Load Test And Ultimate Load Capacity Analysis Of Long Span Concrete Cable-Stayed Bridge

This thesis takes a large-span concrete cable-stayed bridge with the span length of(150+320+150)m as the engineering background.The load test and bearing capacity evaluation of the cable-stayed bridge are carried out,and the bearing capacity evaluation indices are established.The ultimate bearing capacity of the bridge and the parametric studies are analyzed.This thesis aims to grasp the technical status of the cable-stayed bridge through the static and dynamic load test of the bridge,and to grasp the ultimate bearing capacity and actual safety reserve of the bridge through the analysis of the ultimate bearing capacity.The results of the thesis can provide the basis for the design,load test and bearing capacity evaluation of the same type of bridge.The main content of the paper is as follows.1.By using the Midas / Civil software,the finite element model of the cable-stayed bridge is established,and the static analysis,as well as the bridge modal analysis are carried out.Based on the static analysis,the internal force and displacement envelope diagrams of the main girder and the tower,as well as the influence line,which determines the control section and loading condition of the static load test are obtained.In addition,the bridge modal analysis theory are introduced,and the modal analysis results of the bridge and the theoretical impact coefficient according to the specifications are also obtained.2.The static load test program design,field test,and test data analysis of the large span cable-stayed concrete bridge with the main span length of 320 m are studied,and the static test results are obtained.The dynamic test are also conducted.Based on the ambient vibration and forced vibration data,the natural frequencies,damping ratios,mode shapes and impact coefficient of the bridge are identified.3.The bridge bearing capacity evaluation method based on the three evaluation indexes and the field load test is studied.A comparative analysis is carried out.Firstly,the static deflection calibration coefficient is used to evaluate the bearing capacity.Then,the dynamic test frequency calibration coefficient is used to evaluate the bridge.Finally,an evaluation method based on the cross-section bearing capacity surplus coefficient is proposed.The evaluation index based on the cross-section bearing capacity surplus coefficient is established,and the bearing capacity of the bridge is evaluated.4.The spatial finite element model of the bridge is established using ANSYS software.The linear elastic stability analysis and the ultimate load capacity analysis considering dual nonlinearity are studied.The instability modal and failure mechanism are obtained based on the analysis.Finally,a parametric analysis of the influence of the two factors of the bridge form and load distribution on the ultimate bearing capacity of the cable-stayed bridge is studied.