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Minneapolis bridge collapse

Minneapolis Bridge Collapse

The collapsed 35W bridge in Minneapolis seen on August 2, 2007 | Morry Gash/AP

Bridge accident Minneapolis

The Interstate 35W bridge over the Mississippi River in downtown Minneapolis collapsed on August 1, 2007, bringing cars, trucks, and even a school bus plunging into the river below and onto the rocky beach.

13 people died, and 145 others were hospitalized, many of whom were severely injured.

The collapse of the bridge prompted immediate calls in Minnesota and across the country to invest more in repairing and upgrading the country's aged and crumbling infrastructure.

The I-35W collapsed bridge was illuminated by spotlights, while officials shut the neighbouring bridge off while the rescues continued in the night | Richard Tsong-Taatarii, Star Tribune, AP

Analysts claim there have been some improvements a decade later, but so many of bridges still need to be repaired or replaced across the country.

In the immediate aftermath of the 35W bridge collapse, the Minnesota Department of Transportation came under intense scrutiny.

The interstate highway bridge had been classified as structurally deficient, meaning that it was aging and in need of repair. In fact, some repair work was going on when it fell.

Minneapolis Bridge Collapse

Ron Engegbretsen, of shoreview, hugged his daughters Anne left, and Jessica, right, following an new conference, Saturday, aug 4, 2007, in Minneapolis. engebretsen’s wife sherry died in the bridge collapse | Charlie Neibergall, AP

The bridge was also categorised as fracture severe, which means that the failure of just one vital component could cause the entire structure to collapse. However, neither of these categorization suggests that a bridge is extremely dangerous.

The National Transportation Safety Board ruled that the 35W bridge collapsed due to a design defect, not deferred maintenance, negligence, or other issues.

The bridge's massive steel beams were held together by gusset plates that were barely half as thick as they should have been.

The NTSB also found that roughly 300 tonnes of construction materials and equipment stored on the bridge deck for ongoing repair work made a significant contribution to the collapse by putting excessive pressure on the critical gusset plate that failed.

History of construction of Minneapolis I-35W Bridge

Minneapolis' I-35W (Interstate 35 West) bridge across the Mississippi River opened to traffic in 1967. Its Longest span was: 456 ft (139 m).

Thousands of vehicles crossed it every day, but no one could have predicted that a design flaw from more than four decades ago would have such disastrous consequences on a warm evening in August of 2007.

In the early 1960s, a civil engineering firm called Sverdrup & Parcel designed the I-35W bridge, which was given the name "Bridge 9340."

The bridge's construction began in 1964, near the end of the nation's highway construction rise, which aimed to significantly improve the country's traffic infrastructure. In late 1967, the bridge was opened to traffic.

Nine spans of steel multi-girder construction, two spans of concrete slab construction, and the main three spans of deck truss construction constituted Bridge 9340.

In the beginning of 1993, the Minnesota Department of Transportation (MnDOT) was given duty of taking over annual bridge inspection. It was previously inspected by the federal government every year now.

Daubenberger (then a bridge engineer for the state and now the director of engineering services for MnDOT) says the state immediately inspected gusset plates on every single truss bridge in the country to ensure the safety measure.

Within a month of the bridge collapse, the state legislature of Minnesota increased the gas tax and approved a $2.5 billion for bridge reconstruction plan.

"The bill prepared a plan to replace or repair all poorly maintained bridges and critically weak bridges within 10 years" Daubenberger stated.

Minneapolis bridge collapse cause

According to the NTSB, the bridge's ultimate breakdown in 2007 was caused by a mistake committed over forty years before to the collapse.

Over forty years of state and federal inspections ignored the major design fault since checking for such faults after the fact was not normal protocol.

Minneapolis Bridge Collapse

Minneapolis Police Services formed a line that monitors the crowd gathered at the Interstate 35W Bridge on Wednesday night, Aug 1st 2007. | John Domann, St. Paul’s Pioneer Press / AP

The tragedy that occurred in Minneapolis on that July day in 2007 created a rift that spread across the country.

Government officials around the world felt forced to continue increasing inspections and increase funding to renovating and maintaining their traffic infrastructure.

However, as the Minneapolis bridge collapse indicated, local governments frequently lack the funds to resolve decaying infrastructure. 

It is predicted that over a trillion dollars will be required to repair the damages.

This money has been difficult to come by, and local governments across the country are still struggling to keep up with maintenance and safety costs.

Within 14 months, the I-35W bridge was repaired.

According to Daubenberger, 172 Minnesota bridges were found to be structurally weak or fracture-prone. Only routine, precautionary maintenance was found for about 35 of them.

About 120 of them have been fixed or rebuilt, while the remaining 18 are either being built now or will be restored or replaced before the deadline next summer.

Minneapolis Bridge after 14 months

In July 2008, the new Interstate 35W bridge, which replaced the old bridge, was seen. | Jim Mone/AP

Minnesota has also increased and improved bridge inspections, and now uses drones to take images and video of areas on bridges that are difficult to reach with human inspectors.

Bridge design plans are now subjected to independent performance reviews, and the state's bridge maintenance worker training programme has been redesigned.

"Certainly, we've done a lot to assure the safety of bridges so it doesn't happen again," Daubenberger says.

"I'm confident in the improvements we've made in bridge design, construction, inspection, and maintenance, all of which contribute to good bridge safety."

But, whereas Minnesota has taken steps to minimise the number of structurally unsound bridges in the state, what about the rest of the country?

"America's infrastructure is like that of a third-world country," says Ray LaHood, a former Republican congressman who served as Obama's transportation secretary.

The American Road and Transportation Builders Association, which keeps track of how many bridges in each state have design deficiencies, found 55,710 bridges that need to be fixed or replaced.