PSI - Issue 44

Alessandro Mei et al. / Procedia Structural Integrity 44 (2023) 2318–2325 Mei, et al./ Structural Integrity Procedia 00 (2022) 000–000

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The REXEL search was done using a 10% lower and 30% upper tolerance for the average spectral matching in a period range from 0.15 s to 2.36 s. The set of ground motion is reported in Figure 3, in terms of pseudo-acceleration spectra.

Figure 3. Pseudo-acceleration elastic response spectrum of 30 natural time histories.

4. Results Results are reported in terms of the force-reduction factor q obtained for each earthquake, natural period, ductility factor, and constitutive model. Moreover, results are reported averaging the response in terms of maximum displacements over the considered earthquakes since the record-to-record variability is here of minor importance. The analyses were performed using four ductility factors (1.5, 2, 4, 8) and comparing the force-reduction factor q to the one given in E.C. and IBC: (3) Figure 4a shows values of q considering an elastic-plastic law. It is possible to notice the accordance of the code with this constitutive law, typical of ordinary steel or R.C. buildings. Otherwise, Figure 4b shows values of the force-reduction factor considering a pinching constitutive law. The ratio between the q value obtained by the numerical procedure and the value recommended by codes is reported in Figure 5, showing an overestimation for periods T< T. C . 4.1. Case study Since the numerical procedure using exploratory ductility proves that pushover analysis is not always on the safe side for rack structures, the simplified method was then applied to literature experimental pushover tests. Given that both braced and unbraced cases have been tested in literature, only the latter has been chosen. The considered ductility values are reported in Table 1.