Polymer Stirrups Research Articles

Tensile strength retention of glass fibre-reinforced stirrups subjected to aggressive solutions: effect of environmental condition, stirrup shape and stirrup diameter

The aim of this study was to examine how the tensile strength of glass fibre reinforced polymer stirrups is affected by different types of solutions, including alkaline, seawater, tap water, and acidic solutions. The study involved the production and testing of 260 stirrups in two different shapes (L and U) with diameters of 6 and 8 mm. The stirrups were immersed in different solutions for a period of 9 months at different temperatures (25, 40, and 60 °C). The findings indicated that the alkaline solution was the most aggressive environment, resulting in a maximum reduction of 92% in tensile strength after 9 months at 60 °C. Seawater and acidic solutions were the second and third most aggressive environments, causing maximum tensile strength reductions of 34 and 22% respectively, after 9 months at 60 °C. On the other hand, tap water was found to be the least aggressive environment, causing a maximum tensile strength reduction of 20% after 9 months at 60 °C. Furthermore, the study observed that the L-shaped stirrups exhibited slightly superior performance compared to the U-shaped stirrups. However, the diameter of the stirrups was found to be a negligible factor.

Experimental and Theoretical Studies on the Shear Performance of Concrete Beams Reinforced with Fiber-Reinforced Polymer Stirrups.

In this paper, the shear behavior of concrete beams reinforced with FRP stirrups is studied. The shear performances of six concrete beams with a size of 150 mm × 300 mm × 3000 mm under four-point loading up to failure were experimentally analyzed. The critical parameters included the shear span to depth ratio (λ) and stirrup spacing (S). The test results revealed that as λ increased from 1 to 2, 3, and 4, the ultimate shear capacity of the beam decreases by 50.5%, 67.7%, and 69.2%, respectively. Meanwhile, as S increased from 100 mm to 150 mm and 200 mm, the ultimate shear capacity decreased by 16.1% and 44.6%, respectively. A new shear capacity calculation model of concrete beam reinforced with FRP stirrups was also proposed, which further considered the shear capacity of the FRP stirrups on the basis of the shear capacity of an RC beam without stirrups using the strut-and-tie model. Finally, the experiment and calculation results of 56 beam specimens reinforced with FRP stirrups extracted from this paper and previous studies were compared using the calculation models proposed in this paper, in order to evaluate the accuracy of these calculation models.

Shear behavior of concrete beams reinforced with closed-type winding glass fiber-reinforced polymer stirrups

Conventional pultruded fiber-reinforced polymer (FRP) rod stirrups are susceptible to premature bent corner rupture and bond slip failure of overlapping legs. This research proposed a new type FRP shear reinforcement, closed-type winding GFRP (CW-GFRP) stirrups, featuring a fully closed rectangular cross-section. CW-GFRP stirrups completely avoided slip and significantly improved the strength of bent portion of stirrups. To investigate the feasibility of using CW-GFRP stirrups as shear reinforcement, shear test of 8 concrete beams reinforced with conventional pultruded stirrups and CW-GFRP stirrups was conducted. The beams were 300 mm deep and 150 mm wide, and their shear span ratio were 2.07. The effect of the material of stirrups, the spacing of stirrups, and the width of CW-GFRP stirrups were investigated. The test results showed that pultruded stirrups exhibited bond slip failure, in contrast, CW-GFRP stirrups reinforced beams prevented this failure and showed enhanced stiffness, narrower shear crack width and 1.09–1.12 times higher shear capacity. The splitting failure typical of CW-GFRP stirrups was reported, and a smaller stirrups width is expected to avoid splitting and generate greater strain at ultimate. It can be concluded that the new type of CW-GFRP stirrups is an optimized form of FRP shear reinforcement to supersede conventional pultruded stirrups. Strut-and-tie models based on ACI 318-19 and CSA S806-14 were used to predict the shear strength and produced a safe but relatively accurate prediction.

