When plasticity?

Abstract

The paper considers the broad question of when and to what extent the theory of plasticity is useful in the analysis and design of reinforced concrete structures at the ultimate limit state of collapse. It covers early lower- and upper-bound approaches to design, and discusses various objections to the application of plasticity theory to concrete, concentrating on the need for adequate ductility – nowadays perhaps provided by fibre rather than bar reinforcement – and the crucial matter of size effect. It concludes that plasticity theory can be useful for the design of ordinary concrete structures known to have ductile failure modes, but that great care and wariness are needed when attempting to extrapolate its use to unusual structures and particularly to structures of large size without adequate ductility.