Recently, at the junction of Fenggang County, Zunyi City, Sinan County and Shiqian County, Tongren City, Guizhou Province, the Wujiang Bridge, a key control project of the Dejiang-Yuqing Expressway, was successfully completed and opened to traffic.
of Deyu Expressway is 1834 meters long, and the red main bridge of steel structure has a span of 504 meters, which is the world's largest span deck concrete-filled steel tube arch bridge. This bridge with "steel backbone" involves 1. The builders of Wujiang Bridge have made a lot of innovations in structural system, construction control and high-tech materials, and have explored and formed a complete set of technologies of "new structural design, calculation principle research, manufacturing linear control, intelligent control and installation", which has effectively promoted the development of arch bridge design theory. Bridge construction in mountainous areas is developing to a higher level.
Let's get close to this bridge, which represents the world's top level of bridge construction of the same type, and explore its innovative code.
The world's first "full bolting", 220000 high-strength bolts connecting tens of thousands of tons of steel structure
in Wujiang Bridge of Deyu Expressway 1. How to ensure precise splicing and installation at high altitude is a huge problem.
The project department has carried out key technological innovations, pioneered the use of arch, column and beam full-consolidation bearing-free integral stress system in China, and implemented "full bolting", that is, the main arch, column and deck beam of the whole bridge are all connected by high-strength bolts. As a result, Wujiang Bridge
on Deyu Expressway has become the only bridge in the world constructed with full bolting technology, with new structure, high precision and construction difficulty ranking in the forefront of the same type of bridges in the world.
Under the fully bolted assembly system, the steel structure used in the bridge needs to be processed in Chongqing, transported to the construction site by water, and then adjusted repeatedly in the assembly plant along the river before it can be spliced at high altitude. The construction methods of
centralized factory production, efficient water transportation of large component materials and on-site installation have effectively improved the processing quality of arch bridges and the construction quality and efficiency.
"The steel structure of the whole bridge is connected by high-strength bolts, which puts forward extremely high requirements for accuracy, the maximum allowable error is only 3 mm, and the technical difficulty is very great." Wang Zhijin, the project manager of Wujiang Bridge of Deyu Expressway, introduced that all the arch ribs and wind braces of the bridge are connected by high-strength bolts, which means that the position of 220000 bolt holes in the whole bridge can not be misplaced at all.
In the stage of arch rib erection and assembly, facing the difficult conditions of no reference for similar projects and no guidance for specific norms and standards, the project team integrates the control standards and requirements of all participants, solidifies 36 standard construction procedures, 22 process inspections and 17 key control indicators, and realizes the millimeter-level precision manufacturing of stress-free linear arch ribs. According to the introduction, after the precise adjustment of the double assembly process, the relative height difference and axis deviation of the bridge are controlled within 5 mm, and the transverse direction of the bridge is controlled within 3 mm.
Arch rib wind support connection assembly, arch column connection assembly, bridge deck beam connection assembly, UHPC (ultra-high performance concrete) bridge deck assembly.. Under the fully bolted assembly system, the installation and connection of wind braces can be completed in only one day, which doubles the efficiency compared with the traditional welding system. At the same time, the synchronous installation of arch ribs and wind braces can be realized, the stability of cantilever assembly of arch ribs can be increased, and the safety risk can be reduced.
"The efficiency of arch rib hoisting has also been greatly improved, from the original plan of two days to one day." Zhou Chao, general manager of Guizhou Zhongjiao Deyu Company, said that before the arch rib hoisting, the smooth development of various auxiliary work, such as solidified arch rib loading, ship positioning, cable crane inspection, buckle back cable traction and so on, accelerated the site hoisting progress and laid a solid foundation for the smooth closure of the main arch.
All-round precise control, with millimeter-level precision splicing "steel backbone"
Deyu Expressway Wujiang Bridge is located in a mountainous canyon, surrounded by mountains, high altitude gusts raging on the river surface, and changeable wind direction and speed. Before the closure of the arch rib of the
bridge, the maximum cantilever length is 237 meters. Under the complex wind field and other external conditions, its alignment control and stability control are very difficult, and the precise closure of the bridge is facing enormous challenges and pressures. During the construction of Wujiang Bridge
on Deyu Expressway, there is always a "golden eye", which is the use of high-precision measuring equipment.
