钢桥面板纵肋-不锈钢复合钢材顶板焊接细节的疲劳性能研究

The adoption of the stainless steel clad plate (SSCP) in the roofs of the high-speed railway orthotropic steel decks (OSDs) has attracted wide interest. But as a kind of the new fatigue critical details, the long-term fatigue performance of rib-to-SSCP deck welded details in the OSDs remains to be verified. This research project aims at investigating the fatigue performance of the new rib-to-SSCP deck welded details in the levels of steel materials, constructional details and full-scale segmental models. Firstly, a series of standard tests will help to construct the empirical mechanical models, fracture toughness indices and fatigue crack propagation rate models. By using the cutting method and the thermal elastoplastic numerical simulation, the distribution models of the welding transverse residual stress regarding rib-to-SSCP deck details will be established. Then, based on the fatigue data from tests and 3D crack propagation analyses which consider the redistribution of the welding residual stress, the cracking mechanism will be revealed and an effective-notch-stress S-N curve will be proposed for the rib-to-SSCP deck welded joints. Finally, this study, on the basis of finishing the fatigue tests of full-scale segmental models and developing the numerical methods of fatigue cracking identification and crack propagation simulation against multi-target critical details, will explicitly determine the predominant fatigue crack failure mechanism and the relevant fatigue strength of the OSDs including rib-to-SSCP decks. The expected achievement of this project will theoretically and experimentally support the improvement of the current fatigue specification of the OSDs.

不锈钢复合钢板已开始被广泛用于高速铁路正交异性钢桥面顶板，纵肋-不锈钢复合钢材顶板焊接细节作为一种新型疲劳细节，其长期疲劳性能还有待验证。本项目从材料、构造细节到足尺节段模型的层面，系统展开其疲劳性能研究。进行系列标准材性试验，建立不锈钢复合钢材的力学本构模型、断裂韧性指标和疲劳裂纹扩展本构模型；采用切条法和热-弹塑性数值分析，构建纵肋-不锈钢复合钢材顶板细节的焊接横向残余应力模型；通过构造细节疲劳试验和计及焊接残余应力重分布的三维裂纹扩展数值分析数据补充，揭示纵肋-不锈钢复合钢材顶板细节的疲劳开裂机理、提出缺口应力S-N疲劳设计曲线；在开展顺桥向足尺模型疲劳试验和发展面向多目标危险细节的疲劳裂纹开裂识别与扩展失效数值模拟方法的基础上，明确包含纵肋-不锈钢复合钢材顶板细节正交异性钢桥面板的主控疲劳裂纹失效模式及其疲劳抗力，为完善正交异性钢桥面板的疲劳规范提供试验数据与理论技术支撑。

不锈钢复合钢材已被应用于国内20余座大型铁路钢桥的正交异性钢桥面板中，但是不锈钢复层带来的纵肋-顶板焊接细节顶板厚度增加、多次热轧过程对顶板基层桥梁钢材疲劳性能的影响以及采用复合钢材对该疲劳敏感细节焊接残余应力的改变，使得纵肋-不锈钢复合钢材顶板焊接细节的疲劳性能需要进一步探明，因此本项目系统性开展了疲劳性能和评估方法的研究，具体研究内容和研究成果包括：. （1）通过光滑圆棒试样的应变控制疲劳试验和标准C(T)试件的疲劳裂纹扩展试验，明确了不同温度环境对基层Q370qE钢材抵抗疲劳裂纹萌生和裂纹扩展能力的影响规律，并获得相应的疲劳性能表征参数；对比研究了Q235B碳钢及其304+Q235B不锈钢复合钢材单调拉伸、循环特性和低周疲劳性能，标定了可直接用于ABAQUS的Chaboche模型循环弹塑性本构参数。. （2）开展了系列桥梁钢等厚板对接焊缝接头、十字形非传力角焊缝接头和角焊缝搭接接头的高周恒幅疲劳试验，揭示了低温环境对其疲劳失效模式和抗力的影响。进行了共计8个U肋-316L+Q370qE复合钢材顶板焊接细节的热点应力测量、恒幅疲劳试验和沙滩条纹测试；然后基于热-弹塑性数值模拟和测试分析，确立了该新型焊接细节的横向残余应力分布；最后，获得了其热点应力集中系数、探明了疲劳失效模式。. （3）逐次展开了焊接接头和受弯钢梁的三维裂纹扩展分析，发展出了考虑混合型、多裂纹耦合扩展的疲劳分析方法；结合试验结果和数值模拟，揭示了纵肋-复合钢材顶板焊接细节的疲劳裂纹扩展机理，建立了热点应力疲劳S-N设计曲线。. 研究成果为保障采用不锈钢复合钢材顶板的正交异性钢桥面板的运营安全、完善相关疲劳设计规范提供了科学依据和技术支持，有力促进了不锈钢复合钢材在土木工程结构领域的应用和推广。