Fatigue performance of corrosion-damaged beams strengthened with FRP grid-reinforced ECC matrix composites

An investigation on the flexural fatigue behavior of corrosion-damaged reinforced concrete (RC) beams that were strengthened with a fiber-reinforced polymer (FRP) grid-reinforced engineered cementitious composite (ECC) matrix is presented in this paper. The concrete cover, which was damaged by the corrosion of the tensile steel bars, was chipped away and reinstated with an ECC layer that was embedded with an FRP grid. A total of 12 beams were constructed, and 11 of them were subjected to cyclic fatigue loading. The test results indicated that the final failure mode of the strengthened beams was still dominated by the brittle fracture of the tensile steel reinforcements. The fatigue life of the beams increased significantly with increasing strengthening amounts of the FRP grid but decreased with the corrosion ratio and the upper limit fatigue load level. At a sufficient strengthening amount, the fatigue life of strengthened beams could be restored to that of the original uncorroded beams. By regression analysis of the stress range-fatigue life (S-N) curve, a prediction formula for fatigue life was derived with a satisfactory correlation coefficient. In addition, the tested midspan deflections and the results that were calculated using available empirical models or theoretical calculation approaches were compared and evaluated.