Finite Element Analysis Of Seismic Behavior Of Corroded Reinforced Concrete Frame Structures

There are a large number of reinforced concrete frame structures serviced in China.With the increase of service time,the overall seismic performance of the structure will deteriorate due to the deterioration of material performance.There is also the risk of local damage or even collapse when the in-service RC frame structure encounters a fortified earthquake.The existing seismic code has no clear normative guidance for the evaluation of the seismic capacity of corroded structures,this makes the seismic performance evaluation of the in-service RC frame structure lack an effective theoretical basis.China's earthquakes occur frequently,if the seismic capacity assessment of the in-service RC frame structure is neglected,a large number of casualties and economic losses will be caused once the earthquake occurs.In this paper,the seismic performance of RC frame structures under different corrosion conditions is studied by means of finite element analysis with two different model types.ABAQUS was used to establish the fiber model of corroded planar frame structure and conduct the pseudo-static analysis.The seismic performance degradation caused by structural damage in atmospheric environment is simulated,the hysteretic loop curve and skeleton line are observed and the seismic performance indexes(ductility coefficient,energy dissipation coefficient and stiffness degradation coefficient)of damaged structures are calculated,draw a conclusion: with the increase of service time,the lateral bearing capacity,deformation and energy dissipation capacity of the structure become worse,and the stiffness degradation amplitude increases.The effect of single damage factor on the seismic degradation of the whole structure is studied,draw a conclusion: the influence of concrete carbonization damage on the seismic performance of the structure is as follows: the initial stiffness of the structure increases,the brittleness increases,and the energy dissipation capacity decreases;the influence of steel corrosion damage on the seismic performance of the structure is as follows:reducing the lateral bearing capacity,stiffness degradation and energy dissipation capacity of the structure.SAP2000 was used to establish the plastic hinge model of the corroded 3d frame structure and conduct the static nonlinear analysis.The light,medium and high overall corrosion frames were simulated and analyzed,the conclusions are drawn through the analysis of load displacement curve,plastic hinge development and deformation performance of the structure: the maximum base shear degradation rate and the maximum inter-layer displacement angle increase rate are quadratic functions of the corrosion rate,the change rate of them increases monotonically with the increase of corrosion rate;the maximum horizontal displacement increases nonlinearly with the increase of corrosion rate;the development of plastic hinge is mostly beam hinge,and the development degree and speed of beam hinge are larger than column hinge.Considering the actual situation,four local corrosion models(four and below,three and below,two and below,and the bottom)were simulated and analyzed,the conclusions are drawn through the analysis of the structural load displacement curve and the inter-storey displacement angle curve: the maximum base shear degradation rate of each locally corroded structure is a quadratic function of the corrosion rate,the degradation rate increases monotonically with the increase of the corrosion rate,but the increase amplitude of each model is different;the local corrosion of the structure may lead to the change of the weak layer of the structure and increase the uncertainty of the collapse of the structure.The above analysis results are expected to provide some reference for seismic performance evaluation and maintenance and reinforcement of existing frame structures.