CompositesWorld

MAR 2018

CompositesWorld

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47 CompositesWorld.com Grimes, "e two materials actually work compositively to give better performance. e composite shell acts as an external rebar cage to improve the performance, and protects the concrete from corrosion." For the Manahawkin project, a total of 38 piles were required. Finally, the fender system would combine the driven pilings with sturdy, molded fiber-reinforced polymer (FRP) Barforce composite lumber manufactured by Bedford Technology (Worthington, MN, US). Supplied as solid timbers and planks in a variety of sizes, they are made of 100% recycled high-density polyethylene (HDPE), with embedded pultruded continuous fiberglass composite reinforcing rods, or rebar. For the Manahawkin project, 30-by-30-cm (12-by-12- inch) timbers were specified for the horizontal fender elements, as shown on the drawing (p. 45). Bedford also supplied 7.5-by-30-cm planks, also reinforced with the composite rebar, to support the walkway and railings, as well as the necessary composite elements for the walkway surface and railings at each bridge pier. While Bedford typically supplies its Barforce materials in black or yellow, NJDOT specified that the composite lumber be brown in color, for a more natural, wood-like look. Heavy-duty materials To make the piles, says Grimnes, heavy quadraxial fabrics supplied by VectorPly Corp. (Phenix City, AL, US) are combined with poly- ester or vinyl ester resin, supplied by Polynt-Reichhold (Carpen- tersville, IL, US) or other suppliers, in a proprietary manufac- turing process. "It's a vacuum infusion process, combined with centrifugal casting. e closed mold is spun to help compact the fibers during the infusion process," he explains. e quadraxial fabrics ensure that at least 50% of the fibers run axially along the pile length, and about 25% of the fibers end up as hoop direction reinforcement. e remainder are oriented at 45°. Resin choice depends on the project conditions, and all piles are gel coated, with product supplied by Polynt-Reichhold or Marine Fender Project Ashland LLC (Columbus, OH, US) for added durability and appearance. For this project, because of the concrete fill, each pile was equipped with a conical steel driving tip to increase the pile's bearing resistance during driving, while keeping mud and debris out of the pile interior. e 27 kg/m piles were shippable on a standard, over-the-road tractor trailer, but Grimnes points out, "We're able to ship much longer piles, under special permit conditions for over-length loads." e Manahawkin Bridge's height, he explains, prevented use of a bridge-mounted crane to drive piles from above. Instead, a small excavator was situated at water level, on a floating work platform, to do the driving: "e excavator clamped onto a bolted-on steel collar to drive the piles. It's important to note that if the piles had not been composite, this floating platform and excavator method wouldn't have been possible — heavier steel or concrete piles would have required much heavier driving equipment." e hori- zontal composite timbers were attached to the pilings with long stainless-steel bolts, and similar metallic hardware connects the composite walkway and railing elements to the timbers. "Our client sees the benefits of using composites for this appli- cation, since they are essentially maintenance-free and will last for at least 50 years," concludes Grimnes. NJDOT is likely to replace the existing timber fenders associated with the old bridge span with composites as well, over the next several years. It is, appar- ently, an ideal application for customizable composites tailored for site-specific conditions. Sara Black is a CW senior editor and has served on the CW staff for 19 years. sara@compositesworld.com Piles primed for installation The composite piles arrived at the job site on this trailer, with steel driving tips already installed. Source | Harbor Technologies/Kenway

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