UOE line pipe tested in full-scale tests for Strain Based Design

Displacement controlled scenarios such as ground movements may significantly affect transmission pipelines by inducing large amounts of plastic strains, which need to be considered in the Design process. The resistance of a pipeline against multi-axial load scenarios (internal pressure combined with pronounced longitudinal strain from external actions) is still a much researched topic because line pipe performance cannot be predicted fully reliably resorting to theoretical considerations only. Using Strain Based Design approaches, it is important that the pipeline is capable of accommodating adequate plastic strain along its axial extension. In this context, full-scale testing is a possible way to determine proper pipe behavior in the elastic-plastic regime of material behavior. In this paper, buckling behavior of UOE line pipe subjected to internal pressure and bending load was investigated. Full-scale tests on large diameter pipe joints of grade X100 (OD = 914 mm, WT = 13 mm) were performed on a 4-point-bending test rig, which is installed at Salzgitter Mannesmann Forschung GmbH, Duisburg, Germany. The bending tests, which were carried out in displacement control were accompanied by analytical buckling stability modeling.