Numerical Study of Horizontally Bent Buried Steel Pipelines Subjected to Oblique Faulting

Abstract

Buried pipelines may be subjected to different seismic hazards along their path, among which faulting can severely affect their integrity by causing large strains in the pipeline confined to a local zone during an earthquake. Historically, the most catastrophic pipeline damages are the ones resulting from oblique faulting due to the severity of ground distortion and induction of compression in the pipeline. Moreover, in the areas of potential ground rupture, the presence of bends near the fault crossing may lead to large strains in the pipeline. Most design guidelines recommend laying the pipelines without field bends, elbows, and flanges near to fault zone. However, bends are sometimes inevitable in the construction of pipelines, and a situation may arise when the pipeline crosses the fault line at/near the bends. Past studies on the response of bent buried pipelines subjected to oblique faulting are very limited. Therefore, the present numerical investigation aims to examine the response of buried continuous steel pipelines with field bends crossing an oblique fault by performing an extensive parametric study. The results obtained are reviewed and presented in the paper. Suitable relationships in terms of modification factors over the response of a straight pipeline as a function of a few critical parameters are determined using regression analyses. It is concluded that providing bends to the pipeline can significantly affect its structural response when subjected to oblique faulting, especially when it is operating at its design internal pressure.