Structural Consequences of Rib Reduction in Marine Lifting Lugs: A Nonlinear FEA-Based Performance and Failure Mode Assessment

This study presents a comparative mechanics-based assessment of rib reduction in standardized marine lifting lugs to support lightweight and structurally efficient design. A nonlinear finite element analysis (FEA) framework, supported by full-scale tensile validation of a representative LA50 reference specimen, was used to examine the structural response of the LA, LV, and LE lug series under a representative wire angle. Reducing the number of reinforcing ribs from four to two resulted in capacity-dependent strength loss, a reduction in analysis-based derated allowable load of up to approximately 40% within the investigated cases, and a transition from ductile deformation to instability-sensitive collapse dominated by web buckling. The study also discusses an analysis-based wire-angle derating interpretation for rib-reduced configurations within the investigated geometry, material, and boundary-condition assumptions. Integrated analyses with representative ship-block models indicate that selected rib-reduced designs may have limited influence on surrounding structures. The results provide a validation-supported comparative basis for understanding rib efficiency, stiffness degradation, and failure-mode transition in standardized lifting lugs, and they support future development of more performance-informed lightweight design practices.