Ship impact against bridge piers

03-04-2024 | Posted by Joaquín Martí

Impacto barco puente

Once again, a recent accident provides the motivation for the present post. But unlike the Marrakesh-Safi earthquake or the Derna flooding in Libya, both occurred in September 2023, this time we are not dealing with a natural disaster but with a man-made one.  On March 26, 2024, at 01:28 EDT (05:28 UTC), the complete truss section of the Francis Scott Key Bridge in Baltimore, Maryland, collapsed after one of its main piers was destroyed by the impact of the 300 m container ship Dali. The bridge had been named after the author of the lyrics of the American anthem.

It seems that the ship lost propulsion and issued a mayday call that allowed stopping traffic in the bridge but, from a crew of eight construction workers in the bridge, six have been lost. Apart from the human toll, the disruption caused and the financial implications of the collapse are enormous. To get an idea consider that in 2023 the bridge carried 12.4 million vehicles and the port of Baltimore, with its navigation channel interrupted by the collapsed bridge, handled over 43 million tons of cargo.

Bridges with their piers in, or close to, navigable waters are exposed to this type of accidents. Some examples come to mind, like the Severn Railway Bridge, which collapsed in 1960 when two oil barges lost control and struck one of the pillars, destroying the railway link and killing five people. Or the Tasman Bridge in Hobart, Australia, where a bulk carrier collided with two of its pylons in 1975. Or the collapse of the Almö Bridge in Sweden by impact from a bulk carrier in 1980, killing eight people. Or, perhaps better known, the collapse in 1980 of the southbound span of the Sunshine Skyway Bridge in Tampa, Florida, which resulted in 35 deaths. And there are many others.
impacto barco puente

Of course, some measures can be taken to reduce the frequency or the consequences of such accidents. Some non-structural examples are improved navigation systems, collision warning systems, or regulatory limits on vessel manoeuvres.

From the viewpoint of the structure, the piers can be protected with dolphins, artificial islands, or other structures; also, if the ship’s weights and speeds are sufficiently limited, the structure may be designed to withstand the demands imposed by those impacts.

Principia has dealt with this type of problems in many bridges in the past. Indeed, more than five years ago we published a post describing some of the problems and our experience in solving them. This experience includes earthquakes, ground liquefaction, explosions, impacts, winds, temperatures, concrete swelling, faulty design, etc. Specifically on the issue of ship impacts and their effects on the supports, we have worked on bridges such as a potential crossing across the Strait of Gibraltar, the Oresund bridge between Danmark and Sweden, the new Tagus crossing in Lisbon, or the 4th bridge over the Panama Canal.

Our hearts weigh heavily with any calamities affecting mankind, particularly when we have expertise and are active in the areas involved. Let us hope they do not proliferate.