strengthen beams failing in bending under monotonic loading

The use of fiber reinforced polymers (FRP’s) in the context of strengthening Civil Engineering structures has grown in the last decades. Properties such as light weight, high stiffness/weight ratio, corrosion immunity and wide variety of sizes and shapes available are some of the reasons that justify the growing use of this type of materials. They have been applied mostly by two strengthening techniques: Externally Bonded Reinforcement (EBR) and Near-Surface Mounted (NSM). The efficiency of these techniques depends, mainly, on the performance of the bond. This type of reinforcement is applied on the cover concrete, which is normally the weakest region of the element to be strengthened. Consequently, the most common problem is the premature failure of FRP reinforcement, which happens more frequently in the EBR technique. In an attempt of overcoming this problem, other techniques have been proposed. The present one uses multi-directional carbon fiber laminates, simultaneously glued and anchored to concrete. In addition the anchors can be pre-stressed. This technique was called MF-EBR – Mechanically Fastened and Externally Bonded Reinforcement. This paper presents the results of the experimental tests carried out with reinforced concrete beams strengthened with the three techniques previously referred in order to assess the efficiency of each one. An additional beam was casted and was used as the reference beam. For this purpose four reinforced concrete beams of 200×300×2200 mm3 were used submitted to four-point bending tests. The present work describes the carried-out tests and presents and analyzes the most significant obtained results, as well as the numerical simulations performed