Use of Fiber-Reinforced Polymer Composites for Bridge Repairs in Montana

Details

• Creators:
  Ahmed, Emtiaz ; Matteson, Kirsten ; Berry, Michael
• Corporate Creators:
  Montana State University
• Corporate Contributors:
  Montana. Department of Transportation ; United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  Fiber Composites Fiber Reinforced Polymers Field Strength Girder Bridges Infrastructure Laboratory Tests Rehabilitation Repairing Strength Of Materials Wooden Bridges
• Publication/ Report Number:
  FHWA/MT-26-001/10337
• DOI:
  https://doi.org/10.21949/1529573
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States ; Montana
• Edition:
  Final Report (January 2023-March 2026)
• Corporate Publisher:
  Montana. Department of Transportation
• Abstract:
  Montana’s timber bridge inventory includes over 600 state and county owned bridges, many more than 80 years old and showing visible deterioration. Traditional girder repair methods, such as steel hangers and timber or steel sister girders, are heavy, labor-intensive, and often lack well-documented performance verification. Fiber-reinforced polymer (FRP) composites offer a light weight, corrosion-resistant alternative with strong potential for timber bridge rehabilitation, yet their application to timber bridges remains relatively underexplored, particularly at full scale and under field conditions. This report investigates the use of pultruded FRP composites to repair and strengthen deteriorated timber bridge girders to restore capacity and extend service life. Full-scale laboratory testing was conducted on 22 salvaged Douglas-fir/Larch beams from bridges across Montana. Beams were categorized as control, repaired (with pre-existing or induced splits and cracks), or strengthened (intact), and retrofitted using carbon–glass hybrid strips, glass FRP channels, or a combination of both. The channel–strip configuration showed the most robust performance, increasing moment capacity significantly compared to control specimens, while strip-only repairs also improved performance, particularly for moderately damaged beams. To validate the laboratory findings, selected FRP repair techniques were implemented on two in-service timber bridges near Toston, Montana. Installation was completed rapidly using standard tools, demonstrating the constructability of the repair systems under field conditions. A seven-month follow-up inspection indicated no visible deterioration or issues. Overall, this work provides a validated, field-tested approach for rehabilitating timber bridge girders using pultruded FRP composites, offering transportation agencies a practical strategy to extend the service life of aging timber infrastructure.
• Format:
  PDF
• Funding:
  MDT Project # 10337
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:1e5984f6d259867ac8b98c76a14b3f78ea1c103d86532e2ad3425d6b7b6fec97accb17b9380e565abed91a44852304127dfd4f29599da0f836a6958e0cfb4bae
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/89574/dot_89574_DS1.pdf
• File Type:
  [PDF - 18.55 MB ]