Research On Fatigue Life Of Prestressed Concrete Beam Based On Energy Dissipation Theory

The increasing amount of road traffic in China leads to a significant accumulation of fatigue damage of reinforced concrete bridges in active service,and there is a great potential safety hazard.In order to ensure the safety of bridge operations,it is necessary to evaluate the fatigue life of bridges to provide an important basis for strengthening or dismantling bridges.First,based on the basic principles of thermodynamics,it was verified that the energy dissipation theory is feasible for predicting the fatigue life of concrete beams.Secondly,considering the change of post-cracking stiffness of prestressed concrete beams,the relationship between the prestress degree and the energy dissipating density under the fatigue load after cracking of concrete beams is established by means of polar moment of inertia method.Then,ANSYS software was used to simulate fatigue damage process of five prestressed concrete T-beams,The load-deflection curve was obtained by linear interpolation method.The dissipated energy density was obtained by integrating it,and the broken line of the dissipated energy density was obtained by segment fitting.The nonlinear equation between the dissipative energy density,the prestress degree of the beam and the line stiffness during the fatigue damage of the prestressed concrete beam is established,and the non-linear equation of the dissipated energy density and the fatigue life of the fatigue development stage is established.The equation predicts the fatigue life of the L-7beam.Research results indicate that: the energy dissipation density of the prestressed concrete beam during fatigue damage presents a very obvious three-phase law,the ratio of three stages is about 0.15:0.75:0.1,and the proportion of each stage has nothing to do with the magnitude of the prestress degree;The dissipated energy density in the stage of stable fatigue development is negatively correlated with the magnitude of the prestress degree,which is consistent with the theoretical model.Compared with the traditional fatigue life prediction method,the fatigue lifeprediction method based on dissipative energy theory is more accurate and provides a new idea for predicting the fatigue life of prestressed concrete bridges.