Study On Flexural Behavior Of High-strength Lightweight Concrete Beams Reinforced With GFRP Bars

Glass fiber reinforced plastic tendons(referred to as GFRP bars)has high tensile strength,excellent corrosion resistance and relatively affordable price.And lightweight concrete has the advantages of light weight,high strength,good corrosion resistance,good economy.The combination of the two can be better to solve the corrosion of reinforced concrete structures and the shortcomings of poor durability.At present,there are few researches on the structure of FRP reinforced lightweight concrete structure.In order to promote the application in engineering practice,it is necessary to study its mechanical properties.Based on GFRP reinforced high-strength lightweight aggregate concrete beams on flexural performance test,and the flexural performance under two-point symmetrical static loading is analyzed,and the design method for high-strength lightweight aggregate concrete beams with FRP tendons is proposed.The workwasshowed below:(1)The flexural performance tests of nine GFRP tendon high-strength and steel fiber lightweight aggregate concrete beams were completed,and compared with the flexural performance of reinforced concrete lightweight aggregate concrete beams.The results show that compared with reinforced concrete beam,GFRP reinforced lightweight concrete beams have smaller flexural rigidity,faster crack and wider crack width.The incorporation of steel fibers can effectively improve the flexural performance of GFRP lightweight aggregate concrete.The main performance isto increase the ultimate bearing capacity of the components by about 21.9%.The flexural stiffness of the component is increased,and the deflection of the beam is reduced,so that it basically meets the requirements of normal use.However,the crack width still exceeds the specification limit in normal use.Compared with reinforced lightweight aggregate concrete specimens,GFRP reinforced lightweight aggregate concrete beams have poor ductility and the incorporation of steel fiber has improved their ductility.With the increase of the reinforcement ratio of longitudinal reinforcement,the improvement effect of steel fiber is gradually reduced.(2)Based on the "Technical Specification for Fiber Reinforced Composites Construction Engineering"(GB 50608-2010),considering the difference in properties between lightweight aggregate concrete and ordinary concrete,the formulas for calculating the deflection and crack width of GFRP lightweight aggregate reinforced concrete beams are revised.According to the flexural test results of GFRP fiber reinforced lightweight aggregate concrete beams,considering the influence of steel fibers on its bending performance,the correction formulas for the flexural flexibility and crack width of GFRP reinforced lightweight fiber reinforced concrete beams are proposed.(3)By analyzing the flexural calculation model of FRP reinforced concrete with lightweight aggregate,considering the effect of compressed steel reinforcement in lightweight aggregate concrete with FRP reinforcement and the influence of steel fiber on the tension zone of lightweight aggregate concrete,the formula for calculating the ultimate bearing capacity of concrete flexural members is proposed,and relevant suggestions for the design of flexural members of lightweight concrete with FRP reinforcement are proposed.(4)Based on the calculation formulae of flexural deflection and crack width for FRP reinforced steel fiber lightweight aggregate concrete beams,considering the respective development patterns of deflection and cracks during bending,the requirements affecting their normal use deflection and crack width were analyzed.The safety reserve coefficient is defined,and the design method of the FRP reinforced concrete lightweight aggregate concrete member was proposed to meet the requirements of deflection and crack width in normal use.The related work completed by the dissertation can provide experimental basis for the development of relevant standards for FRP reinforced concrete structures,and at the same time enrich relevant experimental data of high-strength lightweight aggregate concrete,promote practical application of lightweight aggregate concrete in domestic projects,and apply to FRP reinforcement concrete structures.The application of lightweight aggregate concrete structures in engineering practice has important theoretical significance.