Behavior Of Concrete Filled Double Skin Steel Tubular Square Columns Under Compression-bending-torsion Loading

Behavior and finite element analysis of Concrete filled double skin steel tubular(CFDST) subjected to compression-bending-torsion loading were investigated includingexperimental and finite element calculated. The practical calculation methods forcompression-bending-torsion capacity were derived.The main achievements were summarized in detail as follows:(1) The relevant researches were reviewed firstly. The main content were selected for thebehaviour analysis.(2) A total of six concrete filled double skin steel tubular (CFDST) columns and twoconcrete filled steel tubular (CFST) column were tested under compression-bending-torsion.The outer steel tube of CFDST and CFST members are square hollow section (SHS), and theinner steel tube of CFDST member are circular hollow section (CHS). The parameter variedin the tests were slenderness ratio, hollow ratio and axial compression ratio. All thephenomena and datas of the tests were analysed in detail.(3) The behavior of concrete filled double skin steel tubular (CFDST) members undercompression-bending-torsion loading were studied by the finite element software ABAQUS.The influence of two kinds of loading path and diverse hollow ratio of the CFDST memberswas discussed from four aspects, including torque-angle relationship curves, shear stressdistributions on the cross section, interactions between steel tubes and concrete and loadsundertaken respectively by steel tubes and concrete. Torque versus angle curves of the testspecimens calculated by the finite element method compared with experimental ones, in orderto verified the reliability of the finite element method.(4) The correlation equation for compression-bending-torsion capacity were derived. Thecalculation by the correlation equation compared with the finite element method andexperiment, in order to verified the reliability of the correlation equation method.