Baltimore bridge collapse: Saturday’s photos show extent of damage, experts explain why
Around 1:30 a.m. Tuesday, the Francis Scott Key Bridge over the Patapsco River in Baltimore, Maryland, collapsed after the 985-foot-long cargo ship named Dali reportedly lost power and struck the bridge’s pylon or pier. India Today obtained satellite images of the bridge before and after the incident from Planet Labs. These show extensive damage to the bridge.
Experts are considering this
“The bridge is 2.6 km long, built in 1977. The supporting structure – the pillars of the bridge – are made of reinforced concrete. The metal truss of the superstructure was continuous,” said Dr. Sotirios Argyroudis, Associate Professor of Infrastructure Engineering at Brunel University. London. “The collapse occurred when a ship struck one of the bridge’s pillars, causing the metal truss to fail. This is an example of a common mode of failure known as progressive collapse.”
In such cases, Argyroudis explained, removing a range of bridge supports – in this case, the pier – causes a redistribution of loads that the metal truss cannot effectively bear, resulting in its progressive collapse.
According to open-source information, the collapsed portion of the bridge measures 805 metres. It was a typical continuous truss bridge with a span of approximately 1,200 feet between two critical pillars, supported by hundreds of struts that maintained the pressure evenly. The collapse of a key pillar increased the pressure on the struts, causing the bridge to lift before collapsing.
This is called progressive collapse – the failure of one structural element leads to the failure of neighboring elements, which cannot support the new load placed on them.
“The collapse of the 804-metre long three-span section of the bridge appears to have been caused by the giant container cargo ship DALI impacting and collapsing one of the two main bridges. It stripped vital support from the steel truss superstructure suspended roadway, such that the entire three-span section suffered catastrophic structural failure and collapsed into the river below,” said California-based marine engineer Alan Hayward.
Experts also said that the forensic investigation could take 1-2 years as laboratory tests and collapse scenarios would have to be analyzed to come up with a plausible/reasonable simulation of what might have happened.
aging infrastructure
Analyzing video and footage of the accident, experts immediately pointed out that the dolphins (small round objects surrounding the pillars) were inadequate to deflect anything other than small vessels.
Referring to the era when the bridge was built, structural engineer Ian Firth said: “Dolphins have become common since the Sunshine Skyway collapse in 1980. However, this bridge was built in the 1970s, so the design These devices would not have been included at the time. The fact that a ship could deviate from its course and collide with the pier is why ship impact protection systems are designed so that a larger ship does not hit critical bridge supports. Could collide”.
“When steel truss road bridges were designed and built in the 1970s, inelastic collapse and structural integrity did not need to be considered. It can be imagined that ships would face the magnitude of today’s ship impacts. The ships were not navigating the port of Baltimore like Dalí during that era, said Toby Mottram, professor of structural engineering at the University of Warwick.
Engineering consultant Robert Bynum said, “I don’t know what arrangements were made for this bridge, but major bridges built over shipping lanes must have adequate protection for piers or pillars. These protections can be either structural protection like sacrificial dolphins.” They can also be in the form of artificial islands; these are for very large ships and mean that the ship will never reach the bridge pier. Clearly, the protection of the piers in this case is inadequate. Was”.
what went wrong?
About 42 percent of bridges in the U.S. are more than 50 years old, Argyroudis said, potentially posing a safety risk in some cases. Aging infrastructure is particularly vulnerable to degradation caused by corrosion and other environmental conditions. Their risk of failure increases due to exposure to various hazards such as earthquakes, floods, storms and human-induced stresses such as collisions and explosions. Further complicating the problem, current traffic loads often exceed those for which these bridges were originally designed. “It is important to assess the resilience of our infrastructure to inform future investments in infrastructure improvements,” he said.
“Normally, in the case of older bridges, if bridge engineers do a structural assessment they will examine the ship impact scenario and what damage it might cause. At this point, the strength of the bridge is critical to avoid progressive collapse. As we saw in the video,” said Dr. Mehdi Kashani, associate professor in structural and earthquake engineering at the University of Southampton.