Numerical study on upheaval buckling of pipe-in-pipe systems with full contact imperfections

• Upheaval buckling responses of pipe-in-pipe systems are analyzed by dimensional analysis and dynamic finite element method.
• Empirical formulas corresponding are proposed to calculate the critical upheaval buckling force of pipe-in-pipe systems.
• The influence of the clearance and stiffness ratio on critical buckling force is unfolded.

Upheaval buckling may occur in high-temperature and high-pressure subsea pipe-in-pipe (PIP) systems. Finite element method and dimensional analysis method are used to investigate the upheaval buckling response and critical buckling force of PIP systems with full-contact imperfections. Results show that imperfections, along with clearance (the gap between the centralizer and outer pipe) and stiffness ratio of the inner and outer pipe, influence buckling response and buckling force. Two empirical formulas that correspond to two typical imperfection profiles are proposed to calculate the critical upheaval buckling force of PIP systems on the basis of dimensional analysis and numerical results. The proposed empirical formulas show good accuracy.