A study on whipping related double bottom response as well as its statistical characteristics based on full-scale measurements

Abstract

Recently, the great enlargement of container ships has brought broad concern on the effect of whipping response. Meanwhile, the accompanying wider width of double bottom may cause more flexible responses of the double bottom structures. The numerical simulation studies have shown that the longitudinal stresses of the hold central bottom of a container ship due to the double bottom bending superimpose on the longitudinal stresses due to hull girder bending in both wave response component and vibrational response component. In this research, the authors firstly extract the full scale measurements data whose sea states are closest to that of numerical simulation among existing time series, with the purpose of analyzing correlation between double bottom bending and hull girder bending in wave response and vibrational response. As a result, studies from full scale measurements well verified the phenomenon that double bottom of larger container ship responds to forced vibration due to whipping excitation as observed in theoretical studies. Then, the statistical characteristics of correlation factor between hull girder bending stress and double bottom bending stress were investigated, based on relatively large number of data with regard to wave height and relative wave direction, as well as the classification between low- and high-frequency-dominant response cases. All these studies may contribute to future optimized operation, maintenance and design of ship.