Superstructure Construction Control Techniques for a Multi-Pylon,Cable-Stayed Bridge Accommodating Road and Rail Traffic on Same Deck in Complex Marine Environments
The Xijiang Rail-cum-Road Bridge in Zhuhai is a cable-stayed bridge accommodating road and rail traffic on the same deck.The bridge features its four pylons that create three main spans of 340 m,flanged on each side by two spans of 116 m and 58.5 m.The two intermediate pylons are fixed with the superstructure and the piers,while the two side pylons are fixed with the superstructure,but connected with the piers via bearings.Measured 49.6 m in full width,the superstructure consists of three-cell steel box girders that are 4.676 m in depth.To facilitate erection,the superstructure was divided into 47 segments,with typical segment length of 24 m.During assembly,the top plates of the two adjacent segments were welded together,and the bottom plates and webs were connected via high-strength bolts.Considering the equipment available and the environments at the bridge site,the steel box girder segments were relatively larger in dimension,weight and depth.The maximum steel box girder segments in the side and end spans,which were 80.25 m long and 2 600 t in weight,were erected by floating cranes.The superstructure was jacked up and lowered in segments,and closed end by end,and the three larger final segments were assembled without bending angles.During the erection of the paired two steel box girder segments on the two sides of each intermediate pylon,the segment on one side was hoisted and installed,and its counterpart on the other side was counterweighted with water bags,creating an asymmetric cantilever assembly of"proceeding in small steps and adjusting balance in multiple cycles",to control the anti-overturning stability coefficient of the structure above 1.5.Active pushing forces were applied at the midspan closure gap of central main span and the structural details at the closure gap were modified to ensure the high-precision closure of the bridge at high temperatures.The internal forces and alignment of the completed bridge reach the design levels.
cable-stayed bridgemulti-pylon rigid-frame systemsteel girderjack-up in segmentswater bag counterweightasymmetric cantilever assemblyactive pushingconstruction control
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