Although the use of near‐surface mounted (NSM) fiber reinforced polymer (FRP) reinforcement satisfactorily enhances the flexural capacity of deficient reinforced concrete beams, the concrete beams strengthened with NSM FRPs typically exhibit brittle behavior. Aluminum alloy (AA) bars possess non‐corrosive characteristics like FRPs but also exhibit a nonlinear tensile response with a clear yield point. This paper investigates the failure modes of reinforced concrete beams strengthened with either NSM glass FRP (GFRP) bars or AA bars. A total of six concrete beams including one control beam were tested under four‐point bending. The effects of NSM reinforcement type, internal steel reinforcement ratio, and NSM reinforcement ratio on the failure behavior of the strengthened beams were examined. The ultimate flexural load capacity, ductility index, energy absorption capacity, strains in steel reinforcement and in concrete, and cracking behavior for each tested beam were determined and analyzed. The results indicated that for the same NSM reinforcement ratio, the NSM GFRP bars provided considerably higher increases in the flexural strength of reinforced concrete beams compared to the AA bars. However, the beams strengthened with AA bars showed more ductile response compared to the beams strengthened with NSM GFRP bars.

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This study explores the flexural behavior of reinforced concrete (RC) columns strengthened with near surface mounted (NSM) shape memory alloy (SMA) bars or carbon fiber reinforced polymer (CFRP) bars. Seven RC column specimens were designed and fabricated to study the influence of different variables on the flexural response of the strengthened columns. These parameters include type of NSM reinforcement (SMA bars or CFRP bars), ratio of NSM reinforcement, and effect of CFRP jacketing. The columns were tested under cyclic lateral loading with constant axial force. The flexural behavior of each specimen was examined in terms of peak load, failure load, drift ratios, displacement ductility, stiffness degradation, energy dissipation, and seismic damage index. The experimental results indicate that strengthening of RC columns with NSM SMA or CFRP bars improves the flexural behavior of the columns through increasing the lateral load capacity, reducing the stiffness degradation and increasing the cumulative energy absorption up to failure. Further enhancement in the lateral response of RC columns was obtained by combining NSM bars and CFRP jacketing as the later provides an additional confinement to the critical sections of the test specimens.

Basalt-fibre-reinforced polymers (BFRPs) are promising economical materials developed in recent years for strengthening or repairing reinforced concrete (RC) structures. The effectiveness of strengthening RC beams with near-surface-mounted (NSM) BFRP reinforcement was investigated in this study. One reference beam and six beams strengthened with NSM BFRP reinforcements were tested under four-point loading. The main test variables were the NSM reinforcement ratio, the tensile reinforcement ratio and the pre-cracking load. The experimental results indicated that, compared with the control beam, both the load-carrying capacity and flexural stiffness of the strengthened concrete beams increased due to use of NSM BFRP bars. For the NSM-strengthened concrete beams, the pre-cracked specimens failed by BFRP bar end cover separation while the directly strengthened specimens (not pre-loaded) were governed by concrete crushing. Analytical models based on the section analysis method were developed to predict the maximum bending moment and ultimate deflection at mid-span of the concrete beams strengthened with NSM BFRP bars. The analytical values of maximum bending moment and ultimate mid-span deflection were in good agreement with the experimental results.

Aluminum alloys (AAs) possess various advantageous properties such as good corrosion resistance and high ductility and have recently gained interest in strengthening reinforced concrete (RC) structures. This paper investigates the potential application of AA bars as the near‐surface mounted (NSM) reinforcement in flexure strengthening of RC beams. A total of seven RC beams including one reference specimen and six specimens strengthened with NSM AA bars were designed and loaded monotonically up to failure. The tensile steel reinforcement ratio, NSM reinforcement ratio, precracking load, and bonding area of NSM reinforcement were selected as the main test variables. Results suggest that both the flexural capacity and stiffness of the strengthened beams improved with the use of NSM AA bars compared to the reference beam, and all the strengthened concrete beams exhibited a ductile failure mode. Nevertheless, increases in flexural load carrying capacities were modest when the AA bars were used as NSM reinforcement. Furthermore, an analytical model, which combined the sectional analysis method and interfacial stress analysis model, was developed to predict the load versus mid‐span deflection relationship of the concrete beams strengthened with NSM AA bars. The developed model was also capable of predicting the load–strain relationships in AA reinforcement. Good agreements were achieved between the analytical results and experimental results.