PSI - Issue 44

Giacomo Iovane et al. / Procedia Structural Integrity 44 (2023) 1870–1876 Giacomo Iovane et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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Seismic risk and climate change, to which the COVID-19 pandemic has gravely added, has motivated huge financial measures applied around three strategic axes, such as: digitalization and innovation, ecological transition and social inclusion (mef.gov.it). To this purpose, in Italy the National Recovery and Resilience Plan (NRRP) has been established, it being incorporated within the Next Generation EU programme released by the European Union. In particular a part of the NRRP funds is devoted to seismic and energetic retrofit of existing buildings, enhancement and conservation of cultural heritage with respect to exceptional actions and containment of carbon dioxide emission. In this framework, the engineering research has taken step forward introducing effective and innovative retrofitting solutions for buildings. The combination of structural and energetic retrofit for obtaining performant buildings, with reduced costs of interventions, using ecofriendly materials and products, in a virtuous life cycle to meet green revolution and ecological transition, is a research challenge with huge impact in practice (Menna et al. 2021). With this regards, timber-based elements are optimal solutions. Just in the last years some researchers started to investigate the effectiveness of employing timber-based elements for combined seismic and energetic retrofit strategy of existing masonry and reinforced concrete (RC) buildings (Cassol et al. 2021, Valluzzi et al. 2021, Sandoli et al. 2021, Aloisio et al. 2022). In particular, further to local interventions on members, timber elements used as endo or exoskeletons, connected to the existing masonry walls, have been proposed, as reinforcement against in-plane and out-of-plane failure mechanisms, ensuring a seismic-resistant global behavior. Typically, they are timber strong backs (Cassol et al., 2021), light-timber (Miglietta et al., 2021) or cross-laminated timber (CLT) panels (Pozza et al., 2017). This paper provides a collection of different timber-based systems, which are suitable to be used for masonry and RC constructions retrofitting and allow the combination of structural and energetic functions, achieving the eco sustainability of the interventions. 2. Strategies for integrated seismic and energetic retrofitting of existing masonry and RC structures Damage scenarios observed in the aftermath of seismic events and climate change highlighted the needs to have sustainable and resilient cities for the future. The high vulnerability and the poor energetic performances of existing buildings is a serious problem worldwide that must be faced with particular attention, trying to optimize resources, time and costs. In Europe, most of existing buildings were built without any energy performance requirements: 35% is over 50 years old and almost 75% are inadequate to the current building standards in terms of energy efficiency (Filippidou et al., 2019). In particular, in Italy 60% and 88% of the building stock were built respectively before the first seismic codes (Italian Law n.64, 1974) and before the first important energy provisions (Italian Law n.10, 1991). Until the last decades, seismic and energetic retrofits were erroneously considered objectives to be achieved separately. However, as independent strategies, they generate waste of money and environmental resources: seismic retrofit alone does not improve the thermal-hygrometric comfort, as well as energy retrofit does not reduce the seismic vulnerability of the buildings (Menna et al., 2021). Based on this, particular attention in the development of seismic and energetic integrated design approaches has been paid recently, with the main scope of achieving contemporarily ( i ) enhancement of the structures safety against seismic actions through the increase of the seismic capacity and ( ii ) reduction of the energetic consumptions of the buildings through suitable insulating systems and technical installations (Menna et al., 2021, Caprino et al., 2021). At the structural aim, techniques emphasizing low invasiveness of interventions, reversibility and low-damage of structural and non-structural components due to medium-high earthquakes, as well as ensuring the usability of buildings during the phases of interventions or in the aftermath of an earthquake, are preferred; as a consequence reconstruction/repair costs due to earthquakes reduce. At the energetic aim, the adoption of eco-sustainable solutions is preferred, matching with objective of containment of carbon dioxide emission pursued throughout the world. Also the compatibility of the interventions with architectural features of buildings must be properly taken into account before any action. At the same time, the choice of an effective retrofit solution depends significantly also from socio-economic and sustainability decisional-making parameters. It is evident that the most adequate retrofitting strategy able to fulfill all the above-mentioned issues is a difficult and not unique task. Among the various systems, those made with timber elements (i.e., light timber panels, CLT and LVL panels, braced systems, etc.) represent suitable solutions to combine seismic and energetic requirements successfully. In fact, timber has high performance in terms of strength-to-weight ratios, thermal and acoustic properties and environmental sustainability. Thanks to this, recently many studies focused on the use of timber-based systems for global or local interventions on existing masonry and RC buildings (Miglietta et al. 2019, Cassolet al. 2021,