Concrete-filled Tubular Columns: Part 1 — Cross-section Analysis

A fiber-based approach is adopted to study the cross-sectional behavior of concrete-filled steel tubes subjected to monotonic and cyclic loading. Constitutive behavior of the cross-section is formulated by explicitly dividing the section into fibers, and uniaxial stress–strain rules for steel and concrete are defined. Interaction curves, Moment–Thrust–Curvature (M–P–φ) relations and Moment–Thrust–Strain (M–P–ε) relations are developed for circular and box-shaped in-filled sections based on fiber analysis. A fiber model is also developed to describe the nonlinear response of concrete-filled steel tubes subjected to cyclic loading. M–P–φ relations are developed for arbitrary loading histories using this simple yet reliable approach. Results are compared with the numerical and experimental data available in published literature, and the accuracy of the proposed model is thus ascertained.