| Steel fiber composite bars(SFCB)is a new kind of composite materials which keep a reinforcement bar as the inner core with longitudinal fiber surrounding outside.It combines high strength and elastic modulus,good ductility of steel,high durability and strength of FRP.What's more,it can effectively reduce the corrosion of reinforcement due to the effect of the surrounded fiber.The experimental results show that the yield components secondary stiffness of reinforced concrete structure can be improved by using composite reinforcement instead of ordinary steel bar,and the residual deformation can be reduced obviously,and it has good repairable ability after earthquake.Just like the reinforced concrete structure,reliable bond behavior between SFCB and concrete is a fundamental issue for reinforced concrete.Therefore,the consideration of bond-slip is of great significance to the study of seismic behavior of SFCB reinforced concrete structures or members.In order to evaluate the seismic behavior of SFCB concrete structure more comprehensively and reasonably,In this paper,SFCB reinforced concrete beams and columns are taken as the research object.The effects of longitudinal bar slip on seismic behavior of SFCB concrete members under monotone and cyclic loads are systematically studied.This thesis aims to draw a conclusion of the previous study:(1)According to the bond slip mechanism of SFCB and the existing bond-slip theoretical model,Combined with the mechanical characteristics of composite reinforcement,the calculation model of bending moment and slip rotation angle at the pole end for composite reinforcement is derived.The theoretical method of determining the relationship between bending moment and rotation angle and the load-slip deformation of the members is also presented by the bond stress-slip relationship of composite bars.(2)Based on the structure analysis method that the addition of nonlinear Spring at the end of the member to consider the slip of Longitudinal tendons,used nonlinear beam column element and zero-length section element of Open Sees software,separately consider the bending deformation and the slip deformation of the longitudinal bar of themembers,using zero-length element to consider slip deformation of longitudinal tendons,Selecting constitutive material model,and established a model of SFCB concrete frame beam including longitudinal bond-slip.(3)based on Opensees Software,the numerical model of SFCB reinforced concrete beam considering and without considering longitudinal bar slip has been established.Then,Obtained the vertex force-displacement hysteretic curve from the considering and disregarding slip model.Compared with the model without considering slippage under the action of horizontal cyclic loading,Considering the bond-slip behavior of longitudinal bars,the model can better reflect the bearing capacity,stiffness degradation and energy dissipation ability of the hysteretic curve,which is in good agreement with the experimental results.The accuracy of the theoretical calculation model and modeling method derived in this paper is verified.(4)Based on Open Sees software,Including bond slip of the SFCB reinforced concrete column was simulated and compared with that of the test result.Then different parameter,including the concrete strength,fiber content and axial compression ratios,were also simulated to study the effect of them on the seismic behavior of SFCB reinforced concrete flame.The results showed that with the increase of concrete strength grade,there is little influence on the bearing capacity of members before yielding,the peak load after yield increases and the hysteresis curve appears to have a certain degree of pinching effect.Increasing the fiber content of the composite reinforcement can effectively improve the secondary stiffness of the column after the column yield.The more axial compression ratio,the peak bearing capacity of the structure is not large,but the ductility and energy consumption get worse. |
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