A visco-elastic-plastic model for fatigue strain of concrete at high levels of stress

Models to predict fatigue strain in concrete are critical to analysing the structural response of concrete under cyclic loading. This paper reviews existing concrete fatigue models and discusses the similarities between fatigue and creep processes. It is theoretically feasible to introduce the often-used creep models into fatigue strain predictions. Based on a visco-elastic-plastic model, a continuous fatigue strain prediction equation with five parameters is proposed. The parameters in the proposed equation, which all vary with the concrete compressive strength, were determined using test results from the literature using least-squares and global optimisation methods. The accuracy of the proposed model was verified with results different from those used to calibrate the model parameters and good agreement was observed. Further applications of the proposed model, including simulation of secant modulus degradation and the damage development of concrete, were performed and the predicted results were compared with test results. The results showed that the three-stage development of fatigue strain, the secant modulus and the damage parameter of concrete at high cyclic stress can be described well by the proposed model.