Research On Performance Of Concrete Beams, Columns And Joints Reinforced By FRP

Reinforcing concrete structures by FRP (fiber reinforced plastics) is a new reinforcement technology developed in China in the late decade, which becomes current hotspot on scientific research and engineering application. In this paper, the experimental and theoretical studies have been carried out to determine the performances of concrete frames reinforced by FRP since 2002. Twenty-eight specimens included beams, columns and joints were tested in the study. The study contains three parts:1) Mechanical performances of perpendicular and diagonal sections in CFRP and HFRP-reinforced concrete beam with different reinforcement ratios are studied based on experimental results of 12 beams. The results show as follows: the ultimate bearing capacity and deformation behavior of FRP-reinforced beam are improved evidently; the HFRP-reinforced beam is more effective in reinforcement than CFRP-reinforced; the strain on perpendicular section of the reinforced beam is in accord with plane cross-section Assumption; there are two typical failure modes in FRP-reinforced bending-resistance beam when high bond strength and good anchorage are assured; the effect of FRP-reinforced shearing-resistance beam depends mainly on the effective strain of fiber; the calculation method of bending and shearing capacities on FRP-reinforced concrete beam is presented. The research results were verified to be applicable by the successful design on strengthening projects and actual load tests.2) Based on experiment of twelve columns under axial compression force, which are in different concrete strength and reinforced by CFRP, high-strength GFRP and HFRP respectively, the bearing capacity and ductility of column under axial load influenced by different fiber and concrete strength are studied. The analysis results are follows: on the premise of equal volumetric reinforcement ratio, the bearing capacity of CFRP-reinforced column is the highest on the increase, the ductility of GFRP-reinforced column improves evidently, and HFRP-reinforced column not only has higher bearing capacity but also better ductility that means its comprehensive performances are the best among three; the bearing capacity and ductility of restricted concrete columns reinforced by FRP have the descendent trend along with the increase of strength of concrete. The restrain mechanism and stress-strain relation of FRP-reinforced columns are analyzed. The bearing capacity strip-shaped model of restricted concrete square column under axial compression load was proposed, and the calculating results show a good agreement with the experimental ones.3) The influences of high-strength GFRP and HFRP on the seismic behavior of the joint, which includes bearing capacity, ductility, dissipation of energy capacity, bearing capacity decrease and stiffness degradation, are studied on the basis of experiments of four T-typed concrete beam-column joints. The results of analysis show that satisfying seismic behaviors can be obtained by using the two kinds of FRP-reinforced joints, and ductility and dissipation of energy capacity of members can be improved by bonding fibers in±45°directions at core zone of the joint. The formula of shearing capacity of FRP-reinforced joint is suggested based on the experimental results, and proposed values of calculating parameters for engineering design are given. The mechanism of shearing-resistance capacity of the joint influenced by key factors, such as reinforcement style, fiber type and angle of fibers bonding, is analyzed. The analytical results indicate: shearing bearing capacity of joint can be effectively improved by bonding fibers in core zone of joint and beam-column end, and directly influenced by the reinforcement style.