Probabilistic Approach to the Estimation of Seamargin

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In this project, the so carred "SEAMARGIN" that has been understood as the design margin or design allowance is investigated. The conventional seamargin was studied from the viewpoint of design engineering and as pointed out that it as not the exact design allowance.A ne concept of seamargin based on the probabilistic approach is proposed. The definition of the new seamargin is the power allowance of main engine to cover the probability of keeping prescribed ship speed. The decrease of ship speed in an actual seaway is represented by the sum of speed loss classified into(1)long-term 'Aging Effect', (2)NEddle-range 'Fouling Effect' and(3)short-term 'Weather Effect'. These effects are discriminated from each other under the assumption that each effect is a random variable of realizing independently.After estimating the probability density function of each effect, the probability density function of speed loss and ship speed in an actual seaway are estimated by the convolution integral of the probability density functions. The probability exceeding the specified threshold design speed is estimated and evaluated.