Behaviour of reinforced thermoplastic pipe (RTP) under combined external pressure and tension

The problem of reinforced thermoplastic pipe (RTP) buckling or collapse as a result of combined tension and external pressure is investigated in this paper. Based on the theory initially proposed by Kyriakides and his co-workers, a two-dimensional (2D) theoretical model, which takes into account transverse shear deformation, the mean radius change, the wall thickness change and pre-buckling deformation, is developed. By means of numerical calculation, pressure-ovalisation and pressure-axial strain curve are presented for T -> P loading. Two failure modes were investigated during the loading path. A three-dimensional (3D) finite element model was further established in ABAQUS to confirm the accuracy of the theoretical model, and the results were found to be in good agreement in the small strain stage. Finally, additional parametric studies were conducted, including the effects of initial ovality, tension, pressure, loading path and pressure-to-tension ratio. Predicted T -> P and P -> T collapse interaction envelopes are presented and useful conclusions are drawn for RTP's marine engineering application.