Ultimate Load Carrying.Capacity Analysis Of Long Span Highway Cable.Stayed Bridge

In this paper,the 828 m main span of Chizhou long span highway bridge over Yangtze River as the engineering background,the spatial three dimensional initial finite element model of the bridge is investigated,The initial state deck measurements and field static load tests were carried out before the bridge was opened to traffic.Based on the initial state deck measurement results,the bridge deck line is taken as the main control objective,while the cable force is taken as the secondary control objective.The geometric position of the initial equilibrium state is obtained by adjusting the main parameters in the initial finite element model so that the initial equilibrium configuration of the bridge is achieved accordingly.Such an initial equilibrium configuration of the bridge is further verified by using the measured static load test results before opening to traffic.The established finite element model can truly reflect the initial static and dynamic characteristics of cable.stayed bridge structure,and it can be used as a baseline for health monitoring and condition assessment of the bridge.Based on the limit point instability concept,the ultimate load.carrying capacity of the bridge is investigated starting from the initial equilibrium configuration.The influence of material nonlinearity on ultimate bearing capacity is analyzed and the failure paths of bridge structural under different live loads are discussed in details.The ultimate load.carrying capacity behavior and safety marginal of the bridge under loadings can be obtained.It can not only provide reference for the design of the same type of bridge,at the same time,it can also provide a baseline for the design of health monitoring system of Chizhou long span highway bridge over Yangtze River.It has very important theoretical research and engineering practical value.The main work and conclusions of this thesis are as follows:1.According to the design drawings of Chizhou long span highway cable.stayed bridge over Yangtze River,the three.dimensional initial finite element model is established.The geometric position of the initial equilibrium state of the cable.stayed bridge,which is determined by the design cable force and dead load,is defined as the initial equilibrium configuration of the bridge.According to the initial state measurement of the bridge before opening to traffic,the method of obtaining the initial equilibrium configuration is given.The obtained initial equilibrium configuration is further verified by using the field measured static load test results before opening to traffic.It is demonstrated that the further calculation and analysis should start from the initial equilibrium configuration.2.Starting from the established initial equilibrium configuration of the bridge,the ultimate load.carrying capacity and failure path are investigated under several loading cases.The effects of geometrical nonlinearity,material nonlinearity and different live load distribution on the ultimate load.carrying capacity of the bridges are studied.The failure paths of bridge structures under different live load distributions are obtained.The results show that the geometrical nonlinearity of such a long span cable.stayed bridge is not obvious before reaching the ultimate load.carrying capacity behavior.It is more harmful to the cable.stayed bridge to apply uniform live load to the main span than to apply uniform live load to the whole span.3.The ultimate load.carrying capacity of long.span cable.stayed bridge depends on the material nonlinear behavior of individual structural members.It can be observed that the ultimate load.carrying capacity is controlled by the material nonlinearity of the stay cable.The ultimate load.carrying capacity calculated based on the concept of limit point instability considering both geometric and material nonlinearity is more realistic.Under the action of different live load distribution,the cable.stayed bridges are failed when the cables first reach strength limit where the deflection of the girder greatly increases.The difference is that the live load distribution is different and the location of the first failure is different.