Non-linear static behaviour of ancient free-standing stone columns

This work investigated the non-linear behaviour of ancient natural stone columns in the Mediterranean region made from multiple blocks or ‘drums’. A two-dimensional custom-made computational model based on the discrete-element method was employed. In the numerical model, the columns were represented as an assemblage of distinct blocks connected together by zero-thickness interfaces, which can open and/or close depending on the magnitude and direction of the stresses applied to them. Through non-linear static analysis, capacity curves and corresponding failure mechanisms of each of the studied models were obtained. The influence of different parameters (the number of drums, geometrical properties and imperfections at columns) was also assessed to observe their influence on the response of drum assemblies. The results of analyses revealed that rigid overturning is the main collapse mechanisms under uniform horizontal forces. A combination of rigid and shear failure mechanisms might also occur, depending on geometric characteristics and the choice of joint material properties. A higher displacement capacity was observed for columns constructed with a larger number of drums. It was also found that imperfections in the ancient free-standing columns have a significant influence on the lateral load resisting capacity. Therefore, structural analysis of undamaged columns may not represent the actual capacity of the columns due to their very sensitive and highly non-linear characteristics.