PSI - Issue 64

1734 Raul Berto et al. / Procedia Structural Integrity 64 (2024) 1733–1742 2 Raul Berto, Chiara Bedon, Andrea Mio, Alessandro Mazelli, Paolo Rosato / Structural Integrity Procedia 00 (2019) 000 – 000

architectural historians and restoration experts against property owners and developers. An evaluation tool, in this context, should be able to consider both qualitative and quantitative criteria, account for decision-making processes characterized by conflicting "cultural and ideological" positions, and consider the temporal performance of various alternatives. This last aspect is of particular importance for the long-term evaluation of possible interventions. In recent decades, in this context, Multi-Criteria Decision Analysis (MCDA) procedures have been proposed. However, the practical use of these techniques for choosing specific options for structural recovery is still sporadic. Dodgson et al. (2009) discussed various possibilities for modelling time in MCDA. Betrie et al. (2013) proposed treating short and medium-term effects as separate criteria in MCDA. Rout and Walshe (2013) discussed the use of discount rates to account for the time value of different criteria. Frini and Ben Amor (2019) presented a generalization of the ELECTRE method for multi-period evaluation. The state-of-art review shows that the temporal aspect in the conservation and reuse of historic buildings is not adequately taken into account. This study employs an outranking-based method, and proposes an efficient adaptation of the ELECTRE method, to support decision-makers and account for the performance temporal distribution of various options. A noble villa in North-Eastern Italy (Pordenone) was chosen as a case-study (Fig. 1a). The Villa has compact plan shape (16×15 m) and four storeys. The second noble floor and the tympanum level were added after a renovation at the end of the 18th century (Fig. 1b,c). Now, the building hosts public offices. Extensive research was performed to acquire technical drawings and characteristics of the walls, made of rubble stone masonry (mean compressive strength f c =2.17 MPa, elastic modulus E=1500 MPa, shear modulus G=500 MPa, specific weight w=21 kN/m 3 ). Their thickness varies from 50 cm (ground floor) to 42 cm (upper storeys). The existing floors consist of timber joists and nailed planks, with beams oriented North-South. Three retrofitting solutions for the floors are herein designed and proposed to increase the global static and seismic performances (Fig. 2). Two proposals consider timber strengthening, by using 25 mm Oriented Strand Boards (OSB) (Fig. 2a) or 60 mm Cross Laminated Timber (CLT) panels (Fig. 2b). Similar timber solutions have good capacity for increasing the bending stiffness, strength and in-plane stiffness (Gubana and Melotto, 2021a, 2021b; Ortega et al., 2018; Scotta et al., 2018). Moreover, thanks to the connection to the perimeter walls, they can avoid the out-of-plane mechanisms of walls (Mazelli et al., 2024). A third solution using a 50 mm thick Light-Weight Concrete slab (LWC, specific weight 16 kN/m 3 ) is also studied (Fig. 2c). Timber panels are supposed connected to the existent beams by means of self-tapping screws, while the collaboration between beams and slab is reached using 45° inclined fasteners. The perimeter walls are connected to the floor using steel bars, chemically anchored to the masonry. Finally, a continuous “L” shaped steel profile is used at the interface between walls and timber panels. 2.2. Attribute definition The attributes selected for analysis cover economic, architectural, structural safety, and environmental aspects. As far as the economic aspect is concerned, the analysis considers the implementation costs of the three interventions, as well as their decommissioning costs. The former incurs in =0 while the latter in =50 (end of life). As for the architectural aspects, it was decided to consider the reversibility and invasiveness of the interventions (Stival et al., 2020), but the performances of these parameters are constant over the different time horizons. Structural attributes belong to two different sets, focusing on the static and the seismic behaviour of the building. The performance increase for SLS (deflection), and ULS (load carrying capacity) were considered under static loads, and the benefits to Damage Limitation (DL) and Life Safety (LS) limit states were examined under seismic excitation. Concerning environmental impacts, the categories analysed were greenhouse gas emissions, or rather, Global Warming Potential-GWP100, and water consumption, or rather, AWARE impact category (Boulay et al., 2018). 2. Material and methods 2.1. Case study building