PSI - Issue 64

Eun-Rim Baek et al. / Procedia Structural Integrity 64 (2024) 1117–1124 Author name / Structural Integrity Procedia 00 (2019) 000–000

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1. Introduction Destructive seismic events around the world (e.g., Loma Prieta, USA, 1989; ChiChi, Taiwan, 1999; L'Aquila, Italy, 2009; Christ Church, New Zealand, 2011) are clear reminders of the often poor structural performance of existing buildings and the urgent need for retrofitting. Amongst the most common building types, infilled RC frames (De Luca et al. , 2014; Ricci et al. , 2011) are particularly vulnerable when built before the introduction of modern seismic design guidelines in the 1980s in many seismic-prone regions, such as Europe, Asia, and the Americas. The high seismic vulnerability of masonry infills has been extensively investigated, including experimental studies by the authors (Kallioras et al. 2022; Baek et al. 2024). At the same time, the building sector remains a major contributor to global energy consumption, mainly for cooling and heating. For instance, buildings are responsible for 40% of total energy consumption and 36% of greenhouse gas emissions in the European Union (European Commission, 2020). Similar trends are seen also in Korea, where buildings account for about 18% of the total energy use (Korea Energy Economics Institute, 2019). These high values are mainly attributed to the poor energy performance of existing buildings (Economidou et al. , 2011). Given the dual challenge of improving both the seismic and energy performance of existing buildings, large-scale renovation initiatives come at a significant financial burden. The concept of integrating seismic and energy retrofitting has thus emerged as an efficient solution to enhance both longevity and cost-effectiveness of interventions (Belleri et al. , 2016; Calvi et al. , 2016). Various hybrid retrofit methods have been introduced and tested, each varying in effectiveness, invasiveness, and environmental impact. Recent advancements in retrofitting technologies, such as mass timber systems, have emerged as sustainable and eco-friendly solutions for the seismic retrofitting of masonry and RC structures (Busselli et al ., 2022; Smiroldo et al ., 2023; Kallioras et al ., 2024). A particularly promising approach for such integrated retrofitting involves textile-reinforced mortars (TRM) combined with thermal insulation materials. TRM is a composite material from lightweight textile reinforcement (e.g., carbon, glass, or basalt fibres) embedded into cementitious mortars. Bournas (2018) proposed the potential of combining TRM with conventional or advanced insulation materials, including capillary tube heating systems. However, as highlighted by Pohoryles et al. (2022), despite the increasing interest in the topic, experimental research assessing the feasibility of such integrated schemes remains limited. The combination of TRM with foamed polystyrene insulation has been recently tested on small masonry wall specimens (e.g., Triantafillou et al. , 2017; Gkournelos et al. , 2020) and was shown to achieve reliable structural performance under in- and out-of-plane loading. Pohoryles et al. (2020) analytically studied the same integrated retrofitting scheme for different building typologies (2 masonry and 3 RC), covering practically the building stock in 20 European cities. They found that this integrated scheme has shorter payback times in medium to high seismicity cases than a simple energy retrofit intervention. Following the principle of TRM, the use of textile sheets as strengthening in precast textile reinforced concrete (TRC) panels has also been investigated, e.g., with embedded Phase Changing Materials (PCMs) for thermal performance improvements (Bahrar et al. , 2018) or in the form of sandwich panels with an extruded polystyrene core (XPS) (de Sousa et al. , 2021). The use of precast panels brings the advantage of a faster onsite application, hence reducing the time and cost of the intervention. The application of such solutions for integrated seismic-plus energy retrofitting of masonry-infilled RC frames or URM walls has yet to be experimentally verified. In a previous study, the authors introduced and experimentally validated a novel retrofit solution using Textile Capillary Tube Panels (TCPs) as an integrated solution for seismic and energy upgrading of buildings (Baek et al. 2022). This hybrid system combines seismic strengthening and thermal efficiency into a single prefabricated panel system, mechanically attached to existing building envelopes. Key innovations of that study include: i. The development and implementation of a novel TCP system, which uniquely combines seismic strengthening and thermal efficiency in one solution. ii. Comprehensive experimental validation through static cyclic loading tests on scaled RC frame specimens, providing robust data on the seismic performance improvements due to TCP retrofitting. iii. Direct comparison with traditional TRM+XPS retrofitting methods, demonstrating superior performance in terms of strength, stiffness, and energy dissipation.