Key Techniques for Incremental Launching of Long Span and Long Continuous Unit Steel Truss Girder

The main bridge of Zhengzhou Huanghe River Rail-cum-Road Bridge is arranged in two continuous units,of which the first unit is a six-pylon continuous composite steel truss girder cable-stayed bridge with span arrangement(120+5×168+120) m and the second unit is a continuous composite steel truss girder bridge with span arrangement(5×120) m.The first unit truss girder of the bridge was erected by the construction technique of multi-point,continuous and synchronous incremental launching and the MIDAS Civil software was used to conduct the calculation of the launching construction.In view of the reaction force and frictional force at the tops of the piers,2 sets of 350-t capacity continuous jacks were provided at each pier.The incremental launching distance of the long span and long continuous unit truss girder of the bridge was 1 080 m and the total launching weight was 27 000 t.The side trusses were launched positively while the middle truss was moved passively and the technique of the multi-point,continuous and dynamic control of computer was applied.The launching nose structure and the main steel truss girder were transformed form the inclined trusses into the straight ones via the connection points of the structure and the girder.The slipway was arranged by the side of the piers and the system of the slip blocks was transformed by the jacks installed at the front end of the slipway to finally satisfy the force condition requirements of the truss girder structure.