NONLINEAR CYCLIC BEHAVIOR OF REINFORCING BARS INCLUDING BUCKLING

The effects of inelastic buckling on monotonic and cyclic behavior of reinforcing steel bars arc studied. Experimental tests show that this phenomenon occurs when the ratio between length and diameter of the bar exceeds 5, and that it leads to a postyield softening, branch in compression that strongly influences the cyclic behavior of the bar. An analytical model of rebars accounting for inelastic buckling is presented, suitable for inclusion in programs for the analysis of r/c sections using the fiber type of discretization. The model employs four hardening rules (kinematic, isotropic, memory, and saturation) as functions of four independent parameters (yield stress, elastic modulus, hardening ratio, and a weighing coefficient), An explicit stress-strain relation in finite terms for loading branches is utilized. The model yields accurate results in predicting the cyclic behavior of rebars, both with and without inelastic buckling, for deformation paths of general nature.