Dynamic stiffness of braided HMPE ropes under long-term cyclic loads: A full-scale experimental investigation

This paper presents a full-scale experimental investigation to study the nonlinear dynamic stiffness of high-modulus polyethylene (HMPE) fibre rope under long-term cyclic loading. Three kinds of ropes with different constructions and diameters were selected as test samples. The influences of mean load and load amplitude on axial stiffness and the corresponding evolution process were respectively studied. The experimental results showed that various braided ropes' dynamic stiffness was slightly different, which was mainly caused by the different twist angles. Furthermore, the non-dimensional stiffness of small-scale rope was lower than the large samples to some extent. This should be related to the small-scale ropes without an outer jacket were much softer and thus had more distinct deformation. The validations against two existing empirical expressions have also been performed. The results pointed out that these equations had some errors predicting the evolution procedure of the dynamic stiffness and the magnitude of small-scale sample's stiffness. On these accounts, a set of empirical expressions, taking into account braid constructions, diameter and input load conditions, has been newly derived. The comparison against the present experimental results proved its good reliability.