Due to a dynamic development of infrastructure, engineers around the world are looking for new materials and structural solutions, which could be more durable, cheaper in the life cycle management, and built quickly. One of prospective solutions for building small-span bridges can be precast lightweight concrete reinforced with glass fiber-reinforced polymer (GFRP) rebars. Thanks to prefabrication, it is possible to shorten the construction time. Using lightweight concrete affects structure weight as well as transportation costs. GFRP rebars can make the structure more durable and also cheaper in terms of life cycle management costs. The paper focuses on the fatigue performance of a real-scale arch (10.0 m (33 ft) long, 1.0 m (3.3 ft) wide, and 2.4 m (7.9 ft) high) made of lightweight concrete and GFRP rebars (LWC/GFRP) in comparison with an arch made of normal weight concrete and typical steel reinforcement (NWC/steel). The fatigue loads ranging from 12 to 120 kN (2.7 to 27 kip) were applied in a sinusoidal variable manner with a frequency of 1.5 Hz. This research revealed that the NWC/steel arch exhibited significantly better fatigue resistance when compared to the LWC/GFRP arch. Differences in the behavior of the NWC/steel and LWC/GFRP models under fatigue load were visible from the beginning of the research. The LWC/GFRP model was exposed to fatigue loads, resulting in gradual deterioration at an early stage. This degradation was evident through stiffness being progressively reduced, leading to increased displacements and strains as the number of load cycles increased. The model did not withstand the fatigue load and was destroyed after approximately 390 thousand load cycles, in contrast to the NWC/steel model, which withstood all 2 million load cycles without significant damages or the stiffness being decreased. However, the prefabricated lightweight concrete arches with composite reinforcement seem to be an interesting alternative of load-bearing elements in infrastructure construction.

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.

The seismic performance of reinforced concrete (RC) structures relies on their ability to dissipate earthquake-induced energy through hysteric behavior. Ductility, energy dissipation, and viscous damping are commonly used as performance indicators for steel-RC seismic force-resisting systems (SFRSs). However, while several previous studies have proposed energy-based indices to assess energy dissipation and damping of steel-RC SFRSs, there is a lack of research on fiber-reinforced polymer (FRP)-RC structures. This study examines the applicability of the existing energy dissipation and damping models developed for steel-RC columns to glass FRP (GFRP)-RC ones, where the relationships between energy indices and equivalent viscous damping versus displacement ductility were analyzed for GFRP-RC circular columns from the literature. In addition, prediction models were derived to estimate energy dissipation, viscous damping, and stiffness degradation of such types of columns. It was concluded that similar lower limit values for energy-based ductility parameters of steel-RC columns can be applied to GFRP-RC circular columns, whereas the minimum value and analytical models for the equivalent viscous damping ratio developed for steel-RC columns are not applicable. The derived models for energy indices, viscous damping, and stiffness degradation had an R2 factor of up to 0.99, 0.7, and 0.83, respectively. These findings contribute to the development of seismic design provisions for GFRP-RC structures, addressing the limitations in current codes and standards.

Developments in the prestressed concrete industry evolved to incorporate innovative design materials and strategies driven towards a more sustainable and durable infrastructure. With steel corrosion being the biggest durability issue for concrete bridges, FRP tendons have been gaining acceptance in modern prestressed technologies, as bonded or unbonded reinforcement, or as part of a “hybrid” system that combines unbonded CFRP tendons and bonded steel strands. Assessments of the efficacy of hybrid-steel beams, combining bonded and unbonded steel tendons. in the construction of segmental bridges and in retrofitting damaged members has been established by several researchers. However, limited research has been conducted on comparable hybrid prestressed beams combining CFRP and steel tendons (hybrid steel-cfrp beams). This paper provides an insight on the flexural behaviour of eighteen prestressed beams tested under third-point loading until failure with the emphasis on the tendon materials (i.e., CFRP and steel) and bonding condition (i.e., bonded, unbonded). In addition, a comprehensive finite element analysis of the beams’ overall behaviour following the trussed-beam methodology is conducted and compared with the experimental results. Results show that hybrid beams, utilizing CFRP as the unbonded element maintained comparable performance when compared to hybrid steel beams. The results presented in this paper aim to expand the use of hybrid tendons and facilitate their incorporation into standard design provisions and guidelines.

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.