The same goes for Canada's "TransCanada Highway", a system of highways that runs through 10 Canadian provinces. Thousands of passengers rely on this highway system to travel. Like many highways, TransCanada also has many reinforced concrete bridges connecting the various highways. However, after prolonged exposure to the sun and rain, the steel structure is corroded, and the bridge will be left with serious durability problems, resulting in structural degradation and expensive repair costs.
In 2013, the Ontario Ministry of Transportation (MTO) launched a $106 million project to replace the Nipigon Riverbridge with two flat-span, four-lane bridges that demonstrated composite fiberglass reinforcement Can replace threaded rebar.
The Nipigon River Bridge is a cable-stayed bridge for Ontario's highway system and the world's first cable-stayed bridge using glass fiber reinforced polymer reinforced concrete (GFRP-RC) decks. This kind of GFRP is composed of vinyl ester resin and boron-free E glass fiber.
However, from an engineering standpoint, cable-stayed bridges are much more difficult to design than conventional bridges because they are subject to pressures of up to 9000 psi (pounds per square inch). Benmokrane said it was logically impossible to repair the deck of a cable-stayed bridge when the concrete started to deteriorate.
It was very important for the MTO to approve a design with a structural component like GFRP that would prove to be very durable as it would not require any major repairs for over 100 years. "Even if there's nothing wrong with GFRP, the tilt could come from the concrete itself," Benmokrane said.
"So you really have to choose composites!"
Last year, Benmokrane and his team researched, built eight panels—six GFRP-RC panels and two rebar panels—and tested them for cracks. The 220 mm wide ultra-high performance fiber reinforced concrete (UHPFRC) connected GFRP bars have high tensile strength and elastic modulus without obvious cracks.
Working with MTO, MMMGroup (now known as WSP) and Buckland & Taylor, Benmokrane designed 480 3 x 7m GFRP-RC panels, as well as 15 and 20mm thick GFRP-RC reinforced walkways. A total of about 350,000 meters of GFRP bars were used on the deck.
Two construction companies, BotConstruction and FerrovialAgroman, accelerated the construction process by precasting the panels within the tower and connecting them with UHPFRC. After building the bridge deck, Bot and Ferrovial drove a total of 182 steel piles 50 to 70 meters deep for the cast-in-place substructure, which is 75 meters high, measured from the bridge's foundation base. They then placed a prefabricated multi-beam center pier about 51 meters above the deck. The beams are connected to the bridge by 66 steel cables.
The bridge was built in two parts.
He believes the bridge is a landmark achievement for the composites industry as it promises to further expand composites into the infrastructure market. At the International Bridge Conference in National Harbor, Maryland, Benmokrane presented the bridge's design and the benefits of FRP. He said he was delighted, “Based on the feedback I got, I really hope that in the future we will see more bridges around the world using this type of reinforcement,” Benmokrane said. "These bridges are very economical, elegant, and have a high aesthetic value," and is optimistic that applications like the Nipigon River Bridge could open doors for many composite companies.
The initial cost of a concrete bridge reinforced with GFRP bars is almost the same as a concrete bridge reinforced with epoxy-coated or galvanized steel bars, he said. The price of stainless steel rebar is also 2 to 4 times that of GFRP rebar.
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