基于统一相场理论和内聚力模型的钢纤维混凝土界面过渡区力学性能研究

为探究数值模拟中界面过渡区不同建模方式对钢纤维混凝土力学性能及其损伤、破坏过程的影响，基于统一相场理论和内聚力模型，针对含单根钢纤维的混凝土拉伸试验，采用2种方法建立钢纤维混凝土界面过渡区的数值计算模型，对比分析不同建模方式对钢纤维混凝土力学性能及其破坏形态的影响，并考察不同因素对含单根钢纤维的混凝土极限抗拉强度的影响。结果表明，对混凝土基体部分采用相场断裂模型、界面过渡区采用内聚力模型，无论是计算结果还是细观破坏形态，都具有较好的准确性和可靠性；初始裂缝位置取30 mm和35 mm的钢纤维混凝土抗拉强度比取25 mm时分别提高30.8%和75.7%,钢纤维埋置角度为15°,30°和45°时的钢纤维混凝土抗拉强度比0°时分别降低12.2%,30.8%和48.9%,钢纤维增强作用受初始裂缝位置及钢纤维埋置角度影响较大，受钢纤维直径影响相对较小。采用统一相场理论可降低分析的难度、保证较高的计算精度，为研究钢纤维混凝土的损伤、断裂过程提供了理论参考。

Study on mechanical properties of steel fiber reinforced concrete interface transition zone based on unified phase-field theory

In order to investigate the impact of different modeling methods of interface transition zone on the mechanical properties, damage and failure process of steel fiber reinforced concrete in numerical simulation, based on the unified phase-field theory and the cohesive zone model, two methods were used to establish a numerical calculation model of the interface transition zone of steel fiber reinforced concrete for the tensile test of concrete specimens containing a single steel fiber to compare and analyze the effects of different modeling methods on the mechanical properties and failure modes of steel fiber reinforced concrete, and the effects of different factors on the ultimate tensile strength of concrete containing a single steel fiber were investigated. The results show that the phase-field theory model for the matrix part and the cohesive zone model for the interface transition zone have good accuracy and reliability in both the calculation results and mesoscopic failure morphology; the tensile strength of steel fiber reinforced concrete with the initial crack location of 30 mm and 35 mm is 308% and 757% higher than that of 25 mm, respectively; the tensile strength of steel fiber reinforced concrete with the steel fiber embedding angle of 15°, 30°, and 45° is 122%, 308%, and 489% lower than that of 0°, respectively; the reinforcement effect of steel fiber is greatly influenced by the initial crack location and the embedding angle of steel fiber, and is relatively less influenced by the diameter of steel fiber. Adopting the unified phase-field theory can lower the analysis difficulty while guarantee higher computational accuracy, which provides theoretical reference for the study of the damage and fracture process of steel fiber reinforced concrete.