Flexural Behavior Of RC Beams Strengthened With FFRP

Fiber Reinforced composites(Fiber Reinforced Plastics/Polymers, referred to as FRP) has became a new popular reinforcement material in civil engineering due to its high strength, installation, corrosion resistance, etc. In recent years FRP has been widely applied to many kinds of structures. However, traditional man-made fiber doesn’t have a good performance in promoting a green and sustainable development.In order to meet the environmental demand and develop sustainable materials, using natural fiber to replace man-made fiber in Fiber Reinforced Polymer/Plastic has a good prospect. Natural Fiber Reinforced Polymer/Plastic has attracted the focus of many countries and regions.The thesis uses flax fiber to replace man-made fiber in FRP. and through the experiment to study the flexural performance of RC beams strengthened with Flax Fiber Reinforced Polymer/Plastic(FFRP). The main research content is as follows:(1) Tensile performance of four types of natural fiber(200g/m2semi-bleached flax, 300g/m2 rain flax, 400g/m2 rain flax and jute) and three thicknesses(2 layers, 4layers and 6 layers) FFRP specimens were tested, and results showed that FFRP which is made of the 300g/m2 rain flax(warp direction) have a stable tensile properties. The tensile parameters of FFRP, including tensile strength, ultimate tensile strain, tensile modulus and stress-strain curves, are acquired.(2) Based on the material test results in this thesis and the material constitutive laws that already exist, analysis of flexural performance of RC beams strengthened with FFRP is carried out. According to the common failure modes of RC beams strengthened with FFRP, the corresponding bending capacity formula was derived.(3) 6 RC beams strengthened with FFRP which considering reinforcement ratio,fiber layers and pre-splitting as the parameters and 2 ordinary RC beam(as the control specimen) are designed for the static load flexural experiments. Through the experiments flexural performance of load-deflection relationship, the load-strain relationship of reinforcement, the load-strain relationship between reinforcement and concrete, ductility of composite beams, are all analyzed in detail. Compared with ordinary RC beams, ultimate strength and ductility of FFRP reinforcement beams increase to different extent. And the conservative calculation values matched well with the experimental verification ones.(4) The beams which tested for bending capacity has not been occurred stripping damage between FFRP and concrete interface. 3 beams strengthened with FFRP of different length are tested to analyze the bonding performance. The beam strengthened with the shortest FFRP occured stripping damage. In order to ensure the good coordination of beam and make full use of material, stretch its FFRP to the beam support is appropriate.