Glass Fiber-reinforced Polymer Spirals Research Articles

Mechanism of distributed composite GFRP bars in circular concrete members with and without spirals under shear

This paper presents experimental data and theoretical studies on the effect of distributed glass fiber-reinforced-polymer (GFRP) bars in circular concrete members. Th experimental program reports the test results of eight full-scale circular reinforced-concrete (RC) specimens with a total length of 3020 mm and a diameter of 508 mm were constructed and tested under shear load up to failure. The test specimens comprised three specimens reinforced with GFRP bars and spirals, three specimens with only longitudinal GFRP bars, and two reference specimens reinforced with conventional steel bars, with and without steel spirals. The various experimental parameters included the longitudinal reinforcement ratio, the type of reinforcement (GFRP versus steel), and presence of shear reinforcement. The shear strengths of GFRP circular concrete specimens, obtained from the experimental results, were compared to current codes and design guidelines as well as to the recently available shear design equations on circular concrete members in the literature. The test results indicate that the use of more GFRP bars distributed uniformly in the cross section, of the specimens with and without spirals, reduces the loss of flexural stiffness after cracking and increase the shear strength. The comparison indicates that some of the available design methods provide reasonable predictions.

Structural behavior of GFRP reinforced concrete columns under the influence of chloride at casting and service stages

Abstract Corrosion attack due to chloride ions is a major problem found in steel reinforced concrete structures when subjected to marine environment. Glass fiber reinforced polymer (GFRP) has become an alternative reinforcement in marine concrete structures due to its excellent corrosion resistance, making it possible to combine with concrete composed of seawater and sea sand. However, the knowledge on the short-term and long-term properties of GFRP reinforced concrete columns is still limited. In order to facilitate the practical application of GFRP reinforced concrete in marine environment, the effect of chloride ions on the structural behaviors of GFRP reinforced concrete columns is investigated here. Numerous specimens consisting of GFRP reinforced concrete columns and steel reinforced concrete columns with different chloride concentrations were fabricated, conditioned and tested. The test results show that GFRP reinforced concrete columns cast with saturated water suffer a deterioration of 27.9% in load carrying capacity, but possess an enhancement of 104% in ductility when compared to those of specimens cast with distilled water. Meanwhile, it is observed that the GFRP reinforced concrete column possess a ductile failure mode, which indicates that the GFRP spirals can provide an effective confinement to the concrete core even in high chloride environment for a prolonged time. Such findings provide solid evidence to the feasibility and application of GFRP reinforced concrete in the offshore structures or artificial islands with great environmental and economic benefits.

Experimental Evaluation of Slender High-Strength Concrete Columns with GFRP and Hybrid Reinforcement

AbstractThe behavior of slender high-strength concrete columns reinforced with glass fiber-reinforced polymer (GFRP) bars and spirals subjected to concentric and eccentric axial loads was evaluated. Large-scale tests were conducted for nine circular concrete columns (three short and six slender) reinforced with internal GFRP-spirals and either steel, GFRP, or a combination of steel and GFRP longitudinal bars. The short and slender columns had slenderness ratios equal to 10 and 49, respectively. Axial load tests were conducted with loads placed concentrically (short columns) and at two eccentricities (slender columns) to observe the general behavior associated with different geometric and loading conditions. The behavior of slender columns with small eccentricity (8.3% of the column size) was governed by material failure, while that of slender columns with large eccentricity (33% of column size) was governed by a buckling failure. The research shows that GFRP spirals and GFRP longitudinal bars are a viable...

Glass Fiber-Reinforced Polymer-Reinforced Circular Columns under Simulated Seismic Loads

This paper presents the experimental results of nine large-scale circular concrete columns reinforced with longitudinal and transverse glass fiber-reinforced polymer (GFRP) bars. These specimens were tested under lateral cyclic quasi-static loading while simultaneously subjected to constant axial load. Based on the measured hysteretic loops of moment-versus-curvature and shear-versus-tip deflection relationships, a series of parameters related to ductility, energy dissipation capacity, and flexural strength are used to evaluate the seismic behavior of each column. The results showed that concrete columns reinforced with GFRP bars and spirals can behave in a manner that has stable post-peak response and achieve high levels of deformability. The results indicate that, as a relatively new material with excellent corrosion resistance and high strength-weight ratio, GFRP bars can be successfully used as internal reinforcement in ductile concrete columns.

Axial Capacity of Circular Concrete Columns Reinforced with GFRP Bars and Spirals

AbstractSeveral codes and design guidelines are now available for the design of concrete structures reinforced with fiber-reinforced polymer (FRP) bars under flexural and shear loads. Yet, because of a lack of research, North American codes and design guidelines do not recommend using FRP bars as longitudinal reinforcement in columns to resist compressive stresses. This paper reports on 12 full-scale circular reinforced concrete (RC) columns that were tested under concentric axial loads. The columns were reinforced with longitudinal glass FRP (GFRP) bars and newly developed GFRP spirals. The 300-mm diameter columns were designed according to code requirements. The test parameters included reinforcement type (GFRP versus steel); longitudinal FRP reinforcement ratio; and the volumetric ratios, diameters, and spacing of spiral reinforcement. The test results indicated that the GFRP and steel RC columns behaved in a similar manner. The average load carried by the longitudinal GFRP bars ranged between 5% and 1...

Axial Load Behavior of Concrete Columns Confined with GFRP Spirals

The writers evaluated the confinement that was provided by glass fiber-reinforced polymer (GFRP) spirals in concrete columns under axial load. Given that GFRP spirals are resistant to chloride-induced corrosion, the option of replacing steel spirals with GFRP spirals was explored to determine whether this would reduce the corrosion of the vertical steel bars in hybrid columns. The writers investigated the axial load behavior of 10 spirally reinforced concrete columns. Six of the 254-mm diameter columns were confined with a GFRP spiral and four were confined with a steel spiral. Some of the columns that were confined with a GFRP spiral utilized steel vertical bars (hybrid columns), whereas others utilized GFRP vertical bars (all-GFRP columns). The stress-strain and load-displacement behavior of all columns was studied. Analytical expressions predicted the axial load capacity of the hybrid and all-GFRP-reinforced concrete columns. Axial compression tests of all-steel-reinforced and hybrid specimens subjected to accelerated corrosion were also carried out. The latter exhibited a smaller corrosion rate, similar axial load capacity, and equal or higher ductility relative to steel corroded columns.