SOLUTIONS TO TORSIONAL MOMENTS, HOGGING, AND SAGGING IN ULTRA LARGE CONTAINER VESSELS (ULCVs) AND SIMILAR SHIPS

Abstract

ABSTRACT Ultra Large Container Vessels (ULCVs) present a fundamental structural paradox in navalarchitecture: they behave as thin-walled, open-top cross-sections lacking a continuous strength deck.Consequently, dynamic torsional moments (MT ) and shear stresses (τ ) induced by oblique and headseas concentrate severely along the hatch corners and upper torsion boxes, driving warping distress,bi-moment amplification, and low-cycle fatigue. This paper introduces a quantitative analyticalframework for two novel structural paradigms designed to supplement traditional 90◦ orthogonalgrillages: (1) Diagonal Reinforced Arched Frames, acting as an elastic space-truss system acrosstwo consecutive bay modules to arrest warping deplanation (ω) and dissipate dynamic torsionalenergy; and (2) Diamond Shear Relief Structures, engineered to redirect vertical-longitudinalshear flow (τzx) into pure membrane tension-compression paths, elevating the plate elastic bucklinglimit (ks). Furthermore, roll dynamics and transverse accelerations are formulated as a functionof the transverse metacentric height (GMT ). We demonstrate that hard-chined, flat-bottomedhull forms induce excessive inertial racking forces (> 0.70 g) at upper container tiers (Tiers 10–13), exceeding the safe working load of standard ISO lashing assemblies. An optimized roundedbilge profile softens the roll period, prevents stack collapse, and significantly improves operationalseaworthiness.