疲劳荷载对橡胶混凝土损伤和断裂性能的影响

虽然橡胶混凝土塑性和疲劳性能较好，但由于掺入橡胶，其在疲劳荷载下离散性增大，损伤过程及最终的断裂机制均不明确。为研究橡胶混凝土在疲劳荷载下的损伤和断裂性能，基于声发射开展了不同橡胶掺量的混凝土在疲劳荷载下的三点弯曲疲劳断裂试验。计算有效裂缝长度，分析疲劳荷载下不同橡胶掺量的混凝土裂缝长度a的变化规律，并利用裂缝长度a和声发射累积能量E_AE分别定义了损伤变量D_a和D_AE；分析疲劳荷载下不同橡胶掺量的混凝土断裂能G_F的变化规律；利用声发射中的信号持续时间分析疲劳荷载下橡胶混凝土中裂缝出现和扩展的规律。结果表明，混凝土的断裂能随橡胶掺量的增加呈线性增加；在疲劳荷载下，裂缝长度a和D_a均呈倒S型规律变化，而D_AE呈正S型规律变化；声发射信号持续时间表明，在疲劳荷载下，橡胶混凝土中的裂缝总在荷载较小时出现或发生扩展。 

Effect of fatigue load on damage and fracture properties of rubber concrete

Although rubber concrete has better properties of plasticity and fatigue, due to the incorporation of rubber, its dispersion increases under fatigue load and the damage process and the ultimate fracture mechanism are not clear. In order to study the damage and fracture performance of rubber concrete under fatigue load, the three-point bending fatigue fracture test of concrete with different rubber contents under fatigue load based on acoustic emission was carried out. The effective crack length a was calculated and the change law of the crack length a of the rubber concrete with different rubber contents under the fatigue load was analyzed. The crack length a_c and the acoustic emission cumulative energy E_AE were used to define the damage variables D_a and D_AE.The variation law of the fracture energy G_F of the rubber concrete with different rubber contents under the fatigue load and the law of the occurrence and propagation of cracks in the rubber concrete under the fatigue load were analyzed using the signal duration in the acoustic emission. The results show that the fracture energy of the concrete increases linearly with the increase of the rubber content. Under the fatigue load, both a and D_a change in an inverted S-shaped law, while D_AE shows a positive S-shaped law; The duration of the acoustic emission signal shows that the cracks in the rubber concrete always appear or expand when the load is small under the fatigue load.