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 most segmented pipelines have limited axial pullout capacity, they may be able to accommodate substantial rotation without leakage. Full-scale tests to characterize joint performance under combined axial and rotational deformation were performed at the Cornell University equipment site of the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES). These types of tests are essential for evaluating jointed pipeline response to extreme loading conditions. This paper reports on a series of specially designed four-point bending experiments to characterize 150-mm-(6-in.)-diameter DI push-on joints. The DI pipelines used in the experiments were manufactured by the U.S. Pipe and Foundry Company and supplied by the Los Angeles Department of Water and Power (LADWP). The full-scale tests were designed to investigate how the rotation capacity of the joint is related to the level of axial pullout. The results were used to develop a relationship between rotation and metal binding as a function of axial pullout, as well as to determine the magnitudes of rotation and moment that initiate joint leakage.