Evaluation of external transversal reinforcement strains of RC beams strengthened in shear with FRCM composites

Research carried out in recent years has proven that Fibre Reinforced Cementitious Matrix (FRCM) composites are a valid alternative to traditional techniques used for the strengthening of reinforced concrete (RC) structures. Unfortunately, the available experimental evidence is still limited, and research on the topic is needed. Regarding the behaviour of RC beams strengthened in shear with FRCM composites, questions such as the actual value of strain reached by the composite still need to be answered. Bearing this in mind, an experimental campaign was carried out in order to provide insight on the aforementioned issue. In this study, RC beams were strengthened in shear using FRCM composites with carbon and steel fibres in a U-wrapped configuration. The beams were tested in fourpoint bending, and strains in the composite fibres were measured throughout the load response. Strains recorded at peak load were compared to strains computed using available models. Results show that FRCM composites with both carbon and steel fibres were able to provide a significant increase in the shear capacity of strengthened beams. Strains measured in the fibres at beam failure were lower than half of the strain corresponding to the tensile strength of carbon and steel fibres