Gianluca Ruocci

Modal Identification of an Experimental Model of Masonry Arch Bridge

The erosion of the river bed material at bridge pier foundation produced by scour events is one of the main causes of the observed masonry bridges failures and collapses. Foundation settlements and rotations derived from the reduction of the footprint under the piers threaten masonry arch bridges integrity more than any gravity load. The resulting effect on the structure is the development of cracking mechanisms on the arches which may affect the dynamic behaviour of the whole bridge. A scaled experimental model of a masonry arch bridge has been built in the laboratory of the Dep. of Structural Engineering at the Politecnico di Torino. The aim was to better understand scour damage scenario and to identify early structural symptoms of pier erosion. A preliminary dynamic identification is carried out on the intact structure and a comparison with the FEM results is performed. The set of identified modal parameters is adopted as the reference system that will be compared with those acquired after the application of damage of increasing extent.

Multi-domain feature selection aimed at the damage detection of historical bridges

The aim of this study is the analysis and comparison of several sets of features selected from different domains for the detection of damage induced by scour on historical bridges. A scaled experimental model of a masonry arch bridge was subjected to differential settlements of the pier to simulate the occurrence of scour events. Damage states of increasing extent were introduced to verify the sensitivity of each feature and the accuracy of the damage detection method. The vibration measurements were acquired after each damage step using sensors located in different positions on the structure and different sources of excitation. The Kernel Density Estimation (KDE) was employed to characterise the correlation between the vibration signatures acquired in the time domain. The identified natural frequencies and the sampled range of the transmissibility spectrum were used in the Outlier Analysis (OA) to identify the novelties coming from the damage steps. All the selected features proved to be sensitive to damage, while showing pros and cons depending on the feature domain.

Experimental and Numerical Analysis of a Two-Span Model Masonry Arch Bridge Subjected to Pier Scour

A scaled model of a two-span masonry arch bridge has been built in order to investigate the effect of the central pile settlement due to riverbank erosion. The bridge model has been equipped with different Non Destructive Testing (NDT) instruments and subjected to incremental settlement of the pier. The evolution of the pier scour has been investigated experimentally by means of a hydraulic model and reproduced accordingly. The numerical interpretation of damage, carried out by finite element analyses, has been compared with the results of the Acoustic Emissions (AE) monitoring. Several ultrasonic emissions have been detected and main damage source areas have been localized.