Nonlinear Analysis Of Compressive Performance Of Rac-filled Circular Steel Tube And Profile Steel Composite Columns Based On Opensees

With the continuous improvement of the level of urbanization,the construction area has grown rapidly,resulting in over-exploitation of sand and gravel resources,and a large amount of construction waste has been generated.Moreover,China's construction waste resource utilization rate is much lower than that of developed countries.How to effectively use waste Concrete has become an important task in the field of construction.The application and promotion of recycled aggregates concrete(RAC)technology,on the one hand,can consume a large amount of waste concrete,which fundamentally solves the problem of difficult construction waste disposal,on the other hand,it can reduce the mining of natural aggregates,which is in line with China's establishment of a resource-saving society and promotes a circular economy strategic goals for development.In this paper,RAC-filled circular steel tube and profile steel composite columns studied,which take full advantage of the three materials,and the longitudinal reinforcement and stirrups can be eliminated during the production process,which effectively solves the problems of steel reinforced concrete construction difficulties and buckling instability and failure of concrete-filled steel tubes.This type of composite column has high bearing capacity and good ductility,and can be applied to actual projects.The effects of 4 design parameters of the recycled coarse aggregate replacement ratio,diameter-thickness ratio,profile steel ratio,and slenderness ratio on the mechanical properties of 11 axially compressed columns,and the effects of 6 design parameters of recycled coarse aggregate replacement ratio,diameter-thickness ratio,profile steel ratio,eccentricity,strength grade of recycled concrete,and slenderness ratio on the mechanical properties of 14 biased columns were studied through experiments.Based on the experiments,this paper uses OpenSees finite element software for numerical simulation.The fiber cross-section division method,element type and material constitutive selection during the modeling process are introduced in detail.The load-displacement curve obtained by OpenSees simulation is in good agreement with the test results,and the relative error rate of finite element calculation bearing capacity is less than 10%.A finite element model suitable for studying the axial compression and bias test of RAC-filled circular steel tube and profile steel composite column is established.On this basis,the parameters are also extended and analyzed.The results show that the conclusions of axial compression column and the bias compression column are similar.The ultimate bearing capacity of the composite column decreases with the increase of the recycled coarse aggregate replacement ratio,and the initial stiffness is not significantly affected;The ultimate bearing capacity and initial stiffness of composite column decrease significantly with the increase of diameter-thickness ratio and slenderness ratio;The ultimate bearing capacity of composite column increases with the increase of profile steel ratio,recycled concrete strength grade and steel strength,but the overall bearing capacity of the eccentric column is lower than that of the axial column;The eccentricity has a significant effect on the bearing capacity of composite columns.When the composite columns change from axially loaded to eccentrically loaded,the bearing capacity declines most obviously,and with the increase of eccentricity,the ultimate bearing capacity and stiffness of composite columns decrease significantly.In addition,based on the twin shear unified strength theory,a calculation method of axial and eccentric load-carrying capacity for composite columns is proposed.The average value of the ratio of theoretical calculation value and test value of composite columns is 0.990 and 0.949 respectively,and the standard deviation is 0.022 and 0.024 respectively,which has high calculation accuracy.