摘要
本文采用平面尺寸分别为3.6×3.0,3.0×2.5,2.4×2.0,1.8×1.5m的大型紧凑拉伸试件测试了混凝土断裂能G_F,结果表明,在所试验的试件尺寸范围内,所测试的断裂能G_F是一个与试件尺寸无关的稳定常数值,其平均值为498.4N/m.采用大面积布置电阻应变片测点辅以高速的计算机数据采集系统求得缝端应变场分布,其高应变集中区为一狭长的带状形,形态与光弹性贴片法和激光散斑法所得结果相一致,由上述方法发现:大型试件在失稳断裂前存在着主要裂缝的稳定扩展过程,其稳定扩展长度与大型试件的试件尺寸无关,平均值约为200mm.对此进行有效裂缝长度修正后求得的等效断裂韧度K_c也与本文的试件尺寸无关,其平均值为2.56MPam^1/2。
Tensile tests for determining fracture energy of concrete were conducted on huge compact specimens having different dimensions of 3.6×3.0, 3.0×2.5,2.4×2.0, and 1.8×1.5m, with the same thickness of 0.2m. Test results show that the measured values of fracture energy of concrete are independent upon the size of the specimen, and average 498.4N/m. The strain field near the tip of a notch was measured by strain gauges up to 172 pieces, the data of which were acquired and analysed by MTS' data collection system and computer system. It is found that the high strain concentration zone is a long narrow and irregular band, its shape is similar to that obtained by laser speckle photography and photoelastic coating. Moreover, it is found that there is an evident stable propagation process of a main crack in the specimen before unstable fracture occurrs. The average length of stable main crack propagation is independent upon the specimen size, and is about 200mm. The effective crack length is the sum of the length of stable crack propagation and the initial length of the notch. The effective fracture toughness of concrete K Icr is calculated based on the measured maximum load, the effective crack length by using formulas developed from liner elastic fracture mechanics. Similarly, the average value of the effective fracture toughness of concrete calculated in this way is also independent upon the size of specimen and is 2.563MPam^(1/2).
出处
《水利学报》
EI
CSCD
北大核心
1991年第11期17-25,共9页
Journal of Hydraulic Engineering
基金
水利水电科学基金
