局部高密度钢纤维混凝土疲劳裂纹扩展实验研究

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，它可以用近似的价格获得高得多的力学性能，本文对PHPFRC缺口试件在循环载下的裂纹扩展规律进行了研究，发现裂纹并非是由一条主裂纹循序渐进地发展，而是随着循环次数的增加，呈多条短裂纹陆续出现，弥散式发展的趋势，说明在高密度纤维的增强下，混凝土的疲劳断裂由脆性向专心性转变，根据实验及分析结果得出了两种纤维掺量下PHPFRC度件的Paris参数，并且用一个分维值D的变化描述了裂纹的演经过程，发现裂纹失稳扩展前的临界分维值D随着纤维掺量的增加而增加。

Fatigue Crack Propagation in Partially High Percentage Fiber Reinforced Concrete

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 a bending component. PHPFRC possesses much higher strength, rigidity, fatigue and fracture properties than the convention steel fiber concrete (SFRC), and its price is similar to that of SFRC. In this paper, some notched specimens of PHPFRC were tested under cycle load and the law of crack propagation was investigated. It was discovered that instead of a single crack propagation during the loading process, in the vicinity of the notch tip there were some short cracks gradually appearing at random state. It was also found that, with the reinforcement of fibers, the fatigue fracture of the PHPFRC specimens exhibited a tough manner. For two fiber volume fractions, the formula parameters based on the Law of Paris were given according to the experiment results. Besides, a fractal dimension D was used to describe the evolution of the cracks on the surface of the specimens, and it was found that, with the increasing of the fiber volume fraction, the critical fractal dimension D c increases.