ATTEN: Manager Liu
ADD: Longhua Development Zone, Jing County, Hengshui City, Hebei Province
2. Analysis of key points and difficulties in manufacturing 21 steel truss 2.11 Because the total length of steel truss box girder is about 215 meters, it needs to be processed in segments. How to ensure the quality of the joints between segments is the technical focus of this project. 2.2 steel truss chord and truss are bolted between segments and between webs and chord rods. Its joints are complex and have a large number of holes. The precision of fabrication is high, and the difficulty of fabrication is 2.1.3. The insertion connection method is adopted between the web and the chord joints of steel truss. As a result, the requirements for the opening size and the section size of Web joints between chord joints are greatly increased. In addition, the requirements for the smoothness of the contact surfaces are also raised correspondingly, which is the process of Engineering processing. The two sides of the lower chord of the Medium-controlled heavy A1.4 steel truss are connected with the steel box girder on the bridge deck and the pedestrian bracket on the bridge deck by bolt-welding connection. Higher requirements are put forward for the opening dimension of the lower chord as the lifting part and the assembly and welding accuracy of the diaphragm. 2.2.1 Steel box girder on the bridge deck is 2.2.1. Because the width of the steel box girder on the bridge deck reaches 30m, it is necessary to divide the top and bottom slabs into allowances in advance. The accuracy of plate elements of different sizes (flatness of plate surface, opening dimension of U-ribs, etc.) directly affects the quality of steel box girders and the accuracy of plate elements is one of the key points in the control of this project.
222 Because 48 U-ribs are distributed along the width direction of the lower opening of the roof, the opening size of the U-rib center varies from 600 to 900, 36 U-ribs are distributed along the width direction of the bottom plate, and the opening size of the U-rib center varies from 640 to 1075. After ensuring the processing accuracy of each plate unit, the overall accuracy of each plate after single splicing (the overall flatness of the plate surface) should also be guaranteed. 2.2.3 single diaphragm with a total width of 30m is divided into five longitudinal webs with a minimum width of 135m and a maximum width of 1225m (20 U-shaped slots are distributed at the top and 15 U-shaped slots at the bottom). Stiffeners in vertical and horizontal directions are also installed on the diaphragm, and the diaphragm is divided into five longitudinal webs with a minimum width of 135m and a maximum width of 1225m (20 U-shaped slots are distributed at the top and 15 U-shaped slots at the bottom). Cutting accuracy and processing accuracy after assembling and welding is another major difficulty in engineering control. 2.4 During the manufacturing process of steel box girder, the welding of the roof unit leads to the deformation of the box body. How to control the deformation is another key point to be controlled in this project.
5. Segmental connection of steel box girders on bridge deck, welding of top and bottom plates, bolting of longitudinal webs are the third most difficult point in the manufacturing process of this project because of the large width and high height of sections and the consistency of weld clearance. In addition, the accuracy of perforation of high strength bolt holes in butt joints between webs is the third most difficult point. The third key point of Engineering control. 2.2.6 Steel box girders on bridge deck are connected with steel truss box girders on both sides. The top and bottom plates are welded, and the diaphragms are bolted, which is the same as above. The cross-section size and weld gap of the interface between bridge deck box girders and steel truss box girders on both sides are the fourth most difficult point in the process of Engineering manufacture. Accuracy is the fourth key point of Engineering control.