增韧超高性能混凝土（STUHPC）加固RC桥梁的抗弯承载机理与计算理论

How to deal with the deteriorated or unsafe in-service reinforced concrete (RC) bridges has attracted global concern and the demand of safe and durable strengthening for these bridges is great. After learning the fact that it is impossible for conventional strengthening methods applied in RC flexural members to guarantee the durability, the innovative strengthening methods for RC flexural members by using the Super-Toughness Ultra-High Performance Concrete (STUHPC) will be developed. With UHPC being its matrix, STUHPC has excellent durability and further improved tensile strength, leading to a higher efficiency in flexural strengthening. With the methods as theoretical analysis, experimental tests and field tests for real bridges, numerical studies, the following basic works will be accomplished: the toughness-increasing mechanism of STUHPC, the flexural bearing mechanism of RC beams strengthened by STUHPC, and the shear failure mechanism at the STUHPC-RC interface under complex stress conditions will be revealed. The tensile constitutive formula, failure criterion and the theoretical model for shrinkage calculation of STUHPC, the calculation theory for the cracking and flexural strength of the reinforced beams, and the calculation method of the interfacial shear capacity will be proposed. The temperature effect across the STUHPC-RC composite section caused by steam curing will be figured out. Based on the studies, the core calculation theories and design methods can be developed for flexural members in RC bridges strengthened by STUHPC, which will fill the blank of research on UHPC flexural strengthening in China and lay a solid scientific foundation to realize the comprehensive reinforcement of bending strength and durability protection for in-service RC bridges.

危旧RC桥梁处治已成为全球性问题，安全、耐久的加固维修需求巨大。项目针对常规RC桥梁抗弯加固耐久性无法保证的现状，基于UHPC的超高抗拉强度和超强耐久性，并通过增韧UHPC来提高抗弯加固效率，研究增韧超高性能混凝土（STUHPC）抗弯加固RC桥梁新方法。项目采用理论、试验与实桥测试、数值分析等方法完成以下基础性工作：揭示STUHPC加固材料综合增韧机理、STUHPC-RC加固梁抗弯承载机理和复杂受力状态下组合STUHPC-RC结合面剪切破坏机理；提出STUHPC拉伸本构关系、破坏准则和收缩计算模型、加固梁抗裂与抗弯承载力计算理论以及STUHPC-RC结合面抗剪计算方法；明确STUHPC-RC复合截面的热养温度效应；最终建立STUHPC抗弯加固RC桥梁的核心计算理论与设计方法。项目研究成果将填补国内UHPC抗弯加固的研究空白，为在役RC桥梁实现抗弯补强+耐久防护的综合加固奠定坚实的科学基础。

危旧RC桥梁处治已经成为了当今世界的重大问题，损伤桥梁维修加固迫在眉睫，任务繁重。本项目以提升RC桥梁结构抗弯加固耐久性为切入点，利用UHPC的超高韧性和超强耐久性，研发了增韧超高性能混凝土（STUHPC）加固RC桥梁抗弯新方法。本项目主要从UHPC综合增韧方法、加固后UHPC-RC组合受弯构件抗弯性能、UHPC-NSC湿接缝与界面粘结性能以及高早强UHPC材料性能研究等方面开展了研究工作。研究结果表明：提出的配筋、纤维化学处理与纤维定向的增韧方法可进一步改善UHPC受拉力学行为并提高加固效率；基于STUHPC的各种抗弯加固方法有效提高了损伤RC结构的刚度、抗裂性能与承载能力，加固交界面粘结效果总体较好，有效确保了加固层与RC结构共同受力；探明了不同参数对UHPC-NSC界面粘结性能影响规律，合理施工的UHPC-NSC界面抗剪、抗拉强度高，表明UHPC在加固及湿接缝中应用可行有效；UHPC-RC组合梁抗裂、裂缝宽度、抗弯（剪）承载力计算理论与试验吻合良好，UHPC-NSC界面抗剪承载力计算方法可指导界面构造设计；高早强UHPC在不同自然养护条件下强度发展速度均较快，表明高早强UHPC在加固与大跨梁桥悬臂拼装快速化施工中具有应用前景。本项目的STUHPC加固技术、界面粘结性能研究、相应的计算理论和设计方法为实现既有RC结构高效耐久加固提供了可行方案和技术支撑，丰富了RC桥梁加固体系，促进了UHPC-RC组合结构与UHPC湿接缝的发展。项目研究成果为UHPC工程应用提供了科学依据，社会经济效益显著，具有重要的推广应用价值和科学意义。