Performance of FRP-Strengthened RC Beams with Surface Out-Of-Flatness

Abstract

Fiber reinforced polymer (FRP) has become increasingly popular for the repair and retrofit of reinforced concrete structures. Surface condition of the substrate, in particular its flatness, plays a significant role on the performance of retrofitted structure. This paper reports on the effects of out-of-flatness as a surface defect on the flexural performance of FRP repair systems. The experimental program includes a total of nineteen specimens with two different FRP repair systems (wet lay-up and precured), and two different levels of surface unevenness in the form of peaks or valleys. Tests showed that the peaks on concrete surface, in the range studied, did not have a significant effect on the performance of FRP systems. However, valleys or depressions deeper than 1.6 mm over a length of 305 mm (1.38 × 10⁻⁴ mm⁻¹ curvature) could reduce the strength of FRP systems. Typical failure mode was FRP debonding observed in both FRP repair systems. Test results and threshold recommendations were verified using a nonlinear finite element analysis. Bond-dependent coefficient for various surface flatness levels were analyzed and compared with the results available in the literature.

Keywords

bond concrete fiber reinforced polymer (FRP)finite element analysis repair surface flatness

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