Sustainable Marine Structures

This paper develops and validates a simple, nondimensional decision metric for jetty berthing that compares the combined environmental disturbance loads from wind and current against the effective corrective capability provided by assisting tugs. The approach formulates wind-induced lateral force using a drag-based expression on the vessel’s exposed lateral area and current-induced force using a hydrodynamic drag formulation on the projected underwater area, while tug control is represented through the sum of available bollard pull adjusted by an efficiency factor. These components are combined into the Approach Safety Index (ASI), defined as the ratio of total environmental forcing to effective tug-assisted control, where lower values indicate greater controllability and values approaching unity indicate insufficient control margin. Model performance is evaluated through a full mission Wärtsilä simulator exercise using a Handysize bulk carrier in ballast, supported by two ASD tugs rated at 36 t bollard pull each, with wind and current progressively increased across scenarios. The computed ASI values align closely with the harbour pilot’s qualitative controllability assessments, distinguishing clearly between manageable, marginal, and unsafe operating states. Based on the simulation outcomes, provisional empirical screening bands were identified to support first-pass pilotage judgement under simplified live berthing conditions. The findings suggest that ASI can serve as a practical decision support and screening tool for pilots and port operators using limited readily available inputs.