Table of ContentsIntroductionWest Gate BridgeSeongsu BridgeLessons LearnedIntroductionConstruction failure has been recognized as one of the main causes of bridge collapse. However, this does not attract public attention because approximately 80% of bridge collapses caused by construction failures occurred during construction. It is understandable that this type of collapse does not affect the current traffic situation and does not pose a threat to citizens. Unfortunately, the lives of construction workers will be put at risk and the expense of demolition and reconstruction will be significant. Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the original essay. It's also worth noting that there is still about a 20% chance that bridges will collapse over their lifespan. As we all know, most catastrophic consequences are attributed to collapse during the service life. Therefore, construction defects should not be neglected and engineers can learn how to avoid them from relevant cases. The purpose of this assignment is to highlight the importance of construction, illustrate two cases of construction failure, and present what can be learned from them. The cases discussed below include the West Gate Bridge and the Seongsu Bridge.West Gate BridgeBackgroundThe West Gate Bridge, located in Melbourne, Victoria, Australia, is a steel box girder cable-stayed bridge, which spans the Yarra River separating the city ​​center and suburbs. Its height above water is 190 feet. The width is enough for eight lanes and the total length reaches 8,473 feet. The span between the pillars consists of 67 meter long concrete slabs and five steel box girders. The daily traffic flow is 160,000 people. Due to its unique curved shape, the West Gate Bridge is one of the most notable architectures. Collapse On October 15, 1970, after two years of construction, the 2,000 tons of span between piers 11 and 12 buckled and then fell to the ground and into the river. Below the span were several cabins for construction workers. When the collapse occurred, some workers had taken a lunch break in their cabins and others were still working inside the beams. In the end, this failure left 35 dead and 18 injured. The collision of the ground and the span caused an explosion of dust and mud that spread and shook houses hundreds of meters away. The deafening noise could be heard 20 km away. CauseAfter the collapse, a royal commission was commissioned to investigate this disaster, and ultimately, they attributed the collapse to the method of construction. According to Sean Bardy (2016), the construction method adopted was to halve each span along its length, prefabricate these half-spans, and then raise them to the top of the piers. With this approach, the lifting load was reduced by half, but the number of lifts had since doubled. However, things did not go as well as expected when this approach was put into practice. Between platforms 10 and 11, one of the bays on the east side encountered a problem. When the half-span was located on the pillar, losing the support of the temporary trestles, the buckling occurred along the upper flange of the span since the axis of the bridge was lowered when the two halves were joined. -spans. thought the loop would be eased when the span was in the final position, so they continued to raise and slide the span to the final position, instead of lowering the span to the trestlestemporary to eliminate the loop. However, once the span was placed in its final position, there was nothing that could be done to move back. Subsequently, the loop was not reduced significantly when contractors completed the lifting and sliding work. Therefore, the decision was made to remove some bolts from the transverse splices on the top flange, thereby locally mitigating the compressive stress resistance of the top flange. So the two top flanges can connect to each other after reducing the compressive resistance of the top flanges to flatten the buckling. To prevent the same buckling from occurring, the contractors took measures to stiffen the upper flange of the span on the west side. To achieve this, longitudinal stiffeners were used and diagonal supports connecting the bottom and top flanges were also placed. This method has proven to be effective. However, another problem emerged: the vertical gap between the east side span and the west side span was so large that they could not be completely connected to each other. The next step taken to resolve this problem was to place high mass concrete blocks across the half span to reduce the space. Unfortunately, this approach proved to be erroneous as it caused the entire upper flange of the span on the west side to distort. Although preventive measures were taken, the massive load of the concrete blocks exceeded their limits. A month passed before the contractors made the decision to do something about it. They decided to adopt the same method as that used for the east side span, removing the bolts from the transverse splices on the upper flanges, but they forgot one important condition: massive concrete blocks were still standing on the span . The neutral axis and cross section continued to decrease with bolt removal. Ultimately, the span on the west side could no longer support the heavy load and therefore fell easily. The east side span subsequently collapsed due to its partial connection with the west side span.Seongsu BridgeBackgroundThe Seongsu Bridge, located in Seoul, South Korea, is a cantilever bridge that 4 lanes wide and 1,160 meters long. It is an important transportation hub connecting Seongdong and Gangnam districts and spanning the Han River. Construction began in April 1977 and was completed in October 1979. Collapse Early in the morning during rush hour on October 21, 1994, 15 years after it was commissioned, the Seongsu Bridge collapsed during its duration of life. One of the slabs in the middle of the bridge suddenly fell into the Han River. Unfortunately, cars and a bus fell with the slab. The height of fall is approximately 20 meters. This collapse left 32 dead and 17 injured. Subsequently, the government decided to rebuild this bridge because the deficiency in this bridge was too significant to be repaired. CauseAfter investigation into the failure of this bridge, several factors were responsible for the collapse. Firstly, poor welding is the main cause. Specifically, the structure beneath the slabs consisted of steel trusses, in which welding played an essential role. However, the weld was found to be insufficient, claiming that the weld strength did not meet standards. The fatigue crack therefore initiated at the root of the weld and continued to propagate until failure. At first glance, the fatigue crack was attributed to the collapse, but the truth is that the weld was not strong enough to resist the development of the crack. Additionally, contractors were supposed to check whether.