初始应力作用下钢桥面板疲劳失效准则研究

The orthotropic steel deck is widely used in bridge engineering. The crack damage is inevitable for its structural properties and will threaten the operation safety of the bridge once cracks happen. There are several assessment methods judging the failure of the bridge while the assessment results show deviation from the practical conditions for the current fatigue assessment overlooks the influence of initial stress on steel decks.In this research,the fatigue failure principle of the steel bridge deck considering the effect of initial stress was studied through fatigue experiment and theoretical analysis. First, the fatