Influence of Ground-Motion Selection Strategies on the Seismic Fragility of Buried Pipelines

This study investigates how ground-motion selection affects the seismic fragility of buried pipelines. Records were grouped by magnitude, epicentral distance, and site conditions and analyzed using a Winkler beam-on-foundation model and incremental dynamic analysis. A benchmark was established from 1,000 repeated random selections; fragility-deviation indices and state probability analysis quantified group differences. Within this database and benchmark, magnitude-based grouping showed the largest between-group fragility deviation. Deviations were greatest at low intensities and for severe damage. Random selection may underestimate severe-damage risk in groups with large magnitudes, shorter epicentral distances, and soft sites, highlighting the importance of site-specific, hazard-consistent record selection.