Abstract
Container ships are becoming larger and larger in recent years, requiring more evident assurance of the structural safety. To achieve this, it is essential to grasp actual stress history experienced by the ship structures to facilitate efficient design and maintenance, and to use them for optimal operation of the ship. To perform accurate estimation of these stress histories, it is important to precisely estimate the sea state which the ship is actually encountering. In this study, the authors studied a new method to estimate directional wave spectra using measured ship responses and discussed the following three cases. The first one is the combination of two components, vertical bending stress and horizontal bending stress. The second one is the combination of three components, vertical bending stress, horizontal bending stress and double bottom bending stress. The last one is the combination of three components of ship motion (pitch, roll and heave). The estimated sea states are compared with the ocean wave hindcast database and radar data, and then, accuracy and selection of appropriate combination of the responses are discussed.
Highlights
Container ships are becoming larger and larger in recent years, requiring more evident assurance of the structural safety
Regarding large container ships with their length greater than 300 m, the ship will not respond to relatively high-frequency waves, and it is concerned that the wave spectrum in the high-frequency zone cannot be estimated accurately
The second one is the combination of three components, vertical bending stress, horizontal bending stress and double bottom bending stress
Summary
Container ships are becoming larger and larger in recent years, requiring more evident assurance of the structural safety. [2], but usage of measured ship responses for the wave estimation is considered to be promising, taking account of its good. We can see that ship motions have been the most frequently used responses for sea state estimation. In 2017, Yoshihira et al proposed a method to estimate ocean wave spectrum using measured hull girder vertical bending stress using these container ships [24]. In 2018, Chen et al used two methods (the parameter method and the discretized wave spectra method) to discuss the wave state based on longitudinal bending stress and ship motion (pitch and roll) [25]. The estimated sea states are compared with the ocean wave hindcast database and radar data, and accuracy and selection of appropriate combination of the responses are discussed
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