Bridges are one of the most important engineering structures in the world. Why? Because they connect people and societies all around the world! However, like any other structure, safety must be the top priority when building these bridges because people’s lives are at stake if something happens to the bridges. The following content will talk about some of the worst bridge collapses in history and the engineering issues around them.
1. Ponte des Barcas aka “Boats Bridge” in Porto (or Oporto), Portugal
In Porto Portugal, there are 6 bridges that represent one of the most visually appealing structures in the region of Porto. Many tourists who visit the region take the famous 6 bridges tour, which is a tour on a boat that goes through the 6 bridges over the river Douro.
In 1806, the first Porto bridge was inaugurated. However, the design of the bridge was very particular. At the time, the bridge was built by connecting several wooden boats together instead of building it with cables or structural members. At the time, the first Porto bridge was considered to be stable and could be dismounted and reassembled at any given time. However, in 1809, a tragic event happened. The French attacked the city of Portugal and over 4,000 people started to cross the bridge. The bridge at the time was not designed to hold so much weight, so it eventually collapsed, causing a lot of deaths. What’s more tragic was that even after the bridge collapsed, people had no other choice but to jump into the Douro river because the French troops were pushing the people out of the city. This incident is recorded as the worst bridge collapse because it caused the deaths of at least 4,000 people.
2. Eitai-Bashi Bridge in Tokyo, Japan
Constant monitoring and maintenance of a structure are important for its structural health. If a structure is not taken care of, it will eventually be worn and become structurally unstable under different loads. A perfect structure that showed such issues was the Eitai-Bashi Bridge in Tokyo Japan. The wooden bridge was built in 1698, but the people living on either side of the bridge started arguing about who should be paying for the bridge repairs and maintenance. Under such disputes, the Eitai-Bashi Bridge was eventually left without taken care of, and during a big festival, the bridge became overloaded by the people crossing it that it collapsed and killed nearly 1,400 people.
After the event, a second bridge was built using a stronger material (iron). Furthermore, the people living at each side of the bridge decided to keep good maintenance of the bridge and pay for any repairs if there were any structural issues. However, the bridge collapsed again during the Great Kanto Earthquake. In 1926, the bridge was once again rebuilt using a muscular design as well as technologies and materials that could make the structure able to withstand the constant earthquakes happening near Japan. This bridge structure is a great example in which engineers and designers can learn from their mistakes and make improvements accordingly.
3. Angers Bridge in Angers, France
Structures around the world are subject to two main types of loads: Static loads and Dynamic loads. Static loads are those loads that are stationary and do not move but are applied to the structure, like self-weight. Dynamic loads, on the other hand, are live loads that are applied to the structure such as wind loads, earthquake loads, traffic loads, etc. Calculating and designing for dynamic loading requires very intense structural analysis and design, and engineers and designers must be able to understand what kind of loadings will be applied to the structure so that they can design it taking into consideration every single factor.
The collapse of the Angers Bridge is a great example of a structure subjected to different dynamic loads. In 1850, when troops and 4 civilians were trying to cross the bridge, the commander ordered its troop to break step and space themselves around the bridge. Furthermore, a powerful storm was hitting the bridge in all directions. To make things worse, the wires supporting the suspension bridge separated from the cementing material, thus eventually corroding the wires. The combination of the dynamic loads, as well as material failure, eventually caused the bridge to collapse, causing the deaths of at least 226 people.
4.Whangaehu River Rail Bridge in Tangiwai, New Zealand
The Whangaehu Rivel Rail Bridge collapse was one of those disasters that happened unexpectedly. One night before Christmas in 1953, water from the crater of Mt. Ruapehu in New Zealand was suddenly released and was coming at a high speed down the Whangaehu River. What made matter worst, the wave that was coming from Mt. Ruapehu was lahar (mudflow or debris flow composed of water, ice, mud, rocks, etc), so the impact force of the wave had enough strength to destroy one of the concrete pylons of the Whangaehu River Rail bridge. The collapse of the bridge became known as one of the worst bridge collapses in the world because of the disaster that happened at that specific time. A train carrying around 285 people was passing the rail bridge at the time the pylon of the bridge had suffered the damages. The bridge collapsed, and the first 6 carriages of the train were sent straight to the river, instantly killing 151 passengers.
5. Tacoma Narrows Bridge
The last structure that will be seen in this content is a bridge structure collapse that got the interest of many civil engineers: The Tacoma Narrows Bridge.
In 1940, the Tacoma Narrows Bridge was built. This bridge was the very first bridge that incorporated a cable suspension design and was considered the third largest suspension bridge at the time. However, sometime after the completion of the bridge, engineers witnessed that the bridge was undulating even under light winds. Eventually, the bridge suffered a disastrous failure when it was hit with winds of speeds reaching 19 m/s. Many engineers gathered to understand the reason for the failure of the bridge. They designed a 3-D scaled model and applied the same loads that were present at that time. What engineers found out was that the bridge was aerodynamically unstable along the transverse direction. Furthermore, engineers found out that in contrast to ordinary bridge design, where the structure incorporates trusses for the deck, the Tacoma Bridge had a bulk design. Therefore, the wind could not pass through and have to move above and below the structure, creating flow separation. This flow separation leads to the vortex development and ultimately caused the oscillations of the bridge leading to its failure. Thankfully, no deaths occurred during this bridge collapse because engineers took the necessary measures. In 1950, the new Tacoma Narrows bridge was built. However, for this bridge design, engineers strengthen the bridge road deck by adding a truss design in order to decrease wind oscillations. Furthermore, deep dynamic and modal analysis was performed for the design of the Tacoma Narrow Bridge, which led structural engineers to the development of the finite element analysis (FEA) as a tool for designing complex engineering structures. The Tacoma Narrow Bridge collapse was the epitome for civil engineers to develop complex engineering software that could analyze all different kinds of loads ranging from simple static loads to complicated dynamic loads.