Repairing/Strengthening of Bridges with Post-tensioned FRP Materials and Performance Evaluation.

摘要

One of the challenges that transportation agencies are facing is to keep bridges in good condition during their service life. Numerous bridges are classified as structurally and/or functionally deficient in the country. In the state of Louisiana, 4,591 bridges, or 34 percent of the total 13,426 bridges, are classified as substandard. Load capacity degradation, increased gross vehicle weight, and increasing traffic demand lead to the deficiencies. One of the most effective ways to solve the problem is to use composite materials to strengthen existing bridges. As rapidly developed over the past several decades, different kinds of composite fiber reinforced polymers (FRP) have been regarded as one of the best solutions to several problems associated with transportation and civil engineering infrastructures. Some of the major benefits of FRP include high strength to weight ratio, high fatigue endurance, excellent corrosion resistance, low thermal expansion, and the ease of fabrication, manufacturing, handling, and installation. The main objective of this research was to develop a flexural resistance designing process using post-tensioning prestressed carbon reinforced polymers (CFRP) laminates adhering to bridge girders to avoid various possible flexural failure modes. It is noted that, in the original plan, a steel bridge and a concrete bridge was to be rehabilitated with prestressed FRP laminates or rods and the bridge performance was to be monitored. However, the sponsor decided not to pursue the field implementation due to cost. This report presents a review of the up-to-date work on bridges strengthened with FRP materials. Mechanical properties of FRP fibers and composites were presented in detail. Investigators presented previous research findings on experiments of FRP composite materials used as various prestressed tendons, and the analyses for different failure modes were introduced. To investigate the effect of rehabilitation with prestressed CFRP laminates, two 3-D finite element analyses were conducted to examine the deflection and bottom fiber stress at the mid-span. A detailed designing process of rehabilitation with prestressed CFRP laminates was presented in this report. A feasible plan to enhance the flexural capability of an existing bridge with externally prestressed CFRP laminates according to AASHTO and ACI code specifications was also proposed in this report.