中文摘要：

混凝土作为一种人工石材，由于浇筑过程的影响，其断裂破坏过程不可避免地存在一定随机性。利用声发射实时动态无损监测技术，分析了带预制裂缝混凝土三点弯曲梁试件裂缝扩展发生偏移和钢筋混凝土三点弯曲梁破坏荷载循环增减等特殊试验现象存在的客观性。试验分析发现，预制裂缝尖端粗骨料的存在，致使裂缝并非沿着预制裂缝直接向前扩展，而是出现绕道扩展的现象；配筋率过大时，钢筋混凝土三点弯曲梁试件的破坏荷载值将维持在钢筋极限屈服强度附近循环变化。可见，钢筋混凝土三点弯曲梁试件的失稳荷载取决于配筋率的高低。研究成果表明声发射技术可为开展混凝土损伤断裂试验提供一种新的研究手段。

英文摘要：

As a kind of artificial stone, the fracture failure process of concrete must have some randomness owing to impacts caused by concrete placement. Based on the acoustic emission dynamic nondestructive detecting technology, the objectivity of special test phenomenan has been analyzed for both the crack propagation with deviation of notched concrete three-point bending beam and the failure load reciprocating increase and decrease of the reinforced concrete three-point bending beam. It is found from the experimental results that the cracks propagate around the coarse aggregate rather than along the prefabricated crack because the coarse aggregate is just poured in the prefabricated crack tip. When the ratio of reinforcement is too high, the failure load of the reinforced concrete will vary near the yield strength of the bar cyclicly. It is thus clear that the instable load of the reinforced concrete three-point bending beam specimen would depend on the level of the ratio of concrete reinforcement bar. The research results indicate that the acoustic emission technology can be taken as a new research method for damage and fracture of concrete.