C60混凝土高温后低周循环受压疲劳性能研究

为了研究高强混凝土所经温度高低、加温时间长短与低周受压疲劳损伤之间的关系，对经历200、500、800℃高温后的C60混凝土在低周循环受压荷载下的疲劳性能进行了试验研究。结果表明：高温后高强混凝土的色泽变浅，试块整体较疏松；经不同高温后高强混凝土在低周循环受压荷载下最大纵向总应变符合三阶段发展规律；相对于应力水平对高强混凝土疲劳应变的影响，高温历程对其影响更大，尤其是受热最高温度影响最为显著。根据应变发展的第二阶段提出了疲劳寿命的估算公式。分别定义疲劳变形模量比和相对残余应变为损伤变量，建立了经历不同高温后高强混凝土受压疲劳损伤模型，并根据疲劳变形模量比建立的损伤模型对高强混凝土的疲劳寿命进行了预测，预测值与实测值吻合良好。

Research on fatigue properties of C60 concrete after high temperature under low cyclic compressive loading

To study the relationship among the temperature levels to which the high strength concrete is subjected, the time the high strength concrete is heated and the low cyclic compressive fatigue damage of the high strength concrete, fatigue tests were performed on C60 concrete under low cyclic compressive loading after temperatures of 200, 500, 800℃. Tests results show that the color of high strength concrete turns lighter after high temperature, and the structure of specimen is looser. The maximum longitudinal total strain of the high strength concrete after high temperature under low cyclic compressive loading is in accordance with the three-stage development law. Compared with the stress level, the effect of high temperature process on the fatigue strain of high strength concrete is more significant, especially the influence of heating temperature. Estimation formula of fatigue life was proposed based on the second stage of strain development. Fatigue deformation modulus ratio and relative residual strain were defined as damage variables, respectively. And the relationship models between the high temperature process and the fatigue damage were established. According to the damage model established by fatigue deformation modulus ratio, the fatigue life of high strength concrete was predicted. The calculation result has a good agreement with the test result.