Seismic assessment is a paramount issue and a valuable instrument towards the conservation of vulnerable structures in seismic prone regions. The past seismic events have highlighted the vulnerability of masonry towers that is exhibited by severe structural and nonstructural damages or even collapses. The preservation of existing structures, mainly focused on the built heritage, is emerging and imposing substantial enhancements of numerical methods, including pushover analysis approaches. The accuracy of the estimated seismic capacity for these structures is correlated with the assumed strategies and approximations made during the numerical modeling. The present paper concerns those aspects by exploring the limitations and possibilities of conceiving pushover analysis in the finite element method environment. The most crucial target is tracing in a pushover capacity curve the corresponding initiation of structural damages, maximum load-bearing capacity, and the ultimate displacement capacity. Different recommendations for achieving this target have been proposed and illustrated for practical utilization. Three representative geometrical towers, adopting three different materials and five different load patterns, are investigated in this study. The load pattern’s role and necessity of the displacement-like control approach for the pushover analysis are exploited. This paper highlights the load-bearing capacity overestimation when the force-controlled are implemented. The material model influences the achievement of softening branch with a distinguishable displacement capacity.

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.

Two earthquakes struck the NW region of Albanian territory on 21 September 2019 (M_w = 5.6) and on 26 November 2019 (M_w = 6.4). The epicenters of the seismic activity were located offshore NW Durrës, one of Albania’s most populated cities, located 30 km from the capital Tirana. Various aftershocks followed subsequently. While there were no reported injuries, a number of buildings sustained significant damage near the epicenter following the initial event. Subsequently, during the second event, there was loss of life and extensive damage to civilian structures, resulting in multiple collapses. This study focuses on the earthquake damages observed in residential and public buildings in the earthquake-affected region. The earthquakes predominantly affected low-rise masonry buildings, while the newly constructed RC structures built according to the latest seismic rules were almost unaffected. The commonly encountered building typologies in the region, together with photos showing the amount of destruction are presented here. As observed by the authors during the reconnaissance visit to the stricken area, examples of various damage patterns are presented, along with a technically substantiated description of the reasons for those damages. Although modern buildings during recent earthquakes in the region show acceptable performance, the detailed surveys from the Durrës Earthquakes showed that there is still an important level of deficiency in current masonry buildings built by conventional methods and materials. This problem may reoccur in future earthquakes that may hit other rural regions of Albania, which must be focused on systematically in the near future.