Design and Functional Requirements for the Floating Container Terminal at Valdez, Alaska

ABSTRACT The City of Valdez, Alaska, will be pioneering in container terminal facilities when it installs the first floating dock designed for the operation of a 40 LT container crane in late 1982. The terminal is designed to service ships up to the 50,000 LT class and barges up to 15,000 LT. The floating dock system will consist of three key elements: a 100 foot wide by 700 foot long by 30 foot deep prestressed concrete floating dock, the mooring arrangement, and the fender system. It will be constructed as two separate, 100 foot wide by 348 foot long by 30 foot deep prestressed pontoons, in Tacoma, Washington. The pontoons will then be towed to Valdez, Alaska" and joined together, while floating in Valdez Harbor to form an integrated floating dock unit. The dock will use an innovative mooring arrangement consisting of steel transfer ramps and a taut line mooring system to provide a stable work surface. The mooring system design is based on a predictable failure mode and will include a Pack-up system in case this overload occurs. The fender system will consist of cellular rubber fenders connected by a rubbing frame. The fenders are designed to limit reaction forces from berthing vessels to allow for economical design of the floating concrete dock's exterior bulkheads. This paper will present some of the challenging design requirements and operational considerations that were resolved by the design team. Specific topics include:Deve1opment of environmental loadings during the delivery voyage and also at the site.Design of two 100 foot wide by 348 foot long by 30 foot deep prestressed concrete pontoons.Design of in-the-water pontoon integration procedure.Motion studies of the free floating and moored dock.Design of the mooring system.Design of the fender system.Design for container operation using a 40 LT container crane. INTRODUCTON Floating docks are a practical alternative in areas where large tidal fluctuations, very deep water, or poor soil conditions make pile-supported structures unfeasible or uneconomical. One of the beneficial features of moored floating docks is their ability to raise and lower with the tides, thus the changes in freeboard (or draft) between moored vessels and the dock are primarily caused by vessel loading and unloading operations. The site plan and cross section with features of the Valdez Floating Dock are shown in Figures 1 and 2. A primary purpose of this floating dock is to provide a stable surface for working container cranes. The stability of the structure is affected by environmental loads, and crane operations. Vertical and horizontal movements of the floating structure present unique problems at the connection points of the mooring dolphin walkways and the transfer ramps. The connections are designed to accommodate six degree-of-freedom motions and impact forces. The connections consist of rubber fenders to dissipate impact loads and a combination of systems which a11ow 1imited rotations and disp1acements; i.e., pot bearings, sliding bearings, hinges and torsion ally flexible structures.