Impact of the Code-Based Near-Fault Factor on Buried Steel Pipelines via the Design Response Spectrum: Seydişehir–Ermenek Case Study

This study investigates the influence of the code-based near-fault factor on the seismic response of buried steel natural-gas pipelines through the design response spectrum approach prescribed in the Turkish Seismic Code for Pipeline Systems and Liquid Storage Tanks (2023). The novelty lies in explicitly incorporating both the maximum-direction and near-fault factors into a spectrum-based finite element assessment and quantitatively evaluating their effects on displacement- and stress-based seismic demands. A planned pipeline route between Seydişehir (Konya) and Ermenek (Karaman), Türkiye, was selected as a case study, and seismic hazard parameters were obtained from the Turkish Seismic Hazard Map. The pipeline was modeled using four-node shell elements, while soil–pipe interaction was represented by linear elastic Winkler springs. Response-spectrum analyses were performed for DD-1, DD-1a, DD-2, and DD-3 ground-motion levels. For the DD-1 level including the near-fault factor, the maximum vertical displacement reached 10.42 mm, and the maximum axial membrane stress was approximately 62 MPa. The inclusion of the near-fault factor increased the maximum vertical displacement by 41% and raised the axial strain and membrane force demands by about 30%. The results demonstrate that neglecting this factor may lead to unconservative estimates of deformation demands in buried steel pipelines near active faults.