Evaluation On Seismic Performance And Earthquake Resilience Of RC Frame-wall Structures In Acidic Atmosphere

Reinforced concrete(RC)structures located in an acidic atmosphere not only face the threat of earthquake disasters,but also suffer from the corrosive effects of erosion medium,such as hydrogen ions,sulfate ions and nitrate ions in the environment.The continuous erosion will result in corrosion of concrete and its internal steel bars,causing series of problems such as cracking and peeling off of cover concrete,weakening in the effective cross-sectional area of steel bars,and degradation of bond strength between the concrete and steel bar.Deterioration caused by corrosion will eventually degrade the seismic performance and resilience of the RC structures,and aggravate the earthquake disaster risks including potential loss of life and property.At present,this issue has received extensive attention from scholars at home and abroad,and certain research progress has also been made.However,domestic and foreign research on the cross-field of durability and seismic performance of RC structures under acidic environment is relatively lagging,and cannot provide scientific theoretical support for the evaluation of seismic performance and resilience of RC structures in this environment.Therefore,in order to reduce the casualties and property losses caused by the earthquake disaster,it is necessary and urgent to carry out the seismic performance and resilience evaluation of RC structures in acidic environment.This paper takes the seismic performance of corroded RC shear wall members under acidic atmosphere as the starting point,and then extends to the seismic resilience study of RC frame-wall structures in which RC shear walls are the main lateral force-resisting member.The main work and conclusions are as follows:(1)Based on the artificial climate technology,9 RC shear wall specimens with different design parameters were subjected to simulate acidic atmospheric for different accelerated corrosion cycles,and then pseudo-static loading tests were carried out.The test results show that the erosion of the acidic atmospheric will significantly affect the failure process and failure mode of the RC shear wall,and weaken its bearing capacity,deformation,energy consumption,stiffness and other seismic performance.In addition,RC shear wall with different design parameters shown different seismic performance with varies of the corrosion degree.(2)Based on the existing durability research results,the constitutive relationship of concrete and steel bars was modified to consider the effect of corrosion;then,the shearresisting parameters in two-dimensional RC panel constitutive model FSAM were recalibrated based on the experimental data in this paper.Moreover,a bond-slip constitutive model considering the corrosion effect was developed and incorporated into the zero-length fiber section element.Finally,the above models were applied into the SFIMVLEM elements which can capture the interaction between flexural and shear responses under reversed-cyclic loading conditions,thus the numerical modeling method of corroded RC shear wall was proposed and verified based on experimental data.(3)Based on the the random forest algorithm,a large number of existing RC shear wall test data was digged and learned,thus an efficient identification method of RC shear wall failure mode was proposed and validated by the test results of corroded RC shear wall in this paper.Combining the proposed failure mode identification techniques and the numerical simulation method of corroded RC shear walls,numerical seismic tests on2304 corroded RC shear walls under different failure modes were carried out,and then the exsisting formulas of shear resistance were revised based on the simulation results of corroded walls.Finally,formulas suitable for RC shear walls in acidic atmosphere were proposed and verified.(4)Based on the engineering measured data and theoretical analysis,the timedependent model of the corrosion degree of concrete and steel bars in the acidic atmosphere as well as dividing method of the damage state of corroded RC components were established;Considering the variability of material strength and the uncertainty of corrosion degree,900 numerical models of RC shear wall,beam and column components with different service ages and design parameters were built;Combined with the numerical simulation method and maximum likelihood estimation and hypothesis testing methods,probability distribution of the drift ratio of each component with different service ages and damage states were obtained,then the fragility model of the main structural members of RC frame-wall structure in the acidic atmosphere is established based on the Weibull cumulative probability distribution.(5)The typical archetypes of RC frame-wall structure in acidic atmosphere were established through engineering statistics and corresponding simplified methods,then seismic response of typical archetypes under different earthquake intensity was obtained based on the IDA analysis method;The earthquake loss and recovery analysis method in“Standard for seismic resilience assessment of buildings” was revised,then combined with the fragility model of corroded RC members,the distribution of direct economic loss and recovery time under different earthquake intensity were acquired.Furthermore,the functional loss was calibrated by economic loss and the functional recovery model was proposed,then the function-time-intensity resilience surface of different typical archetypes was drawn.Finally,a quantitative evaluation framework that can be used to characterize the comprehensive seismic resilience of corroded RC frame-wall structures was established,and the relations between seismic resilience and service age as well as number of floors for RC frame-wall structures in acidic atmosphere were obtained.