Planning and design of floating berths for passenger-only ferry terminals

Describes the design criteria, interface requirements and design concepts used to guide the planning and design of a series of floating concrete berths for passenger only ferry terminals for the Washington State Ferries division of the Washington State Department of Transportation. The planning of these facilities must consider the full range of passenger access requirements, as well as the important vessel berthing requirements. The facilities must accommodate the geometrics involved with the full 5-meter (15 ft) range of tidal variations typical of Puget Sound in Washington State. Design criteria includes definition of design loads resulting from both normal and extreme vessel berthing, wind and wave effects, and geometric constraints resulting from both vessel configuration and pedestrian access requirements. Draft and trim of the floating facilities must be controlled within close limits. One of the benefits of a floating facility is that the interfacing requirements become more straightforward in areas of high tidal variation and variable site conditions. The paper highlights how the advantages of simplified interfacing are taken advantage of in practice. The design of floating concrete facilities using high-strength prestressed concrete is a discipline that is in its fourth generation of floating facilities in the Puget Sound region. Design procedures and details that provide reliable, durable, and long-lasting facilities are outlined. Floating concrete facilities must be designed with the construction and installation process in mind. Often, large facilities must be designed to be constructed in sections so that they can be assembled in existing dry dock or launch facilities. Installation mooring and installation methods must be tailored to allow quick and efficient installation at busy ferry terminal locations that often must remain in operation throughout the construction activity.