1. The bridge, the Francis Scott Key Bridge, was designed by Parsons Brinckerhoff (now WSP), one of the top three bridge design firms in the world. PB was forced to sell itself due to the big dig accident and was eventually bought by the Canadian company WSP. Although the main cause of the accident was the collision of the ship, the designer of this bridge estimated that he was trembling at home at the moment and silently checking the calculation, for fear of making a mistake. Bridge designers are responsible for life, and the responsibility and risk are huge.
2. The bridge is a steel arch continuous truss bridge. It straddles the Patapusko River and the outer harbor of the Port of Baltimore, and carries Maryland Highway 695, connecting Cape Hawkins to Dundalke. With a main span of 1,200 feet (about 366 meters), the bridge is the third longest continuous truss bridge in the world. The total length of the entire bridge is 8,636 feet (about 2,632 meters). The bridge opened on March 23, 1977, and is the second-longest bridge in the Baltimore area, after the Chesapeake Bay Bridge.
3. The container ship that hits the bridge is 300 meters long and 48 meters wide, and a ship of this size usually has a gross tonnage of about 100,000 tons. Considering the vessel's size and operating parameters, its impact force on the bridge at speeds of 4 to 6 knots (well below the average speed of 13.4 knots due to having just left port) can be tentatively calculated between 20,000 and 30,000 kips (90 to 130 meganewtons) according to Section 3.14.8 of the American Association of Interstate Highway and Transportation Officials (AASHTO) Code for the Design of Highway Bridges, 9th Edition.
If the piers of the highway bridge were not protected, the designed vehicle impact force was 600 kips, and this time the impact force of the ship was 50 times that of the vehicle. It's still big!
4. The bridge, inaugurated in 1977, is a symbol of the engineering ethos of the time, with its main span built as a continuous Baltimore truss bridge, characterized by a suspended deck. This type of structure, named after its name and place of origin, improved the Pratt truss design by employing subdivision panels at the junction with the bridge deck. In addition, the slender piers reflect the lightweight truss configuration. It has not yet been clearly determined whether the design took into account the impact force of this magnitude exerted by a ship of this class, since there were no ships of this class among the sea ships of that era.
5. At present, the design of sea-crossing bridges of this level, the piers generally have a protection system, and the old bridges may not be required by the specifications at that time.
6. With the increase of traffic demand, the general old bridge will regularly evaluate its bearing capacity, scientifically known as load rating, and then carry out the corresponding weight limit. However, substructures, such as piers, are generally not evaluated separately unless there is significant damage.
7. This event underscores the urgency of a complete reassessment of existing infrastructure to withstand contemporary and future maritime developments. As a result, the engineering community is called upon to take action to reimagine bridge design parameters to pre-integrate the growing maritime developments.