Numerical models for simulating the dynamic behaviour of freestanding ancient columns

In this contribution, three numerical models are considered and compared, with the main purpose of simulating the dynamic behavior of monolithic and multi-drum freestanding ancient stone columns. The behavior of such classical and historic structural elements, typical of the Mediterranean area and that are frequently subject to seismic actions, is characterized by a strong nonlinearity due to sliding and rocking. A simple and effective rigid beam model, able to numerically solve the equations of motion of the column also accounting for Housner’s hypotheses, is introduced for first and validated with respect to a software based on the Discrete Element Method (DEM), which has already proven its effectiveness in representing the behavior of columns and, more generally, masonry structures. Furthermore, a rigid block model accounting for the nonlinear behaviour of the interfaces between the blocks is considered. On one hand, the rigid models can represent columns behaviour with a not significant computational effort; on the other hand, the DEM is able to better describe the strong nonlinearity of columns behavior, with the detection of new contacts and the results in terms of collapse mechanisms characterized by large displacements that may be experienced by the blocks during the dynamic excitations. In this contribution several preliminary comparisons between the models are carried on by considering a multi-drum column and an equivalent monolithic one subject to a set of harmonic excitations with varying input frequency and acceleration amplitude.