Experimental Study On The Flexural Behavior Of Concrete Beams Reinforced With BFRP Bars

Basalt fiber reinforced plastic(BFRP) bar has a bright future in the concrete structure field with many advantages such as high strength, lightweight,corrosive resistance and so on, combined with the nature sources of materials,environmental protect in productive process and production technology of autonomy in our country. In recent years, the concrete structures reinforced with BFRP bars are widely used in order to solve the durability problem of traditional reinforced concrete structures, and it has become a research focus in the civil engineering. For strengthening the further understanding of the concrete structures reinforced with BFRP bars, five simple-supported concrete beams reinforced with BFRP bars have been tested to study the influence rule of reinforcement ratio of BFRP bars and concrete strength on flexural property, and the main research content is as follows:(1)The law of strain and load for BFRP bars and concrete is studied under three points loading. The curve of concrete strain and beam section height is drawn based on the data from the test, and the plane hypothesis is verified. The mid-span strain of BFRP bars in tensile area is tested and the variation of stresses is analyzed, based on this we can get the degree of BFRP bars' performance.(2)The cracking moment and ultimate bearing capacity of concrete beams reinforced with BFRP bars are studied. Considering the plastic deformation of concrete in tensile zone, the equivalent trapezoidal model of elastic-plastic height ratio for 1:1 is imported, and the calculation model for cracking moment of concrete beams reinforced with BFRP bars was established finally. Based on the plane hypothesis and material characteristics of BFRP bars, the calculation formula of ultimate bearing capacity is obtained. The minimum reinforcement ratio, limit reinforced ratio and maximum reinforcement ratio which are suitable for concrete beams reinforced with BFRP bars are redefined.(3)The crack mechanism and failure mode of concrete beams reinforced with BFRP bars under flexural load are analyzed. Refer to the crack mechanism of ordinary reinforced concrete beam, combined with the material properties,based on the stress state and strength theory in mechanics of materials, a new interpretation for crack mechanism and the crack width calculation formula ofconcrete beams reinforced with BFRP bars are put forward. According to the experiment phenomenon and recordings, the crack developing, crack distribution,the number of fractures, crack spacing, fracture height, and the final failure mode of concrete beams reinforced with BFRP bars under different reinforcement ratio of BFRP bars and concrete strength are studied.(4)The deflection of concrete beams reinforced with BFRP bars under flexural load is analyzed. Based on the theory of bending deformation and short-term section stiffness, the calculating formula of the deflection for BFRP concrete beams was derived, and the feasibility of theory calculation formula is verified combined with the test data.