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本文主要分析讨论了混凝土在等幅重复应力作用下的疲劳破损机理。试验分析表明,混凝土的疲劳损伤和疲劳变形的发展可以分为三个不同的阶段,占疲劳寿命大部分的第二阶段的应变发展几乎为线性变化,进入变形迅速发展的第三阶段时的混凝土纵向总变形与应力历史无关,是一个材料常数,可以作为判断混凝土发生疲劳破坏的准则。分别利用混凝土第一次加载时的最大应变与混凝土裂缝失稳扩展时的纵向总应变之比来表示所施加荷载的最大应力水平及混凝土应变发展第二阶段的应变增长速率,建立了二个估算混凝土等幅疲劳寿命的计算公式,计算结果与试验结果吻合较好。
This paper mainly analyzes and discusses the mechanism of fatigue damage of concrete under the effect of repeated amplitude stress. Experimental analysis shows that the development of fatigue damage and fatigue deformation of concrete can be divided into three different phases. The second phase of the fatigue life, which accounts for most of the fatigue life, develops almost linear changes, and enters concrete when the third phase of rapid development of deformation occurs. Longitudinal total deformation has nothing to do with stress history. It is a material constant and can be used as a criterion for judging the fatigue failure of concrete. The ratio between the maximum strain at the first load of the concrete and the total longitudinal strain at the time of the instability expansion of the concrete cracks is used to represent the maximum stress level of the applied load and the strain growth rate of the second stage of concrete strain development, and two estimates are established. The calculation formula for the fatigue life of concrete with constant amplitude is in good agreement with the experimental results.