PSI - Issue 44

Dario De Domenico et al. / Procedia Structural Integrity 44 (2023) 633–640 Dario De Domenico et al. / Structural Integrity Procedia 00 (2022) 000–000

634

2

Nomenclature su ε

ultimate strain of steel bars ultimate strength of steel bars y f yielding strength of steel bars rebound index measured in SonReb tests compressive strength of concrete Ø u f

ultrasonic pulse velocity measured in SonReb tests

diameter of steel reinforcement bar Reduction of the resistant cross-sectional area of the corroded bars is accompanied by other critical aspects affecting the structural safety (Zeng et al. 2020; Imperatore et al. 2017), like spalling of concrete cover (Coronelli & Gambarova 2004), deterioration of bond behavior at the concrete-corroded steel interface and reduction of confinement action of transverse reinforcement (Meda et al. 2014; Guo et al. 2015; Yang et al. 2016). These phenomena imply dramatic reductions of structural lifetime and increase the seismic vulnerability (Di Sarno & Pugliese 2020). In this context, it is of utmost importance to develop numerical procedures, calibrated on experimental basis, to predict the increase of the seismic vulnerability of RC bridge piers in corrosive environment (Domaneschi et al. 2020; Pelle et al. 2021). 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 from the literature, to describe the constitutive relationships of concrete and steel 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, besides the uncorroded configuration. 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. 2. The case study: the Zappulla viaduct The Zappulla viaduct was constructed around fifty years ago (first 1970s) in the municipality of Rocca di Capri Leone, approximately 2 km in front of the Tyrrhenian Sea (De Domenico et al. 2022). Belonging to the A20 highway connecting Messina to Palermo, the multi-span viaduct is composed of two separate carriageways and includes 18 spans (of equal length 45.2 m and identical structural scheme).

Fig. 1. Photograph of the Zappulla multi-span viaduct (left) and original drawings of RC piers with hollow, two-cell, rectangular section (right). units in [m]