Recently, the main line viaduct of the Nanjing 312 National Road Reconstruction and Expansion Project undertaken by China State Construction Engineering, a subsidiary of China State Construction Group, was officially opened to traffic. A prefabricated "air expressway" stands up on the main urban road and drives along the ramp to the viaduct. The 5km elevated is unobstructed and only takes more than 3 minutes, which brings great travel benefits to the surrounding citizens.

As the first prefabricated highway bridge project in Jiangsu Province, a major traffic project in Jiangsu Province, and a key livelihood project in Jiangsu Province, this project has become the "directional sign" for the upgrading of Jiangsu highway traffic. After opening to traffic, the travel time from Nanjing city to Zidong area will be reduced. By shortening it by 20 minutes, the travel time from Nanjing to Zhenjiang will be shortened to one hour. It is a "fast corridor" to improve the urban regional road network and promote the integration of Nanjing, Zhenjiang and Yangzhou.

Green and environmental protection, speed up and refuel

As a prefabricated highway bridge project with the widest bridge width and the heaviest capped beam segment tonnage in China, the project uses the above-ground bridge components to carry out standardized and centralized prefabrication in the prefabricated base, and then transports to the site to assemble into a bridge assembly technology, which guarantees The normal travel of surrounding residents minimized the impact of noise and dust, and completed the construction tasks that originally took 2 years to complete in only 15 months, and the labor input was also reduced by half.

"Assembled bridge construction is generally called the process of'building blocks' and'building blocks', which is not only green and energy-saving, but also safe and efficient." said Xie Qi, chief director of the Nanjing 312 Reconstruction and Expansion Project of China State Construction Engineering Co., Ltd. Walking under the bridge, a large modern bridge component manufacturing base installed and constructed by China State Construction Engineering Co., Ltd. appeared in front of you. The surroundings were clean and tidy. There was no piled earth and no “wet work” for concrete pouring. The factory area covers an area of 150,000 square meters, with one row. The large-scale automated machinery and equipment are distributed in 4 standardized and green prefabricated production lines. The 2,755 bridge components required for the project are all delivered in batches from here.

If the conventional on-site concrete pouring construction method is used in the past, not only the construction period is long, the occupation area is wide, the pollution is high, and the safety control is also very difficult. Only the road guidance and renovation, the surrounding greening restoration, and the removal of construction waste have caused dust around the construction site. Nowadays, the prefabricated construction technology is used to solve the "green" problem.

"From the start to the completion of the project, there is no pollution. The way is refreshing and refreshing. It is not easy!" Mr. Zhou, who lives on the 312 Elevated Xianlin Section, praised it. More space above and below the bridge is released, traffic under the bridge can maintain normal traffic, noise pollution is reduced, and even night construction can meet the noise environmental protection standards. "The project has been awarded a green demonstration site in Jiangsu Province. We hope that this green construction method will help The masses bring more convenience, benefits and sense of gain." Project production manager Yang Yuebiao said.

Smart and safe

Smart mobile factory system, smart construction site system, advanced CNC steel processing equipment, automatic spray system, hydraulic slidable formwork, component identification system, pre-stressed intelligent tension and grouting equipment, full-process BIM technology, binocular Camera technology, sleeve multi-channel synchronous grouting technology, 3D laser scanning technology...went into the prefabricated base of China State Construction Group to install intelligent bridge components, and various large-scale intelligent equipment quickly operated. During the construction of the project, the people's livelihood project, which integrates more than ten smart technologies and applied to it, has been described as the "black science and technology encyclopedia" of prefabricated highway bridges.

Before leaving the factory, every bridge component here has a traceable "identity card" buried. "Using the radio frequency receiving equipment to scan, you can trace all the production cycle and inspection process of the component, which is convenient for the long-term maintenance of the bridge after operation." Project manager Yang Yuji said.

On the box girder prefabrication production line, two steel rails extend from the prefabrication plant to the box girder storage yard. The fully automated hydraulic sliding steel formwork automatically completes the overall demolding through the vertical and horizontal hydraulic systems, and then moves along the rails to the next box girder production The pedestal does not require manual and large-scale gantry cranes to assist in disassembly and assembly. It is easy and quick to operate and has no obvious seams, which greatly reduces labor and equipment investment, improves standardized production efficiency, and promotes safe and quality construction.

If the construction is carried out according to the traditional method, the original viaduct needs to be erected on-site with scaffolding, which increases the safety risk of the construction site. Now all components are manufactured in the prefabricated base, and only assembly operations are retained on site. The amount of labor is reduced, and the safety factor is naturally improved. The project team used BIM technology to combine the construction plan, construction simulation and on-site video monitoring to accurately analyze the tonnage, maximum lifting weight, arm length, and collision coefficient of the spreader, providing a scientific basis for the safety of the assembly plan. In addition, the project team also carried out simulations and three-dimensional dynamic visualization of hazard sources, allowing operators to easily grasp safety precautions, ensure safe construction, and effectively reduce the hidden dangers of safety and quality in the construction of the whole bridge.

The "Behavior Safety Commendation Card" was issued and the "Behavior Safety Star" was selected, and the project department encouraged the operators to change "I want to be safe" to "I want to be safe" to ensure zero accidents in safe production from start of construction to opening to traffic. Since the start of the project, it has been rated as a "safe construction site" for road and water transportation in Jiangsu Province every year, and has undertaken large-scale emergency drills in Nanjing for two consecutive years.

Quality craftsmanship pursue the ultimate

The prefabricated bridge construction technology brings not only the "connotation" of science and technology, but also the "precision" quality. Different from traditional cast-in-place technology, the method of "building blocks" bridges requires millimeter-level requirements for component production and assembly accuracy.

The CSCEC installation project team started from the "source" and established a set of standard and standardized flow production lines in the prefabrication base, providing a complete set of "traveled" production lines for the prefabrication of components such as steel bar blanking processing, mold clamping and pouring, and mold removal. The "model book" of "followable", workers only need to implement one by one through a procedural and modular production process, which provides advanced technical support and quality assurance for component production. Here, every component that is shipped is "Top Students".

During the on-site assembly stage, the project team has almost perfect and strict requirements for the assembly of each component. After the simulation assembly confirms that there is no deviation, the components will be assembled on-site. The assembly accuracy is strictly controlled within 2 mm, and the stitches are tight.

At the same time, the project team has accumulated a lot of technical experience through uniting universities and enterprises, and focused on promoting the subject research, and has successively produced a number of outstanding scientific research results, patents, papers and research reports. The project team also participated in the inspection and acceptance related to the prefabricated bridge construction in the province. Standards are prepared, and the project acceptance standard experience is planned to be replicated throughout the province to form a complete set of "Guidelines for Prefabricated Bridge Construction." Editor/Tian Zengpeng