EXPERTS ADVISORY

The Francis Scott Key Bridge in Baltimore collapsed early Tuesday morning after being struck by a cargo ship that reportedly lost power. University of Michigan experts are available to discuss issues surrounding shipping as well as the bridge.

Sherif El-Tawil, the Antoine E. Naaman Collegiate Professor of Civil and Environmental Engineering, is an expert on mitigating natural and man-made hazards, due to earthquakes, blasts and impact, as well as how structure and infrastructure systems respond to extreme events.

“The impacting ship in the Baltimore situation is massive and, with an assumed 120,000 tonnage, I estimate that the applied force is in the range of 10 million pounds,” he said. “The ship was so large that the flared bows came in contact with the piers and applied this massive load. This caused one member of the A-frame pier to fail. The bridge weight caused the other to collapse.

“I am surprised that a protection system was not built for this bridge. The protection system would have diverted the ship away from the piers, protected the bridge, protected the community from the loss of a critical bridge and protected the ship itself. I suspect that the cost of a protection system would likely be extremely high and is likely the reason it was not implemented.

“Ship collisions with bridges that cause this kind of damage are extremely rare. There are about 40 recorded events in the past 65 years. The most significant event of this sort that occurred in the U.S. is the Sunshine Skyway Bridge in Florida. That event led to the development of ship collision specifications for bridges, i.e., provisions that bridge owners must meet to mitigate the effects of ship collision.

“The ship collision guidelines came into effect in the early 1990s so they were too late in this case. The Key bridge was built in 1974, so it was likely not designed for ship collision.”

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Timothy McCoy is a professor of practice in naval architecture and marine engineering, specializing in marine power and energy systems.

“Containerships, like the MV Dali, are typically powered by a single low-speed diesel engine directly coupled to the propeller. Unlike cars, ships and boats do not use brakes to stop,” he said. “They use their engines to reverse thrust to slow and eventually stop the vessel. With a low-speed direct drive diesel, that is accomplished by stopping the engine and then restarting it in the opposite direction of rotation.

“A ship of this size will generally have a steering system that is hydraulically actuated and powered by electric motor-driven pumps. Both the steering pumps and the control system are considered ‘essential loads’ that are powered from both the main ship’s power grid as well as the emergency generator.

“A loss of electric power from the main grid onboard should not cause a loss of steering control. However, the ship’s rudder becomes ineffective at very slow speeds (just like an airplane’s wing doesn’t work without forward speed). At this point, I don’t know enough to speculate as to why the ship veered off course.”

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Ravi Anupindi is the Colonel William G. and Ann C. Svetlich Professor of Operations Research and Management and professor of technology and operations at the Ross School of Business. His main research areas include technology and business innovation, global supply chain management, economic development, and environmental and social sustainability. He serves as a faculty expert on a Global Supply Chain Task Force to look into supply chains and national security issues. 

“It was shocking to hear of the bridge collapse in Baltimore. Beyond the loss of lives, which is tragic, there will surely be impacts on the supply chain,” Anupindi said. “Baltimore is one of the top 20 ports in the U.S. It primarily handles containers, autos and some commodities. Significant auto trade between the U.S. and EU happens through East Coast ports, and Baltimore plays a very important role here. 

“While there is sufficient capacity in other East Coast ports, it may take a bit of time for the traffic patterns to adjust. Beyond just the ships redirecting to alternate ports, a bigger challenge may be the rest of the infrastructure adjusting to ships coming and going from alternate ports, e.g., ships carrying autos will need to have auto carrier trucks to take the vehicles away from the ports and bring them to ports.”

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