IndexIntroductionWest Gate BridgeSeongsu BridgeLessons LearnedIntroductionConstruction failure has been recognized as a major cause of bridge collapse. However, it does not attract public attention because approximately 80% of bridge collapses caused by building failures occurred during construction. It is understandable that this type of collapse would not affect the current traffic situation and would not pose a threat to citizens. Unfortunately, the lives of construction workers will be put in jeopardy and the costs of demolition and reconstruction will be significant. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay Additionally, it should be noted that there is still about a 20% chance of bridges collapsing during their service life. As we all know, most catastrophic consequences are attributed to collapse during the service life. Therefore, deficient construction should not be overlooked, and engineers can learn how to avoid it 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 Bridge Background The West Gate Bridge, located in Melbourne, Victoria, Australia, is a cable-stayed steel box girder bridge, spanning the Yarra River separating the city center and suburbs. Its height above the water is 190 feet. The width is enough for eight lanes and the total length reaches 8473 feet. The span between the pillars consists of 67 meter long concrete slabs and five steel box beams. The daily traffic flow is 160,000 people. Thanks 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-ton span between Piers 11 and 12 buckled and then fell to the ground and into the river. Under the span there were several huts for construction workers. When the collapse occurred, some workers took a lunch break in their huts, while others were still working inside the beams. Ultimately, this failure caused 35 deaths and 18 injuries. The collision between the ground and the span caused the explosion of dust and mud, which spread and shook houses hundreds of meters away. The deafening noise was heard 20 km away. Cause After the collapse, a royal commission was appointed to investigate the disaster and they ultimately blamed the collapse on the construction method. According to Sean Bardy (2016), the construction method adopted was to halve each span along its length, prefabricate these half spans, then raise them to the top of the piers. In this approach, the lifting load was reduced by half, but in the meantime the number of lifts was doubled. However, when this approach was put into practice, things did not go as expected. Between Piers 10 and 11, one of the spans on the east side experienced a problem. As the half-span was placed on the pylon, losing the support of the temporary trusses, the buckle was induced along the upper flange of the span as the centerline of the bridge moved downwards as the two half-spans came together. So, the contractors thought the buckle would be relieved when the span was in the final position, so they continued to lift and slide the span into the final position, instead of lowering the span onto the temporary jack stands to clear the buckle. However, once the span has been brought to its final position,nothing could be done to move it back. Subsequently, the buckle was not significantly reduced once the lifting and sliding work was finished. Therefore, the decision was made to loosen some bolts of the cross joints on the top flange, thus locally alleviating the compressive stress resistance of the top flange. Therefore, the two upper flanges can connect to each other after reducing the compressive strength of the upper flanges to flatten the buckle. To prevent the same buckling from occurring, contractors took steps to stiffen the top flange for the west side span. To achieve this, longitudinal stiffeners were used and diagonal supports connecting the lower and upper wings were also placed. This method has proven to be efficient. However, another problem arose: the vertical gap between the east-side span and the west-side span was so large that they could not fully connect to each other. The next action taken to address this issue was to place high mass concrete blocks on the half span to reduce the void space. Unfortunately, this approach proved to be wrong because it caused the entire top flange of the west side span to buckle. Even though preventive measures were taken, the extremely massive load of the concrete blocks exceeded the permissible limit. A month passed before the contractors made the decision to remediate. They decided to adopt the same method used on the east side span, removing the cross joint bolts on the top flanges, but there was one significant condition they forgot: massive concrete blocks were still standing on the span. The neutral axis and cross-sectional area continued to lower as the bolts were removed. Eventually, the west side span can no longer support the large load on it, so it falls easily. The east side span subsequently collapsed due to the partial connection to the west side span.Seongsu BridgeBackgroundThe Seongsu Bridge, located in Seoul, South Korea, is a cantilever bridge with 4 lanes in width and 1160 meters in length. It is a major transportation hub connecting Seongdong and Gangnam districts and spanning the Han River. Construction was started in April 1977 and finished in October 1979. Collapse At dawn on October 21, 1994, during rush hour, 15 years after commissioning, the Seongsu Bridge collapsed during its service life. One of the slabs in the center of the bridge suddenly fell into the Han River. Unfortunately, some cars and a bus fell along with the slab. The fall height is approximately 20 metres. This collapse caused 32 deaths and 17 injuries. Subsequently, the government decided to reconstruct this bridge as the deficiency of this bridge was too great to be repaired.CauseAfter investigating the failure of this bridge, several factors were responsible for the collapse. First, the main cause is poor welding. Specifically, the structure under the slabs was made up of steel trusses, where welding played a fundamental role. However, the weld was deemed insufficient, stating that the strength of the weld did not meet the standard. Therefore, the fatigue crack initiated at the weld toe and continued to propagate until failure. At first glance, fatigue cracking was attributed to the collapse, but the truth is that the weld was not strong enough to resist crack development. Additionally, contractors should have checked whether the welding was sufficient using X-rays or other techniques. Secondly,.