同时确定钢纤维高强混凝土的断裂韧度及拉伸强度

考虑钢纤维高强混凝土试件细观非均质性对宏观断裂的影响机制，将钢纤维掺量、长度、直径及钢纤维抗拉强度等细观层面的钢纤维特征参数，引入钢纤维高强混凝土宏观断裂模型的虚拟裂缝扩展量的具体计算公式，从而发展了考虑钢纤维特性的可同时确定钢纤维高强混凝土的断裂韧度与拉伸强度的模型及方法。采用变化参数为钢纤维掺量和混凝土水灰比的三点弯曲试件，基于所提模型，同时确定了钢纤维高强混凝土的断裂韧度与拉伸强度，确定值与试验拉伸强度值以及尺寸效应模型计算的断裂韧度吻合良好。基于测试数据离散性为钢纤维高强混凝土固有属性的事实，采用确定的断裂韧度及拉伸强度，建立起钢纤维高强混凝土塑性——准脆性——线弹性不同结构断裂模式的±20%全曲线，其可涵盖实验室条件下的所有试验数据。该文所提模型及方法适用于钢纤维高强混凝土及高强混凝土，可为钢纤维高强混凝土等复合材料真实断裂韧度与拉伸强度的确定，及个性化结构断裂破坏的预测等关键科技问题提供依据。

SIMULTANEOUSLY DETERMINING FRACTURE TOUGHNESS AND TENSILE STRENGTH OF STEEL FIBER HIGH-STRENGTH CONCRETE

Considering the influence mechanism of steel fiber high-strength concrete specimens meso heterogeneity on macroscopic fracture, the calculation formula for fictitious crack growth of teel fiber high-strength concrete macroscopic fracture model is improved by accounting for steel fiber characteristic parameters at meso level of steel fiber content, length, diameter and steel fiber tensile strength, which provides the model and the method to consider steel fiber characteristics for simultaneously determining the fracture toughness and tensile strength of steel fiber high-strength concrete. Based on the proposed model, the fracture toughness and tensile strength of steel fiber high-strength concrete are simultaneously determined by using three point bending specimens with different steel fiber content and water cement ratio of concrete, which are in good agreement with the tensile strength obtained by experiment and the fracture toughness from the SEM. Based on the fact that the discreteness of the test data is the inherent property of steel fiber high-strength concrete, the ±20% complete curves of steel fiber high-strength concrete describing different structural fracture modes of plastic, quasi-brittle and linear elastic are established by using the determined material parameters (fracture toughness and tensile strength), which can cover all test data under laboratory conditions. The model and the method proposed in this paper are applicable to steel fiber high-strength concrete and high-strength concrete, and can provide a basis for the determination of real fracture toughness and tensile strength of composite materials such as steel fiber high-strength concrete, the prediction of fracture failure of individualized structures and other key scientific and technological issues.