Parametric Study on the Effect of Geometric Imperfections on the Bending Capacity of High-Strength Linepipes

It is important to determine the bending capacity of linepipes for strain-based design. Several empirical formulas have been proposed in order to evaluate the bending capacity of linepipes, which are presented in terms of the D/t ratio, the internal pressure, the yield ratio and the material strength. FEAs considering these parameters have been performed, however, it has been reported that the results do not always agree with experimental results. It has already been clarified that the geometric imperfections must be considered so that two types of results agree. This paper presents the results of a parametric study examining the effect of geometric imperfections on the bending capacity of linepipes. In addition, the effect of combining two or all of three types of geometric imperfections on the bending capacity was also investigated. When a single imperfection was taken into consideration in the FE models, it was quantitatively clarified that the bending capacity of linepipes improves with a decreasing geometric imperfection. Moreover, when combined geometric imperfections were taken into consideration in the FE models, it was also clarified that the largest imperfection tends to dominate the results and the smallest imperfection does not necessarily affect the bending capacity of the linepipes.