Quality control and safety assessment of prestressed concrete bridge decks through combined field tests and numerical simulation

This paper presents a systematic approach for the quality control and safety assessment of existing bridge decks through combined field tests and numerical simulation. The methodology is described in the context of a case study represented by the Zappulla multi-span viaduct (southern Italy), whose deck is realized with simply supported prestressed concrete girders and overlying reinforced concrete slab. Quality control is carried out through an extensive in-situ testing campaign comprising concrete coring, carbonation tests, sclerometric tests combined with ultrasonic pulse velocity for concrete strength evaluation, as well as pachometer and georadar tests for identification of steel reinforcement and prestressing tendons, respectively. Additionally, field tests including static and dynamic loading tests are performed to investigate the bridge response under serviceability conditions. Field-test results along with experimental findings on the material characterization are used to calibrate a finite element (FE) model of the bridge deck, which is subsequently adopted for structural safety assessment of the bridge deck at ultimate limit state (ULS). Two methods for evaluating the safety conditions at ULS are comparatively investigated, namely the Eurocode-compliant semi-probabilistic partial factor method and a deterministic method that computes the global safety factor of the bridge deck in its actual working conditions based on nominal values of loads and resistances. In addition to linear analysis, incremental non-linear static analysis is performed to determine the push-down response of the bridge deck via a concentrated plasticity approach. The proposed procedure, inherently encompassing both serviceability and ultimate loading conditions and synergistically combining material characterization and field-test results with a critical statistical interpretation, accompanied by numerical FE simulation with an eye to design code requirements, provides a reliable tool for the quality control and safety assessment of other similar existing bridges.