Non-destructive characterization of stone columns by dynamic test. Application to the lower colonnade of the Dome of the Siena Cathedral

The paper describes the in-situ non-destructive dynamic tests performed on a lower colonnade of the Dome of the Siena Cathedral (Italy). Tests were aimed at both measuring the fundamental natural frequency of stone columns and identifying their boundary conditions (pinned or clamped). Eight columns were dynamically investigated four times under subsequent impulsive loads (hammer impact test) for a total number of 32 dynamic tests. These tests were a part of a larger experimental campaign aimed to assess the actual static behaviour and the seismic vulnerability of the whole Cathedral. In the paper the tests on the stone columns are described at first; secondly the main results, together with the techniques adopted for the signal analysis, are reported in detail. The results of several parametric numerical analyses are also discussed and eventually the use and limitations of the obtained results are critically discussed.