Seismic vulnerability assessment of reinforced concrete bridge piers with corroded bars

Reinforced concrete (RC) structures located in aggressive environment, for example, RC bridge piers close to the sea and experiencing chloride attacks, may be exposed to an increased seismic vulnerability. This requires practical yet effective safety assessment strategies aimed to determine the seismic behavior by incorporating corrosion deterioration phenomena. An easy-to-use phenomenological model is here developed to describe the seismic behavior of corroded RC elements based on a fiber hinge formulation wherein the corrosion-induced mechanical degradation of concrete and steel is implemented through appropriate constitutive laws at the fiber level. The developed fiber hinge formulation is first validated against experimental cyclic tests of corroded RC columns from the literature. Then, the proposed approach is used for the seismic vulnerability assessment of the Zappulla multi-span viaduct (southern Italy), whose RC bridge piers (with a box-shaped, two-cell hollow rectangular cross section) are exposed to carbonation and chloride-induced corrosion. A comprehensive in-situ testing campaign is conducted for the mechanical characterization of the materials in the RC piers. Corrosion potential mapping, carbonation tests and tensile tests on corroded bars extracted from RC piers are critically interpreted to calibrate the constitutive laws of the fiber-hinge model. Motivated by experimental findings, numerical seismic analyses (including linear dynamic, nonlinear static and nonlinear dynamic analyses) are performed under two different corrosion scenarios to quantify the impact of corrosion on the resulting seismic vulnerability conditions of bridge piers with corroded bars. The proposed approach is characterized by low computational cost and lends itself to large-scale seismic vulnerability assessment of other existing RC bridges placed in corrosive environment.