Abstract

ABSTRACT Safe execution of a marine operation (MO) such as a jack-up leg lowering depends on two main design parameters i.e. the characteristic value of an impact velocity and its corresponding operational limit. While the former is lower than the latter, a workable weather window (WOWW) is identified, and the operation can be executed. However, various sources of uncertainty can affect the design parameters and make the operation unsafe. This paper introduces a methodology to assess WOWWs including uncertainties in forecasted directional (2D) wave spectra for various lead times, errors from an efficient machine learning algorithm used to predict dynamic responses, and uncertainties in the actual operational limit. A simple semi-probabilistic response-based load-resistance factor design (LRFD) format is proposed to assess WOWWs. The factors are calibrated using a limit state function and an acceptable MO-dependent failure probability. For a jack-up leg lowering operation, the summer operability decreases from 86 (deterministic) to 23% (semi-probabilistic) when including these sources of uncertainty. This study offers a robust and simple method to find WOWWs and help superintendents make on-board decisions. Findings from this paper can be used as a guide for future improvement of MO design standards.

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