Main frequency of slender masonry towers by semi-empirical formulations

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.