Geometric Nonlinearity And Parameter Sensitivity Analysis Of Single-Pylon Hybrid Girder Cable-Stayed Bridge

The main girder of hybrid girder cable-stayed bridge consists of two different materials.The whole or part of its main span girder is the steel girder.Which has the advantages of smaller self weight and greater spanning capacity.The rest of the girder is concrete girder with a larger weight.Which plays the role of anchorage and it can be used to reduce the deformation and internal force of the main girder.The large span cable-stayed bridge is a high-order hyperstatic structure.The problem of large deformation of the flexible structure and the joint action of bending moment and axial force make its geometrical nonlinearity become more significant.Therefore,it is very important to analyze the geometrical nonlinearity of the construction stage and the completed stage.On the other hand,the construction technology of the hybrid girder cable-stayed bridge is complex,and there are various factors that affect the goal of the bridge.If we can't eliminate all kinds of deviations,it may lead to the bridge status of cable-stayed bridge may not conform to the design requirements.So it is necessary to analyze the parameter sensitivity of cable-stayed bridge.In this paper,the structural characteristics of the cable-stayed bridge are introduced,and the research status of the geometric nonlinearity of the cable-stayed bridge is summarized.Then three factors that affect the geometric nonlinearity of the cable-stayed bridge are described,and three basic numerical solutions of the geometric nonlinear equations are introduced.Finally,this paper takes Yuekou Hanjiang Bridge as the engineering background.The influence of different geometric nonlinear factors on the construction stage and completed stage of the hybrid girder cable-stayed bridge was studied through the Midas civil finite element software.And in the case of considering geometric nonlinearity,the parameter sensitivity analysis of the Yuekou Hanjiang Bridge is designed to provide reference for the construction process.The conclusions are obtained as follows:(1)When considering all geometric nonlinear effects together,the effect on the structure is the greatest.And considering all the geometric nonlinear factors acting together is not equivalent to the simple superposition of several geometric nonlinear effects alone.(2)Compared with the bridge state,the geometric nonlinearity has great influence on the maximum cantilever construction state.The bridge state structure is relatively stable and the stress of the structure is more reasonable.So the impact is relatively small.In addition,geometric nonlinearity has great influence on displacement compared with internal force.Especially for the vertical displacement of the main span steel box girder.(3)Geometrical nonlinearity has different influence on different parts of bridge structure.Its influence on the important parts of the hybrid girder cable-stayed bridge should be paid more attention.For example,the change of internal force of steel mixing section and the deviation of main tower.All geometrical nonlinearities should be considered in actual design and construction.(4)The self-weight of the steel box girder,the construction load,the initial tension force of the cable and the local temperature difference have great influence on the completed stage.They are sensitive parameters.The self-weight of concrete box girder,the stiffness of main girder,the stiffness of the cable and the overall difference in temperature have little effect on the completed stage.They are secondary parameters.(5)The change of different parameters has a great influence on the line shape of the girder,and it has little influence on the cable force.The initial tension force of cable has great influence on the girder linear shape.When the tension is reduced by 5%,the maximum stress increment is 14.59 MPa.And the maximum of the cumulative displacement difference is 266.75 mm.(6)The changes of cross-section stress and geometrical shape of the steel box girder in the intermediate spans are far greater than those of the side span concrete.And the stress in the lower flange of the main girder.is more sensitive to parametric change than that in the upper flange of the main girder.In the process of construction monitoring,the change of the lower flange stress of the section should be paid attention to.