Damage mitigation of fault-crossing elbowed water transmission pipes using flexible joints

The 2023 Mw 7.8 Türkiye earthquake caused significant damage to water, natural gas, and crude oil transmission pipelines, resulting in widespread service disruptions. Notably, the 2.6m-diameter Duzbag water transmission steel pipeline with elbow joints ruptured due to a 5.0m offset at the Sogutlu fault crossing. This study investigates the damage progression of that pipe segment as a model problem and examines the use of flexible joints as a damage mitigation countermeasure while considering fault mapping uncertainties. A three-dimensional nonlinear soil-structure interaction model was developed and calibrated based on field observations. The results revealed that the numerical model successfully identified not only major and minor damage but also undetected hidden damage, which was later validated through field investigations by pipe operators. It was also found that stresses and deformations along the pipeline were concentrated at the flexible joints, while stresses in the pipe segments between these points were significantly reduced. Three pipe-fault intersection scenarios were analyzed to account for fault mapping uncertainty. In all cases, the proposed damage mitigation measure performed well.