Research On Simplified Design Method Of FRP/Steel-Concrete Composite Beams

Fiber Reinforced Polymer(FRP)is widely used in engineering structures for its corrosion resistance.However,due to the small elastic modulus of FRP materials(especially GFRP),the deformation resistance of pure FRP structures combined with FRP structures is weaker than that of traditional reinforced concrete structures.Based on this,this paper combines FRP with steel to form a new type of FRP/ steel composite material,which has considerable strength,good elastic modulus,stable post-yield modulus and excellent corrosion resistance.Considering the combination of the new FRP/ steel composite material and concrete to form the FRP/ steel-concrete composite beam,the beam has the characteristics of controllable deformation and high durability.At present,the research on the FRP/ steel composite and its composite structure is still in the preliminary stage in China.Therefore,this paper aims to study the basic mechanical properties of the new type of FRP/ steel composite,as well as the mechanical properties analysis and preliminary design of the FRP/ steel/concrete composite beam.The main research contents of this paper are as follows:Firstly,uniaxial tensile tests of BFRP/ steel composite plate and CFRP/ steel composite plate were conducted to study the stress-strain relationship of FRP/ steel composite plate under different fiber cloth and different steel plate volume ratio,and the test results were compared with the theoretical predicted values.The results show that the theoretical predicted values are in good agreement with the experimental values,and the theoretical model can well predict the uniaxial tensile mechanical properties of composite plates,and both FRP/ steel composite plates have large elastic modulus,stable quadratic stiffness and superior economic performance.Secondly,a new type of FRP/ steel-concrete composite beam is formed by combining FRP/ steel and concrete,various failure modes of composite beam are introduced,simplified design method of composite beam section is proposed,and corresponding design steps are given.Finally,the finite element model of FRP/ steel-concrete composite beam is established based on the design example,and the finite element calculation results are compared with the theoretical formula calculation results.The good agreement between the two results proves the correctness of the finite element model and the rationality of composite beam design.Then,based on the above calculation examples,finite element analysis is carried out,and the influence of design parameters such as concrete strength,FRP type,concrete height and steel plate volume ratio on the mechanical performance of composite beams is studied with the coordination of economy.