PSI - Issue 78

Annarita Palmiotta et al. / Procedia Structural Integrity 78 (2026) 489–496

490

Seismic isolation, while effective, often leads to large movements at the isolation level, which can be problematic for different reasons (i.e. incompatibility with technical joints). To mitigate these large displacements, dissipative devices are often integrated with other components, such as the U-Shaped Dissipative Devices (USDDs). They act as steel hysteretic dampers, and their energy-dissipating properties depend on the shape and material of their steel plates. The early applications of hysteretic dampers, as investigated by Kelly et al. (1972), explored the energy dissipation potential of rolling strips, twisting square and rectangular bars, and bending short, thick beams. Building on the initial work proposed by Kelly et al. (1972), a significant body of analytical and experimental research on USDDs has been published. For example, Baird et al. (2014) conducted parametric analyses using experimental tests and numerical simulations to study the initial and post-yield stiffness of USDDs in coupled shear walls, and Taiyari et al. (2019) proposed a new system of bracing validated with experimental tests. This paper presents a numerical investigation of U-shaped dissipative devices (USDDs), which were initially described in Coniglio et al. (2024a) and Coniglio et al. (2024b), and subsequently validated through experimental tests already shown in Coniglio et al. (2025). In particular, it analyzes the interaction between the USDD connection plates and its U-Shaped Flexural Plates (USFPs). The main objective is to determine how this interaction affects the overall performance of the device and its ability to dissipate energy. To this end, the study considers the influence of various constraint conditions of the USDDs, including examining cases where the USDDs are used without connection plates. These numerical investigations aim to explore the performance of cheaper USDDs, which would have fewer components and require less material. 2. USDDs description and experimental tests The USDD considered in this study is composed of U-Shaped Flexural Plates, briefly USFPs (3), working coupled in parallel to dissipate energy when horizontal displacements occur. These plates (2) are attached to an external case (1) and to a central slider (4), which has a pin at its end. This pin is then connected to a fixed contrasting element during the experimental testing. The external casing itself is hooked up to an actuator applying the desired cyclic displacement (Fig.1). Fig. 2 shows the USFPs geometrical details used during the experimental campaign. The dimensions were derived from the design straightening force F P and the displacement d bd consistent with those of the intended isolation system for an existing building located in Potenza, South Italy (Coniglio et al., 2025). The USFPs were made with stainless steel EN 1.4401 according to EN 10088 – 2 2024, having an elastic modulus E 0 equal to 210.000 MPa, and a Poisson’s ratio ν equal to 0.3. a b

Fig. 1. USDD components