waterborne Transport Infrastructure.
Eighteen of those collapses happened in the U.S., including in 1980 when a 609-foot freighter slammed into the Sunshine Skyway Bridge in the Tampa Bay area of Florida.
The freighter, Summit Venture, was navigating through the narrow, winding shipping channel when a sudden, blinding squall knocked out the ship’s radar. The ship sheared off one of the bridge’s supports, dropping a 1,400-foot section of concrete roadway into the water during the morning rush hour.
Seven vehicles, including a bus with 26 aboard, fell 150 feet into the water. At least 35 people died.
Following the tragedy, a replacement bridge was constructed, and its piers were protected by several circular sheet pile cells known as dolphins. The protective infrastructure is also known as a fendering system. The area around the larger piers was also buffered with concrete and rocks for added protection, while the shipping lanes for vessels to pass through were widened.
On April 29, 1987, the day before the new bridge was scheduled to open, the new bridge’s protective bumpers were hit head-on by a 74-foot-long shrimp boat. The bumper sustained minor damage – but the bridge was not affected and was opened at a later date. The shrimp boat took on water and was towed out of the channel into shallow waters, where it sank.
Jennifer Homendy, the chair of the National Transportation Safety Board, said at a Tuesday press briefing that protective structures would be a part of the investigation into the collapse of the Maryland bridge.
“There’s some questions about the structure of the bridge – protective structure around the bridge or around the piers to make sure there isn’t a collapse,” she said, responding to a reporter’s question. “We are aware of what a structure should have. Part of our investigation will be how was this bridge constructed? It will look at the structure itself. Should there be any sort of safety improvements? All of that will be part of our investigation.”
At least six construction workers who were on the bridge at the time of its collapse are presumed dead at the time of this report.
Harichandran said other more cost-effective systems can be used to alert bridge users.
“You could have trip wires and have more sophisticated warning sensors that would warn of approaching the bridge much earlier,” Harichandran said.
“For those kinds of remote sensing approaches, you could potentially have given an earlier warning of a disaster that could have gotten people out of the way. I know there was a warning because of the radio call, and it helped stop traffic and so on but an earlier warning might have warned the authorities sooner,” Harichandran added. “Think of a trip wire that is set up a mile before the bridge and if a ship is not to going the way it is supposed to it would set it off and warn people that something is amiss, and you could close the bridge.”
