Nishimura, Macba, Ishikawa, Ueda
# 1998 Gothenburg
In the Great Hanshin-Awaji Earthquake, dthough leak and cracking occurred mainly in joints of small-diameter steel pipes with screwed joints, no damage occurred to polyethylene pipes. To secure aseis~uicresistance of gas pipeline, polyethylene pipes are expected to come into wider use i n the future. To deternune the influence of ground movement on polyethylene pipes during earthquakes etc., we carried out experiments in which displacement was applied to polyethylene pipes and evaluations of plastic-deformed parts with a tensile test and a stress rupture test. The delbrrn~tionbehavior of polyethylene pipes and joints under displacement was studied by conducting tensile tests and high-speed tensile tests on actual pipes. The results reveal that even pipes using the shortest polyethylene pipe satisfies the displacement absorption requirement of 5 cm which is specified in the seismic design guideline. Displacement causing plastic delbrn~ationwas applied to polyethylene pipes, and the molecular structure of plastic-deformed p m s was studied to evaluate the shon-term and longterm strength of polyethylene pipes. The result shows that polyethylene pipes have no problem in practical use.