A Constitutive Theory for Brittle Solids with Application to Concrete

A single-flow surface model unifying damage mechanics and plasticity is developed for quasi-brittle solids in general and concrete in particular. The necessity of using both plasticity and damage mechanics is discussed, and the preference for developing a single-flow surface model over the existing bi-surface models is outlined. The model is cast within the general setting of the continuum thermodynamics with internal variables. Invoking the internal dissipation inequality and guided by physical arguments, a flow surface is developed via introducing pressure functions. The flow surface displays both hardening and softening. The model is capable of predicting the essential features of material inelasticity including dilatation, anisotropic degradation, inelastic flow, and enhancement in strength and apparent ductility with lateral pressure, and is simple for computer implementation. These features are shown together with comparisons of theoretical and experimental data.