Calibration of a Flexible Pipe Tensile Armour Stress Model Based on Fibre Optic Monitoring

The present paper addresses calibration of a flexible pipe tensile armour stress model based on fibre optic monitoring. A full-scale flexible pipe was instrumented with fibreoptic Bragg grating (FBG) strain sensors in the inner tensile armour, enabling measuring the axial stress due to friction effects and the bending stresses due to bending about the strong axis of the tensile armour tendon. The measurements were used to study the dynamic stress as a function of global loading providing data for model calibration. A brief description is given of the applied sensor technology, how the sensor was integrated in a flexible riser, the test set-up and the test program. The paper focus on how these data were used and which parameters that are critical in order to provide a model that gives a best fit estimate of the dynamic stress distribution. A simple theory of shear interaction is presented. The theoretical model was implemented into the computer code BFLEX and comparisons made in terms of stress history plots including both the tested and predicted values.