Dynamic monitoring of Mallorca Cathedral
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Monitoring is a fundamental key in the multi-disciplinary approach based on the scienti c method for the analysis of historical constructions. It is complementary to the historical research, the diagnosis and the structural analysis. More speci cally, the dynamic monitoring is the only way to get useful information (in terms of frequencies and modal shapes) on the global structural behavior of a building to validate a nite element model. According to the modern conservation criteria that require the minimum intervention as possible, dynamic monitoring is a valid instrument to detect the causes of structural problems before the planning of restoration works. In this work, data obtained from a dynamic identi cation campaign and from a new dynamic monitoring system installed in the Cathedral of Mallorca were post-processed and analyzed. This Cathedral is one of the most impressive masterpieces of the Gothic architecture. It has a lot of structural problems as the displacement of the piers, the out of plumb of the main façade and an extended crack pattern that can in uence the dynamic behavior. Natural frequencies and modal shapes were obtained by means of the power spectral density processed with the data obtained from an ambient vibration dynamic identi cation campaign characterized by 15 setups. Between the modes detected with a global and a setup by setup analysis, four of them were particularly clear. Subsequently the gradual change of the frequencies associated to these modes through the time was analyzed and correlated with the variation of the temperatures. A period of 3 months during the winter was initially considered and later other 2 weeks during a warmer period in May were chosen to see eventual di erences. The e ects on the Cathedral of two di erent earthquake detected by the monitoring system were also analyzed.