Replacing steel stirrups with natural fiber reinforced polymer stirrups in reinforced concrete Beam: Structural and environmental performance

This paper comprehensively evaluates the feasibility of using the environmentally friendly natural fiber reinforced polymer (NFRP) stirrups in reinforced concrete structures. The evaluation is conducted in terms of structural performance and environmental impact. Flax fabrics impregnated in epoxy resin were wrapped around longitudinal reinforcement to form close-type stirrups. A total of eight specimens were prepared using NFRP stirrups, and then subjected to three-point bending load. The structural performance is presented in terms of load-deflection relation and the shear capacity contribution. The obtained structural performance indicated that the NFRP stirrups provided sufficient shear capacity and maintained satisfactory ductility. The optimum design of the NFRP stirrups used narrow and thick NFRP stirrups at large spacing. The environmental impact assessment using cradle-to-gate life cycle assessment (LCA) showed that the NFRP stirrups yielded slightly lower environmental impacts than the steel stirrups. The benign environmental impacts of the flax fibers were totally nullified by the negative effects of epoxy resin.

Effectiveness of Glass Fiber-Reinforced Polymer Stirrups as Shear Reinforcement in Glass Fiber-Reinforced Polymer Reinforced Concrete Edge Slab-Column Connections

Effectiveness of Glass Fiber-Reinforced Polymer Stirrups as Shear Reinforcement in Glass Fiber-Reinforced Polymer Reinforced Concrete Edge Slab-Column Connections

Behavior of Reinforced Concrete T-Beams Strengthened in Shear Using Closed Carbon Fiber-Reinforced Polymer Stirrups Made of Laminates and Ropes

Behavior of Reinforced Concrete T-Beams Strengthened in Shear Using Closed Carbon Fiber-Reinforced Polymer Stirrups Made of Laminates and Ropes

Shear Capacity of RC Beams with Carbon Fiber-Reinforced Polymer Stirrups with Rectangular Section

AbstractExperimental observations were made for the shear capacity of reinforced concrete beams with carbon fiber-reinforced polymer rectangular stirrups (CFRPRS). In total, 12 concrete beams were tested under three-point loading. Each beam measured 1,400 mm long, 150 mm wide, and 250 mm deep. For comparative studies, different parameters were considered: different sectional shapes (circular and rectangular CFRP stirrups), material types (steel and CFRP), and reinforcement ratios of stirrups (0.0038 and 0.0096). All beams were subjected to three-point loading. Test results indicated that concrete beams reinforced with CFRPRS stirrups could maintain shear behavior comparable to that of the concrete beam reinforced with steel stirrups. Compared with the beams with conventional CFRP stirrups with circular sections, superior shear behavior was observed for the beams reinforced with CFRPRS stirrups in terms of shear strength and crack width.

Performance of Carbon-Fiber-Reinforced Polymer Stirrups in Prestressed-Decked Bulb T-Beams

AbstractEleven decked bulb T beams were constructed, instrumented, and tested under shear loading to failure. Nine beams were reinforced and prestressed with carbon-fiber composite cable (CFCC) strands, whereas one beam was prestressed with conventional low-relaxation steel strands and one beam was reinforced with non-prestressed CFCC strands. Half the span of each beam was reinforced with CFCC stirrups, whereas the other half was reinforced with conventional steel stirrups. Both ends of each beam were tested to evaluate the performance of CFCC stirrups versus that of steel stirrups. The investigation addressed the shear performance with respect to several shear parameters, including shear-span-to-depth ratio, stirrup spacing, prestressing force, and type of longitudinal and transverse reinforcement. All test beams failed by crushing of concrete in either the web or the top flange. No rupture of CFCC stirrups was experienced in any of the test beams. The performance of CFCC stirrups was analogous to that ...

Bend Strength of Complete Closed-Type Carbon Fiber-Reinforced Polymer Stirrups with Rectangular Section

AbstractComplete closed-type carbon fiber-reinforced polymer stirrups with a rectangular section (CFRPRS) were developed and tested in the research reported in this paper. The use of a CFRPRS is intended to relieve stress concentrations and reduce the number of kinked fibers at the bent portion. A total of 16 B.5 specimens were tested with consideration of the bend strength of the CFRPRS as well as carbon fiber-reinforced polymer (CFRP) stirrups with circular sections. Observations were made regarding the bend strength and failure modes. Three different types of CFRPRS were tested with different width-thickness ratios (34.4 for a sectional area of 27.9 mm2 and 4.5 or 8.0 for 72 mm2) and three different ratios of the bend radius to the area-equivalent bar diameter (1.5, 3.0, and 4.5). The test results indicated that CFRPRSs exhibited improved bend strength as compared to its counterpart, the conventional CFRP stirrups with circular sections. CFRPRSs possessing a larger stirrup width-thickness ratio provi...