Influence of Corrosive Phenomena on the mechanical behaviour of R.C. Elements

A computational approach, suitable to deal with the analysis of R.C. elements exposed to damaging environments and with steel bars subjected to corrosion is presented. For a given environmental exposition and under an assigned loading condition, the effects of the diffusion of aggressive agents, of the onset and of the development the corrosion state in the reinforcement and the corresponding mechanical response are studied. As known, the propagation and the widening of the cracks foster the damaging process. So, the damage development and the mechanical behaviours must be dealt as coupled phenomena. The analytical models assumed to describe the diffusion of the aggressive agents, of the reduction of the steel sections due to corrosion and of the mechanical behaviour of R.C. with corroded reinforcement are presented. The methodology allows us to simulate different degradation scenarios. By means of the F.E.M., R.C. beams are modeled as membranes structures, having non-linear behaviour and susceptible of cracking. The general hypotheses and the biaxial stress-strain relationships according to the Modified Compression Field Theory are assumed. Special attention is paid to study the coupling between the damaging acceleration and the cracks widening and propagation. In order to assess the reliability of the model, a set of experimental tests reported in Literature and concerning R.C. elements subjected to damage actions along time, have been selected and comparative numerical analyses have been carried out. The benchmarks regard the modelization of the rate of penetration of carbonation and of chlorides into R.C. elements at different levels of cracking and the progression of corrosion and its influence on the ultimate load carrying capacity of slender beams with corroded reinforcement.