Structural dynamic assessment of the Gravina Bridge (Southern Italy) using Engineering and Geophysical NDT

We here present an innovative engineering and geophysical approach for the structural dynamic assessment of civil infrastructures, such as bridges. To this purpose, expeditive, costeffective, non-invasive and non-destructive remote and in situ sensing techniques were adopted. Their pertinence to the aim of our study was tested on the Gravina Bridge, Southern Italy, a bow-string bridge which was opened to the vehicular circulation in 2016. Therefore, a twofold aim was pursued: 1) to validate the presented approach; 2) to provide an initial characterization of the dynamic properties of this infrastructure and to investigate its possible interaction with its base isolation system and foundation soils. The subsoil properties of the shallowest layers were evaluated through three high resolution resistivity tomographies, 1 bidimensional seismic array and two single station seismic noise measurement. The main structural features of the Gravina Bridge, that is its eigenfrequencies, the related damping factors and mode shapes, were retrieved by adopting both seismic and electromagnetic techniques. The collected, independent, data were analyzed by means of several processing techniques, in both frequency and time domain, which provided consistent results. These allowed us to confirm the reliability of estimations of dynamic properties and to validate the proposed approach.