纤维对混凝土梁开裂弯矩和弯曲韧性的影响

Investigation into the influence of fibers on cracking moment and flexural toughness of concrete

为了研究纤维对混凝土开裂弯矩和弯曲韧性的影响,结合钢纤维、聚丙烯纤维混凝土梁的四点弯曲试验,考虑受拉区混凝土的塑性变形,推导了纤维混凝土开裂弯矩的计算式,并分析了纤维对于混凝土开裂时塑性发展的影响。结果表明,钢纤维掺量超过40 kg/m^(3)、聚丙烯纤维掺量超过4 kg/m^(3)时,纤维可以提高受拉区混凝土塑性变形的能力,从而一定程度上提高开裂荷载。同时,结构型钢纤维与聚丙烯纤维对混凝土弯曲韧性有较为显著的提高作用。结合传统理论中的截面塑性发展系数,将纤维的作用以提高系数的形式加以考虑,可以在设计中较为简便的使用。

To investigate the influence of fibers on the cracking moment of concrete and the properties of the post-cracking behaviors,the present paper derives formula of cracking moment of the concrete considering the plastic development in the tension zone,based on the results of four points loading test.It shows that fibers can increase the cracking moment of concrete,when the dosage of the steel fibers is more than 40 kg/m^(3) and PP fibers more than 4 kg/m^(3).The reason is that the fibers can improve the ability of the plastic development in the tension zone of concrete.Marco-steel and PP fibers can significantly increase the flexural toughness of concrete.It is convenience for the designer to use if the form of increasing factor is adapted to consider the influence of fibers.