Nonlinear damage behaviour of concrete structures

Abstract

Concrete structures are becoming more and more sophisticated and submitted to severe conditions, for example: high stresses and temperatures, cyclic loadings, earthquakes, etc. It is therefore necessary to simulate correctly the behaviour and damage of such structures. However, the behaviour of this material is among the most complex ones: various phenomena are observed experimentally, such as, loss of stiffness, irreversible strains, stiffness recovery and dissymmetric behaviour to mention a few. If all these effects are taken into consideration, it would lead to models that use numerous parameters. In this paper, a framework for damage mechanics of concrete is presented and used to simulate the nonlinear behaviour of concrete using finite element method (FEM). A relatively simple isotropic damage model, containing essentially no adjustable parameters is shown to produce results in remarkably good agreement with experimental results. Indeed, the damage law requires only the fracture energy to be completely defined. A special form of damage surfaces is constructed to illustrate the application of the model. A new damage criterion, defined as an equivalent strain norm, is proposed to take into consideration the dissymmetric behaviour of concrete. To verify the FEM program including the model, the predicted deformations are compared with experimental results and results from other nonlinear constitutive models.Key words: elasticity, quasi-brittle materials, damage, cracking, nonlinear behaviour, concrete modelling, finite element, simulation.