Ambient vibrations-supported seismic assessment of the Saint Lawrence Cathedral’s bell tower in Genoa, Italy

Abstract

Post-earthquake damage surveys systematically highlight the seismic vulnerability of monumental structures, calling for simple assessment procedures to address the design of effective retrofitting interventions. The structural complexity characterizing monumental structures, however, makes a reliable prediction of their seismic response a relevant challenge of engineering interest. Ambient vibration tests (AVTs) provide valuable support to achieve such a task, improving the knowledge of the actual dynamic behavior of the structure and, consequently, the reliability of the seismic assessment. In this context, the paper illustrates the integration of AVTs outcomes with the evaluation of the seismic performance of historic masonry structures by presenting the comprehensive application to a case study, the bell tower of the Saint Lawrence’s Cathedral in Genoa, Italy. The research combines the assessment of the global seismic response of the tower, investigated through a simplified mechanical model, with the local verification of the pinnacles placed at its top, referring to a displacement-based approach on a macro-block model. An extensive ambient vibrations measurement campaign carried out in May 2020 allowed for a comprehensive operational identification of the bell tower and its pinnacles, clarifying the ongoing dynamic interaction with the main body of the church. This valuable information was successfully employed, first, to accurately reproduce the actual constraint conditions induced by the church on the bell tower, a determining factor in the modeling of its global seismic response and, second, to reliably quantify the seismic amplification caused by the tower filtering effect to be used as the seismic input for the local verification of the pinnacles.

Historic Building Information Modeling for Conservation and Maintenance: San Niccolo’s Tower Gate, Florence

“…Another non-invasive investigation tool employed was dynamic identification testing [29]. This is a highly significant activity that provides crucial information about the dynamic behavior of the structure in the presence of ambient vibrations, including frequencies and modal shapes.…”

“…During the restoration in the 1930s, th facade reintroduced corbels to support a projecting walkway with machicolations (over hanging a total of 1.5 m), and merlons were reconstructed with a thickness of 45 cm alon the entire perimeter of the top of tower.To understand its genesis, composition, and functioning, an intensive knowledg path was undertaken, as stipulated by the relevant Italian regulations[1], calibrated fo assessing the structural performance of the construction. Given its historical nature, th use of new technologies and indirect investigative tools proved essential to preserve th structure from further detrimental interventions on materials.Another non-invasive investigation tool employed was dynamic identification test ing[29]. This is a highly significant activity that provides crucial information about th…”

An Equivalent Frame Digital Twin for the Seismic Monitoring of Historic Structures: A Case Study on the Consoli Palace in Gubbio, Italy

“…On the one hand, these issues encourage the research community in integrating experimental data and mechanical models [13] towards the development of DT of historical masonry structures [14,15]. On the other hand, the computational burden of structural simulations is a limiting factor in employing physically based structural models as DT of historical buildings, particularly when dealing with almost real-time SHM.…”