Why bridges fail

And when it came to the consequences of these failures as opposed initiating cause , partial collapses were the most likely result, with 80 occurring in the data set. There were 12 cases of total collapse and 17 cases of bridges experiencing distress. But there were a whopping cases where there wasn't enough data to determine if the failure had been total collapse, partial collapse, or distress.

Now the authors do say that while it was usually possible to readily interpret the cause of failure from the data available, this issue of incomplete data was a real challenge in determining consequence. Further, more sophisticated information, such as the human and procedural causes of these failures, was essentially non-existent.

It is very difficult to genuinely learn from failure without this sort of data. How can we as an engineering profession learn from failures when we don't even talk about them? Technical causes of failure What were the prime culprits in terms of causation? In some cases multiple causes contributed to failure, but the authors focused on the cause that primarily failed the bridge.

And in terms of primary causes they found that design and construction errors caused few failures — only 2. But we need to be a little careful here, because the authors believe that the term 'flooding' also appears to relate to, or at least is interchangeable with, scour. And if you are unfamiliar with scour, it is the erosion of a riverbank or riverbed or sea bed by flowing water, which undermines a bridge's foundations. Moving from hydraulic actions to the second highest cause of failure takes us to collisions.

These accounted for Collisions relate to vehicles striking a structure. In this data set bridges were impacted by 14 trucks, three trains, 10 ships and barges, with 32 collision causes remaining unknown. A later study by Cook, Barr, and Halling, which included nine pedestrian bridge failures, found that eight failed because of collisions — the ninth failed due to a lack of lateral bracing in construction. The third primary cause of failure was overloading. A total of 8. There were two pedestrian bridges in this study, and both failed due to overloading.

An interesting aspect of overloading failures, highlighted by Cook and Barr, was that of the seven bridges in their data set that failed due to overloading, six were load restricted to below the legal limit.

Further, five of these seven bridges were classed as structurally deficient before the collapse. The authors concluded that there was certainly a relationship between overloading failures and load restricted bridges. While this may sound obvious, the lesson I take away is that these overloading failures are perhaps less an issue with dramatically overloaded vehicles, but rather an issue with under strength bridges. Now the striking thing is that hydraulic, collision, and overloading failures account for The vast majority of failures were caused by what the authors called external events.

Your choices will not impact your visit. NOTE: These settings will only apply to the browser and device you are currently using. We use cookies to ensure you get the best experience. When a bridge collapses, there may be a number of contributing factors, but these five are the most common: 1.

Natural disasters When Mother Nature strikes with a vengeance, bridges pay the price. Ineffective design No one is perfect, including the talented men and women who design bridges across the country. Construction failures A lot of work goes into bridge construction, but construction sites can be lethal. Poor maintenance Perhaps the most troubling aspect of bridge collapses is the fact that many of them are preventable. Learn how bridge asset management software can help prevent bridge collapses:.

Better planning, including installing storm drainage systems or bridge reinforcements, could have avoided this hardship. Countless bridge incidents happen because of unanticipated structural or design-related issues. The good news: Computer modeling and testing make it easier for engineers to see how different bridge designs hold up against a broad range and combination of unexpected conditions. Prior to being completed in , it underwent significant scale model, wind tunnel, and computer testing.

This led to innovations that improved the design of this bridge and others that followed. Bridge engineers must plan for all types of incidents, including those caused by vehicles that exist today and ones like driverless cars, larger ocean tankers, and cruise ships, along with pilotless drones that could impact bridges in the near and distant future. Back in , a plane took off from Washington National Airport and 30 seconds later, crashed into the 14th Street Bridge over the Potomac River.

Seven vehicles traveling on the bridge were struck by the plane and drove into the freezing water. Four of the people in them perished. Amazingly, only a few hundred feet of guardrail and wall from the side of the bridge were torn away. Some bridges never make it to completion. They fail during construction. Back in , an epic bridge failure happened during construction in Quebec City.

Designers were made aware that the bridge weighed eight million pounds more than estimated at a certain point in the construction process. Soon after, an onsite engineer noticed the frame of the bridge was starting to bend. Not long after, the structure came down, killing 75 workers. However, floods dramatically increase the force and volume of water affecting the bridge, and the damage to sediments can cause a bridge to collapse immediately or even days or months later.

A study by the American Society of Civil Engineers determined that 53 percent of all bridge collapses are caused by flood and scour [source: Wardhana ]. The Schoharie Creek Bridge is an example of a collapse caused by flood and scour.

The bridge carried the New York State Thruway over the creek. In , spring flooding caused high water levels. This washed sediment out from under one of the bridge piers, causing it to fall into a hole nearly 10 feet 3 meters deep. A surprising number of bridges collapse as they're being built. You might think these types of collapses aren't as serious because no one was driving on the bridge at the time of the collapse. Unfortunately, some of the deadliest bridge collapses in history have occurred during the bridge's construction.

While a functional bridge may only have a few vehicles on it when it collapses, it takes hundreds of workers to build a bridge -- all of whom may be in dangerous positions in case of collapse.

The collapse of the Quebec Bridge crossing the St. Lawrence River at Quebec City shows how engineering miscalculations can lead to disaster. The bridge was only partially constructed, but parts were already bending and breaking from the weight of the bridge itself.

Engineers were concerned, but unable to take action swiftly enough. When it collapsed, 74 workers were killed [source: Structurae ].

Amazingly, when the bridge was being rebuilt in , it collapsed again, killing 13 more workers. It was finally completed in and remains in use today. Some bridge collapses are mysteries when they first happen. It isn't until a detailed investigation is completed that the true cause is revealed.

Combing over the wreckage, engineers and accident investigators piece together the bridge's history, looking at inspection reports and witness accounts of the collapse. At times, the simple failure of a small piece of the bridge caused the entire collapse. Sometimes low-grade or faulty materials were used, rendering the entire bridge too weak to withstand the rigors of time. In truth, the collapse was due to a manufacturing defect in one of the steel eyebars that held the bridge up.

Years of corrosion worsened the defect until it eventually failed, resulting in the deaths of 46 people [source: LeRose]. The collapse of the Seongsu Bridge in Korea was due to poor quality steel in some parts of the bridge and improper welding techniques in the bridge's construction.

The investigation revealed that some aspects of the bridge's construction were done incorrectly and not according to the design, and that inferior quality concrete became too weak to support the structure. There are bridges whose collapse was inevitable before the bridge was ever built. The fault lies not with the construction of the bridge, but the design itself. The bridge is doomed to failure from the moment it was laid out on a blueprint.

One of the worst accidents in U. The walkways connected various parts of the second, third and fourth floors, overlooking the hotel lobby below -- they were essentially pedestrian bridges inside the hotel. On July 17, , the fourth-floor walkway collapsed, crashing onto the second-floor walkway which was directly below it. Both walkways then fell onto the lobby. Both the lobby and walkways were crowded with people watching or participating in an evening dance contest.