Analysis Of Ultimate Bearing Capacity And Vulnerability Of Single-Pylon Cable-Stayed Bridge

Cable-stayed bridge is widely used because of its good structural performance and aesthetics.Due to the increasing of tower height,and the using of thin-walled box girder and high-strength materials,the overall and local stiffness of the structure decreases,so the structural stability of cable-stayed bridges becomes especially prominent.At present,with the rapid increase of highway traffic in China,the requirements for highway traffic safety are getting higher and higher.Bridge safety or bearing capacity has become one of the key problems in bridge design and operation.Therefore,how to evaluate the bearing capacity of new bridges or existing bridges has important theoretical significance and practical value.This thesis bases on a(80 + 100)m concrete-filled steel tubular single tower cable-stayed bridge project.ANSYS finite element software is used to analyze its elastic stability、 ultimate bearing capacity and bridge vulnerability.This thesis draws relevant conclusions to provide reference for bridge operation and design units.The main work of this thesis is as follows:(1)ANSYS and Midas / Civil finite element software are used to establish the numerical model of concrete-filled steel tubular cable-stayed bridge,and the key structural simulation process in the ANSYS model is expounded.The calculation and analysis are carried out from two aspects of static performance and dynamic characteristics.The results show that the strength of the cable-stayed bridge have a large safety factor,and deflection is less than specification limit and its dynamic characteristics are close to those of similar cable-stayed bridges,which verifies the rationality of the model.(2)According to the first type of stability theory,the eigenvalue buckling analysis of the whole cable-stayed bridge is carried out.Firstly,the buckling coefficient and buckling mode of the structure under the combined action of dead load and live load are obtained,and the buckling live load coefficient of the structure under four different live load conditions is further analyzed.(3)Considering the geometric nonlinearity and material nonlinearity,the ultimate bearing capacity of cable-stayed bridge is analyzed,and the live load coefficient under different working conditions is calculated.The change process from bridge completion to structural failure and the failure mechanism of the final structure is revealed.(4)From the two different angles of structural section design and cable-stayed bridge operation management,the design parameters such as the height of the main beam section,the thickness of the bottom plate and the boundary conditions are selected.At the same time,the factors such as across-wind load and cable damage are considered.The variation law of ultimate bearing capacity of cable-stayed bridges under different parameters is further analyzed,which can provide reference for the design and operation management of the similar cable-stayed bridges.(5)The vulnerability of main girder and stay cable of cable-stayed bridge is analyzed to find out the vulnerable parts of bridge structure in the operation stage.The harmfulness of cable-stayed bridge after cable fracture is simulated and analyzed the influence of cable fracture on the static performance and ultimate bearing capacity of bridge structure,which provides a theoretical reference for the traffic management and health monitoring of the bridge in the operation stage.