Abstract: Through the experiment of 32 pull-out specimens with HRB600 high-strength steel bars and ultra-high performance concrete (UHPC), the influence of steel bar diameter, anchorage length and relative cover layer thickness on the interfacial bond performance was systematically analyzed, and the methods for calculating the critical anchorage length and bond strength were proposed. The research results indicate that the test specimens mainly exhibit three failure modes: unyielding pullout of the steel bar, yielding pullout of the steel bar, and breakage of the steel bar. When the relative cover layer thickness is constant and the steel bar diameter is 12mm, the anchorage length is increased from 48mm to 72mm, leading to an approximate increase of 94.1% in pull-out resistance and an improvement of 29.4% in bond strength. When the relative anchorage length remains the same and the relative cover layer thickness is about 3, the steel bar diameter is increased from 14 mm to 22 mm, and the pull-out resistance is improved approximately 158%. The lower limit of the critical anchorage length between high-strength steel bars and UHPC is found to be 5 times the diameter of the steel bar, and it tends to decrease as the diameter increases. It is recommended that the designed anchorage length should not be less than 10 times the diameter of the steel bar. Based on the statistical analysis of 41 sets of pull-out test data, a formula for calculating bond strength is established, which exhibits minor errors and is suitable for estimating the bond strength between high-strength steel bars and UHPC within the specified parameter range. Furthermore, when the bonding area remains relatively constant, appropriately increasing the thickness of the relative cover layer can help to enhance the bond strength.

Key words: bridge engineering; ultra-high performance concrete (UHPC); HRB600 high-strength steel bars; bonding performance; failure modes

摘要： 通过32个HRB600高强钢筋与超高性能混凝土(UHPC)拉拔试件的试验，系统分析了钢筋直径、锚固长度及相对保护层厚度对界面黏结性能的影响，并提出了临界锚固长度及黏结强度的计算方法。研究结果表明：试件主要分为钢筋未屈服拔出、钢筋屈服拔出和钢筋拔断这3种破坏模式。当相对保护层厚度一致、钢筋直径为12 mm时，锚固长度由48 mm增至72 mm，抗拔力提升约94.1%，黏结强度提高约29.4%；在相对锚固长度相同、相对保护层厚度约为3时，钢筋直径由14 mm增至22 mm，抗拔力提高约158%。高强钢筋与UHPC的临界锚固长度下限为5倍钢筋直径，且随直径增大呈减小趋势，建议设计锚固长度不小于10倍钢筋直径。基于41组拉拔试验数据的统计分析，建立了黏结强度计算式，该式误差较小，适用于参数范围内高强钢筋和UHPC的黏结强度估算。在黏结面积相对固定时，适当增加相对保护层厚度有助于提高黏结强度。

关键词: 桥梁工程； 超高性能混凝土； HRB600高强钢筋； 黏结性能； 破坏模式