Evaluation of seismic fragility of an underground gas pipeline considering mainshock-aftershock sequences

Abstract

however, no study cases were found for underground structures, such as buried pipelines. Therefore, in this study, seismic fragility analyses considering the effect of mainshock-aftershock sequences were evaluated for a high-strength steel underground gas pipeline, API 5L X70. A 3D analytical pipeline model was created using Elasto-Plastic beam elements with circular hollow cross-sections and the Beam on Nonlinear Winkler Foundation (BNWF) model was adopted to simulate soil-pipeline interactions (SPI). Next, nonlinear dynamic analyses were performed using 9 different historical input ground acceleration time series data, and the maximum axial output strain responses of the pipeline were recorded. Based on numerical analysis results, failure probabilities were determined according to a predefined damage state for the following scenarios: mainshock, mainshock-aftershock sequences, and aftershock, and their fragility results were compared.

Seismic activities consist of a large mainshock and subsequent aftershocks, which may lead to massive loss of life, structural damage, as well as substantial economic losses. Past studies have focused on analyzing the effect of aftershock sequences on superstructures