Continuous monitoring of the Milan Cathedral: dynamic characteristics and vibration-based SHM

Abstract

The traditional collaboration between Politecnico di Milano and Veneranda Fabbrica del Duomo di Milano  the historic Institution established by Gian Galeazzo Visconti in 1387 and having in charge all operational aspects related to the Milan Cathedral since more than 600 years  recently focused on the design and installation of a structural monitoring system, with the objective of assisting the condition-based structural maintenance of the historic church through the continuous interrogation of sensors installed in the structure and the extraction from measured data of features which are representative of the current state of structural health. The new monitoring system of the Milan Cathedral includes different types of measurements and sensors: quasi-static acquisition of strain in selected tie-rods and biaxial tilt of selected piers and the main spire, monitoring of inner and outer environmental parameters and dynamic measurement of the velocity response at the top of 14 piers and at 3 levels of the main spire. After a concise description of the historic church and of the monitoring system, the paper focuses on the dynamic characteristics of the Milan Cathedral, their evolution during the first months of monitoring (since October 16th, 2018) and the lessons learned in view of the Structural Health Monitoring of the monument. The presented results from the vibration monitoring highlight that: (a) 8 global modes of vibration are automatically detected in the frequency range 1.0-5.0 Hz; (b) the resonant frequencies exhibit a distinctive trend of variation, which is mainly driven by temperature; (c) the mode shapes of the Cathedral do not show appreciable fluctuations associated to the environmental effects.

Long-Term Dynamic Monitoring of Medieval Masonry Towers

“…In fact, as pointed out in the previous sections, several longterm ambient vibrations campaigns have demonstrated that the natural frequencies of monumental masonry buildings are influenced by environmental factors such as temperature, humidity, etc. (Ramos et al, 2010;Saisi et al, 2015;Gentile et al, 2016Gentile et al, , 2019Ubertini et al, 2016Ubertini et al, , 2017Baraccani et al, 2017;Masciotta et al, 2017;Tsogka et al, 2017;Barsocchi et al, 2019). In particular, for masonry towers the amplitudes of natural frequencies are increasing functions of temperature, and for the structures monitored in Saisi et al (2015) and Azzara et al (2018) their relative yearly differences are on the order of 5%.…”

Structural Monitoring in the “Santa Maria de la Asunción” Cathedral of Chilpancingo, Guerrero, Mexico; through Topogeodesic-Photogrammetric Surveying and Ambient Vibration. A Methodological Proposal

“…Another structure with a static and dynamic monitoring system is the Milan Cathedral [13]. The structure was built from 1386 to 1765, and it is a mix of Gothic style and regional Lombardy style, where also neo-classic, neo-gothic.…”

First Results of Long-Term Monitoring of Portico Varano in the Camerino Ducal Palace (Italy)

“…[6]. Examples of recent structural monitoring studies in the Italian architectural heritage include: the Consoli Palace in Gubbio [7], the church of Santa Maria in Collemaggio in L'Aquila [8], the San Pietro belltower in Perugia [9], the Milan Cathedral [10], the San Vittore bell-tower in Arcisate [11], and the Rubbianello Bridge [12]. This paper adds to the above list and presents the first results from a structural monitoring system installed in the quadriporticus of the Ducal Palace in Camerino, within the field activities planned in the European research project named ARCH (Advancing resilience of historic areas against climate-related and other hazards -https://savingculturalheritage.eu/) funded in the Horizon 2020 framework for the years 2019-2022.…”