Lightweight, low maintenance and strong, fiber-reinforced polymer (FRP) bridge decks finally are crossing the line from specialty projects to wider general applications, but that's creating a new hurdle for manufacturers: Most contractors don't know how to install their products.
Composite Advantage of Dayton, Ohio, has come up with a way to bridge the gap between FRP deck customers and inexperienced installation crews, particularly when it comes to pedestrian, bicycle and trail bridges.
Co-owners Andy Loff and Scott Reeve have established a partner company called FRP Constructors LLC, which has a staff of six employees trained to install polymer bridges — and not just Composite Advantage's FiberSpan products.
“Most construction companies aren't familiar with working with fiberglass material,” Loff said. “The contactors need a lot of help to put in the FRP because they don't understand what things they should and shouldn't be doing. We primarily started FRP Constructors for this reason.”
Some of the skills that contractors lack involve piecing together bridge components with the modern decks, which are made of fiberglass sheets that have been molded with a closed cell foam core reinforced by fibers at 45-degree angles. The fibers are infused with a resin and placed close together for strength.
Composite Advantage uses Derakane 610 vinyl ester, which was introduced in 2011 specifically for the emerging FRP infrastructure market. The resin is said to have good molding properties, strength, durability, moisture resistance and a pigment added to inhibit UV degradation.
“Most contractors are very good at dealing with steel, concrete and wood,” Loff said. “Just like you do things differently with wood versus steel, fiberglass has some of those same nuances with how you drill, how you connect things, and what type of coatings you put on for different purposes. It's not so much that it's difficult to work with. It's actually very easy to do but they have never done it before.”
Composite Advantage ended up sending support crews to work with so many contractors, it made sense to start up an installation arm of the company.
“There are obviously thousands of contractors in the U.S. and every single time we do a project we have a different contractor to reeducate about how to work with the materials,” Loff said. “It saves us a lot of effort to just do it ourselves.”
It should save customers money, too, he added, because FRP Constructors is able to price installation costs more competitively than general contractors.
“The feedback we get from contractors is that they really like the material once they have done it but because there so many unknowns going in, they typically put extra cost in there,” Loff said. “When they have never done it before, they don't know what they are getting into. When we do it, we know exactly what it takes. By making the installation part a lot cheaper, it makes the overall cost to the customer cheaper.”
In addition to putting bridge decks in place, FRP Constructors will remove existing structures, perform abutment work, make bridge repairs, and install helical piles. However, they stop short of doing anything more than deck installation for vehicle bridges.
“Doing the construction on an entire vehicle bridge is difficult,” Loff said. “You have a lot of excavation work, demolition and other stuff that is frankly bigger than we're willing to do.”
Composite Advantage has manufactured and installed some major vehicular FRP bridge decks, including one of the world's largest at 18,776-square feet. The deck reaches across the Merrimack River in Massachusetts and has been linking the towns of Haverhill and West Newbury since the horse-and-buggy days of 1883. The state Department of Transportation opted to replace the concrete deck with FiberSpan to increase the weight load for heavy trucks, accommodate a hand-operated, center-swing span that moves for boat traffic, and preserve the look of the six-span steel truss structure. The project cost $13 million.
Price can be barrier for some bridge owners. Fiberglass costs more than concrete and steel. Even so, the material is increasingly popular for pedestrian, bicycle and trail bridges, especially in remote areas. An eight-inch thick FRP weighs 25 pounds per square foot compared to 119 pounds per square foot for a standard 9.5-inch thick concrete deck. The lighter weight makes it possible to drag the prefabricated deck through thick woodlands with a four-wheeler ATV and then install it without heavy equipment.
“You can install them with basically more of an Egyptian method using pulleys off of trees instead of having to bring in a crane,” Loff said. “That lighter weight makes it very compelling for owners on the install side. If you're going to put a steel bridge back in that wilderness, the overall bridge may be cheaper than our fiberglass, but when you factor in the install cost we're a lot cheaper because it's so much easier for us to work in these remote locations.”
Although he doesn't think fiberglass bridges will displace steel and concrete for the majority of bridge projects in North America, Loff said FRP decks are finding a place in more pedestrian and recreation areas from urban downtowns to national forests.
“We just started several months ago and we're pretty busy,” Loff said. “We have crews out all the time doing installation work generally in the Midwest region like Ohio, Kentucky, Indiana, Illinois, Michigan and Missouri.”