Research On Concrete Filled Double-skin Steel Tubular Columns Subjected To Compression Bending Torsion

Concrete filled double-skin steel tubular (CFDST) is a new type of composite structurefilled with concrete between two concentric steel tubes. It can offer many advantages, such ashigh bearing capacity, good plasticity and malleability, convenient construction, high fireresistance, high bending rigidity, light deadweight. The cross-section of the outer and innersteel tube are various, such as circle, square, rectangle and some others. One kind of CFDSTsection tubes was studied in this paper, that is, the outer steel tubes are circular hollowsections (CHS), while the inner steel tubes are CHS.The compression torsional and compression bending torsion behavior of concrete filleddouble-skin steel tubular columns is the basis of the behaviour of CFDST subject tocompression-torsion, compression-bending-torsion, and compression-bending-shearing.Behaviour and mechanism of concrete-filled double-skin steel tubular columns wereinvestigated in this paper including experimental and theoretical studies. Through theparametric analysis, the practical calculation methods for compression torsional andcompression bending torsion capacity were developed.The main achievements were summarized in detail as follows:(1) The relevant researches were reviewed firstly. The finite element method and testprogram were selected for the behaviour analysis of concrete filled double-skin steel tubularcolumns subjected to compression torsion and compression bending torsion.(2) Seven concrete filled double-skin steel tubular columns and two soild steel pipeconcrete were tested under compression torsion and compression bending torsion. Theprimary parameters in the tests were axial compression ration and slenderness ratio, and thephenomena and data of the tests were analysed.(3) Torque-angle relationship curves of concrete filled double-skin steel tubular columnssubjected to compression torsion and compression bending torsion were analyzed by finiteelement software ABAQUS. The numerical results are compared with the experimentalresults. The calculated results were in good agreement with experimental data, the reliabilityof finite element model was verified. Work mechanism on the composite columns wasanalyzed at three aspects: Failure modes of the composites, stress distributions of steel andconcrete and interactions between steel and concrete.(4) Based on the finite element method, parametric analysis was performed on thebehaviors of Torque-angle relationships for the compression torsion columns. The selectedparameters were the nominal steel ratio, the inner and outer tubes yield strength, hollow section ratio, concret compression strength,slenderness ratio, etc. Finally, practical calculationmethods for compressin torsional capacity were put forward, which can serve the engineeringdesign.(5) Based on the finite element method was performed on the behaviors of Torque-anglerelationships for the compression bending torsion columns. a large amount of circle hollowcompression bending torsion columns are calculated and analyzed, and the reference circle ofsolid concrete filled steel tube compression bending torsion correlation equation. Finally,practical calculation methods for compressin bending torsional correlation equation were putforward.