Performance of FRCM-Strengthened RC Beams Subject to Fatigue

Fabric-reinforced cementitious matrix (FRCM) is a relatively new material system developed for the repair, retrofit, and rehabilitation of reinforced concrete (RC) and masonry structures. Structures such as bridges experience high traffic volumes and varying vehicle axle weights causing repeated cyclic loading throughout the lifetime of the structure. Cyclic loading may cause progressive damage to the structure, a phenomenon known as fatigue. Due to the novelty of FRCM technology, there is a lack of research regarding the long-term performance of FRCM systems for RC strengthening. This study investigated experimentally the parameters that most influence the flexural fatigue performance of polyparaphenylene benzobisoxazole (PBO) FRCM-strengthened RC beams. Specimens are subjected to both static and cyclic (fatigue) loading. For members subjected to cyclic loading, the following parameters were investigated and discussed: amount of supplemental reinforcement, ultimate strength, applied stress range, fatigue life, failure modes, and residual strength. Results were used to develop a stress ratio versus the number of cycles (S-N) curve with the objective of defining the endurance limit of the FRCM strengthened RC beams.