Simple Estimation Method for Long-term Distribution of Wave Induced Load based on the Severest Wave Condition Approach

Abstract

This report is concerned with a simple estimation method for a long-term distribution of wave induced stress on a ship hull structure. Authors had examined the relation between the statistical property of supposed wave condition and the long-term distribution of wave induced load based on linear response prediction is studied. Authors had clarified that the maximum wave induced load in the vicinity of the probability of exceedance around 10-8on the long-term distribution and the parameter could be governed by the severest short-term wave condition which has the largest value of short-term wave induced distribution parameter.The physical meaning of the severest wave condition is a broad sense of resonance between the response amplitude operator (R. A. O.) and wave spectrum when both the maximum peak value of R. A. O. and wave spectrum share the same frequency. So that the maximum peak value of R. A. O. and the frequency become the key ward of the severest wave condition and the severest short-term parameter. Authors introduce a simple estimation method for a long-term distribution of wave induced stress on a ship hull structure by using the maximum peak value of R. A. O. and the frequency. The method is applied for the numerical estimation of long-term distribution of a 210, 000 DWT bulk carrier.