Vulnerability Analysis Of Single Tower Steel Box Girder Cable-stayed Bridge

Cable-stayed bridges have been widely used in municipal engineering,highway and railway fields in recent years thanks to the advantages of large span,light foundation,reasonable force distribution and beautiful shape.Yet due to the cable structure,cable-stayed bridges are also easy to be damaged by corrosion which will result in accidents.Therefore,real-time monitoring and timely handling of broken cables are in urgent needs.In this paper,the component damage caused by the cable breakage and the safety assessment of the whole bridge structure are analyzed based on the analysis of a certain bridge under construction in Anhui Province by using Midas/civil and ANSYS,two large-scale finite element analysis softwares to simulate the cable breakage.Firstly,this thesis discusses cable breakage analysis from two main points,namely the numbers and different locations of damaged cables.It defines the forms of cable breakage at various typical locations.On this basis,the thesis calculates and analyzes the changes of the parameters resulting from the main beam,the tower and the remaining cables after the cable breakage at different locations to find out the changing trend so as to assess the static characteristics of damaged bridge.Secondly,The dynamic and static parameters of the cable breakage under different working conditions are used to obtain the dynamic amplification factor at different locations of the cable-stayed bridge when the cable is broken,which will lay the foundation for subsequent calculations.Then,the damage forms of each component are defined,and the damage degree of each component and its occurrence probability are analyzed when different numbers of cables are broken.So the vulnerability curve of the whole bridge is obtained by the damage probability.Finally,by introducing the Pareto optimization analysis method of economics,the vulnerability of the bridge is evaluated from three aspects under the condition that maximum stress of the main beam,deflection of the main beam and different parameters of the difficulty degree of cable breaking,and several working conditions with the highest vulnerability of the cable fracture are obtained.The evaluation will help to find out where the vulnerable cable is located whose structure is easily damaged due to former breakages.Based on the above research,it can provide a clear reference for the sensor placement of the safety detection system and provide a basis for the cable maintenance replacement frequency,which can become a reference for the research method of the cable breakage vulnerability of the cable-stayed bridge.