Condition Assessment of Fiber-Reinforced Polymer Strengthening of Concrete Bridge Components

Fiber-reinforced polymer (FRP) wrap strengthening of deteriorated, damaged, or structurally unsafe concrete bridge components is an increasingly popular technique. The method is economic, durable, convenient, and labor-friendly, being employed now by many highway agencies. The long-term in situ performance of the external FRP-epoxy-concrete interface bonding is a primary concern due to the potential for age-related environmental degradation, and also any possible lack of quality control during the FRP installation. In this study, the carbon FRP wrapping on eight selected concrete bridges in the Dallas-Fort Worth metroplex area was evaluated for current on-site current condition. In addition to visual inspection, FRP pull-off testing was performed on site on selected retrofitted columns and girders in the target bridges to assess the current condition of the interface FRP bonding. A majority of the test FRP pull-off samples failed in the concrete substrate (the preferred mode of failure indicating strong bond presence). However, the test data on failure modes and pull-off strengths were scattered, possibly due to environmental degradation or a lack of proper quality control during the initial FRP application. The age of each bridge did not correlate well with the percentage of samples failing in the preferred mode, indicating that environmental degradation could be eliminated as a possible factor. Good record keeping at the initial FRP installation, proper quality control at that initial installation, and proper pull-off test procedure are essential in ensuring good performance of the FRP strengthening and efficient in situ performance testing.