A Study on the Extensional-Torsional Response of a Damaged Flexible Pipe

Inspections in flexible risers have detected a considerable number of damages in their top section caused by the installation process or generated during their operation, due to the contact with another riser or components of the floating facility. Among the most common damages detected, the rupture of the tensile armor wires is critical to the structure integrity as its load capacity may be significantly reduced. The objective of this work is to present the main results involving pure tension and torsion with tension tests in a 4” unbonded flexible riser with five damaged wires in its outer tensile armor. These tests were carried out at the Structures Laboratory of Federal University of Rio de Janeiro (LabEst). Besides presenting full data concerning the internal structure of the riser, this paper describes the experimental procedures used to perform the tests and the main results obtained such as axial and torsional stiffness and the redistribution of forces in the wires. Comparisons between numerical simulations with those obtained experimentally are presented. A brief discussion about results and some simplifications assumed on the numerical model are presented at the end of the work.