Publish and Present
In 2014 the Virginia DOT implemented a project to replace the failure-prone timber pile cluster dolphins at the Jamestown-Scotland Ferry with a system better suited to resist impacts from increasingly larger ferry vessels. After an initial study, large diameter Fiber Reinforced Polymer (FRP) monopiles were selected as the replacement dolphin system. While this application of large diameter FRP piles was largely unproven in practice, it was selected for its combination of strength, flexibility, resistance to corrosion, and low life-cycle cost. The initial JSF dolphin study was described to the 2016 PORTS conference in McCarty et al. (2016) A Case Study and Recommendation for Large Diameter FRP Monopile Dolphin Systems. This paper revisits the dolphin system after conclusion of two construction contracts to install the dolphins.
The first FRP monopile installation contract was initiated in the fall of 2016 and encountered multiple difficulties with pile driving including timber pile obstructions and FRP degradation during vibratory pile driving. At the end of that contract, four of the planned eight FRP monopiles were partially-installed; the remaining four uninstalled FRP piles were returned to the manufacturer for storage. A second installation contract was restructured to determine the best method of large FRP monopile installation while finishing the initial planned dolphin installations. Work for the second contract began in the fall of 2018 and concluded in January 2019. Difficulties encountered in the first installation were overcome, pile driving of partially-installed monopiles was completed, and the four remaining FRP monopiles were installed to design pile tip elevations. The next design phase at JSF will gauge performance of installed FRP monopiles using drone monitoring of vessel impacts.
Pile driving difficulties and successes from both FRP monopile installation contracts are discussed. Engineers working on designs with large diameter FRP piles will benefit from the information and recommendations provided.