PSI - Issue 44

Federico Gusella et al. / Procedia Structural Integrity 44 (2023) 790–797 F. Gusella et al./ Structural Integrity Procedia 00 (2022) 000 – 000

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2.3. Displacement history The cyclic response of the bracing system is investigated under the cyclic displacement history illustrated in Figure 4. A quasi-static cyclic loading is applied per the ATC-24 loading protocol (ATC-24, 1992). A symmetric three cycle displacement history is used in all tests: the amplitude of reversed horizontal displacement, at the top of the frame, is increased stepwise after the third cycle of each three-cycle series. The cycles have a peak displacement given as a multiple of 10 mm (10 mm, 20 mm …). Cyclic tests are interrupted at the fuse failure.

Fig. 4. Loading history of cyclic tests.

3. Results The load-displacement (P-f 1 ) curve for specimens with the smaller and greater elastic section modulus W e,xx , listed in Table 1, is shown in Fig. 5. The failure mode of specimens is listed in Table 5, with the absolute maximum load obtained in the cyclic test (P max ). Pictures of collapse modes are shown in Fig. 6 and Fig. 7. Table 5. List of the failure modes of all specimens Specimen Failure mode |P max | [kN] UPN 50m local buckling 138 UPN 50c local buckling – flanges tearing RHS 80m local buckling – weld collapse 148 RHS 80c local buckling – weld collapse UPN 100m local buckling 210 UPN 100c local buckling – flanges tearing RHS 150m local buckling 214 RHS 150c local buckling – flanges tearing

Fig. 5. Monotonic and cyclic curves (P-f 1 ). Test RHS 50 – RHS 150 – UPN 50 – UPN 100