Debunking Myths about Composites in Infrastructure
Composites are often utilized as reinforcing materials in repair and retrofitting of existing infrastructure applications. And more bridge decks are now made from FRP than ever before. Composite features such as light weight, corrosion resistance, and prefabrication reduce assembly and installation time resulting in lower installation and delivery costs for new construction. In retrofit and rehabilitation situations, composites extend the service life of a bridge, are faster to install, and require minimal disruption to the structure. In new construction, composites can provide longer lifetimes and lower maintenance costs than conventional materials. Despite increased use, myths still exist about composites in infrastructure applications, such as:
Composites are unproven
Composites are proven material used in over 500 North American bridges during the past two decades. For more than 25 years, the Federal Highway Administration (FHWA), the American Association of State Highway and Transportation Officials (AASHTO), and the National Cooperative Highway Research Program (NCHRP) have researched and demonstrated the use of composites. In addition to a project database using composites, FHWA has a library of documents and other information that reports on the use and performance of composites. Additionally, the American Concrete Institute (ACI) has a number of publications of technical papers that document use of composites in concrete applications.
Composites aren’t as strong or durable as other materials
Some people worry about how long composite products will hold up compared to metal and wood products. However, composites allow structures to withstand repeatedly applied loads. This is particularly important for infrastructure applications such as bridge decks, which support traffic 24 hours a day. Many of the nation’s deteriorating bridges are being renovated with composites decks, including the Broadway Bridge in Portland, Ore. Spanning the Willamette River in the heart of the Portland Harbor, the drawbridge handles 30,000 vehicles per day in addition to pedestrian traffic.
GFRP should only be used in architectural applications, not bridges
Although composites are susceptible to creep and stress-rupture, in general their use under sustained loads is possible as long as the stress levels do not exceed 25-30%. This has been shown to advantage in the resiliency of glass fiber reinforced pipes and underground storage tanks which have withstood very aggressive environments through the use of appropriate factors of safety.