Buckling response of pipe-in-pipe systems subjected to bending

The buckling response of pipe-in-pipe(PIP)systems subjected to bending is investigated in this paper. A set of parameterized models are established to explore the bending characteristics of the PIP systems through eigenvalue buckling analysis and nonlinear post-buckling analysis. The results show that the length of PIP systems and the height of centralizers are the most significant factors that influence the buckling moment, ultimate bending moment and buckling mode; the other geometric characteristics, such as initial geometric imperfection and friction between centralizers and outer pipes, evidently influence the post-buckling path and ductility of PIPs; the equivalent bending stiffness is dependent on the length and centralizers. Moreover, the range of equivalent bending stiffness is also discussed.