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The paper presents a study based on integrated non-destructive sensing methods aimed at defining the experimental vibration properties of a historical dome by using environmental microtremor measurements only. The integrated approach consists in the use of both contact and remote sensors to acquire ambient vibration data. The measurements of vibration were carried out with a high-sensitive tri-axial seismometer (Tromino) and a coherent radar system (Image By Interferometry System, IBIS-S). Five asynchronous velocimetric stations were arranged over a profile on the external side of the structure to acquire ambient vibration time-series on radial, tangential and vertical directions. In order to detect the displacements of the internal surface of the dome, the radar interferometer was positioned inside the church using three station points of measure along the main axis of the structure, with different geometric configurations for each station. With this technique, synchronous signals coming from the structure were simultaneously acquired and analyzed. Both seismic time-series and microwave signals were processed to derive the experimental vibration properties of the structure, mainly concerning the dynamic behavior of the circular dome. In addition, to evaluate the capabilities of the radar system in the indoor configuration, a Finite Element model of the structure was built, and the experimental results were compared to the numerical outputs. |
