Research on Manufacturing Process of Space Twisting Structural Steel Bridge

With the improvement of people's living standards, and the concept of park city, the demand for architectural landscape is increasing, more and more urban landscape bridges are also appearing, the spatial shape of steel bridges presents a trend of complexity, affected by its complex force situation, often accompanied by manufacturing problems such as ultra-thick plate （more than 60 mm thickness） pressing, and the production process of steel bridges with solid space distortion structure is worth exploring in depth.
The west line span Jiangxi River Bridge is located on the Jiangxi River in Chengdu, the bridge adopts a three-span continuous downward bearing beam and arch combination system steel bridge, the span diameter is (55+175+55)m, the width is 51 m, the plane is located in the radius R=400 m circular curve, the side longitudinal beam and arch rib are in a spatial distortion form, extremely irregular, the spatial configuration is completely determined by the architectural landscape, and there is no arch axis in the conventional sense, the arch rib and the side longitudinal beam are seamlessly integrated. The vault at the center pile is 30 m from the bridge deck, and the inverted angle of the north side arch rib is about 47.69°. The angle of inversion of the rib on the south side is about 24.85°, and the two arches meet in the middle of the span, the length of the joint section is 14 m, and there is no other transverse connection between the arches. The south and north arch ribs adopt a single-box single-chamber steel box structure, bounded by the vault joint section, the two arches are quadrangular sections on the small mileage side, and the large mileage side is a pentagonal section, and the space shape of the arch ribs is very complex. Except for the wall plate of the vault joint section, the rest are twisted hyperboloid versions. In the most complex area of the arch beam joint section, the thickest part of the steel plate is 80 mm, and the angle between the two steel plates is 22°, as a steel structure landscape bridge, the spatial distortion structure of this project has obvious characteristics, the thickness of the steel plate is large, and it is of reference significance to study based on this project.
At the beginning of the project, the main pressing methods of thick steel plate are hot pressing and cold pressing. Because the cost of making molds is too high and the impact of heating on the performance of steel plates, finally the project adopts the trend analysis method+fire correction molding process to achieve the design modeling. The specific process is as follows: firstly, the three-dimensional software is used to analyze the curvature trend of the profiled steel plate and divide the profiled segmentation area, and then the profiled segmentation area is divided into equal parts according to the 50~100 mm spacing to draw the profiled control line, and mark the profiled direction, press the profiled line with a large-tonnage press, and check whether the curvature of the steel plate is satisfied with the inspection sample. After qualifying, the steel plate will be transferred to the vertical tire frame, and after the fire adjustment is fine-tuned, it will be transferred to the assembly area. Before assembly, the tire frame should be made according to the linear shape of the steel bridge, and the tire frame foundation should have enough bearing capacity to prevent the tire frame from settling in the process of assembly, and the tire frame should have enough rigidity to support the steel bridge. The support density of the tire frame is the same as the spacing of the partition, and the tire frame needs to be made continuously. Because it is an irregular shape, the wall plate rib should be assembled after the wall plate and the partition plate are assembled. At the same time, steel beam needs to be welded on the tire frame after the completion of the appropriate trimming according to its ring mouth matching situation to ensure the continuity of its modeling.
According to this process, the west line across the Jiangxi River bridge manufactured avoids the mold making, and the pressing process can form a systematic flow construction, which greatly saves the mold production cost and construction period. The linear shape is beautiful after the bridge is completed, and can be used as a certain reference for the construction of similar steel structure engineering.