GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 RS1 (release from hole), where structural damage involves few loss of containment or a time-distributed; RS2 (catastrophic rupture), representing a structural collapse that leads to the release of large amounts of fluids in a short time-window. So given an intensity value at a pipe segment it is possible to calculate through the use of loss of containment fragility curves the related RS probabilities. A specific event tree is adopted for pipelines components for the assessment of release consequences as shown in Figure 1. Figure 1. Event tree scheme adopted for pipelines components. For each specific consequence event it is possible to define a mean consequence radius which identifies the area affected in case of pipe failure. The consequence radius values estimated as function of the fluid contained in the pipe and its geometrical characteristics can be aggregated in a consequence indicator represented by the weighted sum of each value multiplied by its respective final probability of occurrence. In such way, it is possible to highlight which parts of a pipeline system located in an area prone to seismic hazard are more exposed to potential ruptures caused by quake occurrence. Case-study application A probabilistic seismic risk analysis is performed on a pipe belonging to the Italian National gas pipeline system with the aim to identify the most exposed segments of the pipe in case of occurrence of a specific earthquake scenario, stocastically simulated via a set of ground motion fields. The analysis is focused on the pipe #048, located in the North-Eastern Italy, in the Friuli Venezia Giulia region (Figure 2). The area is highly prone to seismic hazard and was recently subject to the Mw 6.4 1976 Friuli earthquake. The aim of this study is to assess consequences of the potential recurrence of the 1976 earthquake on the pipe #048 from Malborghetto to Flaibano, one of the most important pipes, close to the national import point located in the municipality of Tarvisio.