定侧压混凝土双轴拉-压疲劳累积损伤试验研究

在对有限预应力混凝土桥梁结构进行损伤分析与剩余寿命估算时,为了解混凝土在双轴波动拉-压应力作用下的疲劳强度和损伤特性,通过室内小尺寸的变截面棱柱体试件的双轴疲劳试验,得到了定侧压下混凝土等幅和变幅重复荷载作用下的轴心拉-压疲劳方程和疲劳变形特性。由等幅疲劳变形模量定义了损伤变量,拟合试验结果得到了相应的损伤演化方程;依据损伤演变与损伤状态、加载条件间的相关性,建立了相应的疲劳损伤模型。研究表明:极限疲劳割线模量衰减率可作为混凝土发生拉-压疲劳破坏的标志;用规范化的疲劳变形模量定义损伤变量,建立的损伤累积模型,用于疲劳损伤分析和剩余寿命预测时具有较高的精度。

Experimental research on fatigue cumulative damage of concrete under cyclic tension-compression with constant confined stress

The fatigue strength and fatigue cumulative damage property of concrete under biaxial cyclic tension-compression should be considered in damage analysis and service life assessment of prestressed reinforced concrete bridges. According to indoor tension-compression fatigue tests on tapered prism specimens, the fatigue cumulative damage property of concrete in axial tension-compression under constant and variable amplitude cyclic loading with constant confined stress is investigated in present study. The damage variable is defined with the secant modulus of plain concrete under constant amplitude fatigue loading, and the law of cumulative damage and its evolution is obtained from the data of experiments. According to the correlation between accumulative damage and loading levels, the fatigue damage model is established. The results show that fatigue failure criterion of concrete under tensile-compressive stress can be indicated by ultimate attenuation rate of secant modulus. The precision and validity of the presented fatigue damage model have been verified by the results.