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Jamestown-Scotland Ferry Facility Manager Wes Ripley Weighs in
“We would replace anywhere from three to five timber piling clusters,” says Ripley, who has 31 years of experience in the industry. Most clusters are made up of 37 pilings with an annual maintenance budget of $500,000 to $850,000.” The toll-free vehicle ferry provides a truly “movable bridge” for Virginia State Route 31 across the James River near Williamsburg, Virginia. “We found that certain pilings took more abuse than others based on location. The pilings in the middle of the row seem to experience more wear and tear and were replaced more frequently.” While the VDOT’s primary goal was to strengthen the system’s durability, Ripley adds that a couple of other factors also influenced the decision to go with FRP composite material. VDOT spokeswoman Nina Napolitano noted that the “new pilings won’t leach chemicals such as creosote” into the river. “When it got hot you could see a mini oil slick where the creosote leaked out,” says Ripley. He noted that the FRP piles’ superior strength was a selling point. “Ships are getting bigger,” he says. “Wind conditions increased the potential for impact damage from vessels.”
Design
FiberPILEs are large diameter FRP piles used in fenders with higher impact energy requirements. For this ferry terminal, FiberPILEs with a 48-in. outer diameter were used as monopiles to guide the ferries in. The flexibility of FRP materials allow FiberPILE products to be engineered to any diameter or thickness required. The Jamestown-Scotland Ferry’s unique requirements made FRP a suitable choice. The 100 foot-long FRP monopiles were fabricated with multiaxial E-glass reinforcement. Fifty-nine percent of the glass fibers were oriented at 0 degrees for the lower 80 feet of each monopile [parallel to the longitudinal axis of the pile]. Eight percent of the glass fibers were oriented in a 90-degree orientation with the remaining fibers given an orientation of ± 45 degrees. The specifications for this section of the composite pile were engineered to provide bending characteristics capable of handling overall ferry impact loads. The top 15 ft. of the pile was manufactured with glass fibers focused on the hoop direction with 8 percent in a 0-degree orientation [parallel to the longitudinal axis of the pile]. Fifty-nine percent of fibers had an orientation of 90 degrees [hoop direction} and the remaining fibers at an orientation of ± 45 degrees. This combination allowed the monopile’s upper 15 ft.—the portion above the waterline—to best absorb large crushing loads at the point of impact. Five feet [between the lower and upper portions of the monopile] was used to transition the changing fiber orientation. The outside diameter for each monopile was 2-in. thick. Wood has 42 ft-kip energy absorption. The FRP piles were engineered for 585 ft-kip energy absorption.
Installation
To drive FiberPILE products, a contractor can use standard equipment like a vibratory or impact hammer. Hollow construction, light weight and low driving friction make FiberPILE products attractive to contractors. Installation of FRP monopiles for the Jamestown-Scotland project began right after Labor Day 2018. “We have a short window for installation projects that range from the Tuesday after Labor Day to February 15,” says Ripley. The reason has to do with Atlantic sturgeon making a comeback in the James River. The fish are federally protected. “We want to disturb the river bottom as little as possible,” Ripley says. To distribute costs, a phasing plan was developed that started with dolphin replacement/installation on the Jamestown side first. Setup took a day and required contractors to create a template with I-beams that gave workers access to the monopile. “Once everything was in place, contractors were able to drive a 100-foot monopile 60 ft. into the river bottom in 25 ft. of water in as little as 20 minutes,” Ripley says. “That left about 15 ft. of the pile above the water line. CA also attached collars to the dolphin’s exterior to provide a shelf for an HDPE pipe to act as a sleeve. The low friction, abrasion-resistant material protects the FRP pile from gouges created by the ferry’s edge. Eight FRP monopiles replaced 37 wood piles. Click here to see a video of the Jamestown-Scotland installation.