由钢筋超高性能混凝土（RU）圆管与钢筋（普通）混凝土（RC）芯柱组成的RU-RC柱是一种新型组合结构。RU圆管既是施工中免拆除的模板，又是组合柱的保护层和结构层，可充分发挥超高性能混凝土（UHPC）的超高强度与良好耐久性，为RC芯柱提供紧箍力，提高组合材料使用效率。组合柱具有受力性能好、耐久性高、施工方便等优点，在跨海大桥桥墩中具有良好的应用前景。本项目通过模型试验、数值计算和理论分析相结合的研究手段，开展RU圆管受力性能、UHPC与核心混凝土之间界面性能、RU-RC组合柱受力性能与设计方法研究，探明组合柱协同工作机理、破坏模式和开裂失效机制，提出极限荷载与开裂荷载计算公式，探讨合理构造措施。研究抓住新型组合结构理论基础和实际应用的关键问题，将局部构件、界面和整体结构的研究相结合，将承载力极限状态与使用极限状态相结合，建立组合柱设计计算理论，为推动UHPC材料和组合结构的科技进步做出贡献。

A new composite column (RU-RC composite column) is proposed, which is made of reinforced ultra-high performance concrete (RU) cylindrical pipe and reinforced concrete (RC) core. RU pipe is not only the construction formwork without dismantled for composite columns, but also applied as the protective coating and structural layer of columns. Due to the ultra-high strength, good durability and confining efficiency of the UHPC cylindrical pipe, the new composite column can fully utilize the potential of UHPC. RU-RC composite column has the advantages of composite action, construction ease, and greater sustainability. RU-RC is particularly suited for the piers of sea-crossing bridges. Through experimental tests, numerical analysis and theoretical modeling of interfacial properties between RU and RC, RU cylindrical pipes, and RU-RC composite columns as proposed in this project, the details of composite action, cracking mechanisms, and failure modes of RU-RC composite column will be revealed. Finally the simplified calculation methods of the first cracking and ultimate load for RU-RC composite column will be proposed, and the suitable configuration will be discussed. During the study in this project, the integration of theoretical understanding and practical application of RU-RC composite column will be explored. By combining the interfacial properties between RU and RC, the superior mechanical performance of RU cylindrical pipe and the global structural behavior of RU-RC composite column, as well as considering limit state and service state design requirements, the fundamental design theory of RU-RC composite column will be established. The research outcomes will contribute to the development of UHPC materials and their structural applications, and the advancements of the science and technology of composite structure.