Response - Based Workability

Abstract

This research introduced a response-based workability approach, which refined go/no-go decisions by converting complex 2D wave forecast data into accurate vessel response predictions.

To obtain accurate vessel responses, 2D wave forecast data, derived from forecasting and historical metocean data (e.g.,ECMWF) or real-time wave measurement systems, were integrated with the linear transfer function. The 2D wave spectra provided a comprehensive view of energy distribution across both frequency and direction, enabling detailed analysis of spectral information for each wave train.

Workability calculations were conducted using both weather-based and response-based approaches. For the response-based method, operational windows were established by directly using the most probable maximum (MPM) responses obtained from detailed vessel response analysis. In contrast, the weather-based approach involved an operational assessment to determine and compare forecasted wave heights with allowable operational wave heights.

The comparison of these methodologies demonstrated that the response-based workability approach extended operational windows and revealed critical challenges not identified by the weather-based method. During the tender phase, this approach facilitated the selection of more conservative operational windows, thereby mitigating risks and providing a clearer picture of operational constraints. In the operational phase, it offered crews detailed decision-making tools, highlighting potential challenges that weather-based data might overlook. For instance, it can identify critical responses even with low significant wave heights (\Hs) if the wave frequency aligns with the vessel's critical response frequencies, potentially leading to resonance.

By integrating response-based workability with weather-based methods, this study improved operational assessments, offering a more comprehensive view of vessel performance and constraints. This approach enhanced decision-making and safety, with potential benefits for both planning and real-time operations, leading to better risk management and efficiency.