Study on prediction of stresses by out-of-plane and in-plane bending moments in offshore mooring chain

초록

A fatigue evaluation due to an out-of-plane bending (OPB) and in-plane bending (IPB) moments has been a key engineering issue in the mooring design of a floating offshore unit. Choung and Han recently proposed a numerical approach to predict the fatigue damage which was dependent on the maximum principal stresses at final load step without using linearly superposed stresses at each load step for a hotspot. The proposed approach does not use the nominal OPB/IPB moments and the nominal OPB/IPB stresses therefrom, but it is important to compare them for verification of the proposed approach. Based on the mid-span elastic deflection, the nominal OPB/IPB moments are shown in this study. Since the elastic deflection-based nominal moment increased as the OPB tension angle develops, it was proven that the assumption of the elastic deflection was not suitable. By introducing BV guideline formulas, we show the OPB/IPB moments change along the OPB/IPB tension angles.

키워드