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Three inclined historical masonry towers, located in the city of Ferrara (North-East region of Italy), are analyzed under seismic loads employing advanced numerical models. This study provides a critical review on the conservation state, present vulnerabilities, influence of peculiar structural features, and future need for strengthening interventions. Three scenarios were performed, mimicking the seismic severity of earthquakes for three different return periods: 50y, 200y, and 500y. The mechanical properties adopted for the models were extracted by tuning the dynamic response of the models with ambient vibrations test results. A concrete damage plasticity material, with a simplified multilinear softening in both tension and compression, is here adopted. Three parameters are investigated for an insight into the seismic performance estimation: (i) the damage pattern, (ii) the dissipated plastic energy, and (iii) the top displacement. Nonlinear dynamics simulations show the dissemination of structural damages for relatively low magnitude of ground acceleration, where clear failure mechanisms are prone to be activated. The present case studies exhibit unsymmetrical failure mechanisms due to the geometrical features, favoring the crack propagation in in-tension sidewalls, or stability loss of compressed walls. From a preliminary estimation of their seismic vulnerability, it is deduced that a relatively high risk is still present. [ABSTRACT FROM AUTHOR]

The paper presents some numerical results on a Romanesque masonry church located in Emilia-Romagna (Italy), a region recently stricken by a devastating seismic sequence on 20 th - 29 th May 2012. A full investigation of the damages and their comparison with advanced FE analyses, in both linear and nonlinear range are carried out. FE limit analyses are performed through non-commercial software proposed by one of the authors. A remarkable consistency is found among limit analysis results, real performance of the structure under seismic excitation and advanced nonlinear dynamic analyses. In particular, both damage patterns and active failure mechanisms found numerically are consistent with that observed on the church after the seismic event. The results put in evidence the insufficient strength of the apse for combined shear/bending actions, the columns of the central nave for bending, as well as the façade for overturning of the upper part. A seismic upgrading by means of CFRPs composite materials is proposed, designed and analysed quantitatively using FEs, finding an optimal fit between the required performance and the invasivity reduction. The interaction between CFRP strips and masonry substrate is accounted for assuming the behaviour of the reinforcement in agreement with Italian Guidelines for r.c./masonry strengthening with composite materials (CNR DT200). It is found that, with a targeted design, it is possible to prevent premature collapses of the macro-elements, strongly increasing the load carrying capacity of the structure. [ABSTRACT FROM AUTHOR]