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.

Recently codified language in ACI CODE-440.11-22 provides an equation for concrete shear capacity and imposes a lower bound on this calculation. An experimental study consisting of 39 flexural members without shear reinforcement and tested to failure in shear was used to evaluate the current code provisions, including, most specifically, the lower bound. Comparison of experimental and analytical shear capacities demonstrates that the current code provisions are conservative. More lightly reinforced specimens have a higher variability in experimental-to-nominal concrete shear strength than more heavily reinforced specimens, and this variability appears to be dominated by the depth between the elastic cracked section neutral axis and the depth of the tensile reinforcement, which is the area where aggregate interlock occurs. Based on a comparative reliability study, the lower bound, kcr = 0.16 (5kcr = 0.8), in the code, causes more lightly reinforced specimens (kcr < 0.16) to have lower factors of safety against shear failure than more heavily reinforced specimens (kcr > 0.16). Rather than imposing a lower bound of 5kcr on the current shear strength equation, it would be more prudent to resolve the overprediction of the equation for all specimens.

Fiber reinforced polymer (FRP) composite rebar is a non-metallic concrete reinforcement alternative that has been successfully deployed in hundreds of structural applications globally. The increasing demand for FRP rebar as a metal alternative is driven by its unique value proposition, including lightweight, high strength, magnetic transparency, and most significantly, corrosion resistance. FRP rebar is fabricated through pultrusion, a high throughput composite fabrication process in which, resin-impregnated fiber undergoes rapid cure when pulled through a heated furnace. Considering the open nature of the open pultrusion process, expansion of production capacity for FRP rebar manufacturing demands the use of advanced resins that are free from Volatile Organic Compounds (VOCs), enable high throughput production, and deliver an outstanding translation of fiber properties following cure. In this work, we will present an epoxy system that is inherently VOC Free and is tailored to enable high throughput manufacturing of glass fiber reinforced polymer (GFRP) rebar at scale. Furthermore, the rapid formation of highly crosslinked structures achieved with this resin system during pultrusion is found to enable outstanding fiber property translation resulting in high modulus (>70 GPa) and corrosion resistance (>80 % tensile strength retention without load) that exceeds existing standards such as ASTM D7957.

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 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.