Measurements of the Colosseum response to environmental actions

The Colosseum is the most famous monument of ancient Rome. Differential settlements of its foundations, standing partly on alluvial deposits and partly on stiff soil, and various earthquakes are the main causes of collapses that give the Colosseum its present shape. In order to preserve the monument a number of structural interventions were made during the 19th century. At present, the health status of the monument requires to be monitored against possible degradation phenomena. During the preliminary design stage of a new underground line crossing the center of Rome, at present under construction, further investigations on materials properties and dynamic features have been performed. In particular, twelve accelerometers on two vertical lines in the highest portion of the monument have been installed. In the present paper data gathered with this monitoring system for a long period of time gives the opportunity of a further insight into the health conditions of the structure. The vibration levels induced by road traffic during a long interval of time and frequencies and mode shapes of low modes are identified using ambient vibration. Both these results are compared with the outcomes of an experimental campaign of a few years ago. Finally, the dynamic behaviour recorded during the 2016 Central Italy seismic sequence is analysed and discussed.