NUMERICAL SIMULATION ON THE DYNAMIC BEHAVIOR OF SHORT RC COLUMNS SUBJECTED TO CONCENTRIC RAPID LOADING CONSIDERING CONFINEMENT EFFECT OF STIRRUPS

In order to investigate the behaviour of laterally confined short RC columns considering strain rate effects under dynamic loadings such as earthquake excitations, an equivalent stress-strain relationship of concrete considering both the strain rate sensitivity of concrete materials and the confinement effect of stirrups was introduced to a concrete plastic-constitutive model and the dynamic behaviour of laterally confined short columns under rapid loadings was simulated with a finite element model. The finite element analysis model was validated by comparing the numerically simulated behaviour with experimental data and was able to describe the response of the laterally confined short columns under dynamic loadings with acceptable accuracy. The result showed that the proposed equivalent uniaxial compression stress-strain relationship of concrete is rational. Based on the proposed analysis model, the influence of the following three parameters including the configuration, the spacing of stirrups and the ratio of longitudinal reinforcement on the behaviour of laterally confined short columns considering both strain rate effect and confinement effect was studied. The simulation results show that the axial load carrying capacity increases with the strain rate increasing, but the ductility decreases with the strain rate increasing and the descending branch of the relationship of axial carrying capacity versus axial deformation become sharper. The three parameters studied here have an important effect on the dynamic behaviour of laterally confined RC columns considering strain rate effects.