Creep - Damage interaction in concrete structures

The serviceability of concrete structures is a coupled problem in which creep and damage are coupled. In this paper, we start with experimental investigations on concrete notched beams that involve tertiary creep. We consider residual capacity tests on bending beams and investigate the evolution of size effect due to creep. We show that the fracture characteristics, namely the fracture energy and the size of the fracture process zone, decrease when creep is applied prior to failure. A candidate constitutive relation is presented in the second part. It is a damage-based model in which the relationship between the effective stress and the strain follows a generalised Maxwell chain. The influence of creep on damage growth can be adjusted in order to avoid a coupled effect between creep and damage that is too strong when damage is function of the total strain. Several test-computations are discussed including creep tests at several load levels on bending beams, similar to those predicted by Zhou and Hillerborg. In order to describe the variation of the size of the fracture process zone due to creep observed in the experiments, the internal length in the model should decrease. A first approach is proposed in the closure.