Abstract
The effect of using inclined fiber-reinforced polymer (FRP) U-wrap for preventing concrete cover separation (CCS) of FRP flexural strengthening in reinforced concrete (RC) beams was investigated. The beams measured 3400 mm long, 200 mm wide, and 400 mm deep and were tested under two concentrated loads. The inclined U-wraps were used to anchor the FRP flexural strengthening at its ends. The FRP materials used in both flexural strengthening and end anchorage were carbon FRP (CFRP) sheets. The inclination angle of the FRP U-wraps to the longitudinal axis of the beams was 45 degrees. The area of FRP U-wrap was varied in terms of varying the width of U-wrap. The test results indicated that there is a minimum width of inclined FRP U-wrap required to prevent CCS and shift the failure to another mode of failure, which in this case was intermediate crack (IC) debonding. Increasing the width of inclined FRP U-wrap by 33.3% and 100% above this minimum width was found to not only prevent CCS failure but also delay the occurrence of IC debonding and increase the load-carrying capacity of the beams by 24% and 32%, respectively, higher than the calculated failure load at IC debonding. These results showed superior performance of inclined U-wraps vs. vertical U-wraps in preventing CCS and increasing the load-carrying capacity of the beams. A model for determining the minimum FRP U-wrap area required to prevent CCS including the effect of inclination angle of FRP U-wrap was proposed. The proposed model was able to accurately predict the minimum area of inclined FRP U-wrap of the test beams at which the mode of failure shifted to IC debonding. In addition, the paper presents a proposed method for calculating the load-carrying capacity of FRP-strengthened beams anchored with inclined FRP U-wrap accounting for the beneficial effect of increased capacity of the beams associated with the use of such anchors. The comparison with the experimental results indicated good agreement.