The project team innovatively applied the Leica TS60 fully automatic measuring robot, developed the first segment multi-point constraint fine adjustment bracket and the three-dimensional attitude fine adjustment technology for arch rib installation, and arranged a three-dimensional attitude monitoring prism on the arch rib string tube to automatically monitor the three-dimensional attitude, arch rib alignment and lateral deviation of the arch rib in all weather. At the same time, the digital pre-assembly technology is used to automatically analyze the three-dimensional attitude, and the target coordinates of the control points are precisely adjusted, and the automatic single-point scanning robot is used to monitor and dynamically adjust the three-dimensional attitude in real time. This provides valuable data support for the high-precision installation and positioning of arch ribs.
The project team used a three-dimensional laser scanner to conduct a deep "physical examination" of the arch rib, covering 500000 scanning points, and established a high-precision model component to intuitively and quickly check the errors in the manufacture and installation of steel structures.
In view of the problems that may be encountered in the hoisting of arch ribs, the construction team put forward the optimal control theory of the whole construction process, developed and applied the all-weather intelligent cloud monitoring technology to monitor the stress state and deformation law of the cable system, the fastening system, the anchoring system, the tower structure and the main structure, and carried out the risk warning at different levels. The development and application of rapid automatic continuous early warning and intelligent tensioning equipment improves the accuracy of cable force, strengthens the synchronization control, realizes the automatic coincidence of arch rib closure alignment and target alignment, and ensures the smooth closure of the bridge.
In addition, the project team also proposed a complete set of technologies for precise control and adjustment of column and deck beam installation at high altitude, established an error divergence model for bolted structure, and proposed a manufacturing alignment calculation method for adaptive installation of main beam, which solved the problem of precise installation and control of arch structure of large-span bolted arch bridge.
Technological innovations and breakthroughs have ensured the perfect combination of each steel structure in the air, and cast the strong "backbone" of the bridge with high precision and efficiency at the millimeter level. The construction site of Wujiang Bridge
of Deyu Expressway is a typical karst landform in Guizhou, with narrow site and difficult construction planning and implementation. How to ensure the safety of 150 meters of high-altitude construction on the
surging Wujiang River? The
person in charge of the project introduced that they had launched the application of BIM (Building Information Model) + informatization technology in the early stage of entering the site. Through UAV tilt photography, three-dimensional site planning, three-dimensional simulation of the main bridge scheme, and spatial simulation and optimization of the scheme, a digital model of the initial environment of the project is built to achieve a reasonable temporary construction scheme and a controllable temporary construction cost. In the construction process, the project department uses the BIM application management system of CCCC First Highway Engineering Co., Ltd. for management. The application module covers process inspection, quality management, safety management, BIM visual application disclosure, etc. The space problems that can not be found on the plane drawings are exposed on the electronic screen. Through process simulation, the project department successfully avoided safety risks in the construction.
In the specific construction process, through AR technology, they use BIM + AR construction assistant mobile APP to locate the BIM model in the real environment at the centimeter level, and superimpose it on the construction site and the project site 1:1. Through this operation, we can check whether the embedded parts and other concealed works are accurately constructed, so as to solve the problem of later rework caused by the omission of embedded parts in the traditional construction process, and provide visual reference and guidance for the construction and acceptance links, effectively reduce construction errors, reduce rework costs and improve construction efficiency.
In the construction of the main bridge of Wujiang River Bridge on Deyu Expressway, the construction technology of cable crane + cable-stayed buckle is adopted, which involves many temporary structures and has high safety risk. In view of this situation, the construction unit jointly with the monitoring unit, combined with the later operation needs, developed a cable-stayed buckle monitoring system to monitor the cable force of the buckle back cable, the deviation of the buckle tower, the stress of the buckle tower, the slippage of the rear anchor and the stress of the arch rib, so as to realize the digitalization of the structural safety monitoring. Establish a hierarchical early warning mechanism accordingly, set different thresholds of early warning levels, grasp the status of equipment in real time, issue early warning pertinently, and reduce safety risks. This has played an extremely important role in dealing with extreme weather in mountain canyons and ensuring the safe and efficient construction of the main bridge.
"Digital intelligent construction, build the world's top bridge." In this way, the Wujiang Bridge of Deyu Expressway adheres to the construction of high precision and strict requirements, which provides technical experience for the construction of similar bridges. Its successful completion and opening to traffic will further improve the regional traffic capacity and service level, and is of great significance to promote the upgrading of industrial structure, resource development and utilization, and the development of tourism industry along the line.
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