Key Details

Owner: North Carolina Department of Transportation

Designer: North Carolina Department of Transportation

Contractor: Balfour Beatty

Location: Harkers Island, North Carolina, USA

Date: 2022-2023

The Harkers Island Bridge replacement project is making waves in the world of infrastructure development by embracing glass fiber-reinforced polymer (GFRP) rebar.  It will be the first bridge in the USA to be fully-reinforced using FRP rebar and the largest in the world without any steel reinforcement.

The replacement bridge has 28 spans, is 3.2 miles long, and will use 1,574,618 linear feet of Mateenbar™ Rebar, supplied by Owens Corning Reinforcement Solutions from its North Carolina factory.

Carbon fiber was used in parts of the structure, with GFRP being used as the main reinforcement material:

  • The large diameter piers had carbon fiber prestress tendons with GFRP circular stirrups
  • The smaller piles had carbon prestress tendons with carbon stirrups
  • Pier Caps reinforced with GFRP bar 
  • Wide flange prestressed girders of varying heights all had carbon prestress tendons with GFRP stirrups
  • The Bridge deck 100% reinforced with GFRP bar

Advantages of Using GFRP Rebar on Bridge Structures

Concrete bridges are prone to various forms of deterioration such as corrosion, carbonation, creep, shrinkage, water infiltration, and alkali-silica reactions. Among these, a major issue for steel-reinforced concrete bridges is the corrosion of the steel reinforcement, often leading to significant damage. Rust formation on the reinforcement leads to its expansion, accelerating the overall degradation of the bridge over time reducing asset life and increasing whole-of-life costs.

GFRP rebar provides some clear advantages in bridge applications including:

Corrosion Resistance: GFRP rebar is a game-changer due to its resistance against corrosion. Given the bridge's exposure to saltwater, GFRP ensures the structure remains robust over time, minimizing maintenance costs. This resistance is vital for the bridge's stability, especially in coastal environments

Lightweight: GFRP rebar is lightweight but just as strong as steel. This means the construction process is simpler, requiring less heavy machinery and time. The material's reduced weight also helps during transportation and installation, reducing the project's impact.

Environmental Sustainability: Using GFRP rebar aligns with sustainability goals. Traditional steel production emits significant carbon emissions, whereas GFRP manufacturing is less energy-intensive. Longer-lasting structures with GFRP mean fewer materials used overall, further advancing sustainable practices.

Bridge Replacement provides Research Opportunities for Engineers

As referenced in the research in progress excerpt: Harkers Island Bridge Replacement: Material Characterization and Structural Performance: North Carolina, steel-reinforced concrete bridges are facing corrosion due to harsh environments. This issue is not isolated and poses financial challenges for the North Carolina Department of Transportation (NCDOT).

The Harkers Island Bridge project aims to replace Bridges No. 96 and 73 on Harkers Island Road. Bridge No. 96, built in 1970, was replaced in 2013 after 43 years due to severe deterioration, and Bridge No. 73 from 1969 is currently classified as structurally deficient.

A solution to combat corrosion is to replace the internal steel reinforcement with non-corroding fiber-reinforced polymer (FRP) reinforcement. This method has been successful in extending the lifespan of bridges. The Harkers Island Bridge replacement will be the first fully FRP-reinforced concrete bridge in North Carolina, offering a chance to study material characteristics and performance closely

This research will contribute to improving future bridge design and construction standards, and it has a team well-equipped to achieve these goals. The outcomes will include valuable insights into material properties, construction practices, and long-term performance. 

Future Proofing Bridge Structures with GFRP Rebar

The Harkers Island Bridge Replacement project's use of GFRP rebar is a significant step forward in modern infrastructure and the first of many bridges to embrace GFRP composite technology for greater asset lifecycle and reduction in maintenance costs over its lifetime.