Experimental Study On The Seismic Behavior Of Reinforced Concrete Beam-column Joints Strengthened With Prestressed Steel Strips And Bonded Steel Plate

Due to the higher requirement of design level and the change of working condition,the shear capacity of existing reinforced concrete is insufficient to resist earthquake and it need retrofitting for improvement.As a new method of retrofitting the RC beam-tocolumn joints,the strengthening technology with prestressed steel strips and bonded steel plate could strengthen the joints by winding prestressed steel strips around joint core and steel plate at corners.Therefore,the RC joints would be subjected to more lateral restraint and the seismic performance of joints was significantly improved.Moreover,bonded steel plate could also improve the bending capacity at beam end and benefit the shear capacity of joint as well.Retrofit with prestressed steel strips and bonded steel plate could be considered as an innovative and more effective retrofitted method.In this paper,experimental study on 2 specimens without strengthening and 7 specimens with different forms of strengthening methods were performed under cyclic loads.The effect of the axial compression ratio,amount of steel strips and the interaction between bonded steel plate and steel strips on the failure mode,shear capacity and ductility of joints were analyzed.The results showed that prestressed steel strips and bonded steel plate could work together well with the original RC joint.The failure mode all of the specimens were shear failure of joint core and seismic performance of the retrofitted specimens was improved.In detail,the shear capacity,ductility and energydissipation capacity of the joints strengthened by prestressed steel strips were significantly improved.However,the ductility and energy-dissipation capacity of the joints strengthened by bonding steel plate casing in corner did not improve while the shear capacity and initial stiffness was enhanced effectively.In addition,the combination of prestressed steel strips and bonded steel plate could also greatly improve the seismic behavior of joint such as resistance and deformation capacity.On the basis of the experimental study,the stress mechanism of the joints was analyzed and the method of shear capacity calculation for RC joint with prestressed steel strips and bonded steel casing was proposed based on the theoretical analysis of strutand-tie mode.By comparison,it was validated that the calculated results agreed well with experimental result,therefore,the proposed calculation method could well predict the shear capacity of retrofitted joint and provide basis for practical engineering.