Analysis On Compression-bending Mechanical Behavior Of Concrete Filled Steel Tube With Profiled Steel Under Construction Pre-load

With the increase of super-high-rise buildings with novel shapes and complicated functions,ordinary concrete filled steel tube(CFST)has been difficult to meet the requirements of some buildings.This requires that the load-bearing columns not only have high bearing capacity under heavy load conditions,but also should have good ductility.Compared with ordinary concrete filled steel tube,the CFST with inner profiled steel has higher compressive bearing capacity and better plastic toughness and fire resistance.In the construction process,the CFST with inner profiled steel is generally installed with inner profiled steel and empty tube,and then the assembly of joints and composite beams,and finally the core concrete is poured in the steel pipe.At this stage,the profiled steel and the tube become the concrete support formwork and the vertical support of the floor,which will cause the construction pre-load.The pre-load of construction is the initial stress that will always exist in the profiled steel or the tube due to the load during construction,which may have a certain impact on the later stress of the CFST with inner profiled steel column.In recent years,there are many studies on the mechanical properties of concrete-filled steel tubular members subjected to pre-load,but there are few studies on the mechanical properties of the CFST with inner profiled steel considering the pre-load of construction.Based on this,this paper conducts an experimental study on the axial compression short members considering the pre-load of the outer steel pipe construction.Using the finite element software ABAQUS,the numerical analysis of the axial compression and bias mechanical properties of the composite members when the pre-load is applied to the outer tube and simultaneously applied to the outer tube and the inner profiled steel are carried out.It mainly includes the following contents:(1)Experimental study on mechanical properties of the CFST with inner profiled steel members under construction pre-load.Four axial compression tests of the CFST with inner profiled steel considering the pre-load of the steel tube were completed.The stress and deformation process,bearing capacity and ductility were studied.The test results were analyzed and compared,and the pre-load coefficient was summarized.The influence law on the mechanical properties of the axial compression combined column is summarized.(2)Numerical analysis on axial compressive mechanical behavior of circular concrete filled steel tubular stub columns with inner crossed profiled steel under construction pre-loadUsing ABAQUS finite element software,the numerical model of the CFST with inner profiled steel axial compression short column considering the construction pre-load of the outer tube and the pre-load of the tube and the profile steel are respectively established.The modeling method was verified by the axial compression test results of this paper and the relevant experimental data of other scholars.Calculate the load-displacement whole process curve of the CFST with inner profiled steel short columns with two types of construction pre-load and the bearing capacity distribution curves of the various components.Analyze the contact stress between concrete and tube,concrete and the profiled steel,and its development and distribution status of stress.(3)Numerical analysis on compressive and bending mechanical behavior of circular concrete filled steel tubular stub columns with inner crossed profiled steel under construction pre-loadThis chapter is based on the CFST with inner profiled steel compressive and bending member test and the CFST compressive and bending member test considering the pre-load of the steel tube.The ABAQUS is used to establish the numerical model of the CFST with inner profiled steel compressive and bending columns,that is considering the pre-load of the outer steel tube construction and considering the pre-load of the steel tube and the inner profiled steel construction.The main research characteristics of the stress distribution of compressive and bending member columns under the condition of two kinds of construction pre-load.Analyze the whole process curve and force mechanism of load-deformation.Exploring the stress state of profiled steel,outer tube and concrete.The interaction between concrete and profiled steel and tube is analyzed,and the influence of pre-load coefficient and load eccentricity on the mechanical properties of biased members is investigated.(4)Finally,the parameters of construction pre-load coefficient,component slenderness ratio,load eccentricity,steel content of steel pipe and section steel,yield strength of steel pipe and section steel and compressive strength of concrete were analyzed.The value of the bearing force influence coefficient is calculated.