The main bridge of Jinshajiang River Bridge in Qiaojia County,Zhaotong City is a single-pylon cable-stayed bridge with four spans of 340,72,48 and 32 m.Measured 32.3 m in full width,the superstructure in the 340 m-long span consists of 3.5 m-deep steel box girders of PK cross-section that act compositely with the overlaid precast concrete panels.The bridge crosses a valley in the mountainous area,the steel box girder segments could not be shipped,or transported to the destination via the narrow construction accesses in the valley,and a scheme to prefabricate the plates of the girders and assembly the plates to form steel box girders on the previously installed concrete box girders in the side spans was selected.The prefabricated plates of the steel box girders were assembled at the bridge site,and the geometrical shape of the entire steel box girder segment was brought under control in a"3+1"match-assembly manner.The steel box girders were delivered segment by segment using the specialist 100 t-capacity self-propelled flatbed trucks,to achieve the transportation of steel box girders through the large-gradient and narrow accesses in the mountainous area.The steel box girder segments were assembled on the concrete girders in the side spans and delivered to the locations of the gantry cranes,to improve the assembly and transportation efficiency.The large-tonnage self-launching gantry crane allowing girder feeding from the back of the cable-stayed bridge was developed,and the feeding,rotation,and assembly of the steel box girders were completed with the assistance of the trolley,supporting system,anchor devices and longitudinal moving system.
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