Dynamic Identification and Model Updating of a Masonry Chimney

The paper presents the results of tests performed on a historical masonry chimney and its damage evaluation. The studied masonry chimney exhibits a clear and well visible crack pattern. To evaluate the safety condition and to design rehabilitation interventions, an extensive non-destructive test campaign is performed. The paper describes the dynamic tests, the identification of the structural modal properties, the calibration of a structural Finite Element (FE) model based on the experimental results and the evaluation of the effect of cracks on its dynamic properties. Modal identification is performed using the so called covariance-driven Stochastic Subspace Identification method (SSI-COV) to estimate natural frequencies, mode shapes and modal damping ratios. Then, the model updating is performed to localize the damage starting from the identified modal properties. Instead of adjusting the stiffness properties for all the elements, a stiffness distribution is determined by means of damage patterns. The results of two damage patterns are compared with those of the undamaged model and with the visual inspection carried out on the structure.