Performance of a Bridge Deck with Glass Fiber Reinforced Polymer Bars as the Top Mat of Reinforcement
Kimberly A. Phillips
Roberts-Wollmann, Carin L.
Cousins, Thomas E.
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The purpose of this research was to investigate the performance of glass fiber reinforced polymer (GFRP) bars as reinforcement for concrete decks. Today's rapid bridge deck deterioration is calling for a replacement for steel reinforcement. The advantages of GFRP such as its high tensile strength, light weight, and resistance to corrosion make it an attractive alternative to steel. The deck of one end-span of the Gills Creek Bridge was constructed with GFRP bars as the top mat and epoxy-coated steel bars as the bottom mat. Live load tests were performed in 2003, shortly after completion of construction, and again in 2004. In addition, tests were performed on the deck of the opposite end-span, which had all epoxy-coated steel reinforcing. The results of these tests were used to evaluate the girder distribution factors and impact factors of a GFRP reinforced bridge deck. In addition, a comparison of the results from the two test periods gives an indication of any changes in strains in the GFRP bars and if the deck is behaving differently than when first installed. The results were compared to the design standards specified by the American Concrete Institute in the Guide for the Design and Construction of Concrete Reinforced with FRP Bar to determine if the stresses in the deck were within the specified limits. The performances of the two end-spans were compared to determine if the GFRP reinforcement had any significant influence on overall bridge behavior. There were no significant differences in the behavior of the deck after 1 year of service and there was no visible cracking. The behavior of the two end-spans was similar, and the measured girder distribution factors were less than the AASHTO design recommendations. The impact factors were less than design values for the 2003 tests but higher than design values for the 2004 tests. Stresses in the GFRP reinforcing bars were much less than the design allowable stress and did not change significantly after 1 year of service. The strain gauges, vibrating wire gauges, and thermocouples in the bridge deck were monitored for approximately 1 year using a permanent data acquisition system. Daily, monthly, and long-term fluctuations in temperature and stresses were examined. The vibrating wire gauges were more reliable than the electrical resistance strain gauges, and the main influence on strain changes was temperature fluctuation. A cost/benefit analysis of using GFRP bars indicates their high initial costs are justified when compared to the costs of a concrete overlay.