Hybrid Reinforced Concrete Beam Research Articles

Mechanical performances of concrete beams with hybrid usage of steel and FRP tension reinforcement

Fiber reinforced polymer (FRP) bars have been recently used to reinforce concrete members in flexure due to their high tensile strength and especially in corrosive environments to improve the durability of concrete structures. However, FRPs have a low modulus of elasticity and a linear elastic behavior up to rupture, thus reinforced concrete (RC) components with such materials would exhibit a less ductility in comparison with steel reinforcement at the similar members. There were several studies showed the behavior of concrete beams with the hybrid combination of steel and FRP longitudinal reinforcement by adopting the experimental and numerical programs. The current study presents a numerical and analytical investigation based on the data of previous researches. Three-dimensional (3D) finite element (FE) models of beams by using ANSYS are built and investigated. In addition, this study also discusses on the design methods for hybrid FRP-steel beams in terms of ultimate moment capacity, load-deflection response, crack width, and ductility. The effects of the reinforcement ratio, concrete compressive strength, arrangement of reinforcement, and the length of FRP bars on the mechanical performance of hybrid beams are considered as a parametric study by means of FE method. The results obtained from this study are compared and verified with the experimental and numerical data of the literature. This study provides insight into the mechanical performances of hybrid FRP-steel RC beams, builds the reliable FE models which can be used to predict the structural behavior of hybrid RC beams, offers a rational design method together with an useful database to evaluate the ductility for concrete beams with the combination of FRP and steel reinforcement, and motivates the further development in the future research by applying parametric study.

Investigation of Aramid Fibers Compared with Steel Fiber on Bending Behavior of Hybrid RC Beams

This paper presents an experimental study on bending behavior of aramid and steel fiber reinforced concrete (AFRC and SFRC) members. The objective is to investigate effects of two types of aramid fiber and one type of steel fiber in hybrid reinforced concrete (RC) beams. The term hybrid beam is defined as the beam with fiber reinforced concrete (FRC) cast in tension zone and normal concrete (without fiber) cast in compression zone of the beam. The diameter of aramid fiber (AF) is 0.5mm and the surface condition is twist fiber consisting of two single fibers. The fiber lengths are 30mm and 40mm for two types of aramid fiber. The diameter of steel fiber (SF) is 0.6mm and the length is 33mm with hooked ends. Four reinforced concrete (RC) beams with a dimension of 150×200×2100 mm3 were designed to undergo flexural failure. All the tested beams are with the same reinforcement ratio (0.93%), having a fiber volume fraction (Vf) of 1% for each type of fiber. One RC beam without fiber was prepared and tested as a controlled specimen. The height of the FRC tension zone at ultimate state was calculated to be 170mm. Load capacity, average and maximum crack widths of hybrid aramid and steel fiber reinforced concrete beams (HAFRCs & HSFRC) under four-point bending tests were discussed.

Performance of Hybrid Reinforced Concrete Beam Column Joint: A Critical Review

Large residual strain in reinforced concrete structures after a seismic event is a major concern for structural safety and serviceability. Alternative reinforcement materials like fiber-reinforced polymer (FRP) have been widely used to mitigate corrosion problems associated with steel. Low modulus of elasticity and brittle behavior compared to steel has made the use of FRP unsuitable in seismic resistant strictures. A combination of steel-FRP reinforcement configuration can address the problem of corrosion. Therefore, introducing a material that shows strong post elastic behavior without any decay due to corrosion is in demand. Shape memory alloy (SMA), a novel material, is highly corrosion resistive and shows super elastic property. Coupling SMA with FRP or steel in the plastic hinge region allows the structure to undergo large deformations, but regains its original shape upon unloading. In this study, the performance characteristics of four previously tested beam-column joints reinforced with different configurations (steel, SMA/steel, glass fiber reinforced polymer (GFRP) and SMA/FRP) are compared to assess their capacity to endure extreme loading. Experimental results are scrutinized to compare the behavior of these specimens in terms of load-story drift and energy dissipation capacity. SMA/FRP and SMA/Steel couples have been found to be an acceptable approach to reduce residual deformation in beam-column joints with adequate energy dissipation capacity. However, SMA/FRP is superior to SMA/Steel concerning to the corrosion issue in steel.

Structural performance and serviceability of concrete beams reinforced with hybrid (GFRP and steel) bars

This paper reports on the structural performance of concrete beams reinforced with hybrid reinforcement. Six concrete beams reinforced with a combination of steel and glass fiber-reinforced polymer (GFRP) bars and three other beams reinforced with only GFRP bars were tested in flexure. Over-reinforced hybrid beams showed higher strength and ductility than their GFRP-reinforced counterparts. The CSA-S806-12 equation accurately predicted the deflections of the hybrid-reinforced beams with high effective reinforcement ratios. Based on the test results, a bond coefficient was proposed to predict the crack width of the hybrid-reinforced beams using the ACI-440.1R-06 equation. A modified deformability factor was also utilized to assess the deformability of the hybrid-reinforced beams. Comparison between the experimental and predicted results showed the adequacy of the models used in predicting the load-carrying capacity, deflection, crack widths, and deformability of hybrid-reinforced concrete beams.