PSI - Issue 78

Franco Braga et al. / Procedia Structural Integrity 78 (2026) 2184–2191

2188

• GB 50011-2010 (Ministry of Constr uction; 2010): in the “National Standard of the People’s Republic of China - Code for Seismic Design of Buildings” the “near field” effects have to be considered for structures less than 10km away from active faults. For structures less than 5 km away, the effects are taken into account by amplifying the vertical and horizontal seismic actions by a factor of 1.5, while for buildings located between 5 and 10 km from the fault the same factor is reduced to a value of not less than 1.25; • New Zealand NZS 1170 – part 5 and commentary (NZS, 2004): Near-fault factor (NZS, 2004, Clause 3.1.6, C3.1.6): it is the code that in a more analytical and detailed manner deals with the definition of actions for “near - fault” earthquakes. In particular, the commentary drawn up in support of this legislation highlights how in the event of a "near-fault" earthquake, in the "low period" range, the intensity of the vertical spectrum can equal or even exceed that of the horizontal spectra. On the other hand, it is essential to point out that, in the definition of the seismic action of the project, both the European and the Italian codes do not make any reference to the distance between the source of the expected earthquake and the site where the structure in stands, ignoring, in fact, the “near fault” earthquakes. European seismic code (UNI EN 1998-1) only indicates that "different (elastic response) spectra (from those proposed) can be defined in the national annex, if we take into account the deep geology". The NTC18 do not refer to the aforementioned distance when speaking of elastic response spectra, while, dealing with the possible use of time histories of the ground motion generated by simulating the source mechanism and propagation, they provide extremely reduced prescriptions. As for the characterization of the vertical component of the design acceleration, UNI EN 1998-1 invites to consider response spectra obtained by scaling those relating to the horizontal components through the spectral ratio V / H, constant in any interval of the periods, assumption, as seen , absolutely unjustified for shallow earthquakes. The NTC18 provide an approach similar to that proposed by UNI EN 1998-1, and therefore show the same limits when referring to shallow earthquakes. 4. The structures of the building The masonry building in question was built in the 1950s, following a typical construction configuration of the period. During the 2009 L'Aquila earthquake, it suffered damage, which was repaired through local interventions carried out that same year. 4.1. Finite Element Model (FEM)

Fig. 6:FEMmodel – axonometric view from S-E

To analyse the seismic behavior of the building, a finite element numerical model was implemented using the SAP2000 calculation code produced by CSI Inc. of Berkeley, California (U.S.), and linear dynamic analyses with response spectrum were performed. The modeling was performed using 2-node "frame" elements with 6 degrees of freedom per node for the resisting members (masonry piers and floor spandrels), according to the SAM (Simplified Analysis of Masonry Buildings) method.