ENHANCED CONTINUOUS DYNAMIC MONITORING OF A COMPLEX MONUMENTAL PALACE THROUGH A LARGER SENSOR NETWORK

After recent seismic events in Italy (Umbria-Marche 1997, L’Aquila 2009, Emilia 2012, Central Italy seismic sequence 2016), there has been a growing scientific interest on the preventive conservation of historic monumental buildings. In this regards, vibration-based low-cost and non-destructive Structural Health Monitoring (SHM) systems provide very useful information on the structural behavior. This information includes both global and local mechanisms and results in more accurate seismic assessments and effective retrofits, also allowing detection of small structural damages developing after far-field earthquakes. This paper presents the ongoing research activities regarding the SHM of the Consoli Palace in Gubbio, Italy. A simple and low-cost mixed static-dynamic long-term SHM system has been active since July 2017 with the main purpose of detecting damage-induced anomalies in the time series of the amplitudes of the two major cracks existing in the building and the variation of natural frequencies of global and local vibration modes. The system comprised two crack meters, two temperature sensors and three high sensitivity accelerometers, the latter finalized at the continuous modal identification and modal tracking of the building for damage detection purposes through statistical process control tools. Recently, the SHM system has been integrated with additional sensors, and now comprises 12 accelerometers on three levels of the palace that allow a more detailed detection of the possible vibration modes’ variations, 4 crack meters to monitor the openings of two additional cracks and 4 thermocouples to more accurately remove thermal effects by accounting for the effects of the different solar radiation on the buildings’ façades. The paper presents preliminary considerations about the first results of the new larger sensor network, including (i) a discussion on the role of an enriched identification of the mode shapes, (ii) a preliminary assessment of environmental effects on modal properties of the structure, both the natural frequencies and mode shapes, and (iii) considerations on the removal of such environmental effects and damage detection based on novelty analysis. The differences between previous and new results and the advantages of the adoption of a larger sensor network are highlighted.