PSI - Issue 77

Esteban Cadavid Gil et al. / Procedia Structural Integrity 77 (2026) 248–255 Cadavid et al. / Structural Integrity Procedia 00 (2026) 000–000

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• As bending curvature increases, the transition between the stick and slip regimes becomes more pronounced. At smaller bending amplitudes (TB5, TB6), the stick region is comparatively dominant, whereas at larger am plitudes (TB7, TB10), extended slip behaviour is observed. • The area enclosed by the hysteresis loops increases from TB5 to TB10, indicating greater energy dissipation. This trend suggests that as bending curvature increases more energy is dissipated through internal friction, which can be attributed to relative slip among the cable components, particularly within the stranded wires that comprise the cable cores. Fig. 4(a) and Fig. 4(b) present the evolution of the experimentally determined bending sti ff ness as a function of the number of bending cycles in the stick and slip regimes, respectively. These results, obtained from the four post-processed bending test series (TB5, TB6, TB7 and TB10), provide valuable insight into the overall mechanical response of the tested submarine power cable under cyclic bending and its structural integrity. In Fig. 4(a), bending sti ff ness in the stick regime shows an overall decreasing trend. However, two deviations are observed: at an intermediate stage of test block #7 (TB7) and at the final stage of test block #10 (TB10), where an increase is observed. As previously discussed, the computed bending sti ff ness in this regime is more susceptible to variation and measurement inaccuracies due to the low force and displacement levels involved. Nevertheless, despite these fluctuations, the general downward tendency across the post-processed bending series indicates a progressive reduction in cable’s mechanical performance as a result of cyclic bending. Over the course of the test blocks, bending sti ff ness in the stick zone drops from approximately 165 kN·m 2 at the first captured cycle stage of TB5 to about 73 kN·m 2 at the end of TB10, representing an estimated 56% reduction. In contrast, Fig. 4(b) shows a continuous decline in bending sti ff ness within the slip regime, where the cable’s mechanical response is more representative. These consistent trend confirms that the submarine power cable experienced progressive bending sti ff ness degradation throughout the cyclic bending series. Bending sti ff ness in the slip zone decreases from roughly 16 kN·m 2 at the first monitored cycle stage of TB5 to about 6 kN·m 2 at the end of TB10, corresponding to an approximate 62% reduction.

(b) Fig. 4. Bending sti ff ness evolution: (a) stick regime; (b) slip regime

(a)

5. Conclusions

This study proposes a novel experimental methodology to characterise the non-linear reciprocating bending be haviour of a three-core submarine power cable by combining a cyclic three-point bending test with 3D optical mea surements to track its deformed shape. The experimentally measured bending curvature, together with the computed bending moment, enables the reconstruction of the non-linear bending response at the mid-span in the form of a bend ing moment-curvature diagram. Stick and slip regimes are observed in the non-linear bending response, while the evolution of bending sti ff ness in both regimes throughout the test campaign indicates a mechanical degradation under cyclic bending. With increasing the bending curvature, the transition between stick and slip regimes becomes more