In this study, a continuum-based model was proposed to characterise the flexural performance and damage evolution process of a plain concrete beam under high-cycle fatigue loads. The plain concrete beam under three-point bending load was modelled by combining the damaged constitutive model of concrete and the Euler–Bernoulli beam theory with varied stiffness. The dynamic stiffness matrix method, in conjunction with the discretization technique, was adopted to solve the nonlinear governing equations of motion. A global damage index corresponding to natural frequencies was introduced to quantify the performance degradation of the beam. To improve the analysis efficiency of the high-cycle fatigue problems, the accelerated algorithm, namely the jump-in-cycle method, was employed in this model. It is demonstrated that the numerical results agree well with the experimental data under fatigue harmonic loads. Performance degradation under fatigue bending loads only occurs at the midspan of the beam. Adopting the jump-in-cycle methods significantly improves the analysis efficiency of the high-cycle fatigue problem, and the calculation time is reduced by approximately 90% compared with the cycle-by-cycle method. This model is capable of rationally predicting damage evolutions, stiffness degradation processes, stress redistributions, and loading level-fatigue life (S–N) curves and can provide a basis for simulating the flexural behaviours of reinforced concrete (RC) beams under fatigue bending loads.

在这项研究中，提出了一个基于连续体的模型来表征高周疲劳载荷下普通混凝土梁的抗弯性能和损伤演化过程。通过结合受损的混凝土本构模型和具有不同刚度的Euler-Bernoulli梁理论，对三点弯曲荷载下的普通混凝土梁进行建模。动力刚度矩阵法结合离散技术被用来求解运动的非线性控制方程。引入了与自然频率相对应的整体破坏指数，以量化光束的性能下降。为了提高高周疲劳问题的分析效率，该模型采用了加速算法，即周跳法。结果表明，数值计算结果与疲劳谐波载荷下的实验数据吻合良好。疲劳弯曲载荷下的性能下降仅发生在梁的中跨处。采用周期跳跃方法可以显着提高高周期疲劳问题的分析效率，并且与逐周期方法相比，计算时间减少了大约90％。该模型能够合理地预测损伤的演变，刚度的下降过程，应力的重新分布以及载荷水平的疲劳寿命（与逐周期方法相比，计算时间减少了大约90％。该模型能够合理地预测损伤的演变，刚度的下降过程，应力的重新分布以及载荷水平的疲劳寿命（与逐周期方法相比，计算时间减少了大约90％。该模型能够合理地预测损伤的演变，刚度的下降过程，应力的重新分布以及载荷水平的疲劳寿命（SN）曲线，可以为模拟钢筋混凝土（RC）梁在疲劳弯曲载荷下的弯曲行为提供基础。