Wave-Induced Fatigue Reliability Study of Submarine Pipeline Span by First Passage Failure Approach

Fatigue reliability of submarine pipeline spans under the wave is study based on passage theory of stochastic vibration and reliability theory. A failure criterion is established by fracture mechanics principle and the fatigue failure of the pipeline span is coined as a first passage problem. The long-term stochastic sea state is treated as several discrete short-term states that are described by Rayleigh distributions. Modal approach is used to derive the stress response spectrum of pipeline span under the short-term states. The ratios of expectation crossings of span's stochastic stress responses under the short-term states are calculated by using Poisson model, and then the total fatigue reliability is ascertained. The effects of span length, design life, initial crack size, fracture toughness and crack parameters to reliability are studied by examples. Fatigue reliability changing curve can be used for conference of submarine pipeline design.