局部高密度钢纤维混凝土弯曲疲劳损伤演变规律

DAMAGE AND ITS EVOLUTION FOR PARTIALLY HIGH PERCENTAGEFIBER REINFORCED CONCRETE UNDER FLEXURAL FATIGUE

  • 摘要: 在混凝土弯曲构件底部用高密度钢纤维局部增强称为局部高密度钢纤维混凝土(PHPFRC),与同样纤维掺量的传统钢纤维混凝土(SFRC)比较,它可以用相近的价格获得高得多的刚度﹑承载力和抗疲劳断裂性能.为了能够预测PHPFRC在循环荷载作用下的疲劳寿命,需要确定其疲劳损伤演变规律.本文通过试验发现,局部高密度钢纤维混凝土的弯曲疲劳损伤表现出韧性材料所具有的性质,基本上接近韧性损伤,这与素混凝土及传统钢纤维混凝土有本质的不同;根据其疲劳特性的实验结果,探讨了PHPFRC弯曲疲劳损伤阈值;结合损伤理论,建立了适合于纤维体积掺量为1.2%的局部高密度钢纤维混凝土试件的弯曲疲劳损伤演变方程.

     

    Abstract: Partially High Percentage Fiber Reinforced Concrete (PHPFRC) is a kind of fiber concrete in which fibers are concentrated with high density in the tension region of component under bending. PHPFRC possessesmuch higher load bearing capacity, rigidity, fatigue and fracture properties than conventional steel fiber reinforcedconcrete (SFRC), but its cost is similar to that of SFRC. In the paper, the fatigue damage evolution rule for PHPFRC is proposed to predict its fatigue life under multi-amplitude cycle load. It was observed that the fatigue damage of PHPFRC is tough damage from test results, being different from plain concrete and most SFRC. Based on the continuum damage mechanics and fatigue behavior of the specimens, damage variable D for fatigue of PHPFRC is defined, and the elementary form of damage evolution function is determined. For the specimens in which average fiber volume fraction is 1.2%, the function parameters are given according to the test results.

     

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