Numerical and experimental investigation into the fatigue life of FRP bonded to concrete and anchored with bidirectional fabric patches

Abstract

Although extensive research has been conducted into the use of fibre reinforced polymers (FRPs) in strengthening of concrete structures under static loads, their fatigue behaviour when subjected to cyclic loading still requires investigation. The issue of fatigue performance of FRP strengthening systems is mostly relevant to the strengthening of concrete bridges which are subjected to significant traffic loading cycles throughout their lifetime. In order to offset some of the shortcomings of externally bonded FRPs, anchorage systems are commonly used in bridge strengthening applications in conjunction with FRPs externally bonded to concrete in order to mitigate premature debonding failure. This paper presents a summary of numerical and experimental investigations conducted to evaluate the fatigue performance of externally-bonded FRP laminates anchored with bidirectional fibre patch anchors. The anchored laminates were bonded to reinforced concrete (RC) blocks and subjected to various cyclic loading scenarios. Parameters such as the stress range, peak cyclic stress level, and the corresponding number of cycles prior to failure were noted. The results were used to generate an S-N curve relationships. A finite element model was developed and calibrated based on the experimental results. Good correlation was achieved between the experimental and FE results in relation to the maximum number of cycles, strain distribution, and mode of failure. The outcomes of this study showed that no fatigue degradation was observed when the peak cycling stress level was less than 60% of the ultimate static capacity. Further details of the results and recommendations for future research work are also provided.