Experimental Study On Seismic Performance Of Local Weak Bonded CFRP Reinforced Concrete Columns

As one of the main vertical load-bearing components,columns are widely used in high-rise buildings.Based on the current concept of seismic design requirements,although the traditional reinforced concrete columns meeting the seismic fortification target which will produce large residual deformation,which is not conducive to the maintenance and reconstruction work after the earthquake.With the development of seismic design concept,Self-centering structures have gradually become a research hotspot in the field of seismic design.Self-centering structuresare structures with little residual deformation after an earthquake,Which can keep normal function with simple repair.In this paper,a new kind of concrete column with local weak bond Carbon fiber-reinforced composite(CFRP)reinforcement is proposed.By using the characteristics of high strength and linear elasticity of CFRP reinforcement,and reducing the bond force between CFRP reinforcement and concrete within a certain range from the foundation beam,the characteristics of CFRP reinforcement can be better exerted in the stage of large deformation,so as to reduce the residual deformation of the structure and enhance the self-centering ability of the structure.One steel reinforced concrete column and two CFRP reinforced concrete columns with weak bond lengths of 150 mm and 300 mm were designed and manufactured.The specimens were tested under combined lateral low cyclic reversed load and 0.15 axial compression ratio.The seismic performance such as hysteretic curve,skeleton curve,residual deformation,ductility,rigidity,energy dissipation capacity and strain distribution of CFRP reinforcement were researched based on the test result.The influence of longitudinal bar type and weak bond length on the reinforced concrete was studied.The results show that:(1)Compared with steel reinforced concrete columns,the peak bearing capacity of two partially weak bonded CFRP reinforced concrete columns increase by 19.2% and 22% respectively,reflecting the characteristics of high tensile strength of CFRP bars.After reaching 3% drift ratio,the horizontal load can still keep rising,and the maximum interlayer displacement angle can reach 6%.(2)Using local weak bond CFRP bars as longitudinal bars can reduce the residual deformation of concrete columns by more than 79%,which has a good self-centering ability.With the increase of weak bond length,the residual deformation decreases correspondingly,and self-centering ability also increases.(3)The local weak bond CFRP reinforced concrete column have a large deformation capacity,and ultimate displacement angle of specimens LCC150 and LCC300 are 1/21 and 1/16 respectively,which are2.27 and 3.13 times of the limit value of interlayer displacement angle stipulated in the code,and the bearing capacity can continue to increase under large deformation.(4)The weak bond length of CFRP reinforcement has a great influence on the crack distribution of specimens.crack numbers of specimen with 300 mm weak bond length is significantly smaller than that specimn with 150 mm weak bond length,but the crack width is larger,reaching the interlayer displacement angle of 3%,and the residual crack width of LCC300 is about 2.6 times of LCC150.(5)Ordinary steel reinforced concrete columns absorb a lot of energy by plastic deformation of steel bars,and the energy consumption capacity is higher than that of local weak bond CFRP reinforced concrete columns;the weak bond length has a certain influence on the energy consumption capacity of columns,and the energy consumption capacity decreases with the increase of weak bond length.