FINITE ELEMENT MODELLING AND ANALYSIS OF CONCRETE CONFINED BY STIRRUPS IN SQUARE RC COLUMNS

Concrete confined by stirrups with greater ductility than unconfined concrete has been used widely in reinforced concrete (RC) structures and its behavior is the classic topic. As the computer power is improving, an increasing number of modelling studies of the confined concrete using finite element (FE) methods have emerged in recent years. Aiming at developing a FE model to evaluate the behavior of concrete confined by stirrups in square RC columns, a new uniaxial compression stress-strain relation of concrete considering the confinement effect of stirrups was proposed. In the FE model, the behavior of confined concrete was described by combining the concrete damaged plasticity model with the proposed uniaxial compression stress-strain relation of confined concrete. Then, tested square RC columns confined by stirrups under axial load were simulated and the details of the FE model were described. Though the comparison between the predicted and measured curves of axial load N versus axial strain , the proposed uniaxial compressive model of confined concrete was verified. Finally, a parametric study of the effects of strength of stirrup and equal strength replacement of stirrups on the behavior of confined concrete was conducted.