Study On The Seismic Performance And Fragility Of Corroded RC Shear Wall Members Under General Atmospheric Environment

As the main lateral force-resisting members of reinforced concrete(RC)shear wall structures,RC shear walls have been widely used in many buildings because of its good seismic behavior.However,the RC shear wall structure located in China is not only facing threat of earthquake disaster for a long time,but also affected by the general atmospheric environment erosion,which leads to the corrosion of reinforcement in the interior of the structure to varying degrees and material damage such as deterioration of bond performance between reinforcement and concrete,cracking and shedding of concrete cover,which will weaken structural mechanics and seismic behavior.The accurate evaluation of seismic behavior of structures is the basis for reducing earthquake disaster risk,earthquake casualties and property losses.It is necessary to study the seismic behavior of corroded RC shear wall members in general atmospheric environment.Therefore,the main research work and contents are as follows:(1)A series of accelerated corrosion tests were conducted on 9 RC shear wall specimens with shear span ratio of 2.14 in artificial climate chamber.Then,the quasistatic tests were carried out on all the specimens to study the influence of reinforcement corrosion degree、transverse reinforcement distance and axial compression ratio on the specimens’ failure state and seismic behavior.The experimental results showed that,the bearing capacity,stiffness and ductility of corroded RC shear walls degraded with the increase of reinforcement corrosion degree.Subsequently,more significant bending-shear failure characteristics of the specimens were observed and the cumulative energy dissipation and average energy dissipation coefficient decreased accordingly.The decrease of the transverse reinforcement distance had little effect on the bearing capacity of the specimen,but decreased the ductility and energy dissipation capacity.In addition,with the increase of axial compression ratio,the bearing capacity of specimens constantly increased while the ductility and energy dissipation declined.(2)The macroscopic and shear restoring force model of corroded RC shear wall specimens were established respectively.The restoring force model of uncorroded RC shear walls were established by theoretical method.Then,the correction factor calculation of corroded RC shear wall characteristic point of hysteretic bone curve considering the influence of axial compression ratio and steel corrosion rate was developed by regression analysis of test data on 9 corroded RC shear walls,and the restoring force model of corroded RC shear wall was established.Compared with the experimental results,it was found that the skeleton curves,hysteretic curves and energy dissipation of the specimens were in good agreement with the experimental data.Thus the restoring force model for the corroded RC shear walls can accurately reflect the mechanical and seismic behavior of corroded RC shear wall,indicating it adaptiveness for estimating the seismic performance of corroded RC shear wall structure under general atmospheric environment.(3)The appropriate engineering demand parameter was selected as the performance index to measure the failure degree of corroded RC shear wall members,the performance state and the limit values of the performance indexes of the members were defined.Based on the restoring force model of corroded RC shear wall members,a large sample of RC shear wall specimens was designed by using Monte Carlo sampling method and considering the uncertainty of design parameters and material performance.The numerical simulation method was used to carry out the pushover analysis,and the quantitative results of the performance index limits of the components in different performance states were obtained.The limit value of performance index was analyzed and fitted statistically,and then the fragility function and curve were obtained,and the fragility analysis was carried out.This research lays a foundation for seismic hazard risk assessment of corroded RC shear wall structure subjected to general atmospheric erosion.