China News Service, Chongqing, August 21 (Mao Yufang, Liu Xianglin) At 2 o'clock in the morning on the 21st, five large-span concrete beam bridges with a total length of 383.5 meters and a total weight of 21,500 tons were included in the second horizontal line project of Chongqing Expressway. Under the premise of ensuring the normal operation of the three busy railways, it takes 82 minutes to complete the rotation, breaking many world records.
The picture shows the five bridges at the same transfer. Photo courtesy of China Construction Tunnel
The second horizontal line project of Chongqing Expressway needs to cross 10 railway lines. The construction area of “Five Bridges at the Same Transition” spans the three busy railway lines of Weijing Upper Line, Lower Line and Caige Link Line. There is a train passing by. The shortest distance between the rotating bridge and the outer side of the railway line is only 2.9 meters, and the bottom of the beam is only 0.5 meters away from the top of the railway catenary. The suspended pouring of the rotating bridge body and the bridge foundation are located on both sides of the railway slope with a slope greater than 60 degrees. When the railway is operating at high speed, all construction along the line must be stopped. In order to ensure the normal operation of the railway, the project contractor, China Construction Tunnel Construction Co., Ltd., finally determined that all five bridges will adopt the “first construction and then transfer” plan, that is, “ex-situ pouring first, and then synchronous rotation” to cross three operating railways at one time Line to ensure the safety of railway operations.
The picture shows the successful closing of the five bridges. Photo courtesy of China Construction Tunnel
According to Zhang Wenxue, a professor at the School of Civil Engineering and Architecture of Beijing University of Technology and an expert on swivel bridges, the five bridges successfully swived in the same area and on the same plane at one time, setting the world record for large-span bridge cluster swivel. Previously, the largest number of cluster swivels was the simultaneous swivel of the four bridges.
According to reports, the left line of the rotating construction is composed of three rotating T structures, which is the first case at home and abroad. This puts forward higher requirements for the alignment control of the bridge construction and the adjustment of the closing error after the rotating body is in place. . To this end, the project research team innovatively proposed the "Linear Joint Control Technology for the Construction of a Multi-T Swivel Bridge" and the "Optimization and Adjustment Technology for the Errors of the Closing Dragon after Swivel".
In this rotating construction, a single bridge weighs 4,500 tons, and the total weight of five bridges is 21,500 tons, which is equivalent to the weight of 15,000 cars. “This is the heaviest tonnage among more than 3 large-span cluster swivels, which exceeds the weight of the third-line and four-bridge cluster swivel of Beijing Daxing International Airport by 11,500 tons.” Vice President of Chongqing Bridge Association and Professor of Chongqing Jiaotong University Xiang Zhongfu accepted reporters Said in the interview.
The total length of the bridge after turning and closing is 383.5 meters, which is equivalent to a 110-story building, which is nearly 60 meters higher than the Eiffel Tower. The five bridges rotate simultaneously, and the maximum turning angle of the bridge is 88 degrees, which takes 90 minutes. The railway "skylight period" is completed, and the construction time must be accurate to the second.
According to the principle of the least interference of the five bridges in synchronous rotation, the construction party adopts the unique method of "four reverses and one forward", that is, four bridges rotate counterclockwise and one bridge rotates clockwise. In order to prevent the two bridges from interfering with each other, a phased rotation is adopted. The transfer method is the most unique in this type of construction project.
The principle of the rotating construction process is like a stone mill for grinding the surface, the lower part is fixed, the middle grinding core plays a positioning role, and the upper part rotates at will. That is, a rotating system is installed on the abutment (single-hole bridge) or pier (multi-hole bridge), and the bridge structure rotates the bridge as a whole according to the set parameters under the action of external force through this rotating system.
"The key to the success of bridge rotation lies in the control of the spherical hinge system, rotating support system, rotating traction system, bridge balance system, etc. during the construction process. The five bridges move the whole body at the same time, even if one parameter is millimeter-level. Errors will lead to an exponential increase in the risk probability." Qian Changhong, the project manager of the Second Branch of the China Construction Tunnel, said that in order to ensure the smooth completion of the five bridges, the project team has cooperated with multiple scientific research and technical teams to carry out a lot of Data calculation, repeated simulation and deduction; through the deployment of electronic level and other high-level measurement control network, the use of precision instruments to control the error within 0.1 mm, real-time monitoring and measurement and other measures to ensure that the installation accuracy of the ball joint is controlled within the range of 0.5 mm, which is equivalent to Ballpoint pen refill steel ball size. While fully meeting the requirements for ultra-high precision of bridge swivel, the installation speed is greatly increased.
In addition, the project has also developed key technologies and monitoring mechanisms for construction monitoring of multi-connected multi-span swivel bridges across railway junction areas, key technologies for the adjustment of the body shape of the multi-T structure swivel bridges and construction error control based on vibration response characteristics. 3 feasibility studies on rotation. The independent innovation technology has overcome the 5T structure synchronous swivel control technology and the key technology of safety organization in the cross-railway hub area, and has made a strong mark in the history of large-span cluster swivel bridge construction.
The "same turn across three lines and five bridges" achieved precise docking, opening up the "main throat" for the construction of the second horizontal line of Chongqing expressway, laying a solid foundation for the smooth opening of the second horizontal line. As an important part of Chongqing’s “six horizontal and seven vertical” express road network, the second horizontal line of the expressway runs through Shapingba District, Beibei District, and Liangjiang New District in Chongqing. It is an important part of Chongqing’s implementation of the city’s infrastructure improvement action plan and the mitigation of congestion. The components will further speed up the improvement of Chongqing's express road network and promote the construction of a dual-city economic circle in the Chengdu-Chongqing area.