Ultra-high performance concrete (UHPC) is an advanced class of concrete materials that show superior mechanical and durability performance. While several studies have investigated the bond-slip behavior of steel reinforced UHPC using pullout tests, very limited information is available on the bond-slip behavior of reinforced UHPC from beam-type tests, which produce flexural stress states commonly seen in structural members. This study experimentally examines the local bond-slip behavior of reinforced UHPC using beam-end tests. The test variables include UHPC material designs (one low-cement, green UHPC mix and one typical UHPC mix), fiber volumes (0%, 0.5%, and 1.0%), cover thickness (16 mm–51 mm), steel bar sizes (16 mm–32 mm), and test ages (3 days and 50 days). A total of thirty-two tests are conducted. While the non-fiber UHPC specimens fail in a brittle manner due to splitting failure, all fiber-reinforced UHPC specimens exhibit confined splitting failure and ductile bond-slip responses. The peak bond strength is found to exhibit a linear relationship with the cover-thickness-to-bar-diameter ratio and the square root of UHPC compressive strength. Furthermore, a local bond-slip model is developed, which includes a new bond-strength prediction method that predicts the experimental results with a mean absolute error of 7.6%. Finally, this local bond-slip model is combined with a partial interaction model to explore the global bond stress variations under different embedment lengths and flexural states. Equations are proposed to predict the development length that can lead to reinforcement yielding with minimized bonded length or minimized global slip.

超高性能混凝土 (UHPC) 是一种先进的混凝土材料，具有卓越的机械性能和耐久性能。虽然有几项研究使用拉拔试验研究了钢增强 UHPC 的粘结滑移行为，但梁型试验中关于增强 UHPC 的粘结滑移行为的信息非常有限，梁型试验会产生结构构件中常见的弯曲应力状态。本研究通过梁端试验检验了增强 UHPC 的局部粘结滑移行为。测试变量包括 UHPC 材料设计（一种低水泥、绿色 UHPC 混合物和一种典型 UHPC 混合物）、纤维体积（0%、0.5% 和 1.0%）、覆盖层厚度（16 mm–51 mm）、钢筋尺寸(16 mm–32 mm) 和测试年龄 (3 天和 50 天)。总共进行了三十二次测试。虽然非纤维 UHPC 试样由于分裂破坏而以脆性方式破坏，但所有纤维增强的 UHPC 标本都表现出有限的分裂破坏和延展性粘结滑移响应。发现峰值粘合强度与覆盖层厚度与杆直径比和 UHPC 抗压强度的平方根呈线性关系。此外，还开发了一种局部粘结滑移模型，其中包括一种新的粘结强度预测方法，该方法以 7.6% 的平均绝对误差预测实验结果。最后，将该局部键滑模型与部分相互作用模型相结合，探索不同嵌入长度和弯曲状态下的全局键应力变化。