Issue 51

M. Guadagnuolo et alii, Frattura ed Integrità Strutturale, 51 (2020) 398-409; DOI: 10.3221/IGF-ESIS.51.29 407 Also, in this case the weakest level is the fourth floor in which there is just the 22% of the shear strength of the entire construction. Unlike the previous case, for this type of building, the maximum increase in the safety index (and the related structural improvement) is obtained, for both design approaches, by maximizing both the pier shear strength (If) at all stories in both directions and the failure coefficients of piers and spandrel (Cp, Cs). This is clearly shown in Fig. 11, where the curve representing the gradual increase of the safety index from 0.25 (initial scenario) to 0.52 is obtained by increasing the shear strength by 50% to all levels and assuming a unitary value for all the collapse coefficients Cp and Cs (assumed equal in both the x and y direction). The black points, representative of widespread interventions on the entire building, confirm that in this case the real improvement of the seismic capacity requires a global strengthening intervention on the entire building structure. This type of simplified method is able to identify the weak level of any structure, succeeding in this way to optimize the interventions and to localize them on the weak parts. The interventions aim to increase the compressive and shear strength. Several types of intervention are possible for cultural masonry heritage. There are many strengthening configurations, different in technique and material that achieve the same result and whose geometrical details are difficult to establish in advance. The improvement of the building seismic performances may be achieved using traditional fiber-reinforced composites systems (FRP), suitable as structural reinforcing elements. C ONCLUSIONS his paper deals with some issues concerning the vulnerability assessment of masonry buildings and the optimization of the strengthening interventions to be adopted. The case studies are two stone masonry buildings in the area of Caserta, Southern Italy. Particular attention is paid to simplified assessment methods that require a less thorough knowledge of the structure, leading to results that can be sufficiently reliable. They are of fast application and are particularly suitable for the analysis of large and complex buildings, especially when they are placed in historic centers. The simplified method illustrated allows an optimization of strengthening and has been applied to two buildings representative of a wide number of residential buildings in Caserta: a building in the historic center of Carinola, an area with medium-low seismic hazard, representative of regular buildings made of simple stone, and a second building built in the historic center of Piedimonte Matese, an area of high seismic hazard, highly irregular in its configuration and made with mixed materials of various types. The seismic vulnerability has been assessed using a quantitative method, based on the procedure provided by the Italian guidelines for the assessment and mitigation of seismic risk of cultural heritage. For the first examined building ("Palazzo Petrucci-Novelli"), the analyses show an average vulnerability. In this case the seismic capacity of the building can be improved optimizing the strengthening interventions. In this case, in fact, the adopted iterative procedure allows concentrating interventions only on the structural elements characterized by structural deficiencies, avoiding widespread unnecessary interventions throughout the building (that would not lead to a larger increase in the safety index), and which would therefore be economically unjustifiable. The results obtained for the second building ("Palazzo Ducale") show a high vulnerability. In this case the iterative procedure leads to the same results in terms of increasing the minimum safety index achieved by assuming widespread interventions throughout the building. R EFERENCES [1] De Matteis G., Brando G., Corlito V., Criber E., Guadagnuolo M. (2019). "Seismic vulnerability assessment of churches at regional scale after the 2009 L'Aquila earthquake", Int. J. Masonry Research and Innovation, 4(1-2), pp.174-196. [2] Bergamasco, I., Gesualdo, A., Iannuzzo, A., Monaco, M. (2018). An integrated approach to the conservation of the roofing structures in the Pompeian domus, J. Cult. Herit., 31, pp. 141-151. DOI:10.1016/j.culher.2017.12.006. [3] Cattari, S., Degli Abbati, D., Ferretti, D., Lagormarsino, S., Ottonelli, D., Rossi, M., et al. (2012). The seismic behaviour of ancient masonry buildings after the earthquake in Emilia (Italy) on May 20th and 29th, Ing Sismica., Anno XXIX(2–3)., pp. 87–111. [4] Masi, A., Santarsiero, G., Ventura, G. (2017). Strategie per la riduzione del rischio sismico applicate agli edifici scolastici: un caso studio., Anidis 2017 Pistoia., pp. 2232 – 2240. T