PSI - Issue 78

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

690

(a)

(b)

(c) (d) Fig. 2. Methodology phases: experimental tests on standalone devices (a); numerical model (b) and experimental specimen (c) of RC frame to be retrofitted with SPEAD; 3D RC building prototype to be retrofitted with SPEAD (d), with dashed red line highlighting the frame considered in (b) e (c). 3. Experimental campaign and results The test has been performed at the Laboratory of Structures of the University of Basilicata. The experimental setup is shown in Fig. 3, where the retrofitting devices are placed between two steel plates that simulate the interface between beam and column elements. The loading is applied horizontally by a 250 kN servo -hydraulic actuator, with fixed-end conditions guaranteed by anchorage to a reaction frame. Figure 3 also provides details of the geometry, anchorage, and load path applied by the hydraulic actuator. The device is connected using M24 bolts (class 8.8) and Ø24 mm pins, ensuring a reliable transfer of forces and reproducibility of the boundary conditions. The test is performed on a couples of devices in order to avoid instability problems (sect. A-A’ in Fig. 3). The retrofitting device is subjected to a symmetric cyclic displacement history, with increasing amplitudes defined as fractions of the predicted yielding displacement dy= 3.6 mm. The test is conducted under a constant deformation rate of 0.5 mm/s, ensuring quasi-static conditions and avoiding dynamic amplification. The loading protocol includes eleven target displacement levels ranging from 25% to 600% of dy , each repeated four times to allow stabilisation of the hysteretic response. Table 1 summarises the imposed displacement levels, corresponding amplitudes d, and equivalent frequencies. The maximum displacement imposed is ±21.6 mm.