Investigation On Buckling And Collapse Mechanisms Of Filament-wound Fiber-reinforced Composite Pipe Under External Pressure And Combined Load

Using reinforced thermoplastic pipe (RTP), a kind of filament-wound fiber-reinforced composite pipe, as offshore pipeline for oil/gas transportation has significant advantages. It is a promising work to promote the offshore applications of RTP. Compared with the traditional steel pipe, RTP is more inclined to collapse in subsea environment, and it is the reason that RTP is mainly used in onshore areas. Researches on the offshore application of RTP are insufficient up to now, and offshore applications of RTP have great potential. The main works of the paper are summarized as follows:(1) External pressure tests. External pressure tests for RTP were carried out. The failure mode and failure load were measured. Material test of PE was carried out in accordance with standard GB-T1040-2006to get the data of material property.(2) Buckling and collapse theory and equivalent method for reinforced layers. Based on the nonlinear ring theory, including the effect of one-order shear deformation and pre-buckling deformation, a nonlinear buckling theory was proposed. A method was proposed and used to transform the reinforced layer s of RTP on the basis of’Hui’model.(3) Finite element model. A finite element model was built with solid elements, with truss element embedded, to simulate RTP pipe under the load of external pressure and combined bending and external pressure. Buckling and collapse response of RTP under the above loads was analysed and compared with the result of theoretical method.(4) Parameter study. Parameters affecting the RTP’s capacity under external pressure were studied using theoretical method, such as D/t ratio, shear deformation and pre-buckling deformation. Parameters affecting the capacity of RTP under combined bending and external pressure were studied using theoretical method, such as including initial curvature, initial external pressure, loading ratio and loading path.(5) Practical formulas for external pressure capacity of RTP. The responses of RTP with different geometric dimension and initial imperfections under external pressure were analysed using theoretical method. Practical formulas for external pressure capacity of RTP were proposed based on the existing formulas for PE pipe.