Gianni Bartoli1, Michele Betti1, Antonino M. Marra1 and Silvia Monchetti1
1)  Department of Civil and Environmental Engineering (DICEA), University of Florence
Via di Santa Marta 3, 50139 Firenze, Italy

Keywords: Historic masonry towers, Dynamic identification, Experimental frequencies, Database,
Semi-empirical formulations.

Abstract. The paper is focused on the analysis of the outcomes of some experimental tests carried out in San Gimignano (Siena, Italy), aimed at measuring the natural frequencies of  the medieval masonry towers still present in the historic city centre. The information on the investigated towers were inserted into a wider database collecting dynamic, mechanical and geometrical features of masonry towers. A large amount of data was collected from a literature review, then summing up as many as 48 different case studies. Collected data was then used to identify the main physical parameters influencing the dynamic behaviour of slender masonry towers, and to critically evaluate the existing empirical formulations proposed for the estimation of the first natural frequency of such structural typology. Correlations between fundamental frequencies, geometric characteristics and mechanical parameters are discussed, and a novel semi-empirical formulation is eventually proposed for a reliable prediction of the main frequency of slender masonry towers.