This paper reports the results of an experimental program to investigate the bonding behavior of two different types of fiber-reinforced polymer (FRP) systems for strengthening RC members: externally bonded carbon (EBR) plates and bars or strips externally applied with the near-surface-mounted (NSM) technique. The overall experimental program consisted of 18 bond tests on concrete specimens strengthened with EBR carbon plates and 24 bond tests on concrete specimens strengthened with NSM systems (carbon, basalt, and glass bars, and carbon strips). Single shear tests (SST) were carried out on concrete prisms with low compressive strengths to investigate the bonding behavior of existing RC structures strengthened with different types of FRP systems. The performance of each reinforcement system is presented, discussed, and compared in terms of failure mode, debonding load, load-slip relationship, and strain distribution. The findings indicate that the NSM technique could represent a sound alternative to EBR systems because it allows debonding to be delayed, and hence FRP tensile strength to be better exploited.

The structural performance of reinforced concrete elements is related to the interface behavior of rebars to concrete. In the last decade several research works were carried out to investigate the bond between fiber-reinforced polymer (FRP) rebars and concrete, however some aspects need further studies in order to obtain reliable design indications. In this paper the analysis of bond was performed referring to different kinds of FRP rebars and some varying influential parameters (surface treatment, kinds of fibers, and kinds of test). Results obtained show the role of the investigated parameters on bond stress law; in particular the surface treatments involve different transfer mechanisms passing from simple chemical adhesion and friction, for sanded rebars, to a relevant contribution of mechanical interlocking for deformed rebars. The kind of test utilized influences the most significant parameters of the bond stress–slip law and in different ways depending on the kind of rebars. Finally the kind of fibe...

The use of composite materials in structural engineering is recent, and researchers need to investigate their behavioral features. Design criteria and methods have to be redefined, and several countries have already established design procedures specifically for fiber-reinforced plastic (FRP) use. Generally the proposed code modifications are conservative and the strength capacity of FRP materials is not efficiently used. This limitation is due to the low number of experimental tests on concrete structures reinforced with FRP bars. In this paper, experimental tests on beams reinforced with glass FRP bars are presented and discussed. Significant features of the structural behavior are pointed out regarding curvature, deflection, and crack spacing and width. Furthermore the verifications at ultimate and serviceability conditions are analyzed. Code formulations for deflection and crack width calculation are examined considering the American Concrete Institute and the Eurocode 2 approaches.