Dynamic Behaviour of the San Felice Sul Panaro Fortress: Experimental Tests and Model Updating

Abstract

Abstract. This paper describes the experimental tests and numerical analyses performed to characterize the dynamic behaviour of the principal tower of the San Felice sul Panaro Fortress (Modena, Italy). After the Emilia earthquake that occurred in 2012, the Fortress reported serious damage, such as severe cracks on the walls and collapses of several towers and the roof. As a part of a research that aims at evaluating the vulnerability of the Fortress and designing retrofitting interventions, full-scale ambient vibration tests were performed to evaluate the dynamic properties of the principal tower. Afterwards, a Finite Element (FE) model is calibrated to obtain a good match between the numerical and experimental modal properties. The optimization process is carried out through an improved surrogate-assisted evolutionary strategy. Due to the serious damage of the Fortress, the effective stiffness of the cracked masonry and the efficiency of connection at the interface between the principal tower and the rest of the Fortress are considered the main uncertain quantities to be calibrated. A multi-objective optimization is performed, considering the frequency and mode shape residuals. These are defined as the difference between experimental and numerical modal properties. The multi-objective optimization is reduced to a series of a single-objective optimization adopting the weighted sum method. The set of optimal solutions that form the Pareto front is obtained performing the optimization for different values of the weighting factors. Then, two criteria are used and compared in order to find the preferred solution among the Pareto front solutions. Finally, a comparison of the identified structural parameters obtained varying the weighting factors for natural frequencies and mode shapes in the optimization process is presented, highlighting the importance of a proper choice of the weighting factors.

Ambient vibration-based finite element model updating of an earthquake-damaged masonry tower

“…In Forghieri et al, the influence of the weighting factor α on the identified structural parameters is investigated evaluating the optimal solutions forming the Pareto front. Adopting two different selection criteria, an optimal value of α equal to 0.4 is obtained, although results are observed to be similar for α in the range [0.1–0.8].…”

“…They rely on the identification of structural dynamic characteristics from output‐only records using operational modal analysis (OMA) techniques . The vibration‐based structural assessment includes full‐scale ambient vibration testing, modal identification from ambient vibration response, and FE modelling and identification of the uncertain structural parameters of the model . Results from AVT allow to define reliable FE models to be used for the seismic assessment of historical constructions (see, for instance, D'Ambrisi et al).…”