Abstract
Due to the fact that steel reinforcement is vulnerable to corrosion, FRP bars with light weight, high strength, and excellent durability have become a good substitute for ordinary steel bars. FRP bars have high tensile strength, but their compressive strength is relatively low and often neglected, so the application of FRP bars in compression members has been restricted. This paper proposes a new pultrusion‐winding‐pultrusion method to improve the compressive ability of FRP bars. A hoop FRP layer is winded on the outer surface of the pultruded FRP core, and a longitudinal pultruded layer and ribs are also added on the outermost surface. In this paper, mechanical properties of this novel FRP bar with hoop winding layer are investigated. First, monotonic tensile and compressive tests on traditional and novel GFRP bars were conducted. Then, cyclic tension‐compression loading tests were also carried out on the two types of GFRP bars. Test results showed that the compressive ultimate bearing capacities of GFRP bars with winding layers were 10∼20 kN greater than those of the traditional GFRP bars, and the compressive ductility of the novel GFRP bars was also improved. Furthermore, the tensile stress‐strain behaviors of both GFRP bars were linear‐elastic and the added winding layer did not greatly influence the tensile properties of the GFRP bars. Moreover, for the cyclic loading test, the compressive ultimate load of GFRP bars was 80%∼90% of that under monotonic compressive test, and the tensile ultimate load was 45%∼65% of that under monotonic tensile test. Compared with the GFRP bar without winding layer, the overall stiffness of the novel GFRP bar was greater than that of the traditional one and the ultimate load of the novel GFRP bar was also greater. In addition, seeing that the residual displacement of the novel GFRP bar was greater than that of the traditional GFRP bar, winding hoop fibers on the outer surface of the core is a useful way to improve the energy dissipation capacity of the GFRP bar.
Highlights
Reinforced concrete structure is one of the most widely used structures at present [1]. e steel reinforcements and concrete work together through the bonding force to give full play to their respective advantages, so the reinforced concrete structures can have good load-bearing capacity
It can be seen that the ultimate load of C-H60 specimens was slightly less than that of C-H40 specimens, and the ultimate load of W-H60 specimens was less than that of W-H40 specimens. e ultimate compressive load of the same type of glass fiber-reinforced polymer (GFRP) bars decreased with the increase of height due to the influence of slenderness
The ultimate load of H60 GFRP bars increased by 19.5% with the winding layer. e trend in Figure 7 indicates that the winding layer can help increasing the GFRP bar’s ultimate compressive load
Summary
Reinforced concrete structure is one of the most widely used structures at present [1]. e steel reinforcements and concrete work together through the bonding force to give full play to their respective advantages, so the reinforced concrete structures can have good load-bearing capacity. E steel reinforcements and concrete work together through the bonding force to give full play to their respective advantages, so the reinforced concrete structures can have good load-bearing capacity. Kobayashi and Fujisaki [47] tested the ultimate strength of CFRP, GFRP, and AFRP bars under monotonic compressive and tensile loads and studied the mechanical properties of the three types of bars under progressively increasing cyclic tension and compression load, respectively. A novel method is proposed to improve the compressive load-bearing capacity and ductility of FRP bars, namely, winding hoop impregnated fibers around the outer surface of pultruded FRP bars. After the winding layer is manufactured, a thin layer with longitudinal fibers is added on the outermost surface through the pultrusion; this process can ensure a good surface condition of the FRP bar and protect the hoop winding layer. For the novel FRP bar, the ribs are added on the outermost longitudinal pultruded layer by the filament winding (see Figure 1)
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