NUMERICAL INVESTIGATION OF PIPELINE RESPONSE TO LONGITUDINAL GROUND MOVEMENT

Current efforts are underway to address buried pipeline susceptibility to damage from ground movements triggered by earthquakes, such as liquefaction-induced lateral spreading, landslides, and fault rupture. The linear nature of water and wastewater pipelines promotes failure due to ground displacement at locations of weakness, which for segmented pipelines is typical at joints or fittings linking adjoining sections of pipe. Pipe connections can be characterized as unrestrained (bell-and-spigot joints), fully restrained (continuous systems with bolted or welded/fused connections), or hybrid segmented joints, which provide the ability to displace axially in response to ground movement before locking up and behaving as a continuous system. The joint type and geometry contribute significantly to the expected performance of a given pipe system subjected to axial ground movements. Furthermore, the connection force capacity of the joints is an important limit state for predicting failure of pipe systems for which the joint has less strength than the pipe barrel. To support the development of an American Society of Civil Engineer’s Manual of Practice on Seismic Design of Water and Wastewater Pipelines, this paper presents a numerical model, simulating the response of two different hybrid-segmented pipelines subjected to block ground movement oriented parallel to the pipeline axis: (1) hazardresilient ductile (DI) iron pipe and (2) oriented polyvinylchloride (PVCO) pipe with joint restraints capable of axial deformation. The imposed ground displacement is representative of measured lateral spreads observed during postearthquake reconnaissance. Full-scale experimental results were used for fundamental analysis inputs, including joint axial force-displacement, pipe barrel frictional resistance, and soil-structure interaction associated with the enlarged joint connection displacing relative to surrounding soil. The finite element analysis demonstrates that the maximum elongation capacity of the considered DI pipe system is about 2.8 times greater than that of the PVCO pipeline. Comparison of the numerical results with a closed-form analytical solution, proposed to quantify axial connection force capacity of various pipeline systems, showed excellent agreement between the two approaches, highlighting the importance of assigning appropriate axial friction parameters for these systems. Validation of the proposed analytical solution, through the combination of experimental and numerical analysis, provides a robust first-order measure for characterizing pipeline systems, of any material or jointing characteristics, against seismically-induced longitudinal ground deformation.