混凝土双轴拉压、三轴拉压压变幅疲劳性能研究

利用大型多轴疲劳试验机，进行了拉压双轴和拉压压三轴荷载作用下混凝土两级、三级变幅疲劳试验研究，重点分析了残余应变的变化规律。试验结果表明:混凝土在拉压和拉压压加载工况下的残余应变主要与相对疲劳次数和侧压应力比有关，基本不受加载历程因素的影响。定义相对残余应变为损伤变量，建立了损伤演变方程，并进行了疲劳损伤分析和剩余疲劳寿命预测，为混凝土在多轴变幅疲劳试验研究及疲劳损伤评价提供参考。

VARIABLE-AMPLITUDE FATIGUE PROPERTIES OF PLAIN CONCRETE UNDER BIAXIAL TENSION-COMPRESSION AND TRIAXIAL TENSION-COMPRESSION-COMPRESSION CYCLIC LOADING

Fatigue tests are performed on the plain concrete of two or three grades subjected to variable-amplitude biaxial tension-compression and triaxial tension-compression-compression cyclic loading by using a large multiaxial machine, and the residual strain of concrete is analyzed. The experimental results show that:under tension-compression and tension-compression-compression fatigue loads, the residual strain of concrete is mainly associated with the relative fatigue cycle and lateral compressive stress ratio, but has little relationship with the loading process. Furthermore, the relative residual strain is defined as the damage variant, and the damage evolution equations for plain concrete are established. On this basis, the damage analysis and prediction of fatigue remaining life are conducted, which provides a reference for variable-amplitude fatigue tests and fatigue damage evaluation of concrete under multiaxial loads.