冻融作用下自密实混凝土疲劳寿命可靠性分析

Reliability analysis of fatigue life of self-compacting concrete subjected to freeze-thaw damage

摘要:

为了研究冻融损伤对自密实混凝土弯曲疲劳寿命的影响,对经受不同冻融循环后的混凝土试块进行了不同应力水平下的四点弯曲疲劳试验,并利用矩估计法获得了混凝土试块的弯曲疲劳寿命Weibull分布参数,建立了经受不同冻融循环后的混凝土试块在不同可靠性概率下的疲劳寿命预测模型。研究结果表明:受冻自密实混凝土的疲劳寿命概率分布可以用两参数Weibull分布表征,得出自密实混凝土疲劳寿命的离散性随冻融次数的增加而增大,随应力水平的增大而减小；根据试验数据生成了自密实混凝土的P_f-S-N曲线,可准确预测经受不同冻融循环后自密实混凝土的弯曲疲劳寿命；自密实混凝土的疲劳寿命所需的安全系数随冻融循环次数的增加而不断增大,这说明对经受冻融损伤较严重的自密实混凝土,其弯曲疲劳寿命必须采用较大的安全系数才能保证结构的安全运行。

Abstract:

In order to study the influence of freeze-thaw (FT) damage on the flexural fatigue life of self-compacting concrete, the four-point flexural fatigue tests at different stress levels were carried out on concrete beams subjected to different FT cycles, and the Weibull distribution parameters of flexural fatigue life of concrete beams were obtained by the method of moments. The prediction models for the fatigue life of concrete beams subjected to different FT cycles under different reliability probabilities were established. Results showed that the probability distribution of fatigue life for self-compacting concrete subjected to different FT cycles could be characterized by two-parameter Weibull distribution. The dispersion of fatigue life of self-compacting concrete increased with the increase in FT cycles and decreased with the increase in stress levels. On the basis of the test data, the P_f-S-N curves of self-compacting concrete were generated, which can accurately predict the flexural fatigue life of self-compacting concrete subjected to different FT cycles. The safety factor required for the fatigue life of self-compacting concrete increased with the increase in FT cycles, which indicates that for the self-compacting concrete suffering from more serious FT damage, a larger safety factor should be adopted to ensure the safe operation of the structure.