NUMERICAL STUDY ON TORSIONAL BEHAVIOR OF CARBON STEEL-CONCRETE-STAINLESS STEEL DOUBLE-SKIN TUBE (DST)

One type of submarine composite pipeline structure, with carbon steel-concrete-stainless steel (CCS) double-skin tube (DST), was introduced in this paper. This composite pipeline was expected to make optimal use of the three types of the materials, and provide significant structural and internal corrosion resistance. During installation and service stage, submarine pipelines may experience significant torsion effects. Global response of the system depends on both the behavior of each constituent part and interactions between them. In this paper, an interaction model considering the friction and the cohesive force between the steel tube and the concrete is introduced, and a finite element model of the submarine pipeline under torsion is established by using this interaction model. The developed finite element model was verified through the comparisons between the numerical and experimental determined results, in terms of torque rotation angle histories, stiffness and ultimate torque. The results show that the ultimate strength and stiffness of the model considering cohesive force are increased by 4.6% and 11.9% respectively compared with the model only considering friction force.