EFFECTS OF CONFINEMENT ON CONCRETE COLUMNS - PLASTICITY APPROACH

The theory of plasticity and the deformation compatibility equations are used to evaluate the development of lateral confinement of concrete Columns, and the resulting increases in strength and ductility. Concrete is modeled as an elastoplastic material following a simple Drucker-Prager nonassociative hardening model. The lateral reinforcement is replaced by an equivalent sleeve that surrounds the concrete core. The solution is based on the integration of the elastoplastic relations for the concrete core, the transverse steel reinforcement, and the concrete cover. The lateral pressure on the concrete core is calculated based on the compatibility of deformations of the expanding core and the surrounding reinforcement. The ability of the method to predict the response of confined compression members is demonstrated based on numerous published experimental results. The application of the theory is currently restricted to circular ties and spirals. Future studies will address rectangular confinement.