A critical review on the vulnerability assessment of natural gas pipelines subjected to seismic wave propagation. Part 2: Pipe analysis aspects

Abstract

The socioeconomic and environmental impact, in case of severe damage on Natural Gas (NG) pipeline networks, highlights the importance of a rational assessment of the structural integrity of this infrastructure against seismic hazards. Up to date, this assessment is mainly performed by implementing empirical fragility relations, while a limited number of analytical fragility curves have also been proposed recently. The critical review of available fragility relations for the assessment of buried pipelines under seismically-induced transient ground deformations, presented in the first part of this paper, highlighted the need for further investigation of the seismic vulnerability of NG pipeline networks, by employing analytical methodologies, capable of simulating effectively distinct damage modes of this infrastructure. In this part of the paper, alternative methods for the analytical evaluation of the seismic vulnerability of buried steel NG pipelines are presented. The discussion focuses on methods that may appropriately simulate buckling failures of buried steel NG pipelines since these constitute critical damage modes for the structural integrity of this infrastructure, when subjected to seismically-induced transient ground deformations. Salient parameters that control the seismic response and vulnerability of buried pressurized steel pipelines and therefore should be considered by the relevant analytical methods, such as the operational pressure of the pipeline, the geometric imperfections of the pipeline walls, the trench backfill properties, the site characteristics and the spatial variability of the seismic ground motion along the pipeline axis, are thoroughly discussed. Finally, a new approach for the assessment of buried steel NG pipelines against seismically-induced buckling failures is introduced. Through the discussion, recent advancements in the field are highlighted, whilst acknowledged gaps are identified, providing recommendations for future research.

Optimal intensity measures for the structural assessment of buried steel natural gas pipelines due to seismically-induced axial compression at geotechnical discontinuities

“…12a. The  existence of wall imperfections on the pipeline is again expected to lead in a higher nonlinear axial response of the pipeline, compared to that of an equivalent 'perfect' pipeline-soil system subjected to the same ground deformation pattern [44,[47][48]. This may explain the higher  values reported for imperfect pipelines (i.e.…”

“…The utilization of a 3D continuum model allows for a rigorous simulation of pressurization level of the pipeline, as well as of initial geometric imperfections of the wall of the pipeline, which both are expected to affect significantly the axial compressional response of a buried steel pipeline, including potential localized buckling modes [24,[45][46][47][48]. Additionally, it allows for a rigorous simulation of potential sliding and/or detachment (i.e.…”

“…case of very-well compacted backfill soil and higher soil-pipe interface friction coefficient). The critical effects of pipeline wall imperfections or backfill compaction level on the axial response of buried steel pipelines are further examined in [47][48].…”

“…Previous studies [44][45][46][47][48] have demonstrated that pressurization of steel pipelines leads to initial circumferential tensile stresses, which interact with the axial straining of the pipeline, caused by the seismically-induced ground deformation. In particular, the increase of the internal pressure level of the pipeline tends to lower the axial load-displacement path, leading faster to yielding or instability phenomena.…”

Seismic Assessment of Footbridges under Spatial Variation of Earthquake Ground Motion (SVEGM): Experimental Testing and Finite Element Analyses

“…The authors documented, based on in situ test, that the asynchronous kinematic loading of the structure excited higher modes while reducing the vibrations on its fundamental natural frequency. The seismic assessments based on concept of SVEGM were also presented for other multiple-support structures, like dams, pipelines, or tunnels [19][20][21].…”