冻融循环后高延性混凝土疲劳性能试验及S-N曲线研究

Experimental study on fatigue property and S-N curve of high ductile fiber concrete under freeze-thaw cycles

对高延性混凝土(HDC)进行75次和150次冻融循环后,进行单轴受压疲劳性能试验,研究其在不同应力水平、加荷频率下的疲劳变形特征和疲劳寿命。将常温养护条件下的试件与经过冻融循环试件的疲劳性能进行对比,建立适用于不同冻融条件下HDCS-N曲线模型。试验结果表明:经过常温养护条件下进行疲劳试验,得到疲劳寿命与加荷频率成正比,与应力水平成反比;经过冻融循环后进行疲劳试验,疲劳寿命较常温养护有明显减低,75次冻融循环后最高降低95.3%,150次冻融循环后最高降低97.3%;试件在疲劳破坏后,均具有较好的整体性,属延性破坏。对试验结果进行分析,以加荷频率、冻融次数作为参考值,建立不同冻融条件下HDC的S-N曲线模型,计算出HDC材料的疲劳折减系数:正常养护条件下为0.660~0.674,经过冻融循环后为0.589~0.612,下降约9.2%~12.6%。可为实际工程提供参考。

The test of compression fatigue property of high ductile concrete(HDC)after freeze-thaw cycles of 75 times and 150 times is used to study the fatigue deformation characteristics and fatigue life under different stress level and load frequency.The HDCS-N curve model suitable for different freeze-thaw conditions was established by comparing the fatigue performance of the specimens under normal temperature curing with that after freeze-thaw cycle.The results show that the fatigue life is directly proportional to the loading frequency and inversely proportional to the stress level.After the freeze-thaw cycle,the fatigue life was significantly reduced compared with the normal temperature curing.The maximum decrease was 95.3%after 75 freeze-thaw cycles and 97.3%after 150 freeze-thaw cycles.The specimens have good integrity and ductility after fatigue failure.Based on the analysis of test results,the S-N curve model of HDC under different freezing-thawing conditions was established with loading frequency and freezing-thawing times as reference values,and the fatigue reduction coefficient of HDC material was calculated:0.660~0.674 under normal curing conditions,0.589~0.612 after freezing-thawing cycle,which decreased by 9.2%~12.6%.It can provide reference for practical engineering.