Experimental Study On Seismic Performance Of RC Frame Columns Corroded By Acid Rain

China lies in between circum-Pacific seismic belt and Eurasia seismic belt with frequent earthquakes.The damage caused by earthquake is excessively destructive.In the meantime,many of existing buildings are facing durability problems resulted from acid rain attack.Therefore,it is imperative to combine the durability and seismic performance evaluation of structure and carry out the seismic performance study of reinforced concrete structure corroded by acid rain,which provides the base and support of elaborate modeling of damage and risk assessment of structures in service under earthquakes.In view of this,from the perspective of members,the experiment was properly designed to study the quasi-do response of columns attacked by acid rain and the degraded hysteretic models of RC frame columns were then established.(1)In order to study the seismic performance of RC frame columns corroded by acid rain,12 RC frame columns were designed with shear span ratio,stirrup reinforcement ratio,axial compression ratio and the depth of acidification as variable parameters.Accelerated corrosion under artificial climate was applied to simulate acid rain environment.Finally,the hysteretic curves,skeleton curves,and degradation curves of stiffness,strength,and energy dissipation capacity were obtained by quasi-do tests.(2)The influence of acid rain attack degree on the degradation rule of seismic performance of RC frame columns was analyzed.Failure mode: with the increasing of acidification depth,the failure of RC frame column changed from ductile failure to brittle failure.Mechanical property: with the increasing of acidification depth,the strength,stiffness,ductility,and hysteretic capacity were declined gradually.(3)The hysteretic models of RC frame columns under acid rain environment were established.In the paper,the three-broken line model with negative stiffness was applied and the slope of negative stiffness segment was determined by post-peak rotation and failure load.According to the regression analysis of experimental data,the computational formulas of characteristic points of RC frame columns’ skeleton curves were obtained.Base on the degradation index of hysteretic dissipative energy,the overall consideration have been put on the pinch effect,strength degradation,unloading stiffness and reloading stiffness through the proposed hysteretic models.(4)The hysteretic models of RC frame columns corroded by acid rain were established based on OpenSEES.For the specimens with shear span ratio of 5,the dipBeamColumn in the element of distributive plasticity was applied and the modification of reinforcing bars degradation to Steel02 material was considered.For the specimens with shear span ratio of 2.5,the concentrated plastic model was defined by ZeroLength spring element in OpenSEES.In the meantime,the characteristic points of corrected Ibarra-Medina-Krawinkler degradation model(ModIMKPinching Material)were calculated by the proposed degradation rule.