混凝土三轴受压等幅疲劳力学性能试验研究

为研究混凝土在多轴疲劳应力作用下的性能，进行了0.0fc、0．1fc、0．25fc、0．4fc4个不同初始定侧压级别下的混凝土三轴压静载试验和0．1c、0．25fc两个不同初始定侧压级别下的混凝土三轴压等幅疲劳试验，疲劳试验中最小应力水平均为0．1fc，最大应力水平为1．6fc-2．5fc．根据初始定侧压下混凝土三轴压本构特征，试验中将侧压变化的拐点作为其多轴疲劳破坏的判据．试验分析表明，三轴压疲劳荷载作用下混凝土纵向最大、最小应变表现出同单轴和双轴疲劳一样的三阶段规律，而变形模量则衰减不大．由各侧压级别下的S-N曲线得到混凝土在相应工况下的疲劳强度折减系数，其研究成果可为混凝土结构疲劳设计提供参考．

Research on fatigue properties of concrete under triaxial compressive constant- amplitude cyclic loading

Triaxial static test and fatigue test were carried out on plain concrete subjected to triaxial static loading and constant-mplitude triaxial compressive cyclic loading in this paper. Triaxial loading was achieved by applying compressive loading to concrete cube in longitudinal direction while applying confining loading in two lateral directions. For the static test, the initial confining loading was equal to 0.0fc, O. 1fc, 0. 25fc and 0. 4fc respectively, and 0. 1fc, 0. 25fc for the fatigue test. Based on the concrete triaxial compressive constitutive behavior, the inflexion of confining loading evolution was chosen to be the fatigue damage criterion during the test. Similar to the uniaxial and biaxial fatigue tests, the three-stage evolution rule of the longitudinal maximum and minimum strains were presented too. Test results also indicated that the longitudinal cyclic modulus deteriorated a little even just before failure. According to the S -Ncurves for different lateral loadings, the fatigue strength factors were obtained. The investigation of this paper can provide information for the fatigue design of concrete structures.