A screw of Egongyan Track Bridge in Chongqing is broken. Bridge expert： A comprehensive inspection is needed.
Chongqing Rail Transit (Group) Co., Ltd. (hereinafter referred to as Chongqing Rail Group) announced on the evening of January 19 that at noon on January 18, a sling fork ear screw of Egongyan Rail Bridge on the subway ring line was abnormal, and Chongqing Rail Group immediately launched an emergency plan, and the operation of the Olympic Sports Center on the ring line was suspended from Xiejiawan to Strait Road.
At the same time, Chongqing Rail Group quickly organized relevant experts and technicians to carry out emergency treatment, and technicians will conduct a comprehensive inspection of the bridge sling system.
Zhou Shuixing, director of the Bridge Engineering Department of the School of Civil Engineering, Chongqing Jiaotong University, told The Paper (www.thepaper.cn) after seeing the multi-angle photos on the spot that the screw fracture should be related to the material and stress, and other screws should be inspected comprehensively after this happens. He said that it may only be necessary to replace the screw, which will have little impact on the whole bridge.
Broken sling fork ear screw
Chongqing Railway has repeatedly sent messages saying that it has investigated hidden dangers and apologized.
On the afternoon of January 19th, the news that there was a problem with the sling of Egongyan Track Bridge spread in many WeChat groups in Chongqing. According to the information released by Chongqing Railway Group, the sling failure occurred at noon on January 18th. The Paper checked the official Weibo and found that at 13: 04 on January 18th, Chongqing Rail Group released the news of the first ring road facility failure.
The news said, "Due to the hidden dangers of the subway ring line equipment and facilities, the staff are actively investigating, which has caused the operation of the Olympic Sports Center from Xiejiawan to Haixia Road to be blocked. Please cooperate with the station staff to guide and wait in an orderly manner or transfer to other means of transportation."
At 13: 41 on January 18th, Chongqing Rail Group released the second operation emergency message through Guanwei, saying, "The operation of the Olympic Sports Center from Xiejiawan to Strait Road is blocked due to hidden dangers in the facilities of the subway ring line. In order to maintain the operation to the maximum extent, the Olympic Sports Center is now running through Ranjiaba to Strait Road, and the bus connection between the entrance and exit of the Olympic Sports Center Station 5B and the entrance and exit of Strait Road Station 3A is started."
Since then, Chongqing Rail Group has released information twice at 23: 04 on January 18th and 10: 22 on January 19th, indicating that hidden dangers of equipment and facilities are still under investigation and rectification.
Then, Chongqing Rail Group issued a letter of apology for "the inconvenience of passengers’ travel due to the inability of the loop train to operate normally on time for some reason". In the letter of apology, the group said that it would further improve the maintenance and emergency rescue capabilities of rail transit system equipment, minimize the occurrence of emergencies, and let rail transit give full play to its advantages of "safety, speed, punctuality and comfort".
Upper part of broken sling fork ear screw
Trial operation of the involved track bridge in 2019
The Paper inquired about Chongqing local media reports and found that in 2014, the construction of Egongyan Track Bridge started, which was undertaken by China Railway Construction Bridge Engineering Bureau. In October 2019, the bridge began trial operation of the track loop.
According to chongqing morning post, Egongyan Rail Bridge is located between Haixia Road Station and Xiejiawan Station of rail transit loop, connecting Nan ‘an District and Jiulongpo District of Chongqing, and it is an important node bridge of rail transit loop across the Yangtze River. The total length of the bridge is 1650.5 meters. It is a self-anchored suspension bridge with five-span continuous steel box girder, twin towers and double cable planes, and the main span reaches 600 meters. Its span ranks among the top suspension bridges for rail transit in the world, and it is also the self-anchored suspension bridge with the largest main span in the world.
It is worth mentioning that Egongyan Track Bridge is located about 45 meters upstream of Egongyan Bridge. The height of the two bridges is basically the same, and they are known as twin sister bridges.
Official website, China Railway Construction Bridge Engineering Bureau Group Co., Ltd., said when introducing Egongyan Track Bridge that Egongyan Track Bridge is the key project of Chongqing Rail Transit Loop Phase II. The self-anchored suspension cable of five-span continuous steel box girder with twin towers and double cable planes with a main span of 600 meters is the "most" self-anchored suspension bridge in the world, compared with the self-anchored suspension bridge with the second largest span in the world at that time — — The bridge on Muhu Island in Estonia is 120 meters long. The main tower of the bridge is 153 meters high, which is equivalent to 50 stories high. The main construction difficulties include the excavation of main tower foundation, the construction of main tower, the installation of steel box girder of cable-stayed bridge, the installation of main cable of suspension bridge, system transformation and the construction monitoring of the whole bridge. The construction standard is high, and it is risky and challenging. It is the first case in the world to adopt the method of "cable-stayed first and then suspended cable" in organizational construction.
Broken sling fork ear screw
Bridge expert: Fracture is related to material and stress.
Zhou Shuixing, director of the Department of Bridge Engineering, School of Civil Engineering, Chongqing Jiaotong University, looked at the multi-angle photos at the scene and said that the fracture of the sling fork ear screw was related to its material and stress. It may have little impact on the whole bridge, just change the suspenders.
Regarding "will other screws face the same fracture", Zhou Shuixing said that the bridge should be physically examined every year and inspected daily. Generally, after this problem occurs, other screws should be thoroughly inspected.
However, Zhou Shuixing also said that the vibration caused by the running of the vehicle is somewhat unfavorable to the sling fork ear screw, and vibration reduction measures can be taken. But we can’t find out why until the test results come out.