engleski

Hull girder fatigue strength of corroding oil tanker

The paper describes the fatigue strength assessment of oil tanker hull girder taking into account degradation of ship hull due to the corrosion. Hull girder degradation is represented as time-varying stress increase caused by time-varying loss of midship section modulus. Nonlinear function representing hull girder section modulus loss is based on recently published corrosion measurements on large number of single-hull oil tankers. Fatigue damage accumulation is calculated for different corrosion severities by integrating timevarying instantaneous fatigue damage. Proposed method represents an improvement of the fatigue assessment procedure compared to Common Structural Rules, as the “rule” method is based on simplified assumption that corrosion wastage is constant in whole lifetime of the vessel. The paper also considers the fatigue yielding due to possible worsening of fatigue resistance due to alternating load cases and load variability in addition to the lifetime shortening due to corrosion.

oil tanker; fatigue; corrosion

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