Key Construction Techniques of Extra Wide Steel Box Girders in Main Bridge of Lingang Changjiang River Rail-cum-Road Bridge in Yibin
The main bridge of Lingang Changjiang River Rail-cum-Road Bridge is a two-pylon cable-stayed bridge with a main span of 522 m.The stay cables are arranged in double cable planes.Carrying the road and rail traffic on the same deck,the superstructure that consists of steel box girders measures 63.9 m wide and 5 m deep,with the maximum girder segment weighing 519.6 t.The individually manufactured constituents of the steel box girders were assembled into integral segments in the factory,which were in turn transported to the bridge site for assembly.On the south bank,the steel box girders in the side and central spans were installed by the incremental launching and one-way cantilever assembly methods,respectively,while on the north bank,the girders in the side spans were kept in storage before the balanced cantilever assembly,and the key segments in the central span were match-cut and pushed into position to complete the closure of the superstructure.To effectively control the large welding deformation and improve the manufacturing accuracy of the extra wide steel box girders,multiple techniques were applied,including double-panel assembly of the top and bottom panels of steel box girders,multi-procedure assembly of anchor wedges in steel box girders,and the long-line match assembly with precambers.On the south bank,the steel box girders in the side spans were incrementally launched from the central span towards the bank,facilitating the delivery and hoisting of side spans and avoiding the occupation of service roads.On the north bank,the steel box girders in the side spans were stored at the bridge site in the dry season,to better address the hydrological conditions in the shoal zones and prepare for the subsequent balanced cantilever assembly.The key segments in the central span were match-cut and pushed into position to achieve the accurate closure of the main span.
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