Mooring of vessels is very important for safe and efficient cargo handling of ships in ports, just as safe infrastructure is important. Civil Engineers and Mariners used to have a different approach for the same problem: what should be the safe working load (SWL) of a bollard. Mariners use the Minimum Breaking Load (MBL) of their mooring lines to determine the desired Safe Working Load (SWL) of the bollard, civil engineers are used to use design tables from international standards or guidelines with a relation between displacement of the vessel and bollard loads. There is a big gap between these two approaches, especially concerning the mooring of large container vessels.
Both disciplines meet each other in dynamic mooring analysis (DMA), a computer calculation that calculates the vessel motions and resulting maximum loads in the mooring lines resulting from wind, wave (sea, swell), current and passing vessel forces acting on the moored vessel. As a DMA is a rather complex calculation, a DMA is not carried out for every project and usually not in a preliminary design stage.
This position paper describes a design approach for bollard loads that is understandable and acceptable for all involved disciplines and that is used by the Port of Rotterdam Authority for new builds.