Jointed Pipeline Response to Earthquake Induced Ground Deformation
The earthquake performance of segmental pipelines is strongly influenced by the axial pullout and compressive load capacity of their joints, as well as by the limits on joint rotation during permanent and transient ground deformation. Although ductile iron (DI) pipelines with push-on joints are commonly used in water distribution systems, experimental data related to their performance under large ground movements are lacking. While segmented pipelines have limited axial pullout capacity (approximately 55 mm), they have substantially larger resistance to movement that is oblique or perpendicular to the line. Full-scale tests addressing gaps in knowledge concerning joint performance were undertaken at the Cornell University equipment site of the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES).
This paper reports on a series of four-point bending experiments designed to characterize the leakage potential of 150 mm (6 in.) diameter DI push-on joints. The DI pipelines used in the experiments were manufactured by U.S. Pipe and supplied by the Los Angeles Department of Water and Power, representing the type of DI pipelines commonly used in seismically vulnerable communities. The full-scale tests were designed to investigate how the rotation capacity of the joint is related to the level of axial pullout. Tests were run at internal water pressures of 0, 170, 340, and 520 kPa (0, 25, 50, and 75 psi). The results were used to develop a relationship between rotation and metal binding as a function of axial pullout, as well as the magnitudes of rotation and moment which initiate joint leakage.
A three-dimensional finite element model of the push-on joint was developed to evaluate yielding and joint deformation under high levels of rotation and compressive axial load, and the results of the finite element simulations were compared with the experimental results. Soil-structure interaction simulations of earthquake-induced ground deformation perpendicular and oblique to the longitudinal axis of a DI pipeline with push-on joints are performed to evaluate the response of the pipeline to soil displacement magnitude, distribution of movement along the pipeline, and orientation of movement relative to the longitudinal axis of the pipe.