High-pressure gas pipelines constitute essential components of the global energy network and expensive engineering projects. However, they usually cross areas characterized by the presence of earthquake-related geohazards, such as slope instabilities, fault rupture and soil liquefaction phenomena. Moreover, it is not always techno-economically feasible to completely avoid such areas, while the application of geotechnical and/or structural mitigation measures can be impractical or prohibitively expensive. Hence, the optimal seismic design of pipelines is of paramount importance to ensure their safety and continuous operation and avoid failures with devastating consequences.

Conventional design approaches typically rely -apart from engineering expertise- either on computationally expensive numerical simulations and/or experimental programs that require substantial resources. On the other hand, research on pipeline optimization has quite recently evolved and has been mainly focused on minimizing construction and operational expenses to enhance operational efficiency, but without considering pipeline geotechnics and seismic safety aspects. To address this gap, the present work introduces an efficient optimization framework that enables the fast, reliable and performance-based design of onshore pipelines subjected to seismic fault rupture geohazard.

For this purpose, several realistic pipeline optimization problems are formulated and solved via efficient nature-inspired optimization algorithms, by identifying key geometric and mechanical pipeline parameters, while simultaneously satisfying geotechnical, structural, and operational constraints. The significant potential of the proposed sizing optimization framework is demonstrated by performing an extensive parametric investigation for various fault offsets and soil types, providing insights into the optimal structural behavior of pipelines subjected to this geohazard. In addition, the obtained optimization results are adjusted to available manufactured dimensions, ensuring direct applicability in pipeline engineering practice.