Seismic Testing and Grading of Ductile Iron Water Pipes

Seismic Testing and Grading of Ductile Iron Water Pipes

Ductile iron is widely adopted as a material for buried water pipes due to its mechanical and chemical properties, such as its high toughness, strength, and resistance to corrosion. Ductile iron pipes(DIP) are fabricated in segments, normally 6 meters long, in workshops, and are connected by joints one-by-one on site. During an earthquake, they are inevitably subjected to ground shaking and deformation. Damage may occur in the pipe wall or at the pipe joint under excess seismic actions. In this research, seismic testing of DIPs is performed. DIPs with three different joint types, namely K-type, A-type, and flange, are tested. Pipe specimens filled with pressurized water were deformed separately under tension, compression, and bending loads. It is observed that DIPs with either a K-type or an A-type joint have good deformation capacity, but fail to prevent disengagement at the pipe joint under very small tensile action. DIPs with a flange joint, albeit with very high strength, have very poor deformation capacity and may leak easily once opened or bent slightly. Finally, according to the classification suggested by ISO 16134, the seismic capacity of DIPs with each of the three joints is classified with respect to their expansion, contraction, slip-out resistance, and joint deflection performance, respectively.