The numerical techniques currently utilized in practice for the rigorous performance-based design of pipelines will be initially reviewed. Attention will be drawn to the importance of accurately modelling the non-linear behaviour of pipeline steel, non-linear soil-pipeline interaction effects and second order effects induced by large displacements, which make the corresponding numerical analyses highly demanding in terms of both expertise and computational effort.
Emphasis will be then given to recently-developed simplified analytical methodologies for the estimation of the developing pipeline strains. A series of methodologies will be presented, focusing on strike-slip, normal and oblique fault crossings, as well as on cases of differential settlement or heave. These methodologies are based on simple equilibrium and displacement compatibility equations to derive the axial forces applied to the pipeline, while they adopt a combination of beam-on-elastic-foundation and elastic-beam theory to calculate the developing bending moments.
Large-displacement non-linearities are indirectly taken into account, while material non-linearities are introduced through an equivalent-linear iterative solution scheme that considers the actual distribution of stresses on the pipeline cross-section.
Furthermore, attention will be drawn to the effect of bends existing within the pipeline's unanchored length, where the pipeline strains may even exceed the strains developing at the PGD zone and become critical for the design.
Based on comparisons with benchmark numerical analyses, it will be demonstrated that the proposed simplified methodologies provide fairly accurate predictions while remaining relatively easy to program and utilize, at least for preliminary design and verification purposes.
Finally, the insight provided by the analytical solutions will reveal a number of conclusions of practical interest to pipeline design applications.
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