Estimation of Wave Loads based on Two-dimensional Wave Spectrum by Hindcast

• Published in: Journal of the Japan Society of Naval Architects and Ocean Engineers Vol. 36; pp. 125 - 135
• Main Authors: Oka, Masayoshi, Ma, Chong, Chen, Xi
• Format: Journal Article
• Language: Japanese; English
• Published: Tokyo The Japan Society of Naval Architects and Ocean Engineers 2022; Japan Science and Technology Agency
• Subjects: Bending fatigue; Bending moments; Damage; Deformation; Expected values; Fatigue failure; Mathematical analysis; Peak frequency; Response functions; Ship decks; Ships; Significant wave height; Strip; Wave direction; Wave height; Wave period; Wave spectra
• ISSN: 1880-3717; 1881-1760
• DOI: 10.2534/jjasnaoe.36.125

Long-term expected value of vertical bending moment (VBM) and fatigue damage at mid-ship deck are estimated utilizing the two-dimensional wave spectrum found by hindcast and the response function obtained by the strip method. The estimated value using the two-dimensional spectrum is about 6% larger in long-term value and about 20% larger in fatigue damage than in case of using the wave spectrum which IACS recommend. It did not act in the direction of filling the gap between the value of the on-board measurement and the value based on the numerical calculation. On the other hand, it is able to be said that the selection of the spectrum does not bring much difference to the long-term prediction as long as the representative wave direction, the significant wave height and the average zero-up crossing wave period are matched. It was confirmed that the higher the significant wave height, the greater the concentration of the hindcast spectrum than the IACS recommended value (λ=1). The difference between the two (RHindcast -RIACS) is that if the peak frequency of the wave spectrum match with the frequency at which the response is maximum, RHindcast with a higher degree of concentration is larger. However, if this does not match, the relationship may be reversed.