Bellingham Marine, headquartered in Newport Seashore, Calif., not too long ago put in its first totally GFRP-reinforced Unifloat® concrete dock system in a New Zealand marina. The docks, which function GFRP thru-rods, rebar and beams, are lighter, stronger, simpler to keep up and extra environmentally pleasant than metal and timber-reinforced ones. With an anticipated lifespan of 100 years or extra, in addition they provide excessive sturdiness.
“Most floating docks use handled timber for the walers and metal bolts to carry them onto the floats, that are bolstered with metal rebar,” says Pete Renshaw, enterprise improvement director at Pultron Composites Ltd. in Auckland, New Zealand. “All of those are topic to deterioration over time and restrict the lifespan of the construction.”
The dock system is the fruits of a decade-long collaboration between Bellingham Marine and Pultron Composites to switch timber and metal dock reinforcements with composites. The businesses first tackled the thru-rods, which connect floating concrete sections to walers (structural beams mounted to the deck). To develop the thru-rods, which have been launched in 2015, Pultron relied on its expertise producing GFRP rock bolts for tunnels and mine reinforcement and its work within the sports activities and recreation business.
“We knew that the tie rods could be subjected to fixed wave motion affecting the dock system, so we used a few of our know-how from [GFRP] trampoline rods that we developed, which have excessive flexural fatigue resistance,” says Renshaw.
Whereas the GFRP thru-rods have twice the tensile power of metal, they’ve a low tensile modulus. This enables them to stretch and contract and preserve pressure.
“This has confirmed to be a giant benefit because it saves loads of upkeep,” says Renshaw. “Because the timber dries, it will possibly shrink sufficient for the metal bolts to grow to be unfastened, however the further stretch within the GFRP bolts accommodates this shrinkage so they don’t come unfastened. A lot much less retightening is now required.”
Pultron Composites pultrudes 20-millimeter-diameter thru-rods utilizing corrosion-resistant ECR glass rovings and a proprietary resin system in lengths as much as 12 meters. After fabrication, a purpose-built CNC grinding machine turns the graceful rods into threaded bolts.
“Fairly than slicing the thread, as is generally completed for metal bolts, our threads are floor into the floor utilizing profiled diamond grinding wheels,” says Renshaw. The nuts are injection-molded from glass-filled nylon by Lane Plastics, one other Auckland firm.
After growing thru-rods, Bellingham started efforts to switch the metal rebar in concrete floats with Mateenbar™, a GFRP rebar developed by Pultron and manufactured by Mateenbar Ltd. Though Mateenbar had been utilized in greater than a thousand infrastructure tasks, together with roads, bridges, tunnels, seawalls and aluminum smelters, concrete floats have been new territory. Consequently, Bellingham trialed them in marinas in Australia and Cyprus earlier than introducing them commercially in 2018.
The swap to Mateenbar will increase float lifespan significantly. “The American Concrete Institute developed an accelerated check technique to find out deterioration of GFRP rebar,” says Renshaw. “This check indicated that we must always count on a power retention of round 96% after 100 years.” At 25% the load of conventional rebar, Mateenbar additionally reduces delivery prices and eases set up.
The GFRP thru-rods and Mateenbar have been customary in Bellingham’s Unifloat concrete dock system in New Zealand for the previous three years, together with greater than a dozen tasks. Final yr, Bellingham launched the ultimate GFRP reinforcement into its floating concrete dock system – the waler.
Historically constructed with handled timber, walers are mounted to the facet of a number of concrete floats and fasten them collectively. Pultron manufactures the walers with a pultrusion course of just like thru-rod manufacturing. Nonetheless, along with the ECR glass rovings and polyester resin, the waler has a steady filament mat for transverse power and a floor veil that gives a easy end and extra UV safety.
Measuring 12 meters lengthy and weighing 330 kilos, the waler is the biggest, heaviest profile that Pultron has made.
