Robust seismic fragility curves for masonry towers and their Bayesian updating using experimental data

The recent seismic events in Italy have underlined the vulnerability of the cultural heritage, whose evaluation has become a crucial point in order to ensure their conservation over the time. However, comprehensive assessment of the seismic vulnerability requires both a reliable numerical model able to capture nonlinear features and an explicit consideration of the different sources of uncertainty. For historic masonry buildings, the unavoidable lack of knowledge on the input parameters (material properties, geometry, boundary conditions, etc.) has a relevant effect on the reliability of the seismic response predictions. As a consequence, experimental measurements are commonly performed to reduce the uncertainty of some structural parameters. In the paper, a methodology that, starting from the Bayesian FE-model updating by using experimental data, allows the definition of robust seismic fragility curves for masonry towers is proposed. The towers of San Gimignano (Italy) were herein considered as an effective case study to test this methodology thanks to the availability of both geometric data and experimental measurements.