The Ghirlandina Tower in Modena: an example of dynamic identification.

Within the context of the restoration principles, that claims for preserving the whole integrity of the monument, it should be well accepted that we have not to rush in deciding the stabilizing measures until the behavior of the monument is properly understood. This requires a long term monitoring aimed at identifying the causes of movements, their po-tential increase in rate and requires to distinguish the normal physiological behavior from de-viations. In addition, these observations can be complemented with experimental identification analy-ses, performed in the presence of ambient vibration, that allow to explore in a rather effective way the response of the structure and its interaction with the soil. This chapter is intended to contribute on the subject of preservation of historic towers by high-lighting, throughout the well documented case history of the Ghirlandina tower, the role of continuous dynamic monitoring and identification techniques for an accurate assessment of the response of the structure, including its interaction with the foundation soil.