Buckling behavior of sandwich pipe under external pressure and lateral load

The buckling propagation in deep-sea service sandwich pipes is prone to occur under the influence of third-party loads. Therefore, it is crucial to determine the carrying capacity of the sandwich pipes under combined loading conditions for safety. Currently, the predominant method for studying the carrying capacity of sandwich pipes relies on hyperbaric chamber tests, which fail to reflect adequately the buckling behavior under lateral loads. In this study, the finite element package ABAQUS was used to establish a finite element model that accounted for the lateral load on submarine sandwich pipes. It was solved for the maximum lateral load and compared the results with experimental tests, and then validated the accuracy of our numerical simulation method. This investigation focused on studying the buckling behavior of sandwich pipes under displacement control, and analyzed the relationship between buckling behavior and external pressure as well as lateral load. Furthermore, the comprehensive parametric studies were performed to analyze the impact of initial ovality, inner pipe thickness, and outer pipe thickness on the maximum lateral load of the sandwich pipe. The findings demonstrated that under coupled loads, sandwich pipes exhibited two types of buckling behavior: local buckling and buckling propagation. Moreover, as the external pressure increased, the buckling tendency in sandwich pipes transited from local buckling to buckling propagation. To enhance the capacity of sandwich pipes, there were two strategies proposed: increasing the thickness of the outer pipe and then reinforce the inner pipe to improve overall strength. Finally, based on an analysis of sandwich pipe applications up to 5000 m water depths, the sandwich pipe structure were proposed suitably for various water depths.