ANALYTICAL FORMULATIONS FOR THE NONLINEAR DYNAMIC BEHAVIOUR OF MINARETS

Among the different typologies of historical and religious buildings across the world, bell-towers and minarets can be considered an autonomous structural type, characterized by similar constructive materials, namely stone or brick masonry, large slenderness ratios, an almost uniform cross-section along their height, structural behaviour independent from neighboring buildings such as churches or mosques. Focusing on minarets, thanks to their structural simplicity and to their considerable slenderness ratios, this contribution extends an existing simple and effective Rigid Beam Model for assessing their dynamic nonlinear behaviour and evaluating potential collapse mechanisms for varying input parameters. The Rigid Beam Model was recently introduced for simulating the dynamic behavior of slender freestanding structures or structural elements, such as masonry columns, cantilever walls, and tall chimneys. In this contribution, such a model is adopted and improved for studying stone masonry minarets by subdividing them into several portions along their height, and each portion is modelled as a rigid beam element with an annular cross-section. The model adopts the hypotheses of small displacements and no-sliding at the interfaces between the beam elements, following the typical assumptions taken by Housner. Material nonlinearity is considered by means of a moment-rotation constitutive law at interface level, which takes into account structural stiffness and potential material tensile strength. Several numerical tests are performed in terms of harmonic ground motions with varying acceleration and frequency, by considering several existing case studies taken from the literature, also in order to compare the results of the proposed procedure with existing results obtained with traditional discrete and finite element models.