Telerilevamento di vibrazioni delle strutture tramite telesensore infrasonico

Abstract

In the framework of EDISECUR project, funded by the Lazio region, a prototype of speckle tracking remote infrasonic sensor, TIS, for measuring the fundamental angular velocity, and harmonics of a surface subject to oscillations, was developed. TIS is particularly suitable for the detection and monitoring over time of buildings, bridges and other artefacts. Knowing the vibrational state of these structures can be of interest both for their dynamic characterization and for safety. This compact prototype, gives an immediate measure of angular velocity and, with simple operations, it is possible to deduce angular displacements and accelerations. From the angular quantities and the geometric dimension of the surface, it is shown how it is possible to determine other linear kinematic parameters as well. The remote sensor can be used to measure long distance surfaces of various kinds, even where it is not possible to access to perform a direct measurement. The instrument covers a frequency range up to tens of Hz, has a sensitivity and dynamics to detect vibrations induced by industrial noise, traffic, wind and more. This work is mainly aimed at TIS applications in the detection of vibrational state of structures and the methods, limits and advantages of its use are explained together with the errors of this technique. Since the TIS measures a relative movement between the same instrument and the target surface, the errors of the vibrations due to micro seismicity and other environmental causes have been evaluated. Finally, two preliminary examples of measurement on a building structure are presented.