Sens dubte, les autopistes no ens són estranyes. Normalment passem per l'autopista quan viatgem, anem per negocis i visitem familiars i amics. Els vehicles que van i vénen per la carretera, passant per innombrables persones, són un símbol de la ciutat concorreguda. Els ponts que connecten diverses carreteres costaneres també suporten la pressió de tota la ciutat.
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.
Tanmateix, des del punt de vista de l'enginyeria, els ponts-atirantats són molt més difícils de dissenyar que els ponts convencionals perquè estan sotmesos a pressions de fins a 9.000 psi (lliures per polzada quadrada). Benmokrane va dir que era lògicament impossible reparar la coberta d'un-pont atirantat quan el formigó es va començar a deteriorar.
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!"
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.
Treballant amb MTO, MMMGroup (ara conegut com a WSP) i Buckland Taylor, Benmokrane va dissenyar panells de 480 GFRP-RC de 3 x 7 metres, així com passarel·les reforçades de GFRP-RC de 15 i 20 mm de gruix. Es van utilitzar un total d'uns 350,000 metres de barres de GFRP a la coberta.
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.
El pont es va construir en dues 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.
El cost inicial d'un pont de formigó reforçat amb barres de GFRP és gairebé el mateix que un pont de formigó reforçat amb barres d'acer galvanitzat o recoberts d'epoxi-, va dir. El preu de les barres d'armadura d'acer inoxidable també és de 2 a 4 vegades el de les barres d'armadura GFRP.
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