Composites bridge decks, utility poles and pipelines
Hota Gangarao, Ph.D., P.E., is the director of the Constructed Facilities Center and professor of civil engineering, at West Virginia University (WVU, Morgantown, W. Va., U.S.A.). He owns several U.S. patents, has published more than 300 technical papers, supervised 250 M.S. and Ph.D. students and organized and
Recently, researchers at the Constructed Facilities Center, West Virginia University (CFC-WVU, Morgantown, W. Va., U.S.A.) have focused considerable research and development (R&D) efforts on developing advanced fiber-reinforced plastic (FRP) composites for infrastructure applications in highway structures, utility poles and pipelines. The R&D is driven by recent market acceptance of composites, especially in bridge construction. For more than 16 years, CFC-WVU, a U.S. Federal Highway Admin. (FHWA)-designated FRP Composites Center of Excellence, has worked with the West Virginia Dept. of Transportation (WVDOT), other federal and state agencies and private companies to promote and implement FRP composite products in the West Virginia State Highway System. Noteworthy among CFC-WVU successes is the evolution of FRP bridge decks over the past 10 years, leading to a six-fold increase in ultimate strength and a three-fold decrease in unit cost of FRP deck components, which would have been impossible without close cooperation of Bedford Reinforced Plastics Inc. (Bedford, Pa., U.S.A.). CFC-WVU has helped WVDOT build or rehabilitate 24 bridges with FRP composite materials. Some of these bridges are being field monitored for in-service performance, and the FRP composite materials are proving to be economical and durable.
Highway structures under discussion at CFC-WVU include not only FRP bridge decks, stringers, beams, abutment panels, rebar and dowel bars, but also signposts, signboard, guardrail systems, sound barriers and drainage systems (pipe, culvert). Each of these products represents a huge potential market. Approximately $50 billion (USD) was spent on highways and bridges in 1999 and $8.1 billion in bridge projects were funded by the FHWA in 2002 alone. About 36 million highway signposts are in service in the U.S., and about 2 million per year need replacement, due to accidents, generating a market of $100 million to $200 million. Two thousand miles of guardrail are constructed each year on Federal-aid projects, leading to $180 million in material sales for railings alone. The 2 million guardrail posts and spacer blocks required to install the rails generate an additional $60 million. For example, the WVDOT alone uses about 50,000 wood and 200,000 steel guardrail posts annually.
Similar opportunities exist for composite utility poles. Electrical utility companies have 130 million poles in service in the United States alone. New pole installation creates a market of $1.2 billion per year. In addition, about 4 million poles are replaced annually, at a cost of $2.8 billion.
About 98 percent of in-service poles are wood, with less than 2 percent in steel. Wood poles typically require treatment with preservatives, e.g., creosote, copper chromium arsenate (CCA) or pentachlorophenol (Penta), to resist rot and decay sufficiently to yield a service life of 30 to 35 years. But these preservatives are under scrutiny as hazardous materials and soon may be banned. Moreover, more than 70 percent of them are distribution poles in class 4 or class 5, measuring 40 ft or less in height. Composite poles could easily sustain the respective 1,500 lb and 1,900 lb horizontal loads defined by ANSI O5.1. And with less than 0.5 percent of in-service poles made of composites, this market is virtually untapped.
Recently, FRP composite poles have received greater attention from electrical utility and telecommunication companies because "breakaway" designs can mitigate automobile/pole collisions, which contribute to 1,200 to 2,000 deaths and 110,000 injuries each year. Breakaway utility poles are designed to break from their bases at a reduced amount of energy, in a plane close to the height of a typical vehicle bumper. Properly designed and tailored, FRP composites can have superior impact energy absorption capability (high ductility) and predictable breakability under impact, making roadside poles more "forgiving" in collision scenarios.
The only deterrent to wide acceptance is economic: Historically, FRP poles have cost about three times more than treated wood poles. But mass production of FRP poles in a more cost-effective manner is the key to greater market share. CFC-WVU has been developing such technologies, using patented through-the-thickness (3-D) stitched fabrics.
Infrastructure pipelines are a third, potentially huge market. There are 161,189 miles of liquid pipelines, over 320,000 miles of natural gas transmission pipelines and 1,100,855 miles of natural gas distribution pipelines in service (U.S. DOT Office of Pipeline Safety Statistics, January 2003). Additionally, large water and sewage systems comprise about 1.5 million additional miles of pipe. Existing pipelines are predominantly made of corrosion-susceptible steel. In 2001, approximately 30 percent of the 129 recorded hazardous liquid pipeline accidents were due to corrosion, accounting for more than $25 million in damages, while 209 accidents involving natural gas pipelines resulted in more than $37 million in damages.
Between 2001 and 2010, more than 50,000 miles of new transmission pipelines are likely to be built in North America, at a cost of more than $80 billion. In order to meet increased demand, improve safety/reliability and be competitive, the pipeline industry is looking at alternatives to conventional steel pipe, for high-pressure/high-volume natural gas transmission. In order to make FRP composites the preferred material for high-pressure, large-diameter natural gas pipelines, R&D will be necessary to improve quality control and to gain a greater understanding of material and joint failure. CFC-WVU has been advancing toward this goal through the Center's R&D efforts.
To make FRP composites the material of choice for highway guardrail and signposts, utility poles and pipelines, they must be economically justifiable, as well. Technological innovations and breakthroughs must be achieved in the areas of material sciences of resins and fibers/fabrics, structural designs, joining mechanisms and manufacturing techniques. One of the approaches used by the researchers at CFC-WVU to tackle these applications is an advanced pultrusion process integrated with patented technological innovations developed at CFC-WVU. These innovations are: 1) 3-D stitching of fabrics; 2) nano-resin systems (thermosetting resin with nanoadditives), including ductile resins; 3) optimized module-to-module joint design; and 4) advanced manufacturing. Additional process innovations are focused on compression molding, RTM and filament winding, as well as research into continuous compression molding coupled with pultrusion for thermoplastic composites.
These activities are part of CFC-WVU's vision for the year 2010, which we hope will result in regional economic development on the order of $1 billion annually. CFC-WVU recently proposed to establish a new composite manufacturing facility in West Virginia, for the purpose of commercializing FRP composite poles, posts, pipes and panels. There is a strong presence of resin and fiber/fabric producers in and around West Virginia. We are initiating research, development and demonstration partnerships with firms from among this group. The near-term goal is to mass-produce high-volume and high-quality structural composite components and systems for infrastructure at competitive prices.