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为确定混凝土材料的真实断裂韧度,分析了几种混凝土断裂韧度尺寸效应规律,提出了三点弯曲梁测试的起裂韧度KIiCni和失稳韧度KIuCn尺寸效应表达式及真实断裂韧度的趋势线外推法。采用在建桥梁上部结构用高强混凝土制作了6组几何相似,最大尺寸为长×高×宽=1280 mm×320 mm×160 mm,总共18根带预制缺口的素混凝土平面应变三点弯曲试件,由载荷-加载点位移、载荷-裂缝口张开位移曲线和裂缝前沿应变等计算得到双K韧度值。结果表明,混凝土双K韧度符合现在提出的尺寸效应规律,而趋势线外推法可用于测定工程中大尺寸混凝土的断裂韧度。
In order to determine the real fracture toughness of concrete, the size-effect law of fracture toughness of concrete was analyzed. The dimensional effect of fracture toughness KIiCni and instability toughness KIuCn in three-point bending test and the real fracture toughness Trendline extrapolation. In the construction of the superstructure of the bridge, six sets of high-strength concrete are used to make three sets of plain concrete plane strain three-point bending specimens with the same geometry and the maximum dimensions of length × height × width = 1280 mm × 320 mm × 160 mm with a total of 18 precast notches , The double-K toughness value is obtained from the load-displacement of loading point, the load-crack opening displacement curve and the crack front strain. The results show that the dual-K toughness of concrete conforms to the size effect law proposed now, while the trend line extrapolation method can be used to determine the fracture toughness of large-size concrete in engineering.