NUMERICAL MODELING OF BURIED SEGMENTED PIPELINE RESPONSE TO EARTHQUAKE GROUND MOTION

Taha Pabuçcu

(Thesis Supervisor: Prof. Gülüm Tanırcan and Asst. Prof. Hasan Emre Demirci)

ABSTRACT

Earthquakes severely impact infrastructure, disrupting essential services like water pipelines. Understanding and improving the mechanical behavior of pipelines and their joints under permanent ground deformations is crucial to minimize potential damage and ensure the continuity of their service.

In this study, three-dimensional numerical models of buried segmented ductile iron pipes were developed to investigate their nonlinear behavior under lateral strike-slip surface faulting. Fault crossing angle, position, and vector were selected as variable parameters, and pipeline performance was evaluated based on different faulting scenarios and two soil models covering a total of 20 cases. The numerical models were validated using experimental and finite element data from the literature.

The results indicate that when the fault crossing angle was perpendicular to the pipeline axis, the system was able to accommodate the most amount of fault displacement. Narrower fault crossing angles induced axial separations or compression to the pipeline. Under compression, the pipeline undergoes joint crushing failure by exceeding the material limits, while tensile forces primarily lead to joint pullout. A joint interlocking phenomenon was observed in tension cases when the fault crossed directly through the joint and effectively delayed or prevented failure by uniting adjacent pipe segments. The results also highlighted the sensitivity of pipeline performance to design criteria, where a 2 cm increase in pullout threshold resulted in up to 20 cm of additional fault displacement capacity. Lastly, the study emphasized that while soil models influenced pipeline response under tension, their effect was limited in compression scenarios due to more premature failure.