On-site construction and installation method of steel box girder

The invention relates to a site construction installation method of a steel box girder, which belongs to the technical field of building construction and comprises the following steps: S1, blanking in a steel box girder factory, manufacturing plate unit pieces, transporting to a construction site assembly site for matching assembly, and adopting a 3 + 1 matching assembly mode; s2, after the beam blocks are assembled in the assembly area, the beam blocks are hoisted from the shortcut in the assembly yard, the beam blocks are conveyed to the pier hoisting area along the beam conveying shortcut by adopting a 110t self-walking type flat car, and after the beam blocks are hoisted by a 120-ton gantry crane on the bridge floor, the flat car continues to go straight forwards, penetrates through the beam conveying shortcut between the adjacent piers and returns to the shortcut in the assembly yard along the beam conveying shortcut; all the beam blocks are transferred in the manner; s3, splicing the concrete bridge flo