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Berthing and mooring large cruise ships: an unconventional anchor solution in Sydney

Sydney’s Overseas Passenger Terminal (OPT) in the heart of the city’s central business district is a busy transport hub for trains, ferries, buses and taxis. While the port is a popular and well-frequented central transport spot, it did not have capacity to accommodate large ships, such as cruise vessels larger than 300 metres in length.

Arup designed an innovative temporary mooring system, using drag anchors, for Sydney Ports Corporation to allow the berthing (parking the ship) and mooring (securing the ship) of large cruise ships at the OPT. This research project involved analysing real measured berthing and mooring data obtained from 19 cruise ship visits at the OPT over a summer cruise season, and comparing these with modelled design values adopted in Arup’s design. The design followed a risk-based approach to establish operational limits that maintain the serviceability and safety of the vessel at berth, and the integrity of the existing quay structure. The design and operational limits were determined by Arup through a berthing analysis, and a numerical mooring analysis using the commercially-available software Optimoor™.

The project team collated data from the port, the Bureau of Meteorology, and from Arup observations, including upper wind speeds and direction, tension forces on each mooring line, berthing velocity at fender impact, and angle of berthing approach to fender line at fender impact. A challenging timeframe, targeted geotechnical investigations and effective collaboration with key stakeholders were some of the factors that had to be addressed for the successful implementation of the anchor solution.

The mooring and berthing analyses undertaken were effective in determining limiting operational conditions to maintain safety and structural integrity during the large vessel visits. The data regarding wind climate (including maximum wind speeds and directions) was obtained during each large cruise ship visit though analysis of raw measurements from the Bureau of Meteorology.  An analysis of wind records and discussions with Sydney Ports Corporation (SPC) pilots allowed verification of modelled scenarios.

The discussions with the SPC pilots and harbour master resulted in a better understanding of berthing and mooring operations and enabled us to validate our design assumptions.

Gaining a good understanding of the seabed soil conditions was a key technical challenge of the project, and useful design data was obtained through the investigations. Flexibility in the installation program and a close working relationship with the contractor allowed a suitable geotechnical location for the anchors to be realised.

The project successfully investigated, analysed, installed and tested the mooring anchor system for the port within a constrained time period.  Since its installation, operational procedures have been established for using and monitoring the anchor system which have worked well.

Two drag anchors were installed to provide moorings at the OPT for berthing and mooring large cruise vessels greater than 300 metres in length. This unconventional mooring solution may be of interest to other port authorities as this case demonstrates how an anchored system it can be used as an effective interim solution rather than conventional, more capital-intensive and intrusive solutions such as mooring dolphins or quay extensions.

The results have generated considerable interest in the maritime and port industry, as they validate the berthing and mooring models that we use regularly on maritime projects, and lessons learnt will inform future modelling exercises on projects leading to better designs.

A conference paper presenting a summary of the work is available online: Dack, D. & Cumbo, N. Unconventional anchor solution to facilitate the mooring of large cruise vessels at Sydney's overseas passenger terminal (in Coasts and Ports 2013: 21st Australasian Coastal & Ocean Engineering Conference and 14th Australasian Port & Harbour Conference; edited by Barton, A.;  Engineers Australia, 2013: pp.250-255).