Flexural Reliability of CFRP-Strengthened Bridge Girders

The reliability of reinforced concrete bridge beams that are flexurally strengthened with externally bonded carbon fiber-reinforced polymer (CFRP) laminates according to current AASHTO design provisions was quantified. The flexural resistance model considers resistance loss due to the effect of bar corrosion, FRP rupture, and debonding. Random variables were used to characterize uncertainties in as-constructed initial beam geometry and material properties, as well as loads and loss of beam resistance due to steel, concrete, and CFRP system degradation. Bond strength loss was based on 19 years of actual in situ data. The effects of various critical parameters on reliability were quantified, including beam span, concrete strength, the modular ratio and unit area of CFRP, the extent of CFRP repair, and the dead/live-load ratio. It was found that a large inconsistency in reliability exists among CFRP-repaired beams designed according to AASHTO provisions, the primary cause of which is variability in debonding potential. The results demonstrate the importance of including a well-developed bond strength model in the design process. Recommendations are provided.