Self-centering reinforced concrete frame is a new type of earthquake resilient structure.Comparing to conventional RC structures,self-centering structure is known for its minimal damage under earthquakes and little residual deformation after earthquakes.Considering the fact that there is none or very little repair needed to restore its functionality after rare earthquakes,self-centering RC frame system is a low cost seismic structure that is very suitable for low-rise frame buildings in high seismic zones.In self-centering structure,beams and columns are connected by clamping force provided by unbonded post-tensioning tendon.By this means,when subjected to severe earthquakes,the gaps at self-centering joints are allowed to open and the columns are allowed to uplift at the base.The opening and uplifting behavior significantly mitigates the damage.After unloading all the gaps between components will close under clamping force,and thus the components restore their original position with negligible residual deformation.The existing researches on self-centering joints were summarized,and the key configuration of self-centering joint was illustrated.Based on this research,a tri-axial self-centering RC frame was proposed.In order to investigate the deformation capacity and mechanical characteristics of the tri-axial self-centering RC frame,a 1:2.5 scaled model frame was designed and tested under quasi-static load.The configuration of the test model and main test results,including deformation pattern,hysteretic curve,skeleton curve,stiffness degradation and residual deformation were otained.The experimental results showed that:the test model has excellent deformation capacity,and no damage is observed expect some minor cracks under 1/38 roof drift ratio.The damage gradually develops in beam end joint area when the structural deformation continues to increase.Until 1/19 roof drift ratio,base shear is still increasing which implies that there is still reserved capacity in the structure.The residual deformation of the model is minimal,and the residual interstory drift ratio is still permissible after the final cycle of the loading process.
