Prediction of the upheaval buckling critical force for imperfect submarine pipelines

Upheaval buckling behavior of submarine pipelines under high temperature and high pressure conditions is a primary concern for structural integrity. The critical axial force is a key factor governing the buckling behavior. There have been already some formulas to calculate critical axial force for some particular initial imperfection shapes. However, there is no universal formula to express the effects of initial imperfection shape and Out-of-Straight (OOS) on the critical axial force. In this paper, the upheaval buckling behaviors of eight groups of pipeline segments with different imperfection shapes and different OOS have been studied using the finite element method. A new parameter is defined to express the differences of imperfection shapes. An approximation and universal formula is proposed to calculate the critical axial force which covers the new parameter and the OOS of pipeline. A case study is presented which illustrates the application of the formula. Finally, comparison between this study and previous research results is conducted, and it manifests that this formula has a greater precision.