钢-UHPC组合桥面板典型焊接节点疲劳性能研究

As a new type of bridge deck structure, the steel-UHPC composite bridge deck has great potential to replace the traditional orthotropic steel deck. However, the research on its fatigue performance is not in-depth. This project aims at systematically investigating the fatigue behavior and failure modes for typical welded connections of steel-UHPC composite bridge deck. Firstly, by employing both experimental and numerical analyses, the hot-spot stress characteristics of the connections will be determined, followed by exploring the influences of various UHPC layer parameters on hot-spot stress and stress concentrate factors (SCF) using numerical simulations. In addition, high-cycle fatigue tests and crack propagation simulations will be conducted, and the fatigue failure process and damage mechanisms will be revealed with respect to crack initiation, propagation and fracture morphology, then the applicability of the existing hot-spot stress S-N curves will be verified, and the fatigue design method based on hot spot stress will also be proposed. Furthermore, an analytical crack propagating mode will be established using Linear-Elastic Fracture Mechanics (LEFM), the ultimate fatigue failure criterion considering degradation of structural rigidity and load carrying capacity of the connections will be proposed based on nonlinear FEA of the connection models with fatigue cracks. Finally, the prediction approach of residual fatigue life for the cracked welded connections of steel-UHPC composite bridge deck will be developed, and recommendations for engineering application will also be proposed based on the above research results. The study will provide a scientific basis for the fatigue design of steel-UHPC composite bridge deck, and help to promote the practical application of this new composite deck structure in bridge engineering.

钢-UHPC组合桥面板是一种新型桥面结构体系，具有取代传统正交异性钢桥面板的巨大潜力，但其疲劳性能的研究尚不深入。本项目围绕钢-UHPC组合桥面板典型焊接节点的疲劳性能开展系统研究。首先采用试验和数值模拟方法对节点的热点应力特征开展研究，分析UHPC层参数对热点应力及应力集中系数（SCF）的影响规律；然后开展节点的高周疲劳试验和裂纹扩展数值模拟，分析裂纹萌生、扩展直至断裂的全过程以及断口特征，揭示节点疲劳破坏过程和机理，同时验证现有热点应力S-N曲线的适用性，并提出基于热点应力的疲劳设计方法；进一步通过断裂力学理论推演和含裂纹节点的非线性有限元分析，建立节点的疲劳裂纹扩展速率模型和疲劳失效判定准则，提出钢-UHPC组合桥面板典型焊接节点开裂后剩余疲劳寿命评估方法；最后给出工程应用建议。研究成果将为钢-UHPC组合桥面板的抗疲劳设计提供科学依据，有助于推动此新型桥面结构在桥梁工程的实际应用。

超高性能混凝土UHPC是一种极具潜力的新型工程材料，在钢桥结构的疲劳加固领域有广阔的应用前景。本项目系统地对钢-UHPC组合桥面板典型焊接节点的疲劳性能开展了研究。建立了钢桥面板的整体有限元模型，确定了钢桥面板中容易发生疲劳破坏的典型焊接构造细节。设计加工了U肋-盖板-横隔板焊接节点试件以及UHPC铺层的构造细节，掌握了UHPC铺层的制备养护方法，制备了钢-UHPC组合RDF节点试件。开展了UHPC加固RDF节点以及裸板RDF节点的静力试验，明确了节点关键部位的热点应力分布特征以及UHPC对热点应力的降低效果。实施了UHPC加固及未加固RDF节点的高周疲劳试验，通过对疲劳试验所得的节点疲劳裂纹萌生扩展、疲劳寿命、刚度退化、破坏模式等性能指标的分析，揭示了节点疲劳破坏过程及破坏机理，定量地评估了UHPC铺层对钢桥面板的疲劳加固效果。基于UHPC加固试件的高周疲劳试验数据，确定了IIW疲劳设计指南推荐的热点应力S-N曲线。基于ABAQUS和FRANC 3D开展了钢桥面板典型焊接节点的疲劳裂纹扩展数值模拟，定量分析了典型焊接节点的疲劳裂纹扩展中的应力强度因子、裂纹扩展速率、裂纹扩展长度以及荷载循环次数等疲劳相关参数，深层次揭示了钢桥面板的疲劳破坏过程和机理。本项目的研究成果可以为UHPC加固正交异性钢桥面板提供理论依据和方法参考，从而促进钢-UHPC组合桥面体系在桥梁工程中的实际应用。