This paper presents the crack monitoring of reinforced concrete beams strengthened with fiber reinforced polymer (FRP) sheets. Emphasis is placed on the development of a smart FRP bonded material that can measure the crack opening of a reinforced concrete beam strengthened by FRP. The reliability measured by a conventional digital image correlation (DIC) and by the proposed smart FRP is employed to assess the contribution of the FRP to control the crack. The monitoring process is based on a large set of experimental database consisting of 19 test beams. The effect of FRP to control the crack opening is studied depending on the steel ratio, FRP ratio and the level of damaged of RC beams when FRP is applied. The results were compared with the theoretical values of crack width and spacing predicted using the Eurocode 2 (EC2) formula, calibrated for non-strengthened RC elements. The corresponding results were compared in order to clarify the effect of external bonded FRP on the cracking behaviour of RC beams.

The serviceability and ultimate limit states of a concrete member are reliant upon the bond of reinforcement. The performance of glass fiber reinforced polymer (GFRP) reinforced concrete structures is influenced by multiple parameters and one of these parameters is the bond length of GFRP rebars. The scope of the present research is to experimentally study the effects of fully and partially bonded rebars on the load-bearing capacity and cracking of GFRP-reinforced concrete beams. The beams with partially bonded reinforcement show reduced capacities compared with those with fully bonded reinforcement, and the former reveals localized cracks. The partially bonded beams fail as a result of concrete splitting, while their fully bonded counterparts fail by concrete crushing.

The current market of utility poles is growing rapidly. The dominant materials that are used for this purpose are generally wood, steel, concrete, and fiber-reinforced polymers (FRP). FRP poles are gaining wide acceptance for what they provide in terms of strength and durability, lack of maintenance and a high strength to weight ratio. Hybrid structures can combine the best properties of the materials used, where each part enhances the structure to provide a balanced structure. This study evaluates a hybrid structure composed of three main layers, an outer FRP shell, a hollow concrete core and an inner hollow steel tube, this whole system is to be utilized as a tapered utility pole. The outer FRP shell provides protection and enhances the strength of the pole, the concrete core provides stiffness, and the inner steel tube enhances the flexural performance while reducing the volume in consequence the weight of the structure compared to a fully filled pole. A new design for a 12-feet long hybrid FRP pole using finite element is presented in this paper. The design was based on a parametric study evaluating the effect of key-design parameters (i.e., the thickness of FRP, the volume and strength of the concrete, the thickness and diameter of the steel tube). Concrete strength affected the general performance of the pole, the decrease in concrete strength due to utilizing lightweight concrete was compensated with increasing the FRP pole thickness. For the same pole configuration, with incremental variation of the FRP thickness values from 3 mm to 7 mm up to the initial concrete cracking load, no significant variation of the pole top deflection was observed. However, at failure load the increase of FRP thickness from 3 mm to 7 mm decreased the ultimate tip deflection by 50%. New hybrid utility poles have the potential to be an interesting alternative solution to the conventional poles as they can provide better durability and mechanical performances.

Corrosion of reinforcement steel is a major issue for many structural concrete components, because it leads to strength reduction and may significantly reduce the service life. For this reason, fiber-reinforced polymer rebars (FRP rebars) have been developed, as they represent a viable alternative that may replace reinforcing steel for structures that are particularly susceptible to corrosion issues. However, structural design philosophies for these new materials are still in development and further research is needed to implement FRP rebars properly and safely in design codes but also to ensure that design calculations properly predict the actual behavior and performance of FRP reinforced structures.

This study was conducted to evaluate the strength and structural deformation behavior of flexural beams that were designed according to Eurocode 2 and, for comparison, according to different design methods pro-posed for FRP reinforced structures. With regard to the development of a uniform design concept for alternative reinforcement materials existing in Germany/Europe, different bending design concepts includ-ing the serviceability limit state were evaluated. In addition, the theoretically calculated and predicted strength/deformation were compared to the experimentally obtained measurements. A total of 15 flexu-ral beams, with ans overall length of 4.5 m (177 in.), a width of 200 mm (7.8 in.), and a height of 400 mm (15.8 in.), were cast; three of these beams (designed according to Eurocode 2) featured traditional steel rein-forcement, to serve as control group. The remaining 12 flexural beams were evenly allocated to capture the two alternative reinforcement materials, while generating three different reinforcement distribution patterns with comparable reinforcement ratios (equivalent cross-sectional areas). Thus, a total of six subgroups –three with GFRP and three with BFRP – each with two specimens, were analized. To test all beam in pure bending and to eliminate the influence from shear forces, two equally increasing loads were applied at the (longitudinal) third-points of the beams. Both deflections and loads were measured at several points to evaluate the structural performance of the FRP reinforced structural members.

The results showed that the deflection of the glass fiber reinforced bars at the design load capacity measured twice as much as the deflection of the control group. Almost three times as much deflection (at the same load) was observed for the concrete beams reinforced with basalt fiber rebars. In addition, it was observed that the concrete beams with glass and basalt fiber reinforcement bars showed a nearly elastic-elastic behavior up to the point of failure, whereas the steel-reinforced concrete beams showed an elastic-plastic behavior. However, the deformational behavior differed between the various beam types. While the prevailing equations properly captured the post-cracking performance of traditionally reinforced concrete beams, they do not adequately predict the deflections of FRP reinforced concrete beams. From the measurements and analyses, it was concluded that the serviceability limit state (SST) is more critical than the ultimate limit state (LTS) for the design of concrete flexural beams reinforced with FRP rebars.

The issues related to deformability, strength and ductility of concrete elements reinforced with FRP (Fiber Reinforced Polymer) bars are critically analyzed and discussed in this paper. The analysis is conducted from an experimental point of view by means of bending tests on concrete beams reinforced with Carbon FRP (CFRP) bars with different amounts of reinforcement, and by an analytical approach aiming to evaluate the deflection and cracking phenomenon (number and width of cracks). The experimental results are compared with the analytical predictions and with predictions developed on the basis of the available codes (ACI, EC2, JSCE). The analysis of the results obtained confirms the most relevant issues of the mechanical behavior of FRP bar-reinforced beams, still worthy of research efforts; some technological and construction solutions that can provide significant improvements are also addressed.