Constitutive Model for Inelastic Buckling Behavior of Reinforcing Bars

A refined constitutive model (called "RDM model") is proposed for simulating the complete stress-strain response of longitudinal reinforcing bars, including the onset of inelastic buckling and subsequent degradation in the post-buckling regime. This model accounts for interactions between lateral ties and longitudinal bars, and is verified using 45 experimental and 58 analytical specimens previously tested by nine research groups. The RDM model is incorporated into a global modeling procedure and validated with six axially loaded columns, 16 axially and laterally loaded columns, and four beams previously tested by nine research groups. The validated procedure is used to study the influences of global second-oreler mechanisms such as geometrical nonlinearities, shear effects, and confinement effectiveness on the local buckling behavior. The proposed RDM model is shown to provide accurate response simulations for the buckling of reinforcing bars with a wide range of mechanical and geometrical properties. This model employs simple equations and defines full-range compressive response from well-known tensile material properties.