Several existing reinforced concrete (RC) bridge piers located in coastal areas or in the nearby of the sea are exposed to chloride-induced corrosion phenomena in the steel bars. Reduction of the resistant cross-sectional area of the corroded bars is accompanied by other critical aspects affecting the structural safety, like spalling of concrete cover, deterioration of bond behaviour at the concrete-corroded steel interface and reduction of confinement action of transverse corroded reinforcement. These phenomena imply dramatic reductions of structural lifetime and increase of seismic vulnerability unless properly foreseen and promptly controlled. In this context, it is of utmost importance to develop numerical procedures, calibrated on experimental basis, to predict the alteration of the seismic vulnerability of RC bridge piers in corrosive environment.

This paper presents an experimental-numerical procedure oriented to the seismic vulnerability assessment of RC bridge piers with corroded bars. The procedure is illustrated in the context of a case study represented by the Zappulla multi-span viaduct (Sicily, Italy), built around 50 years ago close to the Tyrrhenian Sea and whose RC piers are experiencing evident chloride-induced corrosion. A comprehensive investigation for the quality control of this viaduct has been performed, involving carbonation tests, corrosion potential mapping and extraction of corroded steel bars for tensile tests, in conjunction with SonReb tests and concrete coring. Experimental findings are then interpreted critically to identify the level of corrosion in the various piers. The quantification of the corrosion level detected in situ is incorporated, through appropriate mechanical degradation laws, to describe the constitutive relationships of concrete and steel materials within a nonlinear fiber-hinge model of the RC piers. The numerical model with experimentally-calibrated coefficients is used to perform the seismic vulnerability of the Zappulla viaduct under two representative corrosion scenarios. Based on the numerical simulation, it has been found that the corrosion conditions of the RC piers identified from the experimental campaign reduce the safety margins under seismic loading up to 40% in comparison with the uncorroded scenario (representative of the original condition of the RC piers prior to any degradation phenomenon). The proposed procedure is general and can be applied to other existing bridge structures exposed to chloride-induced corrosion.