为探索吊装重量轻、施工便捷、耐久性强的新型组合箱梁，设计制作了以超高性能混凝土（UHPC）为腹板和底板，以普通混凝土（RC）为顶板的新型预应力RC-UHPC组合箱梁。开展受弯试验和有限元参数分析，探究试件的损伤机理和破坏模式。结果表明：试件破坏模式为适筋破坏，表现为受拉纵筋屈服及部分预应力筋断裂后，纯弯段RC顶板被压碎；UHPC抗拉强度、预应力筋配筋率对抗弯承载力影响较大；试件腹板纵向应变在高度方向上基本符合平截面假定。结合理论分析，提出抗弯承载力计算公式，利用所提出公式对试验构件及有限元分析模型的抗弯承载力进行计算，公式计算值与试验值、有限元计算值之比分别为1.014、0.960，具有较高的计算精度。相关研究可为预应力RC-UHPC组合箱梁在实际工程的推广及规范的制定提供理论依据。

In order to explore a new type of composite box girder with light lifting weight, convenient construction and high durability, a new type of prestressed RC-UHPC composite box girder with ultra-high performance concrete (UHPC) as web and bottom plate and plain concrete (RC) as top plate was designed and fabricated. Flexural tests and finite element analysis were carried out to investigate the failure mechanism and failure mode of the specimens. The results show that: the failure mode of the specimen is suitable reinforcement failure, which shows that the RC of the top slab in the pure bending section is crushed after the yield of the longitudinal tensile reinforcement and the fracture of some prestressing reinforcement; the tensile strength of UHPC and the reinforcement ratio of prestressing tendons have a greater influence on the flexural strength; the longitudinal strain of the web of the specimen is basically consistent with the assumption of a flat section in the height direction. Combined with the theoretical analysis, the formulas for calculating the flexural strength were proposed. The ratio of the calculated value to the test value and the calculated value of the finite element is 1.014 and 0.960, respectively, which has a high calculation accuracy. This study can provide a theoretical basis for the promotion of prestressed RC-UHPC composite box girder in practical projects and the formulation of specifications.

U443.22

福建省自然科学基金项目(2019J01779)；福建省交通科技计划项目(202024)