One in 13 bridges in the United States is in “poor” condition. Thousands may perish in the conflict

(CNN) — The container ship crash on Baltimore's Francis Scott Key Bridge draws attention to the potential damage to some of the more than 600,000 bridges in the United States.

The drawbridge has stood for 47 years, and in that time it hasn't shaken enough to make anyone think it's about to collapse. But the bridge collapsed within a minute when the 100,000-plus ton ship Daly collided with it. Although such a catastrophic collapse is not entirely foreseeable, bridge collapses as a result of collisions are not entirely unheard of and could have been avoided.

Key's recent federal safety inspections determined its condition to be “fair,” and Maryland's governor said the bridge was “fully compliant.” But thousands of American bridges are in disrepair.

In the United States, 46,000 bridges have aging structures and are in “dire” condition, and 17,000 are at risk of collapse in one fell swoop, according to the American Society of Civil Engineers and the federal government.

Extreme weather events, collisions from increasingly heavy trucks and large container ships pose significant risks to U.S. bridges, engineers and other infrastructure professionals.

Aging infrastructure

States inspect U.S. highway bridges at least every two years and rate them as “good,” “fair,” or “poor.” A bridge in poor condition has some structural components in a state of “advanced deterioration”.

About 46,100 of the 617,000 bridges in the United States, or 7.5% of all bridges, are considered structurally deficient and in poor condition, according to a recent report. Report Infrastructure by the American Society of Civil Engineers, published in 2021. Every day, 178 million trips are made on these structurally deficient bridges.

While structurally deficient bridges are not inherently unsafe, their maintenance requires substantial investment, the organization says. They are at high risk of being shut down or affected by weight restrictions.

According to the group, the good news is that the number of structurally deficient bridges has decreased in recent years. But the bad news is that the pace of spending on improvements has slowed. According to a recent estimate, bridge repair delays in the country are US$125 billion.

A $1.2 trillion federal infrastructure bill passed in 2021, which includes $110 billion for roads, bridges and major infrastructure projects, will help pay for some bridge improvements.

Climate change and heavy trucks

Many of the nation's oldest bridges are vulnerable to extreme weather events such as earthquakes, hurricanes or extreme heat.

According to the American Society of Civil Engineers 2021 report, nearly 21,000 bridges will threaten their foundations during extreme weather events.

Earthquakes are also a major threat to bridges.

According to a 2016 report by the Congressional Research Service, the seismic resistance of the US highway system has improved in recent decades thanks to investments in new, stronger infrastructure and modernization of existing structures.

However, according to the report, not all highways have been modernized, and there is still no way to build infrastructure that is cost-effective and able to withstand more severe earthquakes.

In addition, bridges are placed under pressure from heavier trucks than originally designed.

According to the American Society of Civil Engineers, these heavy trucks, carrying loads exceeding 40 tons, can overload bridge components, lead to metal fatigue and cracking, and shorten the life of bridges.

Huge inventory

Aging infrastructure, extreme weather and large vehicles are not the only concerns.

More than 17,000 bridges are at risk of collapsing in one fell swoop, known as “critical fracture” bridges. This means that if they are hit in the right place with enough force, a significant portion or the entire bridge will collapse.

The National Transportation Safety Board said Wednesday that the main bridge had a “critical fracture.”

Experts say there is an urgent need to upgrade or protect old bridges to protect them from larger modern ships. The tally, which hit the causeway on Tuesday, was 984 feet long, twice the size of the vessels used when the bridge was built in the 1970s.

Between 1960 and 2015, 35 major bridges around the planet collapsed due to ship or boat collisions, resulting in 342 deaths, according to a 2018 report by the World Water Transport Infrastructure Association.

In the first three months of this year, the Key Bridge collapsed in Baltimore, a bridge was cut in half in southern China and parts of a bridge were severed in Argentina after collisions with large merchant ships.

“Ships have gotten bigger and container ports are focusing on deepening their cargo. While we encourage larger containers, we need to protect bridges in these particular situations,” Container Association President Ananth Prasad told CNN. Florida Transportation Builders said.

To reduce the chance of bridges collapsing with ships, bridges must be built with so-called redundancies: protection around dangerous points on bridges.

These include “dolphins” – structures rooted in the sea or river bed, usually made of wood or steel – or “protectors” – structures that move objects away from the bridge's vulnerable points in the event of an impact.

According to Prasad, adding these safeguards is faster and less expensive than building a new bridge.

“As the ships get bigger we may need to review the safety systems around the bridge columns,” he said.

CNN's Jessie Yeung, Curt Devine, Casey Tolan and Isabelle Chapman contributed to this article.