On the presentation of ship's hull girder section modulus in probabilistic formats

ABSTRACT

A probabilistic analysis for wave-induced hull girder bending stresses is normally evaluated using the so-called ‘annual’ probability density function (PDF) of hull girder section modulus. However, the design wave-induced loads given by Class Rules are specified for the whole design life of a ship. To solve this problem, a kind of PDF of hull girder section modulus considering ‘time period’ was introduced. A parametric study was performed to investigate the effects of the two types of PDFs of hull girder section modulus, namely the ‘annual’ and ‘time period’ PDFs, on the PDF of wave-induced hull girder bending stresses. The results show that the probability of exceeding given permissible hull girder bending stresses calculated using the ‘time period’ PDF of hull girder section modulus is smaller than that calculated based on the ‘annual’ PDF. A palpable difference between the two PDFs of wave-induced hull girder bending stresses occurs after 15 years.

KEYWORDS:

• Ship's hull girder section modulus
• vertical wave-induced bending moments (VWBM)
• hull girder bending stresses
• probability density functions (PDFs)

Disclosure statement

No potential conflict of interest was reported by the authors.