Springing

Steady-state hull-girder vibration excited when the encounter wave frequency matches a natural bending mode — typically the two-node vertical mode for very long ships such as ULCVs and ore carriers. Unlike transient whipping, springing is continuous in moderate seas and acts as a low-amplitude but high-cycle fatigue load on deck connections and hatch corners. ISSC and class research associate springing with hull-girder stress increases of several percent over the rigid-body wave bending moment, prompting class fatigue assessments to include it for ships above ~250 m.