Effect Of Long-term Loading On Mechanical Behavior Of CFST Columns With Inner Profiled Steel Subjected To Bend Loading

With the development of high-rise buildings and severe conditions,super-high-rise buildings and long-span Bridges keep emerging,the heavy load columns in the structure need to have better bearing capacity and ductility.Because the steel tube reinforced concrete can effectively avoid the development of oblique cracks in the core concrete,it has better ductility and seismic performance.Concrete-filled tubular columns with inner profiled steel can be used as the main load-bearing member of the structure.During the service process,the structure is subjected to long-term loading,and the concrete in the column will produce creep deformation,causing internal force redistribution,stress loss,stress concentration,etc.,which will accumulate and endanger the durability and applicability of the overall structure.Therefore,it is very important to analyze the influence of long-term loading on the deformation and mechanical properties of such composite members.Through experimental research and theoretical analysis,this paper studies the influence of long-term loading on such composite members,mainly including the following aspects:（1）With the section steel rate and the slenderness ratio as the main test parameters,Four concrete-filled tubular columns with inner profiled steel axial compression tests are carried out to observe the failure modes of the members.Finite element software is used to calculate the test components and compare their load-displacement curves.According to the ultimate bearing capacity of the two components,the long-term loading value is determined.Experimental study on creep deformation of 8 composite columns under long-term loading is carried out by taking long term load ratio,section steel rate and slenderness ratio as the main experimental parameters.The axial deformation of the specimens under long-term loading increases with time and the influence of various parameters on the creep deformation is analyzed.（2）The effectiveness of the modeling method is verified by experimental results.A numerical analysis model of the CFST columns with inner profiled I-shaped steel subjected to long-term axial loading and bend loading is established by using ABAQUS.The whole process of load-deflection curves,material stress development and distribution,material contact stress of this kind of composite columns are analyzed and compared with those of the composite columns without long-term loading to study the effect of long-term loading on steel-filled steel tubular concrete members.（3）Through finite element analysis,the influence of parameters on the creep deformation,redistribution of internal force and bearing capacity of members is studied in terms of the load time,long-term loading ratio,concrete strength,slenderness ratio,section steel ratio,steel pipe steel ratio and load eccentricity ratio.The k_cr value within the calculation range is given,which provides reference for engineering practice.