Research On Seismic Performance Of Prefabricated Recycled Concrete Column With Rebars Spliced By Pressed Sleeves

Prefabricated structure and recycled concrete technology meet the requirements of high efficiency,energy saving,and environmental protection.They are more and more widely used in engineering.In this paper,the author puts forward a kind of prefabricated recycled concrete column with rebars spliced by pressed sleeves,taking axial compression ratio,longitudinal reinforcement ratio and replacement rate of recycled fine aggregate as parameters,using the methods of seismic performance test,finite element simulation and parametric analysis.The seismic behavior of 9 prefabricated recycled concrete column with rebars spliced by pressed sleeves and one cast-in-place recycled concrete column are studied deeply.The main research work and achievements of this paper are as follows:(1)The author puts forward a kind of prefabricated recycled concrete column with longitudinal rebars spliced by pressed sleeves.The upper and lower columns are prefabricated with recycled fine aggregate concrete in the factory,and a certain length of exposed rebar is reserved at the ends of the column.The sleeve is used in the on-site assembly,and then the connection belt is poured concrete to form an integral force-bearing member.This form has the advantages of firm,reliable connection,convenient construction,and simple operation,etc.The use of recycled concrete is in line with the concept of green environmental protection and recycling.(2)Under the test conditions of this paper,the seismic performance test results of prefabricated and cast-in-place frame column members with the same parameters show that:(1)The failure modes of the two are very similar.The concrete in the compression zone is crushed.The longitudinal reinforcement yields under tension,and the stirrup yields.It shows the typical characteristics of bending-shear failure.(2)After entering the elastic-plastic stage,the hysteretic curves of the two are fusiform,and the hysteretic paths of all levels are similar,indicating that the force transmission of the sleeve is good,the connection is reliable,and the members have good bearing capacity,deformation capacity and energy dissipation capacity.It can be applied to the actual anti-seismic structure.(3)The test results of 9 prefabricated frame column members with different axial compression ratio,longitudinal reinforcement ratio and recycled fine aggregate replacement ratio show that:(1)With the increase of axial compression ratio,the bearing capacity of members increases and the ductility decreases.The energy dissipation capacity of column members with axial compression ratio of 0.15 and 0.3 is the best.(2)With the increase of the longitudinal reinforcement ratio,the bearing capacity of the member increases,the energy dissipation capacity increases,and the ductility increases.However,the member of high longitudinal reinforcement ratio 2.45% is not obvious to increase the energy dissipation capacity and the ductility is reduced compared with the member of longitudinal reinforcement rate 1.59%.(3)When the replacement rate of recycled fine aggregates is 30%,the bearing capacity of the member is less affected,but the greater the replacement rate is,the worse the ductility is.The energy dissipation capacity of the 30% replacement rate is less different from that of ordinary concrete columns.(4)The load-bearing capacity of prefabricated members is better than that of cast-in-place column members,and the ductility is worse than that of cast-in-place column members.The existence of large stiffness sleeve improves the energy dissipation capacity of prefabricated members.(4)The finite element software ABAQUS is used to establish finite element models.The Mander confined concrete constitutive model and the concrete constitutive model of the Code for design of concrete structures are used for the concrete confined area and the not-confined area.The "Friction" contact relation is used to simulate the construction joint.The finite element analysis results fit well with the test results.The axial compression ratio,longitudinal reinforcement ratio,shear span ratio and volumetric stirrup ratio which are not involved in the test are parameterized.The results show that:(1)Under high axial pressure(0.7,0.8,0.9),the load-bearing capacity and ductility of members decrease,and shear failure is easy to occur.(2)Through the extended analysis of the interpolation of longitudinal reinforcement ratio in the test,it is determined that the reasonable range of longitudinal reinforcement ratio is 1.14%-2.28%.(3)The reduction of the shear span ratio can significantly improve the load-bearing capacity of members but the failure of concrete will occur before the yield of the longitudinal reinforcement,so that the failure of members will be changed from moment control to shear control.Concrete is prone to shear damage.(4)The increase of the volumetric stirrup ratio has no obvious effect on the improvement of the bearing capacity of long columns,but the low stirrup ratio will lead to the decrease of ductility and shear capacity,which is prone to shear failure.(5)Finally,based on the test results and the finite element analysis results,the design and construction suggestions of the prefabricated recycled concrete column with rebars spliced by pressed sleeves are put forward.And through calculation,it is found that the bending capacity of the normal section and the shear capacity of the oblique section can be designed according to the current code.