Development and Design of Flexible Dolphins for Jumbo Vehicle Ferry Vessels

To meet the demands of increased commuter traffic on the inland waters of Puget Sound, the Washington State Ferry System (WSF) has initiated a program of building faster and larger ferry vessels. The most recent addition to the fleet is the Jumbo Mark II class of vessels. The introduction of these larger vessels has required that many ferry terminals be upgraded. BERGER/ABAM Engineers Inc. and WSF studied the challenges of accommodating the larger vessels at the existing terminals. One area of concern was the existing dolphins at the terminals. Generally, the existing dolphins were either timber or steel cluster pile dolphins or floating timber dolphins. These dolphins were not positioned to effectively accommodate the new mix of vessels; and, in many instances, the dolphins' capacity to absorb an accidental impact from the larger vessels was not adequate. Many dolphin concepts were considered for replacing the existing dolphins. The new dolphin had to meet the WSF's requirements for an economical dolphin capable of resisting large impacts and soft and flexible during light impacts for passenger comfort. The dolphin concept selected for use was a flexible steel pile dolphin using buckling rubber fender elements. The dolphin absorbs impact energy primarily through collapse of the rubber fenders and cantilever bending of the plumb reaction piles.