Study On Ultimate Bearing Capacity And Seismic Response Of Cfst Arch Bridge By Uniform Corrosion

With the development of transportation in China,concrete-filled steel tube arch bridge has been widely used.However,under the influence of the environment,uniform corrosion or local corrosion will occur to the steel pipe.The corrosion of steel pipe leads to the reduction of effective bearing area,mechanical property degradation,and even structural damage,which ultimately affects the bearing capacity and seismic performance of the structure.At present,there are few researches on the bearing capacity and seismic capacity of concrete-filled steel tubular arch Bridges after uniform corrosion.In this paper,the influence of uniform corrosion on ultimate bearing capacity and seismic response of concrete-filled steel tubular arch bridges is studied by numerical simulation.The main research contents are as follows:(1)For traditional corrosion simulation method(stiffness discount subtraction and wall thickness to fold subtraction)cannot consider steel tube "stress" corrosion problem,a new modeling method will be put forward.This method divides the steel pipe section into sections composed of several thicknesses,and time step and death unit technology to simulation steel pipe corrosion time-varying process in ANSYS.The "stress" corrosion process of steel tube can be realized by this method.An example is given to verify the correctness of the proposed method.(2)Using APDL language of ANSYS,the program for calculating uniform corrosion of concrete filled steel tube arch bridge is compiled.The influence of uniform corrosion with stress on ultimate bearing capacity of concrete-filled steel tube arch bridge under different load conditions is studied through the program.And the program can analysis of uniform corrosion on different steel ratio,steel strength,concrete strength of concrete filled steel tube arch bridge bearing capacity change rule.(3)Based on the theory of metal corrosion,and considering the effect between the environment of concrete filled steel tube and the structure of rust layer,the relationship between corrosion depth and time of steel tube was established.Finally,a prediction formula for uniform corrosion of steel pipe is established.And the correctness of the formula was verified by an example.Using the method of regression,the time-varying formula of bearing capacity of concrete-filled steel tube arch bridge considering uniform corrosion is fitted.(4)The influence of uniform corrosion on the natural vibration frequency of concrete-filled steel tube arch bridge is studied by estimating the natural vibration frequency of arch bridge.And the accuracy of the results was verified by finite element software.Based on the design response spectrum,the seismic wave was input into the finite element model.The variation of internal force and displacement of corroded concrete-filled steel tube arch bridge under earthquake is studied.And the seismic performance of the concrete-filled steel tube arch bridge after uniform corrosion was evaluated by the capacity demand ratio method.