The Research On The Fatigue Theory Of Partially Prestressed Reinforced Concrete Beam With Pure Bending

In recent years, fiber reinforced plastic tendon (FRP) is a possible material instead of the steel tendon because of its material characteristics such as light quality, high strength, non-corrosive, which has been used in concrete structure. FRP tendon has superior fatigue performance and high fatigue strength, and ordinary steel tendon has good ductility and fine mechanical properties, so the FRP and steel tendon reinforced concrete structures give full play to both of those material properties. The static research for FRP reinforced concrete structure has been carried out in great quantities at home and abroad, and the corresponding design specification has been compiled, but the fatigue performance of the structure is not involved yet. The content to be studied is in the following:First of all, the fatigue performance, failure criteria, damage model of concrete, steel and FRP which are put forward by many scholars are summarized. The fatigue loading process, failure pattern and the law of fatigue deformation of reinforced concrete beam with pure bending are discussed. On those bases, fatigue constitutive model and damage model, failure criterion and material fatigue strength of the three kinds of material are presented.Secondly, based on the fatigue property of materials, by using macroscopically deformation compatibility condition, the force’s equilibrium conditions and fatigue stress-strain relationship of material, the whole process theory of fatigue damage of reinforced concrete beam with pure bending is established, in which method the fatigue stress of the cross section in any number of times can be obtained. The theory is suitable for partially prestressed hybrid reinforced flexural component perfectly. The enhancement coefficient between strengthen tendon and concrete is introduced, so that the theory also can be used members with strengthen tendons both in vivo and in vitro. By comparing theoretical values with the test data, the results can show the general laws of the fatigue development.Finally, fatigue crack and fatigue deflection which are the primary factors affecting the normal use are analyzed in theory. By analyzing the development law and characteristics of fatigue deformation, a number of different fatigue deformation calculation theory are established. Through the comparison with the experimental data, applicability and advantages and disadvantages of each theory are analyzed.