Study On Shear Behavior And Reinforcement Of Basalt Fiber Reinforced Concrete Beams

Steel reinforced concrete structures are widely used in building structures due to their good ductility and high compressive strength.However,their development is limited by issues such as cracking,low tensile strength,and corrosion of steel reinforcement.In this study,we designed and produced four mixed reinforcement BFRC-RC composite beams and four side-sticked basalt fiber cloth reinforced hybrid reinforcement BFRC-RC composite beams,using the high tensile strength,cost-effective,high temperature and corrosion resistance,and good crack resistance properties of basalt fiber.Static loading tests were performed on these beams with different stacking heights as variables.A refined parameter analysis of concrete beams was conducted using a nonlinear finite element model,investigating the factors affecting the shear carrying capacity of concrete beams and the enhancement effect of basalt fiber modified materials on beam stress performance.Based on the current standards and the shear characteristics of fiber-reinforced concrete beams,the calculation formula for oblique shear carrying capacity was proposed.The main research results are as follows:(1)Compared with ordinary concrete components,fiber-reinforced concrete specimens with different overlay heights have increased the cracking load of the cross section by17.6%～52.9%and the diagonal cracking load by 16.7%～33.3%.After reinforcement with fiber cloth,the cracking and diagonal cracking loads of the components were increased by 34.6～47%and 28.6%～50%,respectively.In terms of ultimate bearing capacity,with the increase of fiber-reinforced concrete overlay height,the maximum can be increased by 12.1%,and the bearing capacity of the specimens after reinforcement with fiber cloth increased by 3.7%～15%.(2)Eight unfilled test beams all showed diagonal tension failure.In the initial stage of loading,the load-displacement curve of the test beams showed a linear development trend.Compared with the specimens without fiber reinforcement,the fiber-reinforced concrete specimens had a greater initial slope,indicating that the fiber cloth improved the overall stiffness.In the final failure,the largest crack appeared on the line connecting the loading point and the support.The ductility and stiffness of the fiber-reinforced concrete specimens were increased compared with those of the ordinary concrete specimens.(3)Lowering the shear span-to-depth ratio,increasing the reinforcement ratio,adding more layers of basalt fiber cloth,and reducing the spacing between fiber cloth can improve the cracking load and ultimate bearing capacity of concrete beams,and enhance the overall stiffness of the specimens.Increasing the overlay height of the basalt fiber-reinforced concrete can significantly improve the cracking load and ultimate load of the beam,but when the overlay height exceeds half of the full section height,the increase in the ultimate bearing capacity is not significant.(4)When configuring reinforcement with appropriate spacing,as the substitution rate of BFRP reinforcement increases,the ultimate bearing capacity of concrete beams can be significantly improved,but the overall stiffness of the beam decreases significantly.(5)According to the Fiber-Reinforced Concrete Structure Code,the fiber characteristic parameters β_v and λ_f are referenced,and the diagonal bearing capacity calculation formula of fiber-reinforced concrete beams is corrected by considering reinforcement with basalt fiber cloth on the side.