PSI - Issue 44

1872 Giacomo Iovane et al. / Procedia Structural Integrity 44 (2023) 1870–1876 Giacomo Iovane et al. / Structural Integrity Procedia 00 (2022) 000 – 000 3 Valluzzi et al. 2021, Sandoli et al. 2021, Riccadonna et al. 2020, Piazza et al. 2000, Bedon et al. 2020). Concerning the seismic aspects, interventions strategies are generally devoted to improve the seismic capacity of the construction or to reduce the seismic demand. In the case of timber-based elements, to the first purpose, additional endo or exoskeleton or local interventions are applied, giving rise to increments of strength, stiffness and ductility; besides, systems devoted to demand reduction (i.e., base-isolation systems) are generally not necessary due to the low weight of timber material (and then the low seismic demand). As examples, in Figure 1 three different retrofitting timber based systems are shown: Fig. 1a) an endoskeleton made with light timber frame for a two-storey masonry building; Fig. 1b) timber strong-backs to prevent out-of-plane of masonry walls; Fig. 1c) infill CLT panels for reinforcing RC frames. In figures the response curves of static pushover and cyclic dynamic analyses are also presented for both the retrofitted and unretrofitted cases. In all, the comparison between the curves shows significant gain of strength, stiffness and dissipation capacity achieved by the existing structures after the interventions. As far as energetic aspects are concerned, the main source of energy consumption of existing buildings are the facades materials, which are often unable to contrast winter and summer hygro-thermal variations, particularly for RC buildings built before 1970s not provided of massive infill masonry walls, effective insulating systems or details aimed at avoiding heat dispersions (i.e., thermal bridges). Literature studies proved that timber based elements, like CLT, LVL and light timber frame panels, in particular when arranged as endo or exoskeletons, are very effective to fulfill energetic requirements, either if coupled or not with additional insulating materials, giving rise to significant reduction of energy consumption (Fufa et al, 2018; Ingrao et al, 2016; Dodoo et al, 2014; Smiroldo et al., 2021).

retrofitted

unretrofitted

a)

b)

c)

Fig. 1. (a) Two-storey masonry buildings retrofitted with light timber frame (Miglietta et al. 2021), (b) Masonry walls retrofitted with timber strong backs against out-of-plane (Cassol et al. 2021); (c) RC frame reinforced by infill CLT panel (Aloisio et al. 2022). 3. Seismic and energetic retrofitting techniques 3.1. General features Inspired by Di Lorenzo et al. (2020), who presented a typological classification and the definition of the key design parameters for steel exo-skeleton systems, highlighting the improvement of the mechanical behavior of existing RC and masonry structures by using such retrofit techniques, a summary of the most common timber-based seismic retrofitting system, classified in global and local ones, is given in Table 1.

Table 1. Type of global and local timber-based interventions for seismic retrofit. Retrofit system Global interventions Local intervention Endoskeleton Re-construction/repair of existing timber elements / joints Exoskeleton Strengthening of timber members cross-section Reinforcement of timber floors

Global interventions are herein intended as those able to modify the overall behavior of the existing structure, increasing the seismic capacity. Besides, local interventions concern single components of the existing structure, so that they do not modify significantly the global structural behavior, at the same time enhancing the safety level of the structure. Local interventions can aim at the reconstruction and/or repairing of degraded or seismic damaged structural