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This study deals with the structural behavior of concrete-filled oval tubular (CFT) steel columns. The design formulae are proposed approximately on the yield bending moment and full plastic moment of the oval CFT cross section. They are available in the arbitrary loading direction by introducing simple power series of trigonometric function instead of the difficult elliptic integral of the 2nd kind.Experimentally, specimens were tested under reverse-symmetry cyclic loading to investigate the effects of the loading direction of the oval, axial force ratio, and deformation capacity of the CFT columns. The test results verify that these effects depend on the curvatures around the compressive edge of the oval tube sections. Based on the experimentally obtained equivalent diameter -tothickness ratio (D/t) of elliptic tube, simple evaluation formulae are proposed on the confinement effect and deformation capacity of the oval CFT columns.

Concrete filled steel tubular (CFT) columns have become popular as structural member used for buildings. In the current standards on CFT structures, the scope of design formula is limited circular and square section steel tubes. However, not only these steel tubes but rectangular section steel tubes is used for CFT columns. In this paper, the design formula of rectangular CFT columns is specified. Furthermore, this paper discusses the several issues using rectangular CFT columns on practical design. Concrete filled steel tubular (CFT) columns have become popular as structural member used for buildings. In the current standards on CFT structures, the scope of design formula is limited circular and square section steel tubes. However, not only these steel tubes but rectangular section steel tubes is used for CFT columns. In this paper, the design formula of rectangular CFT columns is specified. Furthermore, this paper discusses the several issues using rectangular CFT columns on practical design.

Large deformation analysis by simple model with circumferential direction linear slider * Tooru HIRADE Seismic-resistant retrofitting requires low vibration, low noise and good workability without moving out of the inhabitants. These requirments are fulfilled by closest-packed circular steel tube bearing wall and it has maximum lighting, ventilation and ductility. The out-of-plane bending stiffness resists seismic lateral force, concerning the mechanism, no experiment nor study is found in 2017 currently by the author. This paper proposes a large deformation simple analysis model of of yield line theory with circumferential direction linear slider which allows tensile elongation. The calculated relation between deformation and shear force was verified by the experimental result and good corresponance was indicated.

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