【Haichuan Expands Horizons】Five Bridges Spin Together! 21,000-ton bridge rotated 88 degrees, setting a new world record

Why is it necessary to rotate the five bridges simultaneously? To ensure the normal operation of the three railways below

Why is it necessary to rotate the five bridges simultaneously? To ensure the normal operation of the three railways below

At 00:33, upon the project leader’s command to \"start the official rotation,\" the simultaneous rotation of the five bridges began; the five bridges slowly rotated toward their respective docking points. As a key livelihood project in Chongqing, the Second Horizontal Expressway project requires crossing 10 railway lines. The construction area in Wubridge involves crossing three busy railways: the Weijing Upper Line, the Weijing Lower Line, and the Caige Link Line, with an average of one train passing by every 3 minutes during peak hours. During construction, the shortest distance between the rotating bridge and the outside of the railway line was only 2.9 meters, while the distance from the bottom of the beam to the top of the railway catenary was just 0.5 meters. The cast-in-place construction of the rotating bridge structure and its foundations were carried out on the slopes on either side of the railway, where the slope gradient exceeded 60 degrees. Because high-speed train operations require that all construction along the tracks be halted, not even a needle or a napkin is allowed to fall onto the railway tracks. To ensure the normal operation of the railway, the contractor China Construction Tunnel repeatedly discussed various solutions with the design team and the railway authorities. Ultimately, it was decided that for all five bridges, the approach of building them first and then connecting them later would be adopted: the bridges would be constructed along the railway route first, and subsequently connected through rotation mechanisms. This method allows for crossing all three operational railway lines in a single step, within the shortest possible time, while also ensuring the safety of railway operations.

It is understood that, in accordance with the principle of minimizing interference when the five bridges rotate simultaneously but asynchronously, a unique rotation method of \"four counterclockwise and one clockwise\" is adopted, meaning that four bridges rotate counterclockwise while one bridge rotates clockwise. To prevent the two bridges from interfering with each other, a phased rotation is employed: in the first phase, the four bridges that rotate counterclockwise are turned 15 degrees at a rate of 1.15 degrees per minute, taking 13 minutes to complete this process ； In the second phase, the five bridges rotated simultaneously at a speed of 1.72 degrees per minute, with a maximum rotation angle of 83 degrees; this process took 48 minutes.

A rotating bridge is a bridge constructed using the rotation method. Bridge rotation construction refers to a construction method in which the bridge structure is fabricated (cast or assembled) at a position other than its designed axis, and then brought into place through rotation. It can convert operations over obstacles into operations on the shore or near the ground. Based on the rotation direction of the bridge structure, it can be divided into the vertical rotation construction method, the horizontal rotation construction method (referred to as the vertical rotation method and the horizontal rotation method), and a method that combines both horizontal and vertical rotation; among these, the horizontal rotation method is the most commonly used. It is mainly used in situations where it is not possible to use supports, such as crossing canyons, rivers, railways, and highways. The rotation system of a rotating bridge consists of a lower turntable, an upper turntable, spherical joints, slides, and a traction system. The rotation is generally achieved by using jacks to pull the traction cables, thereby creating a rotational couple.

On the afternoon of November 18, 2014, the cantilevered overpass on Yangling Avenue in the Yangling Demonstration Zone, constructed by China Railway First Group, successfully completed a clockwise rotation of 80.1 degrees for both halves of the bridge within just over an hour. This achievement set new records for the maximum weight of a cantilevered bridge, its bridge deck width, and the difficulty level of such a rotation in the Northwest region. The cantilevered overpass on Yangling Avenue thus became the first municipal highway bridge of its kind in the Northwest with variable cross-sections and simultaneous rotation of both halves in the same direction. The bridge was constructed using the self-balancing dual-span synchronous horizontal rotation method; the left and right spans are separate rotation structures. The rotation section consists of 2×44m segments, the bridge width is 30.95m, the rotation angle is approximately 80.1°, and the weight of the rotating structure is about 12,000 tons. According to the night shift supervisor of the engineering team in charge of the project, construction on this bridge takes place across an active railway line, and due to the expiration date of the construction permit issued by the railway authority, the timeline is very tight. Special safety protection measures and high construction technical challenges are involved during the construction process. At the same time, self-balancing horizontal method is adopted for the rotation construction, and strict weighing and weight balancing are required before rotation. When the two cantilever bridges on the left and right were in place, the distance between the edges of their flange plates was only 0.5 m; therefore, it was necessary to strictly control the synchronous rotation of the two bridges during the rotation process to prevent collision between the bridge girders.