Quality Control Of Super-wide Separated Concrete Boxes-girder Construction On High Support With Segmental Prefabrication And Assembly Method

The concrete girder construction technology of the south span of the JingYue YangZe River Highway Bridge is precastingâ†'movingâ†'savingâ†'Assembling, which is rare at home and abroad. The box girder,with high strength concrete, pouring large volume, prestressed system complexity, is facing high altitude moving distance, beam weight, moving beam system complex, sophisticated technology to fight beams and other construction problems.So the control of the box beam in the key step of constructing is very important. The main contents of this paper are as follows:(1) Introduces the process principle and process flow of construction of the south span concrete box girder,construction technology for the main working procedures are described, and put forward measures to ensureconstruction quality.(2) The hydration heat of the concrete boxes girder in the center guide nozzle was tested, based on our experiments the heat of concrete hydration temperature of the studied beam, reached the maximum values70.2℃, and the maximum temperature difference of interal and external was39.3℃.So this paper propose relevant measures to be taken to avoid the early temperature cracks of following beams.(3) During real-time monitoring of key processes in the moving construction,the most significant of the stress changes at0.83MPa,nearby the supports; Strain changes of each beam strain measurement points are within±15με, the stress changes less then0.5MPa; The maximum stress of the altitude bracket is78MPa, is far less than the allowable stress of the material; The beam distributions and rail distributions don’t appear the phenomenon of excessive local stress; The pile and rail settlement and deform are small. So we can see that,the box side-girder sections running smoothly, construction scaffold has sufficient strength and rigidity, and the beam process of moving is reasonable to meet the design requirements.(4) During real-time monitoring of key processes in the assembling construction, the reaction of the concrete side-boxes girder segments in the bearing replacement and leveling are smooth, the normal reaction force to meet the design requirements; Assembling rebar "secondary stretching" effect is obvious, anchoring retraction loss can be reduced by50%, thus recommended the assembly process of the longitudinal sections rebar take the process of "secondary stretching", and also the use of favorable measures which can further reduce the anchor damage.