Microclimatic monitoring of the Duomo (Milan Cathedral): Risks-based analysis for the conservation of its cultural heritage

Abstract

Typically, the structure of old monumental buildings differs significantly from that of contemporary ones. The massive walls, large indoor air volume and the small windows, compared to the opaque portion, drastically affect the microclimates of such constructions. In such buildings is often quite difficult to perform a detailed monitoring campaign of the main microclimatic parameters. In this regard, experimental methodologies and non-invasive equipment, able to minimize the impacts on the building and on its users, should be adopted. This research describes the methodology applied to carry out the monitoring campaign on the Milan Duomo, one of the biggest Cathedrals in Italy. The campaign was carried out by means of non-invasive measuring instruments, in order to keep the building intact and ensure the smooth running of the activities. In a second stage, sensors for the long-term monitoring were installed according to the most significant and accessible points inside the Cathedral. The data collected during one year of monitoring was used to characterize the hygrothermal behaviour of the Cathedral, in order to assess the risks for the main materials which sacred objects, artworks, organs, sculptures and furnishing are made of. The future developments of this work are oriented towards the realization of a simulation model aimed at designing and planning proper active or passive solutions to improve the microclimatic conditions for both artwork conservation and the comfort of visitors. COVER LETTERDear Editor, historic buildings have an inestimable cultural and artistic value, and contribute to provide a sense of identity for the cities and their inhabitants. The indoor microclimate of such buildings play a significant role in the conservation of the finishing, the construction elements and the artifacts contained in such spaces. In this respect, the present paper aims to analyze the environmental behavior of the Duomo (Milan Cathedral), through an experimental monitoring using non-invasive measuring instruments, in order to keep the building intact and ensure a negligible interaction with other activities. The characterization of the indoor microclimate is fundamental to evaluate the risks and subsequently ensure the proper conservation conditions for the church's materials. The present study aims to analyze the environmental behavior of the Milan Duomo, one of the most famous masonry monument in Italy, using a methodology to characterize the internal microclimate. The selected case-study is particularly relevant due to its size (i.e. the second largest church in Italy), building typology (huge thermal mass), turnout of visitors and churchgoers (more than 4.000.000/year) and presence of different materials (e.g. marble, iron, wood, canvas, etc.). The research work represents the first comprehensive microclimate assessment in the Duomo ever carried out, with the scope to analyse in detail the possible risks for the artefacts and the building itself. The methodology adopted could be used by researchers, specialists...

Long-term monitoring for the condition-based structural maintenance of the Milan Cathedral

“…9b through the minimum, average and maximum value. As expected from previous studies on the microclimatic condition in the Milan Cathedral [19], Fig. 9b highlights a very limited temperature gradient in space, with the range between the extreme values not exceeding 0.5°C.…”

“…Since both the long-term static behaviour and the time evolution of dynamic signatures are expected to be sensitive also to factors other than structural changes [10] and especially the temperature might affect the variation of structural parameters in historic masonry structures (see e.g. [11][12][13][14][15][16][17][18]), the indoor and outdoor environmental parameters (temperature and relative humidity) are extensively measured with the two-fold objective of establishing correlations with the structural parameters changes [11][12][13][14][15][16][17][18] and evaluating the risks for the preservation of the many artifacts present in the Cathedral [19].…”

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

“…11b. As expected from previous studies on the microclimatic condition in the Milan Cathedral [11] and notwithstanding the large dimensions of the church, Fig. 11b highlights a very limited temperature gradient in space, with the range between the extreme values not exceeding 0.5°C.…”

“…11b). Figure 12 shows the minimum and maximum value of the relative humidity measured inside the Milan Cathedral along with the average relative humidity: as expected [11], also the humidity time series are highly correlated, with the correlation coefficients being of the order of 0.90 or larger. Figure 13 shows the time variation of the automatically identified resonant frequencies of the Milan Cathedral from 16/10/2018 to 12/02/2019, whereas the statistical characterization of modal frequencies is summarized in Table 1.…”

“…The designed monitoring system includes a relatively large number of sensors for measuring both static (15 bi-axial tilt-meters and 12 vibrating wire extensometers) and dynamic parameters (36 uni-axial seismometers). In addition, the indoor and outdoor environmental conditions (temperature and humidity) are extensively monitored with the two-fold objective of evaluating the risks for the conservation of the main artifacts present in the Cathedral [11] and establishing correlations with the structural parameters changes. The importance of the latter aspect for historic masonry structures has been shown in the long-term monitoring of towers [12][13], churches [14][15], cathedrals [16] and monumental buildings [17]: all those studies have highlighted that resonant frequencies [11][12][13][14][15][16][17], as well as static structural parameters [14][15]17], are significantly affected by changes in the environmental conditions.…”