Experimental Research On Seismic Performance Of Corroded RC Beam-column Joints In Artificial Climate

Reinforced concrete frame structure is one of the most widely used structure type.With the growth of age, the increased durability damage can make the deterioration ofstructural behavior. Therefore, in order to assess the structural behavior accurately underseismic action, it is necessary to consider the effects of the durability damage, whichcan provide a basis for the vulnerability assessment and the damage cost assessment ofmulti-age urban buildings post-disaster.Under coastal atmosphere, the concentration of chloride ion is very high. The steelhas seriously been eroded, which became the primary destructive factor of the structuredestruction under coastal atmosphere. The accelerated aging structural behavior wasstudied using artificial weathering accelerated aging method in this paper, and theanalysis showed that it is an effective method to simulate the deterioration of structuralin actual coastal environment.Analyzing the RC frame structure, the traditional centerline model is used usuallyfor the new structure, and it is safe to handle in this way. But with age, steel corrosion,especially in beam-column joint region, was more serious relative to beams andcolumns. Error may be produced when analyzing structure without considering jointregional deformation. Therefore, six beam-column joints were designed andexperimentally studied using artificial weathering accelerated aging method, and themechanical behavior were tested on influence of different degree of corrosion and axialcompression ratio. The results showed that the corrosion of hanger bars in the core areais more serious than longitudinal reinforcement of the beam and column. Thespecimen’s ductility and stiffness and the competence of energy dissipation degradedwith corrosion; the influence of axial compression ratio on corrode joint was consistent with non-corrosive joint, namely improving capacity and reducing ductility. Andquantitative analysis of the relationship between the mechanical behavior and thechange factor was made.On the basis of experiments, shear stress and shear deformation in different stateshas been obtained under varying degree of corrosion, the relation curves of shear stressand shear deformation of stirrups corrosion and axial compression ratio were obtainedby fitting the experimental data，a degradation factor based on deformation and energywas introduced to the hysteretic rules，and the restoring force model of corroded jointwas built finally.In summing up the existing macroscopic joint model and based on theexperimental test, a simplified macroscopic joint model was proposed, applying therestoring force model established in this paper to this joint model, Comparing thetraditional centerline model and joint model, the structure’s displacement under rareearthquake was examined in this paper. The results showed that compared with the non-corrosive structure, displacement of the top story of RC frame structures increased withcorrosion rate, the growth pace of the bottom story was larger than the top withincreasing corrosion and the maximum elastic-plastic interlayer displacement can meetthe limit requirements under low corrosion rate. With the increasing of corrosion,corrosion in joint regional is more severe and large deformation is produced at thebottom of structure, making the growth rate of the layer displacement at the bottomsignificantly higher than the top. Overall, the corrosion can make the structural responseincrease. When corrosion is severe, it is necessary to consider the impact of jointregional deformation on the overall seismic performance of RC frame.