How Bridge Engineers Design Against Ship Collisions
Practical Engineering・24 minutes read
A container ship collision caused the Key Bridge collapse in Baltimore, resulting in casualties and infrastructure damage. The incident underscores the importance of designing bridges to withstand vessel impacts and the complexities involved in ensuring bridge safety standards.
Insights
- Collisions between ships and bridges, known as "allisions," have been a persistent issue, leading to significant bridge collapses over the years, prompting updated bridge codes to consider vessel impacts in design and emphasizing the importance of structural engineering to prevent such disasters.
- Engineers aim to minimize the probability of bridge collapse from ship impacts by adjusting factors like pier distance, utilizing protection systems, and employing complex calculations to estimate impact forces, showcasing the intricate considerations involved in designing bridges that can withstand potential vessel collisions.
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Recent questions
What caused the collapse of the Key Bridge?
Collision with a container ship led to collapse.
How did engineers remove debris from the collapse?
Seven floating cranes, including Weeks 533, were used.
What organization is investigating the collapse?
National Transportation Safety Board (NTSB) is conducting investigations.
How can the probability of ship collisions be reduced?
Adjusting the distance of piers from the transit path.
What protection systems can mitigate ship collisions?
Fenders, islands, and dolphins can be used.
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Summary
00:00
Bridge Collapse: Ship Collision in Baltimore
- On March 26, 2024, a container ship collided with the Francis Scott Key Bridge in Baltimore, causing its collapse and resulting in the deaths of six construction workers and injuries to one more.
- The Key Bridge was a steel arch-shaped continuous through truss bridge, different from the truss bridge that replaced the old one in Long Beach, California.
- The collapse occurred due to the container ship losing power and drifting into the southwest pier, causing the truss and deck to fall.
- Salvage and removal of the debris from the collapse required the use of seven floating cranes, including the Weeks 533 crane.
- The collapse led to the closure of the port to shipping traffic, with efforts ongoing to reopen it, including marking a small channel for smaller vessels.
- The collapse also affected road traffic, with thousands of vehicles needing to be rerouted due to the bridge closure.
- Investigations into the collapse are being conducted by the National Transportation Safety Board (NTSB), with a report expected to take a year or more to be released.
- Collisions with bridges by ships, technically called "allisions," have been a recurring issue, with 35 major bridge collapses due to vessel impacts between 1960 and 2014.
- Updated bridge codes now include requirements for consideration of vessel collisions, balancing the benefits and costs of designing bridges to withstand such impacts.
- Engineers aim to design structures with a very low probability of collapsing from a vessel impact, with the annual probability set at 0.01 percent for critical structures like the Key Bridge.
13:01
Ship collision factors and bridge protection strategies.
- Factors affecting ship collisions include water currents and navigation aids.
- Geometric probability of collision is influenced by a ship losing control.
- Normal distribution curves can be used to approximate where an aberrant ship might end up.
- The probability of a ship impacting a bridge can be reduced by adjusting the distance of piers from the transit path.
- Structural engineering plays a crucial role in determining if a bridge will collapse after a collision.
- Impact force from a collision is time-dependent and varies based on various factors like ship size and speed.
- Engineers use an equation based on deadweight tonnage and velocity to estimate impact force.
- Protection systems like fenders, islands, and dolphins can be used to mitigate ship collisions with bridges.
- The new Sunshine Skyway Bridge utilized islands and dolphins for protection.
- Designing bridges to withstand ship collisions involves complex considerations beyond just pier strength.
25:23
Bridge Safety Standards and Key Bridge Collapse
- The decision-making process regarding bridge safety standards is complex, involving considerations of risk tolerance and cost-effectiveness. Implementing measures to ensure bridges can withstand worst-case scenarios like collisions with large ships would significantly reduce the number of bridges constructed.
- The Key Bridge collapse serves as a valuable case study that highlights the intersection of bridge engineering and maritime navigation. Understanding the intricacies of both fields is crucial in preventing similar incidents in the future.
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