PSI - Issue 78

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

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Fig. 9. Force-displacement comparison from base USFP device and experimental curve with (a) first model; (b) second model; (c) third model and (c) fourth model (Coniglio, A. F. et al., 2025)

Fig. 9 shows the comparisons between experimental tests, validated model (Base USFP device) and the new models considered (Model 1, Model 2, Model 3 and Model 4) in terms of force-displacement. More in detail, Fig. 9a and Fig. 9b show the first and second models, respectively, with the first model exhibiting a stiffer response than the second one. The graphs show that the first model (Fig. 9a) consistently demonstrates a response with fuller cycles than the second model (Fig. 9b). The results therefore suggest a direct relationship between the connecting plates, stiffness, and energy dissipation in a USDD. Specifically, thicker connecting plates lead to higher stiffness and greater energy dissipation in the USDD device. For the third model (shown in Fig. 9c), the comparisons demonstrate a drastic reduction in the force required for each displacement, and the cycles are exceptionally tight, indicating a very low dissipative capacity. On the other hand, the fourth model (Fig. 9d) delivers an overall response that's very similar to what was observed experimentally and replicated by the USDD numerical model for the first group of cycles. More details about these results may be found in Coniglio, A. F. et al., 2025. Figures 10 and 11 show the deformation shape of the model at a specific step of the construction stage analysis. In particular, Fig. 10a depicts the deformed shape at cycle 10 for the first model, while Fig. 10b shows the same for the second model. From these figures, it is clear that reducing the stiffness of the connecting plates leads to larger lateral displacements. This explains why lower connecting plate stiffness results in less energy dissipated by the device: greater stiffness restricts the elastic side-to-side movement of the USFPs, causing them to yield during cyclic displacements. Regarding the third and fourth models (Fig. 11), the deformation shape exhibits more pronounced lateral displacements compared to the fourth model, which imposed a displacement increase.