Calculation And Analysis Of Construction Control For Cable-stayed Bridge With Large Span Single Tower Mixed Beam

The main girder of hybrid girder cable-stayed bridge is composed of two different materials of steel and concrete,the main span adopts steel girder with greater spanning capacity,The use of concrete girder at the side span can not only play a very good anchorage effect,also it can reduce the material cost of bridge construction.The singletower hybrid girder cable-stayed bridge is widely used due to its excellent mechanical properties,reasonable cost,and variable shape.In order to ensure that the cable-stayed bridge formed in stages reaches the ideal design state,it is extremely necessary to study the construction control of the cable-stayed bridge.This paper takes a large span single-tower hybrid girder cable-stayed bridge under construction as the engineering background.The main span of the bridge is steel box girder with a variable curvature curve pre-camber,and it is constructed using a step-type multi-point pushing method,The concrete box girder of side span adopts Cast-in-place Construction with the bracket method.The main research conclusions are as follows:First,the whole bridge model was built with the help of Midas/civil,and the initial cable tension was established by the method of load equilibrium about the completed bridge.Then the cable tension were optimized according to the ideal completion state and reasonable completion state,and the cable tension of ideal completion state were determined.Second,the transfer matrix method was used to control the alignment of main span.So we can ensure the splice alignment between beam segments and the stress-free alignment after incremental launching close to the production of camber,and the height of main span over temporary piers and permanent piers reaches stress-free height.We adjusted the height with the help of Midas/civil,analyzed the mechanical behavior of steel box girder and steel launching noses,and ensured the success of incremental launching.Third,we adopted load balancing method and forward iteration method to analyze the construction process with the help of Midas/civil,and determined the initial cable tension and their increment.So the completed state would reach the ideal state.Fourth,we could ensure that the internal force and deformation of the bridge would be reasonable and the construction would be safe after the analysis of construction process.Fifth,According to the parameter sensitivity analysis,we got that the weight of beam segment,the stiffness of structure,cable tension,shrinkage and creep had great influence on completed state,and steel beam was affected more obvious than concrete beam.