FIBER BEAM-COLUMN MODEL FOR CONCRETE FILLED STEEL TUBE CONSIDERING TORSION EFFECT

Based on the assumption of plane section distribution for normal strain and linear distribution for shear strain on the fiber beam section, the solution flow of a fiber beam-column model for a concrete filled steel tube considering torsion effect is proposed. The two dimensional constitutive law of concrete in the rotation soften truss model proposed by Hsu is used for this fiber beam-column model. Based on the user defined subprogram UEL provided by general finite element program ABAQUS, the fiber beam-column model for concrete filled steel tube considering torsion effect is developed using FORTRAN language. The whole mechanical process of a concrete-filled steel tube under combined action of an axial force, a bending moment and a torque could be predicted by the fiber beam-column model; arbitrary loading path could be considered. High solution precision and efficiency are obtained when analyzing concrete filled steel tube under a combined action when use the fiber beam-column model.