高性能混凝土梁在卤水腐蚀下的疲劳性能探究

Study on fatigue behavior of high performance concrete beams under brine corrosion

由于青海地处高原且地下卤水环境对轨道梁的寿命影响不容忽视,展开对轨道梁在卤水腐蚀下的疲劳试验研究十分必要。通过对4种不同配合比的混凝土梁在不同腐蚀条件下的疲劳试验,研究了混凝土梁在水环境及卤水环境下的钢筋锈蚀率、钢筋力学性能变化、氯离子含量、梁疲劳寿命及力学行为失效机理等,并绘制了不同模型的应力比-疲劳寿命（S-N）曲线,拟合出了S-N曲线方程。试验结果表明：卤水能加速钢筋锈蚀并影响混凝土梁的疲劳寿命,且在低锈蚀下能略微提升混凝土梁的疲劳寿命;疲劳破坏包括初裂、裂缝的开展、损伤的积累三个阶段,且箍筋具有一定的抗裂性;强度越高的高性能混凝土梁在相同腐蚀条件下疲劳寿命越长;低锈蚀率的混凝土梁的疲劳寿命很大程度上由其应力比决定。研究结果可为低锈蚀率钢筋混凝土梁疲劳性能评估提供理论依据。

Qinghai is located in the plateau,and the influence of the underground brine environment on the life of the rail beam cannot be ignored,so it is necessary to carry out fatigue test study on track beam under brine corrosion. The fatigue tests of concrete beams with 4 different mix ratios under different corrosion conditions were carried out. The corrosion rate of steel bars,the mechanical properties of concrete,the content of chloride ion,the fatigue life of beams and the failure mechanism of mechanical behavior of concrete beams under water environment and brine environment were studied. The stress ratio-fatigue life（ S-N） curves of different models were drawn,and the S-N curve equation were fitted. The experimental results show that the brine can accelerate the corrosion of steel bars and affect the fatigue life of concrete beams,and can slightly increase the fatigue life of concrete beams under low corrosion; fatigue failure includes three stages of incipient crack, crack development and damage accumulation, and stirrups have certain crack resistance; high performance concrete beam with higher concrete intensity has higher fatigue life under the same condition of corrosion;fatigue life of concrete beams with low corrosion rate is decided to a large extent by its stress ratio. The research results provide a theoretical basis for the evaluation of fatigue performance of reinforced concrete beams with low corrosion rate.