First passage probability of fixed offshore structures with uncertain barrier level to random seismic motion

Offshore structures have inherently uncertain structure characteristics, which lead to the uncertainty of barrier levels. Although the uncertainty of barrier levels may affect the uncertainty of structural failures, there is no guidance on how to conduct an analysis due to a lack of efficient methods, particularly related to the random nature of both barrier levels and seismic motions. This article contributes to the development of an efficient method to compute the probability density function (PDF) of the first passage probability of offshore structures with an uncertain barrier level under random seismic motion. By establishing a transformation relationship between the barrier level and the first passage probability through the curve fitting operation, an explicit PDF of the first passage probability is simplified to the product of the transformation relationship and the PDF of the barrier level. Once the transformation relationship is obtained, the proposed method can quickly calculate the PDF of the first passage probability of structures with an arbitrary PDF of the barrier level. In the numerical studies, a monopile offshore wind turbine subjected to two types of random seismic motions is studied. Three kinds of PDFs of the uncertain barrier level are chosen for each case. The high accuracy and efficiency of the proposed method are validated by comparing with Monte Carlo simulations. Numerical studies confirm that a small uncertainty of the barrier level leads to a very large uncertainty of the first passage probability. It indicates that the first passage probability computed by traditional deterministic methods might be far from the true failure probability. The quantitative calculation of the uncertainty of failure probability is recommended in design to improve the safety and economy of structures.

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  • English

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  • Accession Number: 01846843
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 25 2022 9:35AM