Il Battistero di San Giovanni in Pisa

In 2013, the movement of one of the blocks of northwestern arcs triggered the studies presented in this paper. Although the monuments of Piazza dei Miracoli appear, with the exception of the Tower, solid and stable in time, they reveal the need for continuous maintenance and restoring. In the case of the Baptistery of San Giovanni, the 2013 event provided the opportunity to deepen the knowledge of the monument. In order to obtain more information, a series of investigation activities have been initiated. At first, some information about history of construction has been collected. The information were accurate for the period covering the first 50 years of the construction. After this period the information became poor and in some cases not consistent. In addition to historical information, some investigation regarded the masonry of foundation, the subsoil and the geometry of the whole structure. About the foundation, a specially developed drilling machine has been used to obtain information about geometry of foundation (mainly foundation plan depth) and solidity of masonry. The instrumented perforation confirmed the presence of a sort of reclamation stratum as reported in some chronicles of that time. Investigation of geometry, carried out by means of laser scanner, provided a reliable support for further structural studies and provided some additional elements to clarify construction sequence. In fact, one of uncertainties concerns the construction of floor of first gallery. The measurement of difference in level of floor indicates that the construction of floor occurred after the completion of building. A two-year monitoring of structure allowed a better understanding of structure behaviour as a consequence of environmental conditions changing. Thermal effects seem to be dominant and some movements are not reversible. A specially designed instrumented drilling machine has been used for the investigation of the foundations. The instrumented drilling machine provided the definition of geometry of foundation masonry. It is finally outlined a program for the new surveys and measurements.