What could have caused the Francis Scott Key Bridge in Baltimore to collapse?

Francis Scott Key Bridge

The collapse of the Francis Scott Key Bridge in Baltimore on March 26, 2024, was primarily caused by the container ship Dali striking one of its piers. The ship reported losing propulsion, leading to a collision with the pier and subsequent collapse of the bridge truss.

Here's a breakdown of the incident:

• Loss of control by the ship: The container ship, Dali, reportedly suffered a power failure, leading to a complete loss of propulsion. This left the vessel unable to steer or control its movement.

• Collision with bridge pier: Without control, the Dali struck a critical support pier of the bridge.

• Continuous Spans: The bridge was constructed of three continuous spans. This design increases the efficiency of the bridge, allowing engineers to economically construct long spans, like the one over the shipping channel. However, it also means that when a pier directly supporting two of the spans was incapacitated, even the third span of the bridge, seemingly far from the site of impact, also collapsed.

• Fracture Critical Design: The Francis Scott Key Bridge was likely a "fracture critical" design. This means that the failure of a single critical element, like a pier in this case, could lead to the collapse of the entire or a significant portion of the bridge.

• Redundancy and Progressive Collapse: Modern bridge design principles often incorporate redundancy, meaning alternative load paths exist in case one element fails. This allows for "progressive collapse," where the failure is contained to a specific section, preventing the catastrophic collapse of the entire bridge. It's possible the Key Bridge lacked sufficient redundancy to prevent such a widespread collapse.

The National Transportation Safety Board is verifying the reported loss of power before the collision. Here are some additional details:

1. Victims: At least eight people went into the water when the bridge collapsed. Two were rescued, but the other six, part of a construction crew that had been filling potholes on the bridge, are missing and presumed dead.

2. Investigation: The cargo ship, called Dali, lost power and issued a mayday call shortly before it rammed the bridge. The U.S. Coast Guard boarded the vessel to collect evidence about the exact circumstances of the crash. The National Transportation Safety Board (NTSB) has recovered the data on Dali's voyage recorder.

3. Impact: The collapse is diverting shipping and trucking around one of the busiest ports on America's East Coast, creating delays and raising costs. The economic impact of the waterway's closure has been estimated at $15 million per day.

4. Recovery Effort: More than 1,100 engineering, construction, contracting, and operations specialists from the Baltimore District of the Army Corps of Engineers are providing support to local, state, and federal agencies after the collapse. The Army Corps is helping to clear the channel where the bridge collapsed as part of the recovery effort to remove the debris from the water.

5. Future Plans: Baltimore City Council President Nick Mosby said his priority is to help bring normalcy back to his community. Rebuilding the bridge should remain the focus.