END FITTING EFFECT ON TENSILE ARMOR STRESS EVALUATION IN BENT FLEXIBLE PIPE

The stress evaluation of tensile armor layer in bent unbonded flexible pipe due to end fitting termination is investigated. A preliminary mathematical stress analysis model which accounts for the boundary condition at the end fitting interface is developed. Two shifting parameters are introduced to correct the friction field acting on the tensile wires. Closed form solutions are obtained for the modified friction force, axial stress and displacement. The validity of this model is investigated through a comparison with results obtained using a 3D finite element model. The relationship between the shifting parameters and the initial hoop position of wires is discussed. Studies of local stress elevation on wires with different initial hoop positions are conducted. The results show that end fitting effect could causes a significant stress elevation in a large amount of tensile wires if heavy pipe bending is permitted at the end fitting vicinity.