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Monitoring an iconic heritage structure with OMA: the Main Spire of the Milan Cathedral

  • Ruccolo, Antonello (Department of Architecture, Built Environment and Construction Engineering (DABC), Politecnico di Milano) ;
  • Gentile, Carmelo (Department of Architecture, Built Environment and Construction Engineering (DABC), Politecnico di Milano) ;
  • Canali, Francesco (Veneranda Fabbrica del Duomo di Milano)
  • Received : 2020.07.06
  • Accepted : 2020.11.04
  • Published : 2021.02.25
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Abstract

One of the most remarkable structural elements characterizing the Milan Cathedral is its Main Spire, built in Candoglia marble and completed in 1769. The Main Spire, reaching the height of about 108 m and supporting the statue of the Virgin Mary, is about 40 m high and stands on the octagonal tiburio erected around the main dome. The structural arrangement of the spire includes a central column which is connected through a spiral staircase to 8 perimeter columns and each column is stiffened by inverse flying buttress. Metallic clamps and dowels connect the marble blocks and metallic rods connect the perimeter columns to the central core. A large monitoring system was recently installed in the Milan Cathedral, including seismometers and temperature sensors at 3 levels of the Main Spire as well as a weather station at the top of the spire. After a concise historic background on the Main Spire and the description of the sensing devices installed in this structure, the paper focuses on the dynamic characteristics of the spire and their evolution during a time span of about 16 months. The presented results highlight that: (a) a high density of vibration modes is automatically detected in the frequency range 1.0-7.0 Hz; (b) the lower identified modes correspond to global modes of the cathedral; (c) the normal evolution in time of the resonant frequencies is characterized by clear fluctuations induced by the environmental effects (temperature and wind); (d) especially the dependence of resonant frequencies on temperature is very distinctive and reveals the key role of the metallic elements in the overall dynamic behavior; (e) notwithstanding the remarkable effects exerted by the changing environment on the resonant frequencies, output-only removal of environmental effects and novelty analysis allow an effective monitoring of the structural condition.

Keywords

Acknowledgement

The support of Veneranda Fabbrica del Duomo di Milano is gratefully acknowledged. The authors would like to thank the technical staff of AGISCO and Veneranda Fabbrica del Duomo di Milano for the installation of all monitoring devices, and the technical staff of SARA Electronics Instruments for the assistance during the mounting and the initial operational setting of the seismometers.

