Assessing the Workability of Heavy Lift Vessels in Complex Sea States Using Response-Based Approach

Abstract Weather-restricted operations must be planned within a specific timeframe, identifying a suitable weather window by analyzing the weather forecast and wave characteristics to ensure conditions fall within operational limits. These limits are set through an operability study using second-generation wave models with a vessel model to simulate the vessel’s response to wave conditions. The maximum allowable significant wave height is determined by comparing vessel responses to operational limits. Forecasted wave conditions are then evaluated against this limit for go/no-go decisions. This approach is known as the weather-based workability method. While well-established, this method’s representation of complex sea states can be enhanced by third-generation wave models like those in ECMWF forecasting. A Response-Based Workability approach, incorporating real-time 2D wave spectra from weather forecasts into dynamic simulations, transforms weather forecasts into response forecasts, improving accuracy and operational efficiency. This paper explores the potential of response-based workability by comparing it to weather-based workability. The comparison reveals differences, particularly in relation to vessel headings. In some cases, the weather-based method suggested feasibility for certain headings, while the response-based approach did not, and vice versa. The key difference between the two approaches is the underlying wave spectrum and their capability to capture complex sea states.