PSI - Issue 44

Maria Maglio et al. / Procedia Structural Integrity 44 (2023) 550–557 M. Maglio, R. Montuori, E. Nastri, V. Piluso / Structural Integrity Procedia 00 (2022) 000–000

552

3

, 475 = , � 475 �

1 /

(2) A usual value of k suggested by the code is 3. The mapped values to be ascribed to , , for use in a Country can be set by the relevant Authorities or found in the National Annex. To construct the response spectra for horizontal actions, the spectral parameters must first be identified and the code defines the values of T A , F A , ꭕ . In particular, from table 5.4 of prEN1998-1-1 (2021) are reported: = 0.02 , = 2.5 and = 4 . The spectral accelerations S α and S β should be calculated from formulas: = , = , (3) in which: , = , , , = , , (4) γ , are reported in table 4.4 of EN1998-1-2 (2021), in particular γ , 2 = 1 is the performance factor at Significant Damage limit states; γ 2 = 0.5 is the performance factor at Damage Limitation limit states. For the Fully Operational limit state the value of the performance structure is not provided, so it was set equal to that DL, i.e., 0.5. , = ℎ , where ℎ = 0.3 for moderate seismicity levels namely if , 475 < 5 and ℎ = 0.4 for high seismicity levels that is if , 475 > 5 . = 1.6 � 1 − 0.02 � is the site amplification factor for site category B (from table 5.4 of prEN1998-1-1, 2021). Thanks to the spectral accelerations, it is possible to calculate the other periods: = T B = 0.10s if > 0.10 (5) The value of T D is 2 if , ≤ 1 / 2 while is 1 + , if , > 1 / 2 . The obtained spectra are shown in Fig.1 assuming a reference spectral acceleration of 5.28 m/s 2 for LS of SD, 2.65 m/s 2 for LS of DL and 2.10 for OP. In Table 1 the seismic parameters for these spectra are reported.

Table 1. Seismic parameters for the horizontal response spectra Seismic Parameter LS of SD LS of DL LS of Fully OP 475 60 30 , 1 0.5 0.5 , 5.28 2.65 2.10 , 2.11 1.06 0.84 , 5.28 1.32 1.05 , 2.11 0.53 0.42 1.23 1.28 1.29 1.53 1.58 1.59 6.50 1.70 1.35 3.24 0.84 0.67 6.50 3.40 2.70

Fig. 1. Horizontal elastic response spectra for DC2 ductility class

The reduced spectra are obtained using the behavior factor that includes three contributions for the SD limit state: = = 3,50 (6) For Multi-Storey Moment Resisting Frames (MRFs) and DC2 ductility class they are equal to = 1.50 ; = 1.80 ; = 1.30 . For DC2 the behavior factor for SD limit state must be included in the range 2 < ≤ 3.5 0 and class 1,2 for the cross-sectional are required and in case of DL and OP limit states is obviously taken as equal to 1. The horizontal components of the seismic action for the reduced spectrum, S r (T), are provided by: