Small-scale plain concrete precracked beams strengthened with glass fiber reinforced polymer (GFRP) sheets underwent testing in 3-point flexure to assess variations in the FRP-concrete Mode II interfacial fracture energy after 6 and 13 years of sustained loading in indoor and outdoor environments. The Mode II fracture energy of the interfacial region, GF, was determined by analyzing strain profiles along the length of the FRP sheet, which were obtained using digital image correlation and photoelastic techniques. In the experiments conducted after conditioning, higher GF values were observed as the debonded zone progressed from the region of sustained shear stress transfer to the unstressed section of the interfacial region, particularly in beams subjected to outdoor conditioning. In the interfacial region near the notch, GFRP beams showed reductions in GF in both indoor and outdoor environments. For outdoor beams with GFRP sheets, there was no additional degradation in GF when the FRP was exposed to direct sunlight, in comparison to beams with the FRP exposed to indirect sunlight.

This paper presents an experimental study that investigated the physical and mechanical properties of the helical wrap glass fiber-reinforced polymer (GFRP) bars. The physical tests are conducted to check the feasibility and quality of the production process through the cross-sectional area and evaluation of the fiber content, moisture absorption, and glass transition temperature of the specimens. While the mechanical tests in this study included testing of the GFRP specimens to determine their tensile properties, transverse shear, and bond strength. Four bar sizes (#3, #4, #5, and #6), representing the range of GFRP reinforcing bars used in practice as longitudinal reinforcement in concrete members subjected to bending, are selected in this investigation. The GFRP bars had a helical wrap surface. The tensile failure of the GFRP bars started with rupture of glass fibers followed by interlaminar delamination and bar crushing. The bond strength of the GFRP bars satisfied the limits in ASTM D7957/D7957M. The test results reveal that the helical wrap GFRP bars had physical and mechanical properties within the standard limits.

Recent seismic events demonstrated the high vulnerability of existing reinforced concrete (RC) buildings. Lack of proper seismic details resulted in significant damage to structural components with many collapses and number of fatalities. The destruction of entire cities shield lights on the need of effective strengthening solutions that can be applicable at metropolitan/regional scale. They should be effective increasing significantly the seismic performance, affordable in the cost, fast to apply and with a low level of disruption to the occupants. This research work presents and discusses the preliminary results of an experimental programme on full-scale RC beam-column joints with reinforcement details typical of the existing buildings in the Mediterranean area. After assessing the response of the as-built specimen under a constant axial load and increasing cyclic displacement, a novel FRP-based strengthening system is presented. It combines the use of a quadriaxial CFRP fabric applied on the joint panel with CFRP spikes installed at the end of the beam and columns to improve the bond. The preliminary results pointed out the effectives of this strengthening solution in avoiding the joint panel shear failure and promoting a more ductile failure mode.

This paper presents a new methodology for characterizing the failure mode of structural walls reinforced with glass fiber reinforced polymer (GFRP) bars. An analytical model is used to derive a non-dimensional failure determinant function, which is validated against existing test results. The function involves geometric attributes (wall length, wall height, and boundary element size), reinforcement ratios (horizontal and vertical), and material properties (compressive strength of concrete and tensile strength of GFRP bars). According to the determinant function, structural walls fail in flexure when a high aspect ratio is associated with a relatively low reinforcement ratio in the boundary element. The proposed methodology and design recommendations provide valuable guidance for practitioners dealing with GFRP-reinforced concrete walls.

While reinforced concrete is one of the most used construction materials, traditional reinforcement steel may cause undesirable side effects, as corrosion and the associated volume changes can lead to damages in the concrete matrix and can cause spalling, which may significantly reduce the load-bearing capacity and service life of structures. Alternative reinforcement methods, such as glass or basalt fiber reinforced polymer rebars, can serve as a viable alter-native to reduce or eliminate some of the disadvantages associated with steel reinforcement. In addition to an increased tensile strength and a reduction in weight, fiber reinforced polymer rebars also offer a high corrosion resistance among other beneficial properties. Because these materials are not fully regulated yet and the durability properties have not been conclusively determined, further research is needed to evaluate the material durability properties of FRP rebars. To determine the durability properties of GFRP and BFRP rebars in cold climates, the freeze-thaw resistance of these materials was evaluated throughout this study. Specifically, two types of materials (basalt and glass reinforced polymers) and two common rebar sizes (8 mm (#2) and 16 mm (#5) diameters) were tested. To quantify the freeze-thaw-durability, tensile tests according to ASTM D7205, transverse shear strength tests in line with ASTM D7617, and horizontal shear strength tests as specified in ASTM D4475 were conducted on numerous virgin fiber rebars and on fiber rebars that were subjected to 80 and 160 freeze-thaw cycles. While the results from the virgin materials served as benchmark values, the measurements and analysis from the aged (by freeze-thaw cycles) materials were used to quantify and determine the strength retention capacity of these bars. The results showed that a higher number of freeze-thaw cycles lead to lower strength retention for some rebar types. In addition, it was seen that rebar products respond differently to the aging process; while some material properties notably deteriorated, other material properties were insignificantly affected.