Flexural behavior of RC beam strengthened by FRP grid-reinforced ECC overlay and U-wrap anchor: 2-D FE modeling and parametric analysis

Fiber-reinforced polymer (FRP) grid-reinforced engineered cementitous composites (ECC) exhibit great potential as the overlay for strengthening aging reinforced concrete (RC) beams, particularly in conjunction with U-wrap FRP anchors to mitigate the interfacial debonding. In this paper, finite element (FE) modeling considered the combination use of these two strengthening methods has been conducted. The interfacial behaviors between the RC beam and the strengthening overlay or the U-wrap are carefully simulated using the cohesive contact interface or spring connecters. The FE model was validated through comparison with the measured data in experiments conducted by the authors. Then, a parametric analysis based on 162 models was conducted to investigate the effect of overlay thickness, FRP-grid strength, U-wrap thickness, and width on the ultimate load-carrying capacity of the specimens and interfacial slip at the two bonding interfaces. Based on the parametric study outcomes, the pivotal factor influencing the failure mode and load-carrying capacity was identified as the total axial strength of the FRP grid reinforcement, in which an increase of 25 times in this factor would result in an average increase of 55% in load carrying capacity. Moreover, it exhibited a substantial influence on the interfacial slip distributions between the RC beam and overlay or U-wrap.