Welded pipelines conveying oil or gas have a long history to verify their safety and effectiveness during past earth-quakes. Highly pressurized gas pipelines however have been required to survive even in the strong ground motion after the 1995 Hyogo-ken nambu earthquake which was observed at the city of Robe during the earthquake. Moreover additional design codes have been discussed to take liquefaction-induced lateral spreading into consideration. The deform ability of pipelines is defined by their inelastic axial and/or bending buckling strength. NKK has developed a new line pipe NK-Hiper, which has higher deform-ability and is able to produce higher safety compared with conventional pipes of the same specification. This paper describes material properties and inelastic local buckling strength and nonlinear deformation of NK-Hiper against permanent ground displacements and fault movement.
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