Strengthening Reinforced Concrete Bridges Using Carbon Fiber Reinforced Polymer Composites

The need to develop economic strengthening techniques for the aging infrastructure has received considerable attention in recent years. In Texas, a significant percentage of bridges in off-system roads were constructed in the 1950s and require strengthening to upgrade them to the current load used for design. Therefore, the Texas Department of Transportation (TxDOT) was interested in examining the use of carbon fiber reinforced polymer (CFRP) composites to strengthen existing bridges and avoid replacement.

Four full-scale specimens representative of bridge construction during the 1950s in Texas were constructed, strengthened, and tested in the laboratory to assess the effectiveness of CFRP composites for flexural strengthening. The response of the laboratory specimens is compared with calculations based on an analytical model that was developed to reproduce the measured response and to design future strengthening schemes.

Results from the laboratory tests indicate that composite materials may be used successfully to strengthen existing elements. The maximum strength in the specimens was controlled by debonding of the CFRP composites from the surface of the concrete. The analytical model was able to reproduce the general response of the specimens accurately, but did not replicate the mode of failure experienced in the tests.

Therefore, the model can be used with a modification to incorporate the failure mode observed during the tests for the future design of strengthening schemes. Finally, recommendations for the design of strengthening procedures of similar bridges in the field are presented.