Geometric Nonlinear Analysis Of Long Span Multipylon Cable-Stayed Bridge

Cable-stayed bridge is a cable bearing structure system,consisting of three basic members:the pylon,the cable and the girder,which generally performances for mechanical properties of flexible.Compared with the continuous girder bridge and truss bridge, cable-stayed bridge has more notable geometric nonlinear behavior and more influencing factors, making the geometric nonlinear analysis of long-span cable-stayed bridge more complex.The development situation of the cable-stayed bridge and the research status of geometric nonlinear analysis were firstly introduced in the thesis and the geometric nonlinear analysis theory of cable-stayed bridge and its application in the practical calculation were expounded. The cause of nonlinear factors of cable-stayed bridge and the corresponding analysis methods were discussed.Then,the geometric nonlinear analysis of multipylon cable-stayed bridge under construction stage and finished stage were made on the background of Jiaoshao Bridge, including the influences of geometric nonlinear factors to the deviation and internal force of structure,using Midas/Civil,a large-scale finite element program.According to the comparison between those results,conclusions were obtained as followed:(1)The influences of geometric nonlinear factors to the displacement and internal force of the structure are different. The influence to the displacement is bigger than the bending moment of main girder and the effect on the axial force can be neglected.(2)The geometric nonlinear effect is not obvious when cantilever length is short, when the whole bridge structure stiffness is little and the cable force is at low stress levels and the displacement of main girder is little. While the effect tends to be more obvious along with the rising of the cantilever length.(3)Under secondary dead load the geometric nonlinear effect is obvious,and the cable sag effect and large displacement effect are the main influence factors,while the effect of the combined effect of bending moment is less.(4)Under vehicle load,the effect on the bridge structure of geometric nonlinear factors is very little,and the linear and nonlinear analysis results are very close, so the method of linear analysis can be adopted.(5)The effect on the natural vibration frequency of the cable sag effect and beam-colunm effect and initial geometric stiffness is very little.(6)The effect of the cable sag effect and beam-colunm effect and initial geometric stiffness on the displacement and internal force is very obvious for time-history analysis.