Study On Performance Of FRP Grids-Steel Reinforced Concrete Column

Fiber-reinforced polymer (FRP) materials are enjoying their wide application in engineering due to their light weight, high strength and corrosion resistance. FRP grids possess the advantages of light weight, high strength, bidirectional loading capacity, convenient construction and feasibility of construction in severe environments. There is a lack of researches on FRP grids for the application in newly-built structure due to their few applications in newly-built structure. Furthermore, for the poor stability of the quality of FRP grids, their popularization and application in structure are limited. This paper mainly focuses on the manufacturing technology of high-performance basalt FRP (BFRP) grids with high efficiency and stability, evaluation methods for short-term and long-term mechanical properties and the compressive behavior of FRP grid-reinforced concrete (RC) combination column, to provide the design fundamental for the application methods of FRP-RC combination column. In terms of the above issues, the research was conducted as follows:1.The ultimately manufactured FRP grid products with qualified appearance, tensile strength up to 900 MPa and satisfactory flexibility.2. Test methods applied to BFRP grid were worked out through experiments; Appropriate anchor methods and procedures were proposed for the different depths of BFRP grid;3. Tests of moisture absorption and strength degradation in alkali environment at 40 degree Celsius were conducted to explore the corrosion law of BFRP grids. Fick curves and strength degradation formulas were obtained by the experimental results, which can predict the corrosion law of BFRP grids preferably.4. The strength of fiber reinforced composites was divided into three stages based on their corrosion mechanisms:Fick stage, non-Fick stage 1 and non-Fick stage 2.The corrosion mechanism at Fick stage is that the composites absorb the OH-in the etchant solution and the strength degrades with the rate of v1. At non-Fick stage 1, the corrosion mechanism transforms into resin cracking. Internal fibers are eroded by etchant solution with strength degradation rate of v2; The fibers and resin are both severely eroded at non-Fick stage 2. The strength tends to be stable with the strength degradation rate of v3, where v1> v2> v3;5. On the premise of satisfying the strength and durability requirement, one kind of grid with favorable bending performance was developed. The grid can be wrapped into new constructed column, providing advantageous crack-resistance. Favorable corrosion-resistance of the grid wrapped column can be guaranteed because the crack width is limited by grid, delaying the permeation of corrosion solution towards the inner reinforced bar.6. Axial compression tests were conducted on 48 BFRP grid-reinforced concrete combination columns. The function of FRP grid in combination column was analyzed through experimental phenomena. Comparative analysis was conducted with the parameters comprising the thickness of grid, number of grid layer, grid wrapped height, location of grid, location of reinforcing bar and reinforcement ratio. Characteristics of FRP grid combination column were analyzed from the two points of bearing capacity and ductility.7.The formula of the ultimate stress in BFRP grid-RC combination column was fitted by the experimental data, providing the design and calculation for the FRP grid-RC combination column applied in practical engineering.