Pre-fabrication of the hollow bridge columns takes a few hours in a much less labor-intensive process since the steel pipe and FRP pipe serve as a stay-in-place framework for the poured concrete. In comparison, a concrete bridge column takes 15 to 18 hours to manufacture.
The Missouri S&T report showed encouraging results for GFRP’s potential use in bridge columns. Under extreme axial and combined axial-flexural loads, the rebar in the conventional concrete column ruptured at a drift point of 10.9 percent. In comparison, the hollow GFRP column did not fail until it reached a 15.9 percent drift point and did so gradually when the steel tube finally buckled, followed by a rupture in the GFRP tube.
For vehicle collision testing, the research team used finite element modeling of heavy vehicles traveling at 35 kips (a unit of force equaling 1,000 pounds-force) and high-speed vehicles traveling at 70 mph, looking at peak dynamic force and equivalent static force. Vehicle impact simulations indicated that both designs would withstand the same amount of force. Concrete bridge columns showed localized damage which would require immediate repair. In comparison, modeling of impact showed the force being transferred throughout the hollow column’s structure, minimizing damage to the pillar.
ElGawady also conducted earthquake simulation tests measuring the flexibility of the hollow bridge columns. The expected average flex in bridges during moderate earthquake conditions is 4 percent, but the hollow columns withstood a flex of up to 15 percent. “This should make the hollow columns using GFRP of particular interest in the 36 states where design for seismic force is required,” notes ElGawady.
The report from Missouri S&T calls for additional testing of fiber orientation, resin type and the use of thicker GFRP layers at key points in the column to optimize the hollow column design. The results are likely to create further interest in GFRP’s use for bridges. “The United States has a rapidly aging infrastructure,” says ElGawady. “Over one-fourth of all bridges are structurally obsolete. With this new formation of columns, I see the potential to exceed the typical 50-year lifespan of a bridge.”
Project: Wind turbine blade recycling
School: Washington State University
Location: Pullman, Wash.
Principal Investigator: Karl Englund
Old wind turbine blades go to landfills to die. Yet a single FRP blade contains between 14,500 and 22,000 pounds of material – most of it glass fiber. That is a treasure trove of research material for Karl Englund, associate research professor and extension specialist at Washington State University’s Composite Materials and Engineering Center.
Englund, who has been dubbed “the garbage guy” by colleagues, has spent 10 years working on creating new composite materials out of recycled carpet, wood waste, plastics and agricultural waste from corn cobs to rice husks. Englund turned his attention to wind turbine blades in late 2014 when he received a call from Don Lilly, CEO of Global Fiberglass Solutions (GFSI) in Mill Creek, Wash. “Don asked if I could help him figure out what to do with decommissioned wind blades from wind turbines,” recalls Englund.
Englund was already keenly interested in end-of-life problems with composites, in part because of neighbor Boeing’s recent move to replace cheaply recycled metal airplanes with not-so-easily-recycled carbon fiber ones. He also had a 2014 research grant from Washington’s Joint Center for Aerospace Technology Innovation to study carbon fiber reinforced thermoplastic composite waste recycling. So he agreed to help Lilly.