Time evolution of modal parameters identified using WSN data collected by seismic structural monitoring of a monumental church

The paper analyzes the occurrence of dynamic interactions between the nave walls and the tendons inserted as safety measures in the monumental historical structure, the Basilica S. Maria di Collemaggio, which was heavily damaged in the 2009 L'Aquila earthquake. Several information on the dynamic behaviour are obtained using acceleration data collected during long term structural monitoring which has been purposely designed to detect earthquake-induced vibrations through a wireless sensors network. The Wavelet Transform (WT) and the Short-Time Fourier Transform (STFT) are utilized to evidence the variation on time of modal parameters putting into evidence localization of energy in a certain frequency range. Such phenomena are related to the local vibrations of tendons elements used to protect inner and external walls by out-of-plane failure. Acceleration acquired during release tests and seismic events are used to interpret the dynamic behaviour together with the efficacy of the adopted protecting solution. The large data set is used to identify in the time domain parametric model by SSI procedure. The findings contribute to the general development of procedures to provide automated real-time structural assessment for use in seismic zones.