Numerical Simulation Of Flexural Behavior Of FRP Bars Steel Fiber Reinforced Concrete Beams

To effectively solve the corrosion problem in traditional reinforced concrete structures and improve the flexural performance of concrete structures,steel fiber-reinforced concrete（SFRC）structures reinforced with FRP bars have been widely used in engineering.At present,the research findings and calculation theory on FRP-reinforced SFRC beams are insufficient and incomplete.Finite element numerical simulation is an effective research method.Numerical simulation based on ANSYS can obtain the whole process of the development of internal force and deformation,and can also describe the formation and development of cracks.however,finite element research findings on FRP-reinforced SFRC beams are still limited.The expected research results of this paper will provide a reference basis for the improvement of the calculation theory of FRP-reinforced SFRC beams.Based on ANSYS,the flexural performance of FRP-reinforced SFRC beams was numerically simulated considering the bond-slip behavior between FRP bars and concrete.The load-deflection curves,crack distribution and failure modes were obtained to verify the applicability of the model.The influences of steel fiber volume ratio,concrete matrix strength,FRP reinforcement ratio,type of bars,section size and concrete cover thickness on the flexural performance of FRP-reinforced SFRC beams were discussed.Based on the simulation results,nonlinear full-range analysis was carried out on the specimens,and the calculation method of balanced reinforcement ratio was analyzed.The main research results are as follows:（1）the working stage of FRP-reinforced SFRC beams involved three stages:elastic working stage,crack-involved working stage and failure stage.the tensile stress of FRP bars and the stress of SFRC in compression zone increased slowly with the load before cracking,and increase rapidly after cracking.The load-deflection curve has no yield phase.（2）The increase in steel fiber volume ratio and concrete matrix strength can effectively improve the flexural performance of FRP-reinforced SFRC beams at the initial loading stage and delay the cracking of specimens.The ultimate flexural capacity of beams increased with the increase in steel fiber volume ratio and concrete matrix strength.When the steel fiber volume ratio increased to 1.5%,the ultimate flexural capacity of the beams increased slightly.The concrete strength had a marginal influence on the flexural behavior of the beams when it is greater than 52MPa.（3）The FRP reinforcement ratio and the beam depth have significant effects on the flexural performance of the beams.Increasing the reinforcement ratio and beam depth can effectively improve the overall stiffness of the beams.When the reinforcement ratio exceeds 1.1%,the utilization ratio of the high tensile strength of FRP bars decreased with the increase in the reinforcement ratio.The ultimate flexural capacity increased with the reinforcement ratio but reduced significantly when the reinforcement ratio reached 2.31%.The cracking load and ultimate flexural capacity increased with the increase in the beam depth.When the beam depth exceeds 325mm,the ductility of the beams decreased and the failure occurred suddenly.The stiffness varies significantly among different types of FRP bars（GFRP,BFRP,AFRP,CFRP）,which leads to a more significant influence on the flexural performance of the beams.（4）The concrete cover thickness had a marginal effect on the flexural performance of the beams at the initial loading stage.When the concrete cover exceeded 28mm,the beams exhibited good ductility.However,to obtain a higher ultimate flexural capacity and a smaller deflection,the concrete cover thickness should be conservative.（5）Based on the simulation results,a calculation model for the balanced reinforcement ratio of FRP-reinforced SFRC beams was proposed referring to the calculation method home and abroad.The proposed model considered the tensile effect of steel fibers in the tension zone.