Evaluation of Lashing Pot Structures in RO-RO Ships Using Serviceability Limit State Criteria

In roll-on/roll-off (RO-RO) ships, lashing devices are essential for securing vehicles. However, conventional installation processes significantly increase shipbuilding costs. To enhance production efficiency, this study establishes a rational strength evaluation criterion for an integrated deck structure that unifies the lashing cup and lashing hole. A load equivalent to 1.25 times the minimum securing load was applied to simulate dynamic loads induced by ship motion. The serviceability limit state (SLS) was defined as preventing hook disengagement and limiting permanent deformation to 3 mm in accordance with International Organization for Standardization 23575. Finite element models with various under-deck reinforcement configurations were analyzed using the combined Swift–Voce constitutive equation to accurately capture large-deformation behavior. Nonlinear structural analysis results showed that unreinforced models exhibited excessive permanent deformation, failing to satisfy the SLS criteria, whereas properly reinforced models met the SLS even at the initial deck thickness. For models that did not fulfill the SLS requirements, the deck thickness was gradually increased to reassess structural safety and determine the minimum thickness ensuring integrity. The proposed SLS-based methodology effectively verifies the structural safety of integrated lashing pots, contributing to enhanced reliability and reduced manufacturing costs in RO-RO ships.