In this study, the efficiency of using high strain hardening ultra high performance concrete (HSH-UHPC) on strengthening existing reinforced concrete beams was investigated by experimental and analytical means. First, the HSH-UHPC constitutive relation was obtained using “Dog-bone” specimen under uniaxial tensile test. Then three reinforced concrete beams strengthened with HSH-UHPC layers and one control beam were tested under flexural loading. The midspan deflection, strain distribution, crack propagation and failure mode of the tested beams were described in detail. The tests verified that the middle section of UHPC-NC composite beam basically conforms to the assumption of plane section. The flexural resistance of composite structure can be greatly improved by installing proper longitudinal reinforcement in UHPC layer. Meanwhile, numerical studies have been conducted on the tested beams using the experimentally obtained constitutive relations. The result shows that the finite element analysis results are consistent with the test results. Finally, a contribution factor for the HSH-UHPC layer on the flexural resistance of the composite beam was proposed. At the same time, it is found that the contribution efficiency of the HSH-UHPC to the flexural resistance increases with longitudinal reinforcement ratios in the HSH-UHPC.

中文翻译：

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高应变硬化超高性能混凝土加固钢筋混凝土梁抗弯试验研究与计算方法

在这项研究中，通过实验和分析手段研究了使用高应变硬化超高性能混凝土 (HSH-UHPC) 加固现有钢筋混凝土梁的效率。首先，在单轴拉伸试验下使用“狗骨”试样获得 HSH-UHPC 本构关系。然后在弯曲载荷下测试了三根用 HSH-UHPC 层加固的钢筋混凝土梁和一根控制梁。详细描述了试验梁的跨中挠度、应变分布、裂纹扩展和破坏模式。试验验证了UHPC-NC组合梁中间截面基本符合平面截面假设。通过在UHPC层中安装适当的纵向钢筋，可以大大提高复合结构的抗弯性能。同时，已经使用实验获得的本构关系对测试梁进行了数值研究。结果表明，有限元分析结果与试验结果一致。最后，提出了 HSH-UHPC 层对组合梁抗弯性能的影响因子。同时，发现 HSH-UHPC 对弯曲阻力的贡献效率随着 HSH-UHPC 中纵向配筋率的增加而增加。