Flexural Simulation Of UHPC Beam Reinforced With Steel-FRP Composite Bars

Reinforced concrete is widely used in civil engineering because of its many advantages.However,with the increase of service time of reinforced concrete structures,due to the characteristics of steel bars and ordinary concrete,reinforced concrete structures that serve for a long time in corrosion environments are prone to corrosion of steel bars and cracking of concrete,resulting in insufficient bearing capacity and poor durability of structures,and even damage of concrete structures.The corrosion problem of reinforced concrete promotes the research of FRP and FRP concrete structures.However,the pure FRP material is linear elastic,and there is no yield platform similar to the steel bar.Therefore,the failure of FRP concrete structures is usually brittle failure with poor ductility.Steel-FRP Composite Bar(SFCB)formed on this basis has the advantages of high strength,good ductility,stable secondary stiffness and excellent corrosion resistance.Therefore,SFCB can be combined with Ultra-High Performance Concrete(UHPC)with high compressive and tensile strength,good ductility and excellent durability to form a new type of concrete structure in order to solve the problems of insufficient bearing capacity and poor durability of traditional reinforced concrete structures.In this thesis,the numerical simulation method is used to study the flexural performance of SFCB reinforced UHPC beam in order to provide a reference for the combination of these two materials and their applications in practical projects.The main contents of this thesis are as follows:The flexural performance of SFCB reinforced UHPC beam was numerically studied by using finite element software ABAQUS.The validity of the model was verified by simulating the four point bending test of one FRP reinforced ordinary concrete beam,two SFCB reinforced ordinary concrete beams,two steel reinforced high-strength concrete beams and two steel reinforced UHPC beams.Based on the validity of the model,the effect of concrete type,yield strength of SFCB’s inner steel core,elastic modulus of SFCB’s outer FRP material,area ratio of inner steel core to SFCB cross-section and SFCB reinforcement ratio on the bearing capacity,deflection,ductility and energy dissipation of SFCB reinforced UHPC beam was studied.The simulation results show that:(1)Compared with SFCB reinforced ordinary concrete beam and SFCB reinforced high-strength concrete beam,the flexural performance of SFCB reinforced UHPC beam is significantly improved,and the ultimate bearing capacity and energy dissipation capacity of SFCB-UHPC beam are 2.0 times and 3.6 times of those of SFCB reinforced ordinary concrete beam,respectively;(2)The post-yield flexural stiffness,ultimate moment and total energy dissipation of SFCB reinforced UHPC beam slightly increase with the increase of yield strength of SFCB’s inner steel core;(3)With the increase of elastic modulus of SFCB’s outer FRP,the flexural stiffness,yield moment and ultimate moment of SFCB reinforced UHPC beam significantly are improved,but the ultimate deflection,ductility and total energy dissipation significantly decrease;(4)With the increase of area ratio of inner steel core to SFCB,the flexural stiffness,yield moment and ductility of SFCB reinforced UHPC beam after cracking significantly increase,but the ultimate moment,ultimate deflection and total energy dissipation decrease;(5)Increasing the reinforcement ratio of SFCB can effectively improve the flexural stiffness,yield moment and ultimate moment of SFCB reinforced UHPC beams.However,the ductility and ultimate deflection of SFCB reinforced UHPC beam firstly increase and then decrease with the increase of reinforcement ratio.