Preliminary OMA Results on a Soft Calcarenite Stone Bell-Tower in Mola di Bari (Italy)

This paper presents the work developed to understand the dynamic behaviour of the bell-tower of Santa Maria di Loreto in Mola di Bari (Italy). An initial geometrical survey has been obtained by traditional techniques. The bell-tower has a total height of 38.3 m, with a 6.3x6.3 m base cross section. The wall thickness is equal to 2.0 m from the base up to the height of 15 m. The tower presents a lateral contact with the main church nave up to 9 m. This massive structure was built in soft calcarenite stone between the XVII and XVIII centuries. It is located on the front sea line. These two characteristics and the effect of seagull’s excrements have produced a disaggregation of the material and important surface damages have been detected. In general, many problems due to the humidity deterioration of materials have been detected on the main nave of the church and it can be affected to the bell-tower foundation. In order to evaluate the vulnerability of the tower a dynamical experimental analysis has been performed. Operational Modal Analysis has been carried out using 10 piezoelectric accelerometers to detect bending and torsional frequencies as well as the damping ratios of the main modes. Registers have been developed under ambient vibrations and with forced vibrations with the swings of the main bell of the tower. The setup of the dynamic tests, the finite element model of the structure and the first results of the dynamical analysis are here discussed.