PSI - Issue 78

Angelo Masi et al. / Procedia Structural Integrity 78 (2026) 686–693

687

Keywords: the SAFER-REBUILT project; suistainable solutions; seismic retrofitting; SPEAD device; existing RC buildings

1. Introduction The seismic vulnerability of existing reinforced concrete (RC) buildings constitutes a critical issue in regions exposed to high seismic hazard, particularly for structures designed and constructed prior to the implementation of modern seismic design principles. In the Italian context, the seismic code (Norme Tecniche per le Costruzioni -NTC 2018; MIT, 2018), together with the Ministerial Circular No. 7 issued in 2019 (MIT, 2019), provide a detailed regulatory framework that governs the evaluation and retrofitting of existing buildings. According to these provisions, seismic retrofit interventions are classified into three main categories: (i) comprehensive retrofitting for seismic upgrading, which aims to meet the safety requirements set for newly designed buildings; (ii) performance enhancement interventions, which aim to improve the structural performance with respect to the current state without necessarily achieving the standards for new constructions; and (iii) local strengthening interventions, which are intended to restore or enhance the capacity of isolated structural elements without modifying the overall structural behavior. These categories are regulated by specific performance objectives, verification methodologies, and documentation procedures, as defined in Section 8.4 of the NTC and further elaborated in Sections C8.4 and C8.5 of the Ministerial Circular. Comprehensive seismic upgrades and performance enhancement strategies often require substantial structural interventions. These may include the incorporation of supplemental lateral-load-resisting systems, the installation of energy-dissipating devices, or the adoption of base isolation systems to decouple the superstructure from ground motion (Casolo et al., 2023; Di Cesare et al., 2023). Although such approaches have proven effective in significantly improving the seismic resilience of RC structures, they can be intrusive, economically demanding, and potentially detrimental to the architectural integrity of culturally or functionally sensitive buildings (Manfredi et al., 2021; Santarsiero et al., 2023). In contrast, local strengthening interventions represent a more localized and non-invasive approach. As outlined in Section 8.4.3 of the NTC 2018, these interventions are confined to specific structural components—such as beams, columns, joints, or wall panels—and aim to address deficiencies due to degradation, damage, or insufficient initial design. Their scope is not to alter the global dynamic characteristics of the structure, but to restore local capacity and prevent undesirable failure mechanisms, such as brittle fractures or shear failures. The code requires that these interventions do not adversely affect the structural system’s behavior or lead to unintended redistribution of internal forces. Furthermore, each local intervention must satisfy the relevant limit state verifications and meet the prescribed performance requirements under the applicable loading conditions (ReLUIS, 2011). In recent years, local retrofitting strategies have increasingly relied on innovative energy dissipation devices designed to act at the component level. These technologies are typically installed externally and are tailored to accommodate relative displacements or deformations during seismic events, thereby dissipating energy and reducing damage demand. Notable examples include Steel Plate Energy Absorption Devices (SPEAD) designed for beam– column joint retrofitting (Santarsiero et al., 2020), fiber-reinforced polymer (FRP) wrapping to improve axial and shear strength (Aljabbri et al., 2024), and hybrid jacketing systems that integrate traditional concrete jackets with advanced composite materials (Ro et al., 2023; Alkhateeb & Hejazi, 2024). These solutions are particularly attractive in cases where cost-efficiency, architectural reversibility, and minimal disruption to functionality are paramount design constraints. Although the current Italian standards do not mandate numerical model calibration through experimental data, they emphasize the importance of achieving an appropriate Level of Knowledge (LoK) through structural surveys, in-situ testing, and mechanical characterization of materials (MIT, 2019). In this context, dynamic identification methods— based on the estimation of modal parameters such as natural frequencies, mode shapes, and damping ratios—have gained significant traction as tools for model validation and reliability assessment. These procedures are especially relevant when assessing the impact of localized retrofitting techniques, as they enable the correlation of numerical