PSI - Issue 44

Fabrizio Paolacci et al. / Procedia Structural Integrity 44 (2023) 307–314 Fabrizio Paolacci et al. / Structural Integrity Procedia 00 (2022) 000–000

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30 accelerograms used in the example of section 4, obtained by using a set of 1243 records, the computational time was about 1400 s (about 23 minutes), with a PC equipped with a 4-core i7 processor of 8-th generation. 4. Illustrative example To validate the proposed procedure for the seismic risk assessment of structures, a typical three-dimensional reinforced concrete frame is herein considered (Fig. 1a). In the following, the building is described and its seismic response is evaluated. In this respect two different groups of 30 × 5 = 150 accelerograms, corresponding to five return periods are selected according to the algorithm previously introduced. The proposed risk assessment methodology is then applied to the selected case study with the aim to demonstrate its robustness with respect to the input selection.

(a) (b) Figure 1: a) Main characteristics of the case study, b) Seismogenic zones of the selected area of Central Italy (Amatrice)

The examined RC frame is a 4-floor frame with a plan of 17 × 12 m and 12.7 m-height. The schematic of the frame is shown in Fig. 1. All columns have a cross-section of 30 × 30 cm reinforced with 8 16 longitudinal rebars and 8@100 stirrups. The cross-section of the beams is 30 × 50 cm with the longitudinal reinforcement designed differently at the mid-span and the support, as illustrated in Fig. 1. The stirrups of the beams are 10@100 at the support and 8@200 at the midspan. The weight on each floor is equal to 6 Ú 2 included the self-weight of the beams. The frame has been modeled by using the software OpenSEES, which is widely used for nonlinear structural analysis in seismic conditions, capable of accounting for many sources of non-linearity in reinforced concrete structures. The record selection has been performed with reference to Amatrice city, being infamous for the destructive 2016 Central Italy earthquake, (Masi et al. 2019). Amatrice is located in Italy at a latitude (ED50) of 42.6274, a longitude (ED50) of 13.2836, and it is characterized by soil type B. Five return periods of 72, 224, 475, 975, 2475 years corresponding respectively to the probability of occurrence in 50 years of 50%, 20%, 10%, 5% and 2% have been considered. For this purpose, a probabilistic seismic hazard analysis has been conducted for deriving both hazard curves and UHS. The Matlab scripts "Mathazard" has been used for the generation of the hazard curves and the UHS for the abovementioned return periods. Seismogenic zones numbers from 917 to 923, identified by the Italian zonation ZS9, have been selected (see Figure 1b). Fig. 2a and 2b show, respectively, the generated UHSs and the hazard curve developed considering fully random and deterministic ( = 0, 1). The hazard curves for = 0 have been adopted for the application of the proposed method. The following parameters for the selection of the records from the database have been considered: magnitude range (4-8), fault-site distance range [0-100km], ground type B (according to the Italian Code). The spectra are compared in the range of periods [0, 3.0s] by using a hundred points. For each return period 2 sets of 30 natural records have been selected by using the software SCoReS. For this purpose, the weighting factors and have been set to 1, both for combination and optimization. The scale factors have been constrained to a minimum value of 0.8 and a maximum