钢纤维混凝土的层裂特征

Spall fracture properties of steel-fiber-reinforced concrete

利用大直径Hopkinson压杆作为实验设备,通过试件后面的吸收杆应变波形分析了钢纤维增强混凝土的层裂特征。实验结果表明,钢纤维混凝土的层裂强度与钢纤维含量、混凝土压缩强度以及加载速率有关,并给出了经验公式。和素混凝土相比,钢纤维混凝土具有更高的层裂强度和更好的阻止损伤演化和裂纹扩展的能力。高速摄影结果表明,钢纤维混凝土层裂时,层裂段的飞离是由于陷在层裂段中应力波的动量效应,而且在层裂段中不易出现再次层裂的现象。这些现象和相同加载条件下素混凝土的层裂破坏有明显差别,说明钢纤维可以很好地提高混凝土抗层裂能力,其结论对相关的数值模拟和防护工程设计有重要意义。

A large-size Hopkinson pressure bar equipment was used to explore the spall fracture properties of steel-fiberreinforced concrete （SFRC） by analyzing the strain wave profiles in the absorption bar behind the specimen. The experimental results indicate that the spall strength of the SFRC is related to the steel-fiber volume fraction, the compressive strength of concretes and the load rate. And the proposed empirical formula shows the above relationship. Compared with the plain concretes, the SFRC has higher spall strength and more ability to prevent damage evolution and crack growth. The spall fracture processes of the SFRC recorded with a high-speed camera display that the flaking-off of scabs are due to the momentum effect of stress wave trapped in scabs and there lie few multiple fractures in scabs. These fracture phenomena of the SFRC differ distinctly from those of the plain concretes under the same loading conditions. It explains that steel fibers can improve the ability of concrete to prevent spall fracture. Investigated conclusion is helpful to the corresponding numerical simulation and engineering design.