PSI - Issue 44

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Gianluca Quinci et al. / Procedia Structural Integrity 44 (2023) 251–258 Gianluca Quinci et al. / Structural Integrity Procedia 00 (2022) 000–000

Fig. 4. Fragility curves for vertical tank Fig. 5. Hazard curve of Amatrice (Italy) A careful reader can note that, since the two fragility curves relative the DBE limit state are close for the two sets, the fragility curve for the SSE limit state is close just in the first part, until a PGA level of 0.3g. The reason could be correlated to the hazard level of the site. As a matter of fact, as can be appreciated from Figure 5, the hazard curve shows a rather low probability value for the site for PGA higher than 0.3g, so there is a lack of information at high PGA, also because the accelerograms selected are consistent with the UHS. This difference regarding the SSE limit state is not more appreciated in the risk value, shown in Table 4, because when the integration between hazard and fragility curve is carried out, the low probability value of the high PGA of the hazard curve make the relative probability values of the vulnerability curve negligible. 5. Conclusions In the proposed study the suitability of the PBEE approach in presence of NSCs and their dynamic interaction with the primary structure has been investigated. In this study the main limit states for NCSs (i.e. tanks and piping system) are identified and the related fragility curves of the tank built, in a PBEE perspective, both based on the experimental results and finite element model (FEM) simulations. For this purpose, an innovative algorithm for ground accelerogram selection is used and the mean annual frequency (MAF) of exceedance of the experimentally identified limit states for the tank is carried out. In order to validate the robustness of the method herein proposed, two different sets of 150 accelerograms each one have been selected and the MAF of the tank has been carried out for both the sets. The results in terms of risk for the two sets of accelerograms were very close, showing, for the selected case study, the independency of the risk from the set of accelerograms used also for NSCs, with clear advantages in a PBEE perspective. Acknowledgements The research leading to these results has received funding from the European Community’s HORIZON 2020 Framework Programme [H2020-INFRAIA-2016-2017/H2020-INFRAIA-2016-1] for access to EUCENTRE Laboratory under grant agreement 730900 - SERA project and from the Italian Ministry of Education, University and Research (MIUR) in the frame of the Departments of Excellence (grant L232/2016). References ASCE/SEI, Seismic Analysis of Safety-Related Nuclear Structures., Standard 4-16, 2016 ASCE/SEI . Seismic evaluation and retrofit of existing buildings. Standard 41-17 . 2017 Alessandri A, Caputo A. C., Corritore D., Giannini R., Paolacci F, Phan P.N., Probabilistic risk analysis of process plants under seismic loading based on monte carlo simulations., Journal of Loss Prevention in the Process Industries 136–148, 2018