| Rebar corrosion problem is widespread concerned in the field of civil engineering today. FRP applications provide a good way to solve this problem, which has big advantages in terms of high specific strength, corrosion resistance, anti-fatigue performance, and resistance to electromagnetism. This material can be applied to special performance requirements and rebar under chemical erosion environment. Basalt FRP(BFRP for short) has, following carbon FRP and glass FRP, become another new type of popular building material, with better price/performance ratio than other two. At present, the field of civil engineering for basalt fiber research is mainly focused on the use of fiber reinforced concrete structure, with a few application researches on the use of concrete sheet with BFRP in place of rebar and experimental researches on flexural behavior of the normal section of concrete beams. However, the researches on BFRP or other FRP bars for oblique section shear properties of fiber reinforced concrete beam have not been conducted.Based on the characteristics of BFRP and the research progress of BFRP reinforced concrete structure at present, the current research includes the following contents:The experimental researches on the mechanical properties of C30and C60basalt fiber reinforced concrete were carried out. The cubic compressive strength, axial compressive strength, flexural strength, splitting strength, and elastic modulus of basalt fiber reinforced concrete with different amounts of basalt fibers were investigated, in order to analyze the influence of basalt fiber on the mechanical properties of concrete and preliminarily find out the optimal amount of fibers in the concrete. The results show that for both C30normal strength concrete and C60high strength concrete, the suitable amount of fibers is0.1%of fiber volume fraction.In order to analysis of the interface properties and the strengthening mechanism of the basalt fiber reinforced concrete, the experimental research on micro-properties and pore structure of basalt fiber reinforced concrete were also carried out. The mercury intrusion experimentations on pore structure at micro level were done for the analysis of relationships between the compressive strength and permeability of basalt fiber reinforced concrete and the characteristics of pore structure in it. The suitable mixed amount of basalt fiber was further confirmed by microscopic analysis. The result indicated that the concrete pore size could be reduced, the number of small pores could be increased, and the pore structure of the C30and C60concrete could be greatly improved with0.1%fiber content. Because of the fibers mixed in, the curvature of the tunnels of the pore structure increased and permeability decreased.0.1%of the fiber volume fraction is the best dosage has been further confirmed. The bond properties of BFRP bar and basalt fiber reinforced concrete were studied. The bond-slip curve characteristics and influencing factors of bond strength were also analysis. The results show that adhesive strength increased as the strength of concrete increased, and decreased as anchorage length and the diameters of the fiber bars increased. Mixing certain amount of basalt fibers into the concrete could increase the limit bond strength of BFRP and concrete, and increase the value of the slip corresponding to the limit bond strength, improve bond ductility. The experience formulas for calculating bond strength and anchorage length were acquired based on the results. The bond slip constitutive model of BFRP and basalt fiber reinforced concrete accorded with continuous curve model was also found.In order to study the oblique section shear performance of beam,18BFRP fiber reinforced concrete beams and3reinforced fiber concrete beams were tested. The influence of the different ratios of BFRP longitudinal reinforcement, longitudinal reinforcement types, BFRP stirrup ratios, stirrup types, and shear span ratios on the load of initial crack of oblique section and the damage load of concrete beams were analyzed. The results show that longitudinal reinforcement ratio and stirrup type have less impact on the carrying capacity, but BFRP stirrup ratio, longitudinal reinforcement type, and shear span ratio have obvious impact on the carrying capacity. As the stirrup ratio increase, the load of beams increases. As the shear span ratio increase, the load of beams goes down. When the shear span ratio, the ratio of longitudinal reinforcement, and stirrup are the same, the load of initial crack of BFRP beam is slightly lower than the rebar beam, while the damage load of the two are basically the same. The experience formulas for calculating the crack resistance and limit bearing capacity of inclined section were acquired by conducting regressive analyses of the load of initial crack and limit load of inclined section of14BFRP beams.Based on the Modified Compression Field Theory(MCFT). the numerical analysis model of the sections of BFRP reinforced basalt fiber concrete beams under the combined action of shear and moment was established. The whole test process of FRP reinforced concrete beams were numerical analyzed by this model. It is clearly seen from the results that this model showing high accuracy in prediction in terms of the shear resistant capacity, tension strain of stirrups and the ultimate compressive strain of concrete in compression&shear region.The ductility of BFRP reinforced basalt fiber concrete beams was also analyzed. Effect of different factors on the ductility and shear capacity of energy dissipation were studied through the ductility and energy absorption ratio. From the results, it’s could be found that when the oblique section cracked, with the same load, the deflection and cracks of BFRP concrete beams were bigger than the rebar beams with the same reinforcements; the damage loads and energy absorption ratios of the two were basically the same respectively. |
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