Characteristics of hull stresses measured on a large containership in rough seas

To obtain full-scale data for rationalizing hull structural design of fast fine ships with large bow flare, a series of measurements was carried out on a large containership in the North Pacific Ocean during the winter season. The focus of the measurement was placed on clarifying the short-term characteristics of hull stresses of this type of ship. By direct examination and statistical analysis of measured time histories, characteristics of longitudinal stresses on the foredeck were found to be quite different from those in the midship half-length. Foredeck stresses vary directly with the impulsive forces on the bow flare, while those in the midship portion respond mainly in the form of whipping vibration. As a result, the probabilistic distributions of foredeck stresses do not fit exponential, Rayleigh's, or Gaussian distribution. The probabilistic characteristics of hull stresses suggest that there is a distinct possibility of occurrence in the bow portion of far higher sagging moment than anticipated. It is urged that the design of fine-form, high-speed ships take account of this possibility, and recommendations in this regard are offered.