Slender Beam-Columns

High strength thin-walled concrete-filled steel tubular (CFST) slender beam-columns may undergo local and global buckling when subjected to biaxial loads, preloads or cyclic loading. The local buckling effects of steel tube walls under stress gradients have not been considered in existing numerical models for CFST slender beam-columns. This thesis presents a systematic development of new numerical models for the nonlinear inelastic analysis of thin-walled rectangular and circular CFST slender beam-columns incorporating the effects of local buckling, concrete confinement, geometric imperfections, preloads, high strength materials, second order and cyclic behavior. In the proposed numerical models, the inelastic behavior of column cross-sections is simulated using the accurate fiber element method. Accurate constitutive laws for confined concrete are implemented in the models. The effects of progressive local buckling are taken into account in the models by using effective width formulas. Axial load-moment-curvature relationships computed from the fiber analysis of sections are used in the column stability analysis to determine equilibrium states. Deflections cause