Structural assessment of the tower of the University of Coimbra by modal identification

The University of Coimbra was founded in 1290. Erected between 1728 and 1733, the present Tower of the University is not only the symbol of the university, but the symbol of the city itself. A recent inspection of the tower, conducted to prepare restoration works, revealed some structural anomalies, including degradation of joints and cracking of stone blocks. In this paper we describe a study undertaken to assess rapidly the structural integrity of the tower, in order to minimize the delay of the previously planned non-structural intervention. A finite element model of the tower was built with ADINA software and calibrated with measured data obtained from ambient vibration, namely the mode shapes and the natural frequencies. Results point toward the probable non existence of structural problems. It was concluded that modal identification is a fast and reliable technique that can be used in-situ to establish the structural assessment of this type of construction.