PSI - Issue 44

Sabatino Di Benedetto et al. / Procedia Structural Integrity 44 (2023) 1901–1908 Di Benedetto et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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4. Comparison between the results of the experimental campaigns This paragraph summarises the observed main outcomes by comparing the mock-up's structural response with the typologies of the three analyzed connections. This purpose can be achieved since the three campaigns have been carried out using the same seismic inputs, material and modal properties in all campaigns. As discussed in detail by Di Benedetto et al. (2020, 2022a, 2022b), not all the accelerograms could engage the structure in the plastic range. This occurrence can be ascribed to the overstrength exhibited by the mock-up and the limits of the available experimental set-up, which did not allow the increase of the PGAs. In particular, the Artificial (Test 3) and Santa Barbara (Test 4) ground motions caused the elastic response of the mock-up in all three campaigns. Instead, the seismic inputs of Imperial Valley (Test 1), Spitak (Test 2) and Coalinga (Test 5) were able to engage the structure in the plastic range activating the dissipative fuses both at the beam-to-column joints and at the column bases. In particular, in Fig. 4 and Fig. 5, some graphs expressed in terms of roof displacements, base shear, moment-rotation and dissipated energy of connections 1A are reported concerning only test 2. In fact, due to the elastic behaviour experienced by the mock-up, the diagrams related to tests 3 and 4 are not reported. Moreover, it is worth highlighting that since technical problems occurred in the acquiring data system during tests 1 and 5 referred to all the experimental campaigns, the charts are omitted.

Fig. 4. Test 2: roof displacements (left) and base shear (right)

Fig. 5. Test 2: hysteretic curves (left) and dissipated energy (right) referred to connection 1A

According to the previous statements, the attention is focused only on the results concerning the pseudo-dynamic test during which the Spitak (Test 2) earthquake has been employed. These results highlight that the three connections' typologies highly affect the peak and residual roof displacements (Fig. 4). In fact, the structure with X-shaped T-stub joints appears as the most deformable configuration, while the mock-up with RBSs exhibits high stiffness. Furthermore, referring to the base shear (Fig. 4), it is possible to observe higher values for the structure with RBSs than for the mock-up with FREEDAM and X-