Enhanced RTP Method for Nonlinear Statistical Prediction of Ship Structural Response

Abstract In this study, the ERTP (Enhanced RAO-based Translation Process) method, which is an enhanced version of the RTP method proposed in the previous study, is newly proposed. The RTP method approximates the extreme value distribution in arbitrary irregular waves from the nonlinear response in regular waves based on the idea of the transformation process, in which the nonlinear process is regarded as a transformation of a linear process. However, it was found that the RTP method is inaccurate when the response spectrum has multiple peaks, which is often the case for stresses in ship structures in waves. To solve this problem, the author developed the ERTP method, which defines a nonlinear transformation based on the Lp-norm of the response spectrum. A direct load and structure analysis (DLSA) considering the nonlinearity of wave loads was conducted and confirmed that the proposed method can reasonably estimate the extreme value distribution even for structural elements with a multi-peaked response spectrum with respect to the wave direction.