References

  1. Azzara, R.M., De Roeck, G., Girardi, M., Padovani, C., Pellegrini, D. and Reynders, E. (2018), "The influence of environmental parameters on the dynamic behaviour of the San Frediano bell tower in Lucca", Eng. Struct., 156, 175-187. https://doi.org/10.1016/j.engstruct.2017.10.045
  2. Cabboi, A. (2013), "Automatic operational modal analysis: challenges and application to historic structures and infrastructures", Ph.D. Thesis, University of Cagliari, Italy.
  3. Cabboi, A., Magalhaes, F., Gentile, C. and Cunha, A. (2017a), "Automated modal identification and tracking: application to an iron arch bridge", Struct. Control Health Monitor., 24(1), e1854. https://doi.org/10.1002/stc.1854.
  4. Cabboi, A., Gentile, C. and Saisi, A. (2017b), "From continuous vibration monitoring to FEM-based damage assessment: application on a stone-masonry tower", Constr. Build. Mater., 156, 252-265. https://doi.org/10.1016/j.conbuildmat.2017.08.160
  5. Cigada, A., Scaccabarozzi, M., Zappa, E. and Castiglione, B.M.V. (2020), "Critical measurement issues in the use of wire potentiometers for the structural health monitoring of slender structures: the case of the Duomo di Milano main spire", J. Civil Struct. Health Monitor., 10(1), 119-134. https://doi.org/10.1007/s13349-019-00373-4
  6. Deraemaeker, A., Reynders, E., De Roeck, G. and Kullaa, J. (2008), "Vibration-based structural health monitoring using output-only measurements under changing environment", Mech. Syst. Signal Pr., 22, 34-56. https://doi.org/10.1016/j.ymssp.2007.07.004
  7. Diaferio, M., Foti, D. and Potenza, F. (2018), "Prediction of the fundamental frequencies and modal shapes of historic masonry towers by empirical equations based on experimental data", Eng. Struct., 156, 433-442. https://doi.org/10.1016/j.engstruct.2017.11.061
  8. Elyamani, A., Caselles, O., Roca, P. and Clapes, J. (2017), "Dynamic investigation of a large historical cathedral", Struct. Control Health., 24(3), e1885. https://doi.org/10.1002/stc.1885
  9. Ferrari da Passano, C. (1973), Storia della Veneranda Fabbrica del Duomo (in Italian), Cassa di Risparmio delle Province Lombarde, Milan, Italy.
  10. Gentile, C., Guidobaldi, M. and Saisi, A. (2016), "One-year dynamic monitoring of a historic tower: damage detection under changing environment", Meccanica, 51(11), 2873-2889. https://doi.org/10.1007/s11012-016-0482-3
  11. Gentile, C., Ruccolo, A. and Canali, F. (2019), "Long-term monitoring for the condition-based structural maintenance of the Milan Cathedral", Constr. Build. Mater., 228, 117101. https://doi.org/10.1016/j.conbuildmat.2019.117101
  12. Heylen, W., Lammens, S. and Sas, P. (2007), Modal Analysis: Theory and Testing, KU Leuven, Belgium.
  13. Jolliffe, I.T. (2002), Principal Component Analysis, Springer, New York, USA.
  14. Kita, A., Cavalagli, N. and Ubertini, F. (2019), "Temperature effects on static and dynamic behavior of Consoli Palace in Gubbio, Italy", Mech. Syst. Signal Pr., 120, 180-202. https://doi.org/10.1016/j.ymssp.2018.10.021
  15. Magalhaes, F. (2010), "Operational modal analysis for testing and monitoring of bridges and special structures", Ph.D. Thesis, Faculty of Engineering of the University of Porto, Portugal.
  16. Masciotta, M.G., Roque, J.C.A., Ramos, L.F. and Lourenco, P.B. (2016), "A multidisciplinary approach to assess the health state of heritage structures: The case study of the church of Monastery of Jeronimos in Lisbon", Constr. Build. Mater., 116, 169-187. https://doi.org/10.1016/j.conbuildmat.2016.04.146
  17. Masciotta, M.G., Ramos, L.F. and Lourenco, P.B. (2017), "The importance of structural monitoring as a diagnosis and control tool in the restoration process of heritage structures: A case study in Portugal", J. Cultural Heritage, 27, 36-47. https://doi.org/10.1016/j.culher.2017.04.003
  18. Montgomery, D.C. (1997), Introduction to Statistical Quality Control, John Wiley & Sons, New York, USA.
  19. Nava, A. (1848), Relazione dei ristauri intrapresi alla Gran Guglia del Duomo di Milano, Tipografia Valentini & C, Milan, Italy. [In Italian]
  20. Pappa, R.S., Elliott, K.B. and Schenk, A. (1992), A Consistentmode indicator for the eigensystem realization algorithm, NASA Technical Memorandum 107607, NASA Langley Research Center, Hampton, USA.
  21. Peeters, B. and De Roeck, G. (1999), "Reference-based stochastic subspace identification for output-only modal analysis", Mech. Syst. Signal Pr., 13(6), 855-878. https://doi.org/10.1006/mssp.1999.1249
  22. Potenza, F., Federici, F., Lepidi, M., Gattulli, V., Graziosi, F. and Colarieti, A. (2015), "Long-term structural monitoring of the damaged Basilica S. Maria di Collemaggio through a low-cost wireless sensor network", J. Civil Struct. Health Monitor., 5(5), 655-676. https://doi.org/10.1007/s13349-015-0146-3
  23. Reynders, E., Houbrechts, J. and De Roeck, G. (2012), "Fully automated (operational) modal analysis", Mech. Syst. Signal Pr., 29, 228-250, https://doi.org/10.1016/j.ymssp.2012.01.007
  24. Roselli, I., Malena, M., Mongelli, M., Cavalagli, N., Gioffre, M., De Canio, G. and de Felice, G. (2018), "Health assessment and ambient vibration testing of the Ponte delle Torri of Spoleto during the 2016-2017 Central Italy seismic sequence", J. Civil Struct. Health Monitor., 8(2), 199-216. https://doi.org/10.1007/s13349-018-0268-5
  25. Ubertini, F., Cavalagli, N., Kita, A. and Comanducci, G. (2018), "Assessment of a monumental masonry bell-tower after 2016 Central Italy seismic sequence by long-term SHM", B. Earthq. Eng., 16(2), 775-801. https://doi.org/10.1007/s10518-017-0222-7
  26. Veneranda Fabbrica del Duomo (1885), Annali della Fabbrica del Duomo di Milano: Dall'origine fino al presente (in Italian), Veneranda Fabbrica del Duomo, Milan, Italy.
  27. Vicentini, G. (1906), Il pendolo registratore dei movimenti dell'aguglia maggiore del Duomo di Milano (in Italian), Hoepli, Milan, Italy.
  28. Zacchi, A. (1941), "Private communication", Archives of Veneranda Fabbrica del Duomo, Milan, Italy. [In Italian]
  29. Zonno, G., Aguilar, R., Borosheck, R. and Lourenco, P.B. (2019), "Analysis of the long and short-term effects of temperature and humidity on the structural properties of adobe buildings using continuous monitoring", Eng. Struct., 196, 109299. https://doi.org/10.1016/j.engstruct.2019.109299