finite element model for confinement in reinforced concrete columns

Necessity of easy and realistic modelling of the behaviour of reinforced concrete columns inbending has increased by the rapid development in performance based design methods whichare important for evaluation of existing buildings. There are a lot of assumptions to calculateconfinement pressure in emprical models (Kent and Park 1971, Sheikh and Uzumeri, 1983,Mander et al. 1988, etc.) which are based on existing experiments.Although lateral confinement in reinforced concrete components has been observed before bymany researchers, there are some indefinite issues of fact and a general model can not beoffered because the assumptions in calculation of the confinement pressure applied by lateralreinforcements are not realistic.Confinement that lateral reinforcement applies to the core concrete in reinforced concretecolumns under axial load has been searched in this thesis.Because of not having a formula to calculate the confinement pressure in present reinforcedconcrete regulations using proposed analytical methods in literature is a necessity. In thisconsequences, superfluous reinforcement used for safety may cause an increase in cost, and itwould be convenient to search situations like incorrect usage or selection of lateralreinforcement.In this study, lateral confinement around the core concrete has modelled with a spring systemand some parameters like volumetric ratio of longitudinal reinforcement, number anddiameter of longitudinal reinforcement, space between lateral reinforcements and concretestrength studied to find if the changes in lateral confinement pressure and spring coefficientare suitable with realistic column behaviour (change in column ductility is neglected).3D column models were analysed with LUSAS that uses finite elements method andalteration of parameters mentioned above have been studied by nonlinear analysis with anisotropic damage model. It is emphasized that the changes in these parameters are veryimportant for computing lateral confinement pressure which is a key variable to determine themaximum load carried by columns.Keywords: Reinforced concrete columns, lateral confinement, confinement pressure, lateralreinforcement, nonlinear analysis, finite elements method.