More than 17,000 bridges in the US can collapse after a single impact


The lifespan of Baltimore’s Francis Scott Key Bridge was 47 years. In all that time, it has not experienced such a big shock as on Tuesday, March 26, when the container ship Dali weighing more than 100 thousand tons crashed into it. The bridge collapsed into the river in less than a minute.

Although such a catastrophic collapse may not have been entirely predictable, the collapse of bridges as a result of collisions is not entirely uncommon and could have been prevented, wrote the server of the American television station CNN.

While recent federal safety inspections found the Francis Scott Key Bridge to be in “good” condition, that’s not the case for thousands of others in various parts of the U.S. that are in “poor” condition.

A close-up camera captured the moment a boat crashed into a bridge in Baltimore


Individual states inspect America’s highway bridges at least once every two years and classify their condition as “good,” “fair,” or “poor.” The bridge, which is in poor condition, has some structural elements in a state of “advanced deterioration,” CNN explains.

About 46,100 of the total 617,000 bridges in the United States, or 7.5 percent of all bridges, are in “poor” condition, according to the American Society of Civil Engineers in its 2021 report. In addition, the organization adds that 178 million trips are made through them every day.

While structurally deficient bridges are not inherently dangerous, they do require significant investment in maintenance, added the organization, which estimates that 42 percent of all U.S. bridges are at least 50 years old.

Almost 21,000 bridges have foundations susceptible to extreme weather conditions (earthquakes, hurricanes, extreme temperatures, etc.). Older bridges also suffer from the fact that trucks are heavier than the original bridge designs anticipated. This can lead to cracking of metal structures and an overall lower lifespan.

Aerial footage of a collapsed bridge in Baltimore


But aging bridges, extreme weather and heavier vehicles aren’t the only threats to America’s bridges. According to the U.S. National Transportation Safety Board, more than 17,000 U.S. bridges are susceptible to collapse from a single impact known as “failure critical,” which means the bridges do not have so-called redundancy — protective structures around the bridges’ vulnerable points.

If the bridge is hit with sufficient force at a certain point where redundancy is missing, either a large part of it or the entire bridge may collapse. And this was exactly the case with the Baltimore bridge, according to the authority.

According to experts, there is an urgent need to improve the protection of older bridges against larger and more modern vessels. After all, the Dali ship was 300 meters long, which is almost twice the length of the ships that were used in the 1970s, when the bridge was built.

However, the Business Insider server, citing some interviewed experts, said that even if the Baltimore bridge had redundancy in the form of “dolphins” (wooden or steel pillars rooted in the sea or river bed and protruding above the surface) or “fenders” (structural buffers), then the bridge would not have been able to withstand such a massive blow anyway.

A ship in Baltimore was carrying hazardous material, the damaged containers fell into the water



The article is in Czech

Tags: bridges collapse single impact


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