Snap load dynamics in non-metallic armored umbilical cables under heave excitation

• A lumped-mass model is developed to simulate the dynamics tension of a towing non-metallic armored umbilical cable with neglectable bending stiffness. • A criterion for cable slackness and snap load is established based on the velocity difference between the two ends of the cable. • The model is validated against published quasi-static data and full-scale sea trial measurements with good agreement. • Dynamic tension is primarily influenced by inertial effects, whereas snap loads are governed by transient slack-to-taut transitions. Non-metallic armored umbilical cables have a high strength-to-weight ratio and high corrosion resistance. However, their reduced bending stiffness easily leads to slackness during dynamic response, which can subsequently induce snap loads. This can potentially lead to structural damage and operational failure. In this study, a lumped-mass model is developed to simulate the dynamic response of the cable under towing conditions. The model first computes the equilibrium configuration of the cable under quasi-static loads. A dynamic analysis is subsequently performed under combined wave and vessel heaving excitations. A numerical procedure for handling cable slackness and snap loads is introduced when the tension approaches zero and the vessel's descent velocity exceeds that at the cable bottom. The model is validated against published quasi-static results and the full-scale sea trial data, respectively. Parametric studies are conducted to investigate the effects of wave conditions, cable properties, and towed vehicle parameters on the cable responses. The results indicate that the dynamic tension of the towing cable is primarily influenced by inertial effects. The snap load is governed by the transient slackness-to-tautness transition and is more likely intensified by large wave amplitudes, high wave frequencies, and a light towed mass.