University of Michigan Engineer Discusses History and Protection Against Ship-Bridge Collisions

In the aftermath of the recent Francis Scott Key Bridge collapse in Baltimore, we spoke to civil engineer Sherif El-Tawil to understand the history of ship-bridge collisions, protective measures for bridges, and the implications for future bridge designs.

A History of Ship-Bridge Collisions

According to El-Tawil, ship-bridge collisions are rare events, with approximately 40 recorded incidents in the past 65 years globally. The most influential case was the 1980 Sunshine Skyway Bridge collision in Florida, which led to the development of federal guidelines for designing bridges to withstand ship collisions.

Lessons from Past Collisions

The Sunshine Skyway Bridge disaster prompted the incorporation of specifications into the national design document, requiring bridges to be designed to withstand impact forces from ships or be equipped with protective systems. This shift in design standards aimed to prevent similar tragedies in the future.

Design Considerations for New Bridges

El-Tawil emphasized the need for bridges to be capable of withstanding massive forces generated by today's cargo ships. He calculated that the impact force of the MV Dali in the recent incident was approximately 30 million pounds, highlighting the importance of robust bridge designs to mitigate such forces.

He also outlined various alternatives, such as building islands around piers, constructing rock walls, installing standalone structures in riverbeds, or utilizing energy-absorbing fenders to minimize the impact of ship collisions on bridges.

Feasibility of Protecting Older Bridges

Despite the challenges, El-Tawil believes that it is feasible to implement protective measures for older bridges, including lower-tech solutions such as building islands or using rocks and concrete components to prevent ships from reaching vulnerable bridge piers. Implementing such measures could enhance the resilience of existing bridges against potential collisions.

Implications of Cargo Ship Growth

El-Tawil highlighted the potential implications of the increasing size of cargo ships, emphasizing the need for bridge designs to account for the evolving scale of maritime transportation. He noted that while current specifications may address existing ship sizes, future advancements in vessel sizes could pose new challenges for bridge resilience.

Recovery and Rebuilding Efforts

The loss of a major bridge like the Francis Scott Key Bridge will have long-term implications, requiring extensive planning and resources to rebuild. El-Tawil emphasized the complex nature of reinstating a bridge of such magnitude and span distance, highlighting the significant efforts and time needed for recovery.

As the investigation continues into the causes of the Key Bridge collapse, the insights provided by experts like Sherif El-Tawil shed light on the importance of proactive bridge design, protective measures, and ongoing considerations for the evolving maritime landscape.