No abstract

The dynamic behaviour of two slender structures with very similar geometry has been investigated in order to evaluate the role played by the construction materials; the comparison has thus been conducted on their vibration properties as resonance frequencies, damping coefficients and mode shapes. The studied structures are two bell towers of a church which were built in two different historical times, with an interval of about one century, using different construction techniques and materials. The experimental tests were carried out by means of output-only measurements of ambient vibration using both contact and non-contact techniques. The signals have been acquired using a tri-directional tromometer or two short period seismometers, both placed in prearranged station points on the structures. Furthermore, the vibrations of the structures have also been measured with the IBIS-S microwave interferometer which is able to provide submillimetric displacements along the radar Line Of Sight without need of any contact with the surface. Therefore, the experimental dynamic response of the church-towers system has been estimated integrating both velocity and displacement data. Though the vibration of the structures had low magnitude, both surveys allowed us to identify the main linear dynamic properties of the structures. Based on these passive surveys, a linear finite element model was calibrated in order to confirm the relationship between the materials and vibration properties. The final model has been locally validated by means of in situ acoustic measurements

Detection of the buried antique Roman aqueduct, which supplied fresh water to the ancient town of Karales (Cagliari, Italy), is not a trivial problem because of the small size of its cross section, its depth (about 10 m), and of the presence of shallow conductive layers. In order to determine the best geophysical method to use in the research of the conduit, a test was carried out over a well-known section of the underground aqueduct in its extra-urban part. Taking into account the geological features of the site, time-domain electromagnetic (TEM), very low-frequency (VLF) and electrical tomography methods were chosen. The test was conducted over several profiles. The results showed that among the electrical resistivity arrays, the Wenner-Schlumberger is the most suitable for the detection of the conduit some metres in depth, whereas the other electrical methods did not have enough resolution to distinguish between the aqueduct and other non-related anomalies at the requested depth. The TEM method also showed good capability to detect the presence of the aqueduct in spite of very conductive superficial layers. With the exception of one profile, all VLF profiles showed anomalies that could be correlated to the aqueduct.

This paper deals with the resistivity continuous surveys on extensive area carried out at the Mont'e Prama archaeological site, in Sardinia (Italy). From 2013 to 2015, new research was performed using both non-destructive surveys and traditional archaeological excavations. The measurements were done in order to find geophysical anomalies related to unseen buried archaeological remains and to define the spatial extension of the ancient necropolis. The electrical resistivity of soils was measured by means of the Automated Resistivity Profiling (ARP©) system. This multi-pole method provided high-resolution maps of electrical resistivity in the whole investigated area using a computer-assisted acquisition tool, towed by a small vehicle. Through this acquisition layout, a surface of 22,800 m 2 was covered. The electrical resistivity data were derived in real time with centimetric horizontal precision through a differential GPS positioning system. Thanks to the simultaneous acquisition of ARP and GPS data, the rigorous georeferencing of the tridimensional experimental dataset was made possible, as well as the reconstruction of a detailed Digital Terrain Model. Here, the experimental results are analyzed and critically discussed by means of the integration of the results obtained by a high-resolution prospection performed with a multi-channel Ground Penetrating Radar system and taking into account other information derived from previous geological and archaeological studies. Geophysical results, jointly with topographic reconstruction, clearly permitted the identification of more interesting areas where future archaeological investigations could be focused.

The structures damage conditions assessment requires numerous precautions to ensure the safety of people during site visits and inspections. Among several methods providing useful information about the conservation status of the structures, dynamic monitoring techniques are suitable to retrieve the global behavior of the buildings. The anomalous features diagnosis of the structural dynamic response is an index of alterations of the material state and, in the worst cases, is related to the presence of damaged structural elements. This paper proposes the use of remote control systems for the structural evaluation of the damage state of buildings and describes the results achieved in an interesting application: the experimental dynamic analysis carried out on the inaccessible damaged bell tower of the Church of Santi Giacomo and Filippo in Mirandola (Italy). The study is based on observations performed using the IBIS-S ground-based radar interferometer to remotely measure the displacements of several elements of the building above 0.01 mm amplitude. This totally noninvasive and nondestructive approach has proved to be reliably implemented as a useful method to structural health monitoring procedures and especially for extensive and fast inspection analyses aiming at the first evaluation of the damage level and the soundness of slender buildings after earthquakes.