Behaviour Of Concrete-filled Thin-walled Horizontal Corrugate Steel Tubular Short Columns Under Axial Compression

Concrete-filled thin-walled horizontal corrugated steel tubular(CFHCST)is new type of steel-concrete composite section member,which is composed of horizontal corrugated steel and square steel tube.due to the presence of horizontal corrugated steel,the local stability of the multi-cavity is enhanced,which can provide effective constraint with concrete.Thereby improving the bearing capacity and ductility of the component.while ensuring the compactness of the component,the square steel pipe with four limbs can strengthen the lateral restraint of the core concrete,and it can also increase the compressive and bending bearing capacity of the component.In this paper,experimental research,finite element analysis and theoretical analysis are used to study the behaviour of concrete-filled thin-walled horizontal corrugate steel tubular(CFHCST)short columns under axial compression.The main research contents and the conclusions obtained are as follows:(1)This paper uses the ratio of the cross-section width of the square steel tube to the crosssection width of the composite column(referred to as the diameter-to-width ratio)as the research parameter.Four short columns including three CFHCSTs and one CFST were tested under compression.The effect on failure mode,the load-longitudinal strain curve,bearing capacity enhancement coefficient,ductility and the stress-strain curve of each steel component by different diameter-to-width ratio are discussed.To evaluate the influence of the diameter-towidth ratio on the axial compression performance of the CFHCST short columns.The test results show that,compared with CFST,the CFHCST has good axial compression performance.With the increase of the diameter-to-width ratio,the local stability of the multi-cavity decrease gradually,local buckling of the multi-cavity is easy to occur under the action of vertical load,the bearing capacity and ductility of the specimen increase gradually and the bearing capacity enhancement coefficient decreases gradually.(2)The finite element modelling of CFHCST by using ABAQUS program and the accuracy of program is validated by the test results in Chapter 2.On this basis,firstly,a typical specimen is taken as an example,from the load-longitudinal strain curve of each member,the stress-strain curve of each steel component and the longitudinal stress distribution of concrete are analyzed to investigate its axial compression mechanism.finally,by changing the strength and size of the material,the influence of other parameters on the axial compression performance of corrugated steel sheet-concrete-filled steel tube short column was further evaluated.The Study revealed that bearing capacity of the member is mainly determined by the core concrete and the square steel tube concrete because the axial load could not pass the corrugate steel.The strong confinement area of the specimen section is mainly concentrated at the core of the core concrete section and the square steel tube corner.The weak constrained area is mainly concentrated in the wave center and the inner corner of the steel tube.The steel of crest and trough perform bidirectional tension owing to the uneven force on the surface of the corrugated steel plate and the confinement effect of the crest on core concrete is the best.Parametric analysis shows that the bearing capacity and ductility of member increase and the restraining effect of concrete is also strengthened with the increase of corrugated steel plate thickness and steel tube thickness.With the increase of diameter-width ratio,the bearing capacity and ductility of the specimen increase gradually,but the bearing capacity enhancement coefficient decreases gradually.(3)In this paper,the calculation methods of axial compression bearing capacity of six codes are compared with the experimental and finite element results to evaluate the applicability for the axial compression bearing capacity calculation of CFHCST.The research methods of compressive strength of concrete in steel tube based on Mander model was used to establish the calculation formula of axial compression bearing capacity of CFST section of four limbs and the calculation formula of axial compression bearing capacity of core concrete section is suggested on the basis of finite element parameter analysis.Finally,according to the superposition principle,the formula for calculating the axial compressive bearing capacity of CFHCST is established.The calculation results show that the DBJ calculation results can evaluate better the finite element analysis and test values of CFHCST.Although the restraint effect of steel tubes on concrete is considered based on the "unified principle",but it does not reflect the confinement effect of corrugated steel plate on core concrete,so it is not suitable for the calculation of axial compressive bearing capacity of CFHCST.By using the calculation formula suggested in this paper,the calculated values are in good agreement with the experimental values and finite element analysis,which can provide reference for engineering design.