Study On Reasonable State And Performance Of Hybrid Girder Cable-stayed Bridge

Hybrid girder cable-stayed bridge generally means the edge span and main span across different materials were used, linking sites located in the vicinity of a bridge tower. Girder combination of the use of different materials main purpose is to be a single material does not have the mechanical properties through a combination of steel and concrete to create not only compensate for weaknesses of the two components but also economic. Hybrid girder cable-stayed bridge is a new direction in modern large span bridges. In this paper, the Dongsha Bridge in Guangzhou as the background, many studies of the impact have been carried out in the aspect of reasonable finished dead state, reasonable construction state, geometric non-linearity and structural parameters of hybrid girder cable-stayed bridge.At first, this paper adopt constant-load balance method combined with the stress balance method to determine the initial finished dead state, asking for the maximal deformation of tower and girder to be minimized as control objective to optimize cable tension, the paper solved reasonable finished dead state. A forward-iteration with the constant optimization of the cable tension method for determining the reasonable construction state ,and in accordance with this method of determining a claim of the Dongsha Bridge reasonable construction state. Through theoretical analysis and calculation examples to prove that this method is simple and effective.This thesis introduces the basic theory of geometric nonlinear analysis for cable-stayed bridge . then three principle factors that affect geometric nonlinearity of cable-stayed bridges are described, which are cable sag effects, large displacement and combined effects of bending moment and axial force; then the finite element analysis methods of these three factors affecting the nonlinear are introduced separately. And then, using large-scale finite element program ANSYS to establish finite element model of the bridge and analysis of the geometric nonlinear, author draws the quantitative influence of every nonlinear factor on whole bridge under dead load and live load. According to the comparison between those results with the linear and nonlinear analysis of all load stages under finished stage, conclusions are obtained as followed: the cable sag effects is the main point of nonlinear behaviors of cable-stayed bridges, and the combined effects of bending moment and axial force and the large displacement are relatively small; for hybrid girder cable-stayed bridge, whether living or dead load, the geometry of the main beam of nonlinear effects can not be ignored, so it is nor enough if we only execute linear analysis to cable-stayed bridge, the results of the calculation error will be great.Because the research of hybrid girder cable-stayed bridge's parameters on the entire bridge construction process and the finished dead state is less, based on the parameters of the Guangzhou Bridge deviation sensitivity analysis, we know that the dead-weight of structure, temporary load, structural stiffness, initial cable tension and concrete creep and shrinkage have a greater impact on the cable tension, main beam deflection and stress and structural stiffness of smaller deviation. As hybrid girder cable-stayed bridge, stiffness and initial cable tension deviation of the deflection of steel girder and internal forces cause more significant impact, so these parameters should be manage and control strictly in the construction process and simulate accurately.