Seismic fragility analysis and post-earthquake transport function assessment of long-distance oil and gas pipelines

This paper aims to establish an evaluation methodology for the post-earthquake transport function of buried pipelines based on fragility analysis to facilitate a rational assessment of the functional states. The approach utilizes Abaqus finite element software to model buried corroded pipelines, simulating their nonlinear response process under seismic action to characterize physical damage. By introducing weighting coefficients for quantification, a mapping relationship between "damage states" and "functional states" is established, which converts the results of seismic fragility analysis into a unified index of functional loss. This achieves a quantitative transformation from physical damage to functional performance. The results show that both the pipeline exceedance probability and the functional loss exhibit a non-linear increasing trend with increasing ground motion intensity. Pulse-like ground motions, due to their concentrated energy, lead to an additional 1.14% functional loss over a 50-year service life compared to non-pulse motions. The extension of service life leads to further degradation of the functionality of buried pipelines under seismic action, causing them to enter a state of moderate functional loss at relatively low ground motion intensities. For pipelines serving over 40 years in seismic fortification intensity zone IX, a distinct inflection point appears in the functional loss curve, marking the onset of an accelerated deterioration stage. The assessment method proposed in this paper enables rapid prediction of the impact of earthquakes on pipeline transport function, thereby providing a critical decision-making basis for the informed post-earthquake deployment of emergency plans.