Experimental Study On Seismic Behavior Of CFRP/Steel Bars Composite Reinforced Concrete Column With Magneto-Rheological Damper

Column is an important vertical load-bearing component in building structure,its performance directly affects the safety and stability of the structure,and is the key to ensure the safety of building structure in earthquake-prone areas.After the earthquake,the ordinary reinforced concrete column is badly damaged.After yielding,it produces large residual deformation,which makes it difficult to repair the post-earthquake structure and seriously affects people's production and life.CFRP bars has high tensile strength and the nature of the linear elastic,Magnetorheological damper has the large output,the characteristics of fast response speed and easy to control.In this paper,CFRP bars and magnetorheological dampers are combined and applied to reinforced concrete columns,and this paper studies the use of MRD way of CFRP tendons/reinforced mixing the influence of the seismic performance of reinforced concrete column,in order to enhance the capacity of recovery performance and energy consumption,reduce the residual deformation,thus improve the seismic performance and reparability of structure.In this paper,three concrete columns with shear span ratio of 4.3 are designed and made,one of which is reinforced concrete column,the other two are concrete column reinforced by hybrid steel and CFRP rebars,and the magnetorheological damper(MRD)is placed on the two columns.The quasi-static test of the three specimens with axial compression ratio of 0.15 were completed.By analyzing the experimental phenomena,failure patterns,hysteretic curve,skeleton curve,residual deformation,energy dissipation capacity and damage index of the three specimens,the influence of MRD and its application mode on the seismic performance and recoverable performance of the column was discussed.The test results show that:(1)All the three specimens finally suffered from bending failure.Compared with reinforced concrete columns,the cracks of concrete column reinforced by hybrid steel and CFRP rebars with MRD are more fully developed,more evenly distributedand more extensive.The average crack spacing of the reinforced concrete column is100 mm,and the highest crack height is 800 mm,accounting for 72.7% of the column height,while the average crack spacing of the CFRP/steel barsreinforced concrete column equipped with MRD is 150 mm.The crack distribution height of one specimen with damper is the highest,and the highest crack height is 960 mm,accounting for 87.3% of the column height.(2)The hysteretic curves of CFRP/steel bars reinforced concrete columns equipped with MRD is fully fusiform.Compared with the reinforced concrete column,the bearing capacity of the concrete column equipped with MRD is higher,and the maximum peak load is 40.8% higher.Meanwhile,the ultimate displacement angle of the specimen also reaches 1/25,which is greater than 1/50 of the limit value of elastic-plastic interlayer displacement angle stipulated intechnical specifications for concrete structure of high-rise buildings.(3)MRD has a great influence on the self-resetting ability of the column.For columns equipped with dampers,when the force is unloaded to zero,the MRD power is turned off.Compared with that when the power is turned on,the residual deformation of the specimens decreases significantly,with a maximum reduction of59.2% and the width of residual cracks decreases by the maximum reduction of63.6%.The residual deformation of the specimens with MRD is more than 40%smaller than that of concrete columns.(4)MRD has a significant effect on the energy dissipation capacity of the column.The single cycle energy consumption of the mixed reinforced column equipped with MRD is at most 140% greater than that of the reinforced concrete column,the cumulative energy consumption is more than twice that of the reinforced concrete column,and the energy dissipation coefficient is 1.5 times that of the reinforced concrete column.The contribution of dampers to energy consumption is more than 50% in the middle and late stage of loading.(5)According to the damage analysis of three specimens,under the same inter-layer displacement,the damage degree of concrete column reinforced by hybrid steel and CFRP rebars with damper is less than that of reinforced concrete,indicating that the damage degree of concrete column can be reduced by using CFRP bar andsteel bar mixed.