Critical upheaval buckling forces of imperfect pipelines

•The upheaval buckling behavior of buried pipelines with three typical imperfections was investigated by dimensional analysis and finite element analysis.•Three design-oriented approximation formulas for critical axial forces were figured out by mathematical fitting and their application was illustrated.•These critical axial force formulas are different from the previous approximation formulas in form, which take into account out-of-straightness directly and integrally.

A buried pipeline may have upheaval buckling when it works in high temperature and high pressure (HT/HP) conditions. The upheaval buckling behavior is sensitive to initial structural imperfections. There have already been some approximation formulas of critical axial forces for some particular shape imperfections. However, these formulas did not take into account of the imperfection out-of-straightness (OOS) as a whole. Based on dimensional analysis and finite element (FE) analysis some brand new formulas are presented for the critical axial forces. These formulas are different from the traditional formulas in form and they include the out-of-straightness directly and integrally. Finally a case study is presented which illustrates the application of these formulas.