Nonlinear analysis of a tall historical masonry tower

This paper deals with the nonlinear modeling and the pushover analysis of the Ghirlandina tower of Modena, aimed at the vulnerability assessment of the structure that represents one of the most important towers in Italy. A 3D finite element model of the structure has been set up, calibrated on the available results of an experimental campaign. The nonlinear behaviour of the masonry has been simulated according to the total strain rotating crack model with elastic-perfect-plastic behaviour in compression and linear softening in tension. The soil-structure interaction has been also modelled through springs and dashpots whose stiffness and damping have been evaluated according to the theory of impedances by Gazetas [1]. The seismic vulnerability assessment of the structure has been carried on by means of pushover analysis, according to the current Italian standards and to predefined collapse criteria. The performed analysis investigated the effect of the soil modelling in the seismic behaviour of the tower and pointed out how the current Italian codes overestimate the dissipative capacity of this kind of structures in terms of excessively high values of the behaviour factor q. Moreover the implementation of the material nonlinearity allowed to evaluate the damage levels and the collapse mechanisms of the structure under seismic actions.