The pontoons serve as passenger loading/unloading platforms and were installed to facilitate simultaneous berthing of multiple cruise ships. The design enables operations during tidal variations up to 30 feet without the need for special equipment or measures. Each pontoon will be held in place by mooring dolphins and accessed from an approach dock by a 140-foot-long transfer bridge. WSP’s extensive design experience on the construction of floating concrete structures resulted in a cost-effective and efficient design of the pontoons.
As part of the cruise ship terminal improvement project, two concrete pontoons were installed to facilitate simultaneous berthing of one 1,000- and one 1,100-foot-long cruise ship for the City of Juneau. WSP supported the pontoon fabricator, Concrete Technology Corporation (CTC), with the design of the pontoons. The pontoons serve as passenger loading/unloading platforms between the cruise ships and land by enabling operations during tidal variations up to 30 feet without the need for special equipment or measures. Each pontoon is accessed via a transfer bridge designed by the owner. The transfer bridge is supported on a landing platform that is attached to the pontoon hull at a highly eccentric location with respect to the pontoon center of buoyancy.
Numerous fittings to be incorporated into the pontoon walls and deck, and stringent strength requirements at these connections, led to special design of relevant segments. Design of hull plating and the embedments at the bridge landing connections and mooring frame connections was a major challenge. High-strength anchor rods at bridge landing connections were incorporated into the deck by designing cast-in-place deck segments with special reinforcement. The pontoon walls were strengthened at mooring frame locations through wide flange beams. Fpor the 100- and 50-ton mooring/towing bollards, cast-in-place deck segments were designed to transfer the load to the adjacent precast deck panels. In an effort to minimize anticipated constructability issues, a series of experiments were conducted for optimizing the deck connection details for guardrails designed to resist AASHTO-defined truck loads.
WSP also provided recommendations on maximum wave heights that would not over stress the pontoons during the open-ocean delivery voyage of approximately 1,000 nautical miles.