Collapse of reinforced thermoplastic pipe (RTP) under combined external pressure and bending moment

With shear deformation and pre-buckling deformation included, a 2D mathematical model for composite pipes is developed to analyze the collapse of RTP pipe under pure external pressure, pure bending moment, or combined external pressure and bending moment. The models for RTP pipes are developed based on the models of steel pipe proposed by Kyriakides and his co-workers. Theoretical analyses of collapse of RTP pipe under short-term hydrostatic external pressure, bending moment, or combined external pressure and bending moment have been presented in this paper. The effects of radius-thickness ratios, initial ovality and initial stresses, pre-buckling deformation and modulus of elasticity have been discussed. Through data fitting, formulas of RTP collapse under pure external pressure, pure bending moment, or combined external pressure and bending moment have been developed. A good agreement between the calculation based on formulas and finite element analysis verifies the efficiency of the formulas.