Mechanical Behaviors Study On Steel-Concrete Composite Beam Strengthened By CFRP Sheet

Fiber Reinforced Polymer (FRP) with its lightweight, high strength, corrosion resistance, fatigue resistance, non-electromagnetic and other characteristics have become an effective method of strengthened and repairing of structure. However, FRP also have some drawbacks, such as high strength and elastic modulus along the direction of fiber, but low strength and elastic modulus along the direction of the vertical fiber, that is easy to instability and brittle fracture. In order to avoid shortcomings of FRP and play to the advantages the FRP as a new structural reinforcement material combined with the traditional structure has been widely used in civil engineering. At present, the study on the composite structure of FRP reinforcement is few in the abroad, while it's still fewer at home. Based on the study of steel-concrete composite beams, and combined with the force characteristics of FRP, the experiment research and theoretical analysis are mainly used in this thesis to study the bearing capacity of CFRP sheets strengthened corrosive steel-concrete beams. Furthermore, the mechanical properties of CFRP plates strengthened steel-concrete composite beams are studied. The main contents are as follows:Through the experiment of CFRP sheets strengthened corrosive steel-concrete composite beams, the working mechanism and failure mode of CFRP sheets strengthened corrosive steel-concrete composite beams are studied. The strain distribution of CFRP sheets, concrete, reinforcement and I-beam, the deformation of beam and the distribution of crack are analyzed.The effects of CFRP sheets and initial corrosion on the bearing capacity of steel-concrete composite beams are discussed. The results of experiment show that : bonding CFRP sheets or reducing initial corrosion will improve the bearing capacity of composite beams.The calculation formulas of carrying capacity and ultimate flexural bearing capacity of CFRP sheets strengthened steel-concrete composite beams are established. According to comparison between theoretical results and test results, both are in good agreement.Using the method of elastic mechanics and energy, the calculation formulas of axial force, interface shear and deformation of CFRP plates strengthened steel-concrete composite beams are established. The influence of CFRP plate thickness, connection stiffness and load on axial force, interface shear and deformation are analyzed. The examples have also been done.