Numerical modeling of natural gas buried pipelines under seismic shaking

Seismic fragility curves are essential tools for simplified risk analyses of critical infrastructures, as civil network systems and industrial plants. Generally the most common curves, which are used in GIS-based software such as HAZUS, were based on observational data, which could be affected by errors and uncertainties. On the other side, the same tools, estimated through numerical analyses, are not easy to retrieve; and a very large amount of analyses are required to return fragility formulation which are statistically reliable. Despite of these limitations, the numerical modeling is very important to validate the empirical findings and, in some cases, to fill the gaps due to the scarcity of data. Recently new fragilities have been obtained by Lanzano et al. (2013) for buried steel pipelines subjected to transient soil deformations, which is the common effect due to seismic wave passage. These curves are designed for industrial process analysis purposes, and estimated according to increasing level of damage and risk, related to the possible harmful effect of a containment loss. In order to best fit these empirical tools, different soil/structure interaction mechanisms were associated to different level of damage severity and were studied separately, both for transverse section and longitudinal development of a pipeline. In this paper, a preliminary study to obtain seismic fragility curves for buried pipelines via numerical analyses, has been carried out for the transverse section using PLAXIS 2D. © 2014 Taylor & Francis Group, London.