冲击荷载作用下纤维混凝土动态劈裂试验与分析

A dynamic splitting test and analysis of fiber reinforced concrete under impact load

为研究不同纤维材料对混凝土动态劈裂力学性能的影响以及作用效果的差异,采用直径为100 mm的分离式霍普金森压杆试验装置和V2512超高速数字摄像机,分别对素混凝土、棕榈纤维混凝土以及钢纤维混凝土试件进行了巴西圆盘动态劈裂试验研究。通过DIC软件技术分析不同纤维混凝土试件的破裂过程和裂纹扩展规律,获得不同纤维混凝土试件的动态抗拉性能与动态断裂韧性等。试验与分析结果表明:在相同冲击荷载作用下,纤维的掺入能够提高混凝土的抗冲击韧性,减少试件加载端部因应力集中而产生的崩坏现象,延缓试件的破坏时间并有效抑制裂纹的扩展,其中钢纤维对混凝土的阻裂作用时间长于棕榈纤维。在相同荷载作用时间情况下,棕榈纤维混凝土和钢纤维混凝土的峰值应变都低于素混凝土。钢纤维的掺入能够显著阻滞混凝土试件内部的破裂过程,损伤变量变化相对缓慢,试件开裂后在相同裂纹宽度下,钢纤维混凝土具有更大的残余应力。

To study the influence of different fiber materials on the dynamic splitting mechanical properties of concrete and the differences in their effects,using 100 mm diameter split Hopkinson pressure bar test device and V2512 ultra high speed digital camera,dynamic Brazilian disc splitting tests were conducted on plain concrete,palm fiber concrete,and steel fiber concrete specimens.Analyzed the fracture process and crack propagation law of different fiber reinforced concrete specimens using DIC technology,obtained dynamic tensile properties and dynamic fracture toughness of different fiber reinforced concrete specimens.The experimental and analytical results show that:Under the same impact load,the addition of fibers can improve the impact toughness of concrete,reduce the collapse phenomenon caused by stress concentration at the loading end of the specimen,delay the failure time of the specimen,and effectively suppress the propagation of cracks,steel fibers have a longer crack resistance effect on concrete than palm fibers.Under the same loading time,the peak strain of palm fiber reinforced concrete and steel fiber reinforced concrete is lower than that of plain concrete.The addition of steel fibers can significantly hinder the internal failure process of concrete specimens,and the change in damage variables is relatively slow,after the specimen cracks,steel fiber reinforced concrete has greater residual stress under the same crack width.