Study On Flexural Performance Of FRP-Concrete Composite Beams

The flexural behavior of FRP profiled-concrete composite beam is an important performance index of FRP-concrete composite structures.Based on the detailed analysis of the flexural failure modes of composite beams,the prediction formulas of mid-span deformation and flexural stiffness of composite beams considering various reduction effects are given in this thesis.Based on damage mechanics and composite material mechanics,finite element model is established for the FRP profiled-concrete push-out test with FRP shear key（FSK）and the FRP profiled-concrete composite beam flexural test.The main research contents are as follows:1.Firstly,based on the plane cross-section assumption,different modes of flexural failure of composite beam are analyzed,and the prediction of the ultimate moment under the consideration of slip effect and shear bond reduction effect is proposed.Based on bilinear model,the deformation under sliding effect and shear deformation reduction is established.Considering the influence of sliding effect,shear deformation caused by FRP thin wall and lift effect on composite beam stiffness,a calculation method of flexural stiffness of FRP profiled-concrete composite beam was proposed.2.Secondly,the finite element model is established for the FRP profile-concrete push-out test with FSK.The correctness of the model is verified by analyzing the interface shear stress-slip curve.The typical load-slip curves of the specimen with FSK were analyzed from the interface damage point of view.Based on the third-strength theory,the ultimate shear strength formula of the specimen with FSK can correctly predict the ultimate shear stress between the interfaces,and the FSK design scheme with and without sliding effect can be obtained by elastic analysis and plastic analysis respectively.3.Finally,the 3D refined finite element model is established for FRP profiled-concrete composite beams.The traction-separation model is adopted to consider the sliding effect between the interface,and the progressive damage behavior of concrete and FRP profile is captured based on CDP model and Hashin composite material progressive damage model.The numerical results were verified and compared with the experimental results from six aspects:load-deflection curve,load-slip curve,deflection distribution curve,pseudo-ductility,energy dissipation and failure mode.Based on the model,the deformation and failure modes of composite beams are studied in depth from four aspects:strength of concrete,elastic modulus of FRP profile,anisotropy characteristic coefficient of FRP profile and cross-section form of FRP profile.