BUCKLING OF LONG SLENDER SHIPS DUE TO WAVE-INDUCED WHIPPING

Publisher Summary This chapter discusses the buckling of long slender ships due to wave-induced whipping. Several instances of storm damage to ship structure in areas protected from direct wave action stimulated a vigorous investigation. Analysis of data from full-scale trials, specially arranged and instrumented for the purpose, identified the phenomenon as the superposition of whipping stresses with the frequency of the fundamental mode of vertical vibration on the ordinary wave-induced stress with the frequency of wave encounter. The mode of failure was identified as buckling of the main deck under in-plane loading. The analysis also verified that emergence of the bow was not a prerequisite for the impact that excited whipping. Data from these trials indicated that the required phase relationship for the impact was a fully depressed bow into the crest of a wave. A mathematical analysis depicting the ship and the sea has been developed by adapting the equations of motion for a forced vibration system. To withstand the effects of whipping within the weight constraints imposed by the balanced design, it seems appropriate to dispose the stiffeners in the direction of loading and to space them sufficiently close together so that, in conjunction with properly proportioned plating thickness and suitably rigid stiffener cross-section, the buckling stress of the plate-stiffener combination approaches the yield stress of the material.