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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The primary observations are as follows:

• As expected, the captured non-linear bending response of the tested power cable exhibits the following be haviour: in the stick regime, where friction is su ffi cient to prevent relative displacement between cable compo nents, the bending sti ff ness reaches its maximum (blue slope in Fig. 2(a)–(c)) at small curvatures. As bending curvature increases, sti ff ness gradually decreases as slipping initiates, until full slippage occurs and bending sti ff ness reaches its minimum (red slope in Fig. 2(a)–(c)). • The evolution of bending sti ff ness in the stick regime, denoted as K stick , is shown in Fig. 2(d). An initial increase between the first and second intermediate cycle stages (from 96.87 to 100.59 kN·m 2 ) is followed by a decrease to 81.39 kN·m 2 at the end of the bending series. This trend reflects the previously noted high variability and limited reliability in determining bending sti ff ness in this regime. • In contrast, the bending sti ff ness in the slip regime, denoted as K slip , exhibits a continuous decline over the three monitored cycle stages, decreasing from 9.67 to 8.89 kN·m 2 . This trend, which can be seen in Fig. 2(d), re flects the progressive relative displacement between cable constituents, which contributes to mechanical degra dation due to cyclic bending. Fig. 3 provides a comparative overview of the captured non-linear reciprocating bending behaviour of the tested cable across the four post-processed bending test series listed in Table 1. For ease of visual interpretation, only five bending cycles are shown for each series, while reported average quantities of bending sti ff ness in the stick and slip regimes, critical bending curvature, and corresponding energy dissipation, are calculated over the entire set of mon itored cycles. The analysis emphasizes the progression of the non-linear bending behaviour, as well as the evolution of the bending sti ff ness in both the stick and slip regimes, highlighting the influence of increasing bending amplitude and number of bending cycles throughout the test campaign.

Fig. 3. Non-linear reciprocating bending behaviour of TB5, TB6, TB7 and TB10

Based on this comparison, the main observations are as follows:

• Bending sti ff ness in both the stick and slip regimes ( K stick and K slip , respectively) decreases from TB5 to TB10, reflecting a reduction in the cable’s mechanical performance, likely caused by the combined e ff ects of accumulated bending cycles and increased curvature.