Structural integrity of buried pipelines is threatened by the effects of Permanent Ground Deformation (PGD), resulting from seismic-induced landslides and lateral spreading due to liquefaction parallel to the pipeline axis, requiring accurate analysis of the system performance. Analytical fragility functions allow to estimate the likelihood of seismic damage along the pipeline, supporting design engineers and network operators in prioritizing resource allocation for mitigative or remedial measures in spatially distributed lifeline systems.
To efficiently and accurately evaluate the seismic fragility of buried operating steel pipeline under longitudinal PGD, this study develops an analytical model considering the asymmetric pipeline material behavior in tension and compression under varying operational loads. The validated model is further implemented within a fragility function calculation framework based on Monte Carlo Simulation (MCS), allowing to assess the probability of exceedance of the pipeline performance limit states conditioned to the intensity of PGD.
The evaluated fragility surfaces showed that the pipeline probability of exceeding the performance criteria increases for larger soil displacement and lengths, as well as cover depths, because of the greater mobilized soil reaction counteracting pipeline deformation. Additionally, the performed Global Sensitivity Analysis (GSA) highlighted the influence of the PGD and soil-pipeline interaction parameters, as well as the effect of the service loads on structural performance, requiring proper consideration in pipeline system modeling and design.
Finally, the proposed analytical fragility function calculation framework provides a useful methodology for effectively assessing the performance of operating pipelines under longitudinal PGD, quantifying the effect of the uncertain parameters impacting structural response.