Providing a representative and reliable tensile constitutive model for ultra-high-performance concrete (UHPC) has been challenging in the past due to the absence of standardised test methods. In this paper, the authors have proposed a unified constitutive model calibrated to the most commonly used types of steel fibres within the practical range of fibre content. While the novel model serves as the core, a comprehensive experimental program and results are pivotal for validating the model’s effectiveness. In pursuit of this, the recently approved AASHTO standard test method was employed to offer standardised and comprehensive experimental insights into the direct tensile behaviour of mono/hybrid fibre-reinforced UHPC. A set of predictive equations, derived either empirically or from simple mechanics, to predict the key parameters defining the mechanical constitutive law of UHPC material subjected to uniaxial tension are introduced based on experimental findings. The proposed predictive equations and constitutive model exhibited robust predictions of tensile behaviour, aligning well with both the test results and additional independently tested UHPC specimens.

中文翻译：

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单/混合纤维增强超高性能混凝土（UHPC）的统一拉伸本构模型

由于缺乏标准化的测试方法，为超高性能混凝土（UHPC）提供具有代表性且可靠的拉伸本构模型在过去一直具有挑战性。在本文中，作者提出了一个统一的本构模型，在纤维含量的实际范围内针对最常用的钢纤维类型进行了校准。虽然新模型是核心，但全面的实验方案和结果对于验证模型的有效性至关重要。为了实现这一目标，采用最近批准的 AASHTO 标准测试方法，为单一/混合纤维增强 UHPC 的直接拉伸行为提供标准化和全面的实验见解。基于实验结果，引入了一组根据经验或简单力学推导出来的预测方程，用于预测定义 UHPC 材料在单轴拉伸下的力学本构定律的关键参数。所提出的预测方程和本构模型表现出对拉伸行为的稳健预测，与测试结果和其他独立测试的 UHPC 样本很好地吻合。