Plasticity computations for the design of the ductility of circular concrete columns

Abstract

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 elasto-plastic material following a simple Drucker-Prager nonassociative hardening model. The failure, hardening and dilatational modeling is complicated and features 14 material parameters. However, an extensive study that has been conducted here has shown that these parameters are uniquely related to the unconfined compression strength of concrete f' c, thus establishing a one-parameter model. The solution is based on the integration of the elasto-plastic 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 lateral deformations of the concrete 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.