Experimental investigation of wave severity and mooring pretension on the operability of a moored tanker in a port terminal

Abstract

This paper investigates the influence of sea severity and mooring line pretension configuration on the operability of a moored vessel at a modified berthing site inside a port. A physical model was constructed to replicate the new layout of the port of Leix˜oes in Portugal, including bathymetry and a future 300 m extension of Leix˜oes’ north breakwater. A tanker ship model was tested with novel custom-made mooring system simulators for two fenders and four mooring lines under various offshore sea states and pretension configurations. The experiments focus on acquiring wave measurements at multiple spots within the port, ship motions, and loads on lines and fenders. The data is analysed in time and frequency domains to examine the relationship between waves, motions, and loads. The results are then compared to standard operational thresholds to estimate downtime and operability for cargo loading operations. The analysis of the results yields several conclusions. It is recommended to use the zero-peak amplitudes in conjunction with the maximum peak-to-peak amplitudes to ensure accurate operability analysis. The application of small-scale physical modelling for a moored tanker in Leix˜oes port is a useful tool not only for investigating the feasibility of port modifications in the existing sheltering structures but also for analysing additional soft countermeasures to strengthen operational conditions at the berth. It also provides site-specific experimental data that may help to develop site-specific safety criteria. The applied mooring simulators help to reduce physical model costs.