Numerical Analysis of Pipe-in-Pipe Filled with Various Materials

Abstract

The pipe-in-pipe proposed in this paper is an innovative structural material with more flexible and ductile bending performance than that shown by usual steel pipes. A pipe-in-pipe structure comprises double thin-walled pipes with granular material such as sand filled between the outer and inner pipes. The filling material prevents local failure known as the Brazier effect by transmitting the interactive stress between the pipes. As a result, smooth and flexible bending deformation is realized even under a large bending moment. In addition, when the sand filled in the pipe is frozen, the flexural rigidity of the pipe increases, but the pipe maintains its high ductility. To adopt such a pipe-in-pipe as a practical pipeline material, a numerical method must be established to evaluate the elastoplastic bending behavior. This paper proposes numerical methods for the bending behaviors of pipe-in-pipes and examines the difference in bending behaviors due to the filling materials using the proposed models.