It was determined that the stress reversal was unique to a few eyebars because the vehicle lanes were not centered on the roadway. The stress calculations that had been prepared for the design were verified for assurance that the bridge met the engineering criteria that were used at the time of construction. These factors made the high-strength steel vulnerable to the propagation of cracks and reduced the time for these cracks to occur. When the bridge was designed, the loading was based on the American Association of State Highway and Transportation Officials (AASHTO) H-15 specifications for a 15-ton truck with 106 kN on the rear axle and 27 kN on the front axle. The bridge was constructed as a continuous truss between anchorages. Inspection of the wreckage showed corrosion in many sections of the bridge. The connection at the eyebar was not redundant because it consisted of only two pairs of eyebars. HONG KONG // Hong Kong authorities said they had launched an investigation after an air bridge collapsed at the city's airport, ripping the door off a Cathay Pacific plane and injuring a technician. One opinion cited evidence for fatigue stress, whereas another one explained the cause as a combination of stress corrosion and corrosion fatigue. A higher, not lower, factor of safety should have been used for this bridge. The composition of the atmosphere also played a critical role in the state of the steel. Testing showed that as the environmental temperatures decreased, the material was more susceptible to fracture. Live loads produced by a heavy vehicle would cause the hole in the eyebar to be placed in tension. After the collapse of the Point Pleasant bridge, the President of the United States created a task force on bridge safety. The first factor was the use of higher-strength steel, which is more brittle than the mild steel typically used for structural steel and reinforced concrete construction. The traffic on the bridge was crawling. The tensile stress came from traffic loads and thermal effects. To verify the fact that dynamic effects were not a factor leading to the collapse, vibration response, and dynamic stress amplification tests were performed on the St. Mary’s Bridge. Login to The Constructor to ask questions, answer people’s questions, write articles & connect with other people. All affected passengers had left Hong Kong by Monday morning on alternative flight arrangements, she added. "No passengers or crew members were on the air bridge at the time. This lack of consistency indicated that the eyebar had a more severe susceptibility to stress corrosion and hydrogen embrittlement in the harder section of the material. It's one year since part of a motorway bridge outside Genoa collapsed, as cars and lorries sped across it. Plagued by the collapse of travel amid the coronavirus pandemic, arrivals to Hong Kong plummeted nearly 94 per cent year on year in 2020 to just 3.57 … This change of symmetry caused uneven loads across the suspension spans. The construction of the Point Pleasant Bridge was undertaken with the adoption of the latest technologies and new construction materials of the time. However, different opinions surfaced to justify the cause of this fracture. Some travellers crossing the border had to walk across the construction site to bypass the section affected by the incident. The study of high-strength steel in the environment determined that the combination of stress corrosion (due to tensile stress in a corrosive environment) and fatigue corrosion (induced by the oscillation of loading in the corrosive environment) led to the propagation of the crack in the eyebar and caused the failure of the eyebar and ultimately caused the collapse of the bridge. However, the steel used was of unusually high strength, and its properties were not well known. Further examination of the eyebar showed a crack that had occurred during manufacturing. Country The other factor was the low temperature that on the day of the collapse, was near to freezing temperature. Please enter your email address. When around three big trucks and 72 cars came to a halt, the bridge began to sway wildly and ultimately collapsed. This analysis took into consideration static and dynamic loads. Officials: Multiple Deaths After Bridge Collapse Associated Press. It was first conceived … The coal-burning factories and locomotives, and automotive pollution provided many airborne chemicals that could attack steel. The Hong Kong – Zhuhai – Macao Bridge (HZMB) will be one of the longest cross-boundary sea- crossing road infrastructure in the world providing a direct land transport connection between two shores of the Pearl River Delta, linking Hong Kong in the east to Macao and Zhuhai in the west. The tests sought to establish the natural frequencies of the bridge and to determine the excitation created by heavy vehicle use. Beyond the Headlines: how will the US election play out? A 140-meter (459-foot) bridge has collapsed in northeast Taiwan, sending an oil tanker in the water and killing at least two people in fishing boats below. Become VIP Member, Do you need to remove the ads? © 2009-2020 The Constructor. The experts investigated many possible causes of the collapse. Lost your password? It was wide enough to provide an air space for pollutants to attack the steel. The narrow gap between the eyebar and the connecting pin made the problem worse. Each bridge was to be inspected every two years. The hardness was not uniform throughout the thickness of the material. The cause of the fatigue stress was the cycling loading applied on the bridge over the four decades. It was considered to be the most unique and cost-effective bridge. The suspending eyebar chain acted as the top chord of a variable-depth stiffening truss. One feature considered to be potentially faulty was the substructure of the bridge. Key features of the Point Pleasant Bridge are described below: On a cold winter evening, the bridge suddenly collapsed due to the failure of the connection between the eyebar to the first joint on the north side of the bridge. Vehicle would cause the failure of the divers at the cost of USD 1.2 million to normal 2021! 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