混凝土多轴等幅疲劳性能研究

利用大型多轴疲劳试验机,进行了双轴拉-压、三轴拉-压-压等幅循环荷载作用下混凝土的疲劳性能研究.分析了不同侧压比、不同应力水平下混凝土的多轴等幅疲劳破坏形态、疲劳强度以及残余应变的变化规律,得到了应力水平-疲劳寿命(S-N)曲线及其表达式.结果表明:在等幅疲劳荷载下,混凝土多轴疲劳破坏形态与侧压比无关;残余应变呈三阶段发展规律,受侧压比影响较大,几乎与应力水平无关.定义相对残余应变为损伤变量,建立了损伤演变方程,为混凝土多轴等幅疲劳试验研究及疲劳损伤评价提供参考.

Multiaxial Constant Amplitude Fatigue Properities of Concrete

Fatigue tests of concrete under constant amplitude biaxial tension compression and triaxial tension compression compression cyclic loading were carried out using a large multiaxial fatigue testing machine. Fatigue failure mode, fatigue strength and residual strain of concrete under different lateral stress ratios and different stress levels were analyzed. The stress level fatigue life(S N) curve of fatigue life and corresponding expressions were obtained. The results show that the multiaxial fatigue failure mode of concrete is independent of the lateral stress ratio under constant amplitude cyclic loading; the residual strain develops in three stages, and it is greatly affected by the lateral stress ratio but almost independent of the stress level. Furthermore, the relative residual strain is defined as the damage variable, and the damage evolution equation is established, which provides reference for multiaxial constant amplitude fatigue experimental research and damage evaluation of concrete.