Abstract Oil and gas production in deep and ultra-deep waters in Brazil’s offshore fields is mostly carried out by flexible pipe risers. Flexible pipe risers may experience different lifting and launching by the operation ship to be reused. When the pipeline passes by tension equipment, crushing loads are applied, potentially increasing its initial ovality. Additionally, flexible pipe risers are exposed to external loads in the operation phase and corrosive environment when the pipeline is put in long periods of hibernation. Therefore, flexible life extension or safe decommissioning has to be studied through an assessment of the structural integrity capacity of the pipeline considering the conditions described above. In this paper, an unbonded flexible pipe riser which has been in hibernation for a certain period is studied experimentally and numerically under radial crushing loads. In the test, only the interlocked and polymer layers of the flexible pipe were considered for the studies. The characteristics of the crushing equipment follow the recommendations of API RP 17B. This equipment has four shoes with V-shape, two shoes are fixed and the others movables. The pipe was subjected to 15 loading cycles and after each load cycle, the internal ovalization is measured using laser tracker technology. The pipe has an internal diameter of 101.6mm and a crushing contact length of 1.0 m. The load cycles are trapezoidal, and each cycle is named M1 to M15, where the maximum loads applied for M1 to M6 are 24tf, M6 to M10 are 30tf, and M11 to M15 are 50tf. These loads were obtained through a finite element model in Abaqus software with implicit solved, and non-linearities were considered. The interlocked carcass was modeled considering the helical geometry and pitch using beam elements of type B31OS. Also, the shoes were modeled using analytical surfaces. The results showed an increase in ovalization with increasing loads and the shakedown phenomenon during load cycling.
Quispe et al. (Sun,) studied this question.