Study On Mechanical Behavior Of Circular Concrete Filled Circular Steel Tube Long Column Under Spatial Loading

CFSTs make full use of the advantages of steel pipes and concrete materials,which can significantly improve the stability and load-carrying capacity of structures.They have been widely used in high-rise buildings,bridges,and offshore platforms.In engineering practice,when the structure is subjected to uncertain loads such as earthquakes and wind,or when the structure is unevenly stressed due to foundation deformation,steel-concrete composite columns often experience complex loading conditions.The use of steelembedded steel pipe concrete columns can further improve the performance of steelconcrete composite structures.However,there is currently limited research on their complex stress conditions.Therefore,this paper conducts experimental research and parameter analysis on the performance of steel-concrete columns and steel-embedded steel pipe concrete columns under complex loading conditions.The main work includes:(1)Analysis of the research status of the composite loading performance of steelconcrete columns.It summarizes the development process of steel-concrete columns and steel-embedded steel pipe concrete columns,analyzes the theoretical analysis,numerical simulation,and experimental research methods of scholars in this field,and summarizes the load-carrying capacity,failure mechanism,seismic performance,and bearing capacity of steel-embedded steel pipe concrete columns.(2)Experimental research on the composite loading performance of steel-concrete columns.Two types of steel-concrete column models with different cross-sections(steelconcrete columns and double-layer steel-concrete columns)were designed.Using the Stewart six-degree-of-freedom loading device developed by the research team,quasistatic tests were conducted under different loading conditions,including pure torsion,compression-torsion,bending-shear,compression-bending-shear,bending-torsion,and compression-bending-torsion.The load-carrying capacity,ductility,hysteresis,energy dissipation,and damage evolution mechanism of steel-concrete columns were compared and studied.The differences in the load-carrying capacity of steel-concrete columns under different loading conditions,including compression,bending,shear,torsion,and their coupling conditions,were summarized.A high-precision calculation formula for the torsional bearing capacity of steel-concrete columns was given.(3)Parameter analysis of the composite loading performance of steel-concrete columns.Based on the experimental results,the elastic-plastic finite element analysis of steel-concrete columns under different loading conditions,including compression,bending,shear,torsion,and their coupling conditions,was performed.The analysis results were in good agreement with the experimental results,which verified the rationality of the finite element model.The influence of axial compression ratio,slenderness ratio,and diameter-thickness ratio on the composite loading performance of steel-concrete columns was analyzed under different parameter conditions.