A Model for the Prediction of Strength Enhancement in Concrete Cores under Passive Lateral Confinement

A behaviour-oriented model is proposed for the confinement effectiveness and strength enhancement of concrete under axial compression, passively confined by lateral reinforcement. The model is developed on the basis of three dimensional concrete constitutive law based FEM simulation results and idealized experimental results on laterally confined concrete cores. Confinement efficiency of lateral reinforcement layouts are quantified through a mechanically defined confinement effectiveness index, which is the ratio of induced spatial average confining stress to the maximum potential confinement capacity of lateral reinforcement arrangement. This index is represented by lateral reinforcement detailing as well as material parameters in the model. Influence from uniformity of confining reinforcement layouts on confinement effectiveness was identified through FEM simulation results, which is used to formulate the basic form of the model. Concept of lowest confined section is adopted to formulate the strength enhancement due to confinement, based on average confining stress and double effect of uniformity of lateral confinement layout.