An Extended Model for the prediction of Strength Enhancement in Laterally Reinforced Concrete Columns

A behaviour-oriented model is enhanced for the confinement effectiveness and strength enhancement of concrete under axial compression, subject to passive confinement by lateral reinforcement. The basic Model developed on rationalizing the behaviour of confined concrete on the basis of three dimensional concrete constitutive law based FEM simulation results and idealized experimental results on laterally confined concrete cores was extended on the lines of confinement uniformity afforded by complex lateral reinforcement arrangements and the confinement contribution of longitudinal reinforcement. Confinement efficiency of lateral reinforcement layouts were quantified through 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 Extended Model as well. Conceptual ‘lowest confined section’ was adopted to formulate the strength enhancement due to confinement, under average confining stress and double effect of uniformity of lateral confinement layout.