Earthquake vulnerability of ancient multi-drum columns with a single epistyle

In this research work the seismic behaviour of structures with multi-drum columns under a single epistyle is investigated. In particular, the Discrete Element Method (DEM) is applied in the study of ancient columns undergoing strong ground excitations, by simulating the individual rock blocks as distinct bodies. A specialized software application is developed and utilized, using a modern object-oriented programming language, in order to enable the effective simulation of multi-drum columns and colonnades. Parametric studies are implemented in order to investigate the effect of excitation characteristics on the behaviour of multi-drum columns under earthquake excitations. The analysis results indicate that the frequency and peak ground acceleration of an excitation, significantly affect the d ynamic response of the columns. Particularly, for low frequency ground excitations, the exhibited response is dominated by rocking, while sliding prevails in cases of excitations with very high predominant frequencies. In between the two extremes, the response contains both rocking and sliding phenomena. Furthermore, according to the conducted simulations the acceleration that is needed to overturn multi-drum columns with a single epistyle also increases as the frequency increases. By examining the stability of multi-drum colonnades with a single epistyle under earthquake excitations that were selected from regions where these monuments are often found, such as the Eastern Mediterranean region, the simulations reveal that the columns have the capacity to withstand strong earthquakes without collapse. In addition, the epistyle seems to be the most vulnerable to failure part of the structure under these loads. Finally, the required acceleration to overturn such a system with a single epistyle seems to decrease as the predominant frequency of the earthquake decreases.