ABSTRACT

The primary objective of high strength line pipe is to hold high pressure safely. The property in circumferential direction under hoop stress is the primary target of the line pipe. High strength and high toughness steel at low temperature has been developed for large diameter line pipes, which have been supplied to major gas pipelines. The increase of D/T of pipelines for transportation efficiency tends to decrease deformability. Therefore, application of strain-based design (SBD) has been discussed primarily by the demand of construct pipelines in permafrost regions and seismic regions. In these regions, the pipeline is deformed by compression caused by seismic wave propagation, fault movement, lateral spreading caused by liquefaction and bending caused by frost heaving or thaw settlement in the permafrost regions. To apply the SBD and to perform a reasonable design, it is necessary to consider the ground displacement expected in pipeline construction area, interaction of the ground and the pipeline deformation state caused by the ground displacement and deformability of the line pipe. In general, steel ductility decreases by increasing strength. Thus necessity of SBD in pipeline is discussed more seriously with spreading application of high strength pipes more than X80. SBD indicates two strain limits of deformation in longitudinal direction: tensile rupture and compressive buckling. In this study, (1) effect of material property and wall thickness (WT) of X80 SAW pipes on compressive strain capacity, (2) relation of the compressive strain capacity of the pipes and the strain demand caused by liquefaction were investigated by FE analysis.

INTRODUCTION

The pipeline built by large diameter welded pipe has been served as the backbone of world energy delivery system. Due to the growing demand of oil and gas, the total length of the pipeline has been extended and more pipelines constructions are expected.

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