Research On Flexural Performance Of FRP/Steel-concrete Composite Beam

Fiber reinforced polymer(FRP)is widely used in bridge structures because of its superior mechanical properties.The FRP-concrete composite structure has the advantages of light weight,high strength,and corrosion resistance,but the shortcomings of FRP such as low stiffness,poor ductility,and brittle failure cannot be ignored.Steel has the characteristics of high elastic modulus,good ductility,but easy corrosion.It can be seen that the two have strong complementarity.Therefore,this dissertation considers combining FRP and steel to form a kind of innovative FRP/steel-concrete composite beam.Combined with the National Natural Science Foundation of China Youth Fund "FRP/steel-concrete composite bridge deck beam performance analysis,test and design method" to study its bending performance through theoretical analysis and numerical simulation,the main contents are as follows:First,two sets of FRP/steel laminate specimens were designed and manufactured,and uniaxial tensile tests were conducted.The accuracy of the theoretical model was verified by comparing the test results with the predicted values of the stress-strain theoretical model of the composite plate;Based on the theoretical model,the calculation formulas for mechanical parameters of the laminate(initial stiffness,yield strength,secondary stiffness,ultimate strength,specific modulus,specific strength,and yield ratio)were deduced,and analyzes the influence of the volume ratio of the steel plate on the performance of the composite plate with examples.Secondly,the bending performance of FRP/steel-concrete composite beams in the elastic and plastic stage was analyzed in detail,and the methods of simplified failure analysis,stiffness and deformation calculation for composite beams were proposed.Compared with FRP-concrete composite structure,the stiffness and ductility of FRP/steel-concrete composite structure are improved,and the advantages of FRP and steel are fully utilized.Thirdly,based on the bending test data of the research group,the finite element model of FRP/steel-concrete composite beam was analyzed.The results show that the theoretical value and simulation calculation results are close to the test results,indicating that studying the mechanical performance of composite beams by numerical simulation method is reasonable and effective,and the accuracy of the theoretical calculation method of bending capacity is verified.Finally,according to the above model of the composite beam,by changing the strength,thickness,width of concrete,the inclination angle of web and the cross-sectional form,the influence of each design parameter on the performance of the composite beam was studied.The ultimate bearing capacity of the composite beams is improved by increasing the concrete grade,the width,and controlling the thickness of concrete layer.The change of web inclination angle within a reasonable range has little effect on the bending performance of composite beams.