Experimental Study And Nonlinear Analysis On Seismic Behavior Of Composite Columns Composed Of Recycled Concrete Filled Circular Steel Tube And Profile Steel

Composite columns made of recycled concrete filled circular steel tube and steel profile(CSTSRRC)is a new type of load-bearing member that combines the advantages of green environmental protection of recycled concrete with the advantages of composite structure.The composite column not only provides a new way to deal with the waste concrete,reduces the mining demand for natural resources,but also weakens the influence of the initial defects of recycled coarse aggregate on the mechanical properties of composite columns.Moreover,it is convenient for building,meets the needs of circular development and future engineering construction development and has high application value.This study explores the seismic performance of composite column through a combination of experimental research and finite element analysis.In this paper,11 pieces of CSTSRRC columns are designed and manufactured for quasi-static test,mainly aiming at the replacement rate of recycled concrete,the thickness ratio of outer steel tube diameter,the steel ratio of profile steel,the axial compression ratio and the section form of inner profile steel.The hysteretic curves,skeleton curves and eigenvalues of composite columns with different influence parameters are obtained,and the seismic performance indexes such as ductility coefficient,displacement angle,energy dissipation capacity,strength attenuation and stiffness degradation are analyzed.The strain of each position of the composite column is sorted out and studied,and obtained the strain development law during the failure process.Finally,the influence of the design parameters on the seismic performance of the composite column is studied quantitatively.The experimental results show that the hysteresis curve of the composite column is full in the shape of "shuttle".The composite columns with different parameters have strong ductile deformation capacity and energy dissipation capacity,and the stiffness degradation and strength degradation are stable.In addition,the replacement rate of recycled coarse aggregate has little effect on the seismic performance of composite columns.Furthermore,increasing the wall thickness of outer steel tube and the steel ratio of section steel can significantly improve the bearing capacity and ductility deformation capacity of composite columns,and the increase of axial compression ratio is unfavorable to the ductility of composite columns.On the basis of the experimental study,the numerical model is established by ABAQUS finite element software,and the seismic performance of the composite column is analyzed by finite element method.The calculation curve is in good agreement with the hysteretic curve and skeleton curve obtained from the test,and the error of each numerical characteristic point is within the engineering allowable range,which proves the accuracy of the finite element numerical model.The established finite element model is used to analyze the test parameters of the composite column more comprehensively,and the extended analysis is carried out by adding the strength of recycled concrete,the strength matching of internal steel and external steel tube,the shear span ratio and scale ratio.The results of finite element analysis show that the bearing capacity and stiffness of composite columns can be improved by increasing the strength of recycled concrete,but the increase rate decreases with the increase of recycled concrete strength,and the ductility of composite columns decreases with the increase of recycled concrete strength.Furthermore,increasing the strength of the built-in steel profile can enhance the ductility deformation ability of the composite column,and improving the strength of the steel tube outside the composite column can obviously improve the horizontal bearing capability of the composite column,while the ductility deformation capacity of composite columns is slightly improved with the increase of steel tube strength;The finite element model cannot fully reflect the influence of scale ratio on the performance of composite columns.Based on the experimental study,Using the limit equilibrium procedure,the horizontal bearing potential formula for the composite columns is obtained.In addition,the suggested formula is considered to be in reasonable accordance with the experimental value and can be used as a formula for estimating the bearing potential of composite columns.