Experimental Research And Numerical Simulation On Mechanical Properties Of P.P.C Beam Under Fatigue Loading

At present, the partial prestressed concrete beam is widely used in our country. Especially in the structures of long span.and of having strict requests in cracks and deflections. For the prestressed concrete structures with combined reinforce, the fatigue load is very important in the structures subjected to static and dynamic load under the service load because structures will failed under the fatigue load that is lower than the static ultimate load. Based on the National High Technology Research and Development Plan (863Plan)-"The design method of concrete bridge structures based on fatigue and life"(2007AA11Z133), and studied the mechanical properties of P.P.C beam under fatigue loading. The contents include four aspects as follows:(1) The pattern and characteristics of fatigue fail are discussed and the fatigue performance is analyzed for the partially prestressed concrete beams based on the experimental results. The general rules of top compressive strain of concrete, steel strain and crack under fatigue load are studied, and found all of them are three-stage growth with the increase of the number under fatigue loading, Early and late increase rapidly, in the medium-term growth is slow and it is the main stages of the fatigue development.(2) According to test results, the variation of residual deflection and instantaneous deflection under fatigue loading is studied, considering the main factors, formula is established respectively, and then the computation model of deflection is presented in the entire fatigue life, the factors that lead to increasing of the total deflection before fatigue failure are analyzed, and formulae of amplified coefficient of total deflection is obtained.(3) The static load numerical simulation of P.P.C beam is introduced. First the paper introduced the software ANSYS and the finite element type used in the P.P.C beam; then static load simulation is introduced, it includes establishing constitutive relationship, material models, establishment of model and load-solution settings, at last comparing simulation results with the test results, it proves the model is correct and establishes the foundation for numerical Simulation of Fatigue Performance.(4) According to the material and component damage law under fatigue loading, the full-range fatigue analysis of P.P.C beam is introduced, it includes establishing fatigue constitutive relations, the prestress-loss model and failure criteria of materials, and according to comparing the simulation results with the test results, found the two results except slight deviation and have the same varying trend, it shows that the fatigue model of this paper is accurate.