Marble and heavy stone columns are widely diffused in ancient churches and historical buildings in all the Mediterranean area. Their good mechanical properties allowed carrying great load values, while their bright colours and aesthetical characteristics have been used by a lot of ancient architects to achieve structural solutions with great visual impact.
Despite their good compressive strength, marble columns could be damaged from environmental effects (e.g. long- term effects or thermal loads), which could crack the structural members. In this way, the slenderness of the column increases drastically and the presence of an imposed ground shaking could be critical, since the column will be more vulnerable to rocking motion and to overturning risk.
This paper focuses on the rocking behaviour of cracked granite and marble columns subjected to a pulse type ground shaking. The effect of the presence of circular collars is analysed by means of a mechanical model. The overturning spectra are determined including the presence of the collars, showing their efficiency in reducing the overturning risk. Comparisons are shown with numerical analyses and a simplified design method is proposed.