Dynamic identification of a masonry façade from seismic response data based on an elementary Ordinary Least Squares approach

A low magnitude seismic response of a historical masonry structure, the Santa Maria di Collemaggio basilica, was acquired by a complex monitoring system. Ten FBA accelerometers, nine placed on the basilica facade and one on the ground level, recorded respectively the base accelerogram (Input) and the structural response (Output). By means of an elementary form of dynamic identification, based on an Ordinary Least Square operator (OLS), it has been attempted to identify the dynamic properties of the facade during the seismic event. The results, in terms of mode shapes, natural frequencies and damping factors, identified by the proposed Input-Output method, are compared with the ones identified under operational conditions. Despite the low intensity earthquake, the assumed linearity of the response has been investigated from further analysis on the acquired data.