无腹筋UHPC梁桥剪切疲劳失效机理与计算理论

No reinforced and low reinforced ultra high performance concrete (UHPC) bridge system is a development trend for bridges in the future. Engineering practice has revealed that the shear fatigue performance of UHPC bridges without shear reinforcement is a key science problem. Essential difference on shear fatigue exists between UHPC bridges without shear reinforcement and conventional concrete bridges due to the fatigue evolution difference between the fiber bridging effect and shear reinforcement stress. The project primarily focuses on the fatigue failure mechanism of UHPC from micro-meso-macro multi-scale perspectives. On the micro-meso scale, the evolution mechanism of interfacial fatigue damage between fibers and matrix is going to be investigated, and a theoretical bond slip model will be established. On the macro-meso scale, the shear fatigue crack propagation mechanism and the fatigue failure mechanism of UHPC beams without shear reinforcement will be studied, aiming at revealing the substitution mechanism between fibers and shear reinforcement, and shear fatigue failure mechanism. Finally, the bridging variable between macroscale and mesoscale fatigue performances will be proposed and the corresponding quantitative approach will be provided. As a result, a meso-macro scale integrated shear fatigue calculation theory of UHPC beams without shear reinforcement will be established. This project is an applied basic research and has significant theoretical significance in the popularization and application of new UHPC bridges.

无腹筋或低配筋是超高性能混凝土（Ultra high performance concrete, UHPC）在桥梁工程中应用的一个重要趋势，剪切疲劳问题是无腹筋UHPC梁工程化过程中亟待解决的关键科学问题。纤维“桥联作用”与箍筋应力疲劳演化规律的差异使无腹筋UHPC梁剪切疲劳问题与普通混凝土梁有本质区别。项目拟从微-细-宏观多尺度角度对UHPC材料与结构疲劳失效机理进行试验和理论研究。从微细观尺度研究并揭示纤维与UHPC基体界面疲劳损伤演化机理，建立粘结滑移理论模型。从宏细观尺度研究无腹筋UHPC梁剪切疲劳裂缝扩展机制，揭示纤维等代腹筋抗剪作用与结构剪切疲劳失效机理。研究界面疲劳粘结特性与结构疲劳性能的桥联变量及量化方法，建立无腹筋UHPC梁宏细观一体化抗剪疲劳计算理论。本课题是衔接材料科学微细观研究成果和宏观结构计算理论的应用基础研究，对新型无腹筋UHPC梁桥的应用具有重要的理论价值。

本项目是针对无腹筋UHPC梁桥剪切疲劳失效机理与计算理论的应用基础研究，UHPC的优异力学性能和耐久性能有望攻克传统混凝土桥梁的开裂下挠、服役寿命短等难题，实现桥梁更高韧性、更长寿命和节材减碳的发展目标，但剪切疲劳问题是无腹筋UHPC梁工程化应用过程中亟待解决的关键科学问题。基于此，本项目开展了纤维与UHPC基体间疲劳粘结机理及粘结滑移本构、无腹筋UHPC梁剪切疲劳裂缝扩展机制及疲劳失效机理、无腹筋UHPC梁宏细观一体化抗剪疲劳计算理论系列研究，取得的创新性成果为：.1）揭示了静载与疲劳荷载下UHPC与纤维、钢筋多重界面粘结机理，提出了UHPC细观力学本构模型和钢筋-UHPC界面粘结强度计算模型，为UHPC桥梁结构设计理论的构建奠定基础。.2）阐明了无腹筋UHPC梁剪切疲劳动态裂缝扩展规律，发现了UHPC梁半延性-半脆性破坏特征，揭示了无腹筋UHPC梁剪切疲劳失效机理与破坏模式，建立了疲劳寿命、剩余承载力与加载次数、应力水平等的关系。.3）首次提出有效纤维抗剪区域概念，建立了无腹筋UHPC梁“纤维-基体分离”疲劳剩余受剪承载力计算模型，为相关规范的制定和工程应用提供有力支撑。.经过三年的研究，项目实现了既定目标，在Engineering Structures、Computers and Concrete、《建筑结构学报》、《中国公路学报》等国内外权威期刊上发表论文20篇，其中SCI收录16篇、EI收录4篇。授权国家发明专利3项、实用新型专利2项，人才培养成效显著。该项目聚焦无腹筋UHPC梁桥剪切疲劳性能，在国内开辟了一个新的研究方向，与UCLA、UTK世界知名高校相继展开合作，且在UHPC领域顶级会议International Conference on Ultra-high Performance Concrete Materials and Structures做专题报告，在国际上产生了较大影响。