PSI - Issue 64

Rosario Montuori et al. / Procedia Structural Integrity 64 (2024) 841–848 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Seismic safety and the performance evaluation of strategic buildings are critical aspects within civil engineering and seismic risk management. These elements are essential not only for ensuring the protection and safety of individuals but also for maintaining essential societal functions in the event of seismic activities. The accurate assessment of seismic performance of strategic buildings, such as hospitals, schools, and critical infrastructure, is imperative to identify structural and non-structural vulnerabilities that could compromise their operability during and after an earthquake (Fiorino et al. 2014, Piccolo et al. 2022, Biglari et al. 2022). The adoption of advanced methodologies for seismic safety evaluation, such as seismic response analysis, vulnerability analysis, and risk analysis, allows for quantifying a building's ability to withstand seismic events and to function adequately post earthquake. Furthermore, the evaluation of seismic performance effectively informs the planning of risk mitigation interventions, enabling the prioritization of structural reinforcement and seismic retrofitting actions based on the criticality of buildings and their importance to society. This evidence-based and technical decision-making process ensures the optimal allocation of limited resources, directing interventions towards buildings that, if compromised, would have the greatest impact on public safety and vital community functions. It is well known that most of Italian public structures were built using reinforced concrete (RC) and without seismic criteria. Moreover, the main structural scheme used in Italian structures is the RC spatial frame with the internal beams spanning in only one direction and, consequently, designed without seismic rules. Consequently, they are highly vulnerable to seismic actions. The current Italian and European codes (2005, 2018, 2019) provide the specific seismic rules to endure destructive seismic events without totally or partially collapsing based on the fundamental principles of Capacity Design (Piluso et al. 2017a, 2017b, Montuori et al. 2023, Montuori et al. 2024, Maglio et al. 2024). However, these rules can be used to design new constructions. Generally, to retrofit existing structures, the following logical process could be considered: • Step 1: Definition of geometrical and mechanical properties characterizing the building under investigation • Step 2: Evaluation of reliability index against different Limit States using linear and/or non-linear analyses. • Step 3: Identification of the most convenient interventions for improvement the structural safety. In this work, the attention is focused on the evaluation of seismic vulnerability and on the proposal of two retrofitting interventions of a 7-storey hospital building belonging to the cancer institute “G. Pascale Foundation” of Naples and, recently, the whole hospital complex has been under investigation by AIRES Engineering and Department of Architecture and Industrial Design of Vanvitelli University (Zizi et al. 2021). In their report, they underlined the high seismic vulnerability affecting the buildings belonging to the institute. Starting from the information provided by Zizi et al. (2021), the vulnerability indexes have been provided using linear dynamic analyses and two structural retrofitting solutions have been proposed to increase the reliability level of the structure under investigation. Then, the attention is focused on the pile foundation. In particular, the structural vulnerability has been evaluated by adopting a simple static linear analysis and, consequently, a retrofitting intervention has been developed. Finally, the proposed interventions have been evaluated from the economic and environmental points of view. 2. Geometrical and mechanical characterization of the Day-Hospital Building 2.1. General description The "G. Pascale Foundation" institute comprises five buildings (Fig. 1), with our focus on the Day-Hospital Building. Fig. 2 shows some pictures of the Day-Hospital Building. As depicted in Fig. 3, this symmetric structure features nine reinforced concrete (RC) cores linked by a seven-storey steel frame, using IPE 240 and HEA 260 beams and HEB 260 columns. The first storey has a height of 4.60 m, with subsequent storeys at 3.60 m. Floors consist of steel trapezoidal sheets topped with 50 mm thick concrete, reinforced by horizontal diaphragms and a bracing system for stiffness. The seismic resistance is provided by the nine symmetrically placed RC cores used for staircases and elevators, each with 260 mm thick walls. Some internal structural details are reported in Fig. 4. Foundations rely on bored piles of 50 cm diameter and varied lengths, with 120 cm deep concrete plinths (Fig. 5).