TIME-VARIANT STRUCTURAL RELIABILITY OF R.C. STRUCTURES AFFECTED BY CHLORIDE-INDUCED DETERIORATION

Reinforced concrete structures in service may be affected by aging, which may include changes in strength and stiffness beyond the baseline conditions which are assumed in structural design, in particular when the concrete is exposed to an aggressive environment. For reinforced concrete structures, due to the uncertainties in material and geometrical properties, in the magnitude and distribution of the loads, in the physical parameters which define the deterioration process, the structural safety should realistically be considered time-variant. This paper provides a computational probabilistic approach to predict the time-evolution of the mechanical and geometrical properties of a reinforced concrete structural element (i.e., bridge pile) subjected to corrosion-induced deterioration, due to diffusive attack of chlorides, in order to evaluate its service life or, complementarily, residual service life. Adopting appropriate degradation models of the material properties, concrete and reinforcing steel, as well as assuming appropriate probability density functions related to mechanical and deterioration parameters, the proposed model is based on Monte Carlo simulations in order to evaluate time-variant axial force-bending moment resistance domains, with the aim to estimate the time-variant reliability index. Finally, an application to estimate the expected lifetime of a deteriorating reinforced concrete bridge pile is described