Seismic safety assessment of a masonry building according to Italian Guidelines on Cultural Heritage: simplified mechanical-based approach and pushover analysis

The seismic safety assessment of a case study of a masonry building located in Naples (Italy) was performed together with a critical appraisal of the methods used. Being built before the introduction of proper seismic code provisions, this unreinforced masonry building could be representative of many other vulnerable historic buildings in earthquake-prone urban areas. First, a simplified model of the global seismic response was analyzed according to the LV1 assessment level provided by the Italian Guidelines on Cultural Heritage. The results obtained using old and updated versions of these guidelines were compared. A good agreement was revealed with reference to the detection of the weaker direction and the prevailing failure mechanism, but some differences were found about the calculation of the base shear capacity and the corresponding ground acceleration. Then, the achieved results were compared with those obtained using a more refined approach of nonlinear static analysis according to the LV3 assessment level. The results were reported in terms of damage and collapse mechanisms of masonry walls, pushover curves and seismic safety indexes. A further comparison was carried out between the model with flexible horizontal structures and that with the assumption of all the floor diaphragms as completely rigid. Although the two assessment methods LV1 and LV3 are not alternative to each other, since belonging to two different levels of evaluation, some critical issues were addressed in order to derive useful information on the reliability and the limits of validity of the simplified mechanical model, characterized by a force-based approach