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Bridges constitute important elements of the transportation network. A vast part of the Italian existing infrastructural system dates to around 60 years ago, which implies that the related bridge structures were constructed according to past design guidelines and underwent a probable state of material deterioration (e.g., steel corrosion, concrete degradation), especially in those cases in which proper maintenance plans have not been periodically performed over the structural lifetime. Consequently, elaborating rapid yet effective safety assessment strategies for existing bridge structures represents a topical research line. This contribution presents a systematic experimental–numerical approach for assessing the load-bearing capacity of existing prestressed concrete (PC) bridge decks. This methodology is applied to the Longano PC viaduct (southern Italy) as a case study. Initially, natural frequencies and mode shapes of the bridge deck are experimentally identified from vibration data collected in situ through Operational Modal Analysis (OMA), based on which a numerical finite element (FE) model is developed and calibrated. In situ static load tests are then carried out to investigate the static deflections under maximum allowed serviceability loads, which are compared to values provided by the FE model for further validation. Since prestressing strands appear corroded in some portions of the main girders, numerical static nonlinear analysis with a concentrated plasticity approach is finally conducted to quantify the effects of various corrosion scenarios on the resulting load-bearing capacity of the bridge at ultimate limit states. The proposed methodology, encompassing both serviceability and ultimate conditions, can be used to identify critical parts of a large infrastructure network prior to performing widespread and expensive material test campaigns, to gain preliminary insight on the structural health of existing bridges and to plan a priority list of possible repairing actions in a reasonable, safe, and costly effective manner.

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.

This paper numerically investigates three typologies of Gerber saddle in existing ordinary and post-tensioned girder concrete bridges. The main goals of this work concern the evaluation of the effective load-bearing capacity of Gerber saddles, and the identification of weak points (i.e., lack of enough diagonal reinforcement, loss of pretension in tendons) of existing dapped-end connections, which lead to the re-entrant corner diagonal crack, typical of these kinds of structural elements. At this aim, two analytical approaches, with different level of approximations, are used. First, different strut-and-tie models are arranged for each typology of Gerber saddle considered, and the global safety factor is estimated for several cases. Second, using nonlinear finiteelement method, the results obtained by strut-and-tie models are compared. In addition, several information about the condition of Gerber saddle at collapse are obtained (deformation and stress of concrete and steel rebar, crack patterns) also taking into account the corrosion-damage effects. Moreover, the results of analyses allow identifying the potential modes of crisis of the dapped-end connections and their critical aspects.