PSI - Issue 78

Paolo Ielpo et al. / Procedia Structural Integrity 78 (2026) 1024–1031

1025

Keywords: Life cycle thinking; seismic retrofit; existing buildings; low impact solutions; sustainable strengthening; RC beam column joint; energy absorption.

1. Introduction In the current context, characterized by the climate crisis and the gradual depletion of natural resources, the construction sector is called to address a critical challenge: the systematic integration of sustainability principles into design and rehabilitation processes. The objective is twofold: to improve the safety and durability of structures while reducing energy consumption, greenhouse gas emissions, and the use of non-renewable materials. In this framework, sustainability is no longer an option, but a fundamental requirement for modern engineering practice. The European Union has outlined an ambitious strategy through the Green Deal, aiming for climate neutrality by 2050. This goal is supported by key instruments such as the EPBD Directive and the Renovation Wave, which aim to improve the energy performance of the building stock and to double the renovation rate by 2030. According to BPIE (Buildings Performance Institute Europe) estimates, between 85% and 90% of the current building stock will still be in use by 2050, making it a priority to intervene on existing buildings through integrated, multi-objective retrofitting strategies. These should reduce seismic vulnerability through sustainable approaches based on Life Cycle Thinking (LCT), as described in Biondini et al. (2016), Di Vece and Pampanin (2019), Passoni et al. (2021). Before selecting the most appropriate seismic retrofit strategy, it is necessary to carry out a comprehensive structural assessment that analyses the vulnerability of the structure under seismic actions and considers the capacities and weaknesses of the individual structural elements. Important studies on this topic include those by Pampanin et al. (2002), Masi (2003), and Masi et al. (2013). Intervening on existing structures is a complex process that requires to consider multiple constraints. In addition to evaluating the residual capacity of the building, it is essential to consider physical limitations, such as the availability of surrounding space in densely urbanized areas, limited economic resources, and, most importantly, the need to respect the functional requirements of building occupants during and after the intervention. Within this framework, it becomes crucial to develop low-impact seismic retrofit techniques that minimize both invasiveness and intrusiveness. Gkournelos et al. (2021) presents a comprehensive review of the state of the art in retrofit techniques, providing an in-depth analysis of innovative solutions that minimize impact. Labò et al. (2018) illustrates a seismic retrofit case study on a school building, based on the principles of low invasiveness and incremental seismic rehabilitation, as outlined in the FEMA P-420 (2009) guidelines. Santarsiero and Masi (2015) conducted an experimental study on the seismic behaviour of reinforced concrete beam – column joints strengthened with a local retrofit solution called DIS CAM. The reinforced joint, featuring steel profiles confined by metal straps and connected to dissipative elements, showed significant improvements in both strength and deformation capacity. Manfredi et al. (2021) proposes a seismic retrofit solution called HPDF (High Performing Dissipating Frame), based on external prefabricated reinforced concrete frames rigidly connected to existing structures and equipped with high-capacity shear dissipating devices. Finally, Borghese et al. (2023) highlight the importance of multi-criteria decision-making methods to identify optimal solutions that balance multiple objectives.Of particular interest is the development of procedures based on Artificial Intelligence (AI). Specifically, as reported by Nigro et al. (2023), the application of Genetic Algorithms (GAs) is often considered a suitable approach for optimization problems in civil engineering. Given the frame above, this study proposes a local strengthening technique called the Steel Plate Energy Absorption Device (SPEAD), consisting of a specially shaped steel plate externally applied to reinforced concrete beam-column joints using chemical and mechanical anchors. The system is designed to provide a predefined threshold force, activated by the relative deformation between the beam and column, with the aim of enhancing seismic capacity and preventing brittle shear failure. Furthermore, the device shifts the location of the plastic hinges along the beam, increasing the resistance of the beam-column joint and reducing crack formation in the structural elements. To evaluate the seismic behavior of the joints before and after the retrofit with SPEAD, a nonlinear 3D finite element model was employed, calibrated with experimental data from cyclic tests conducted at the Laboratory of Structures of the University of Basilicata. Preliminary analyses indicate that the SPEAD device significantly increases strength, reduces slip between steel and concrete, and limits damage to the joint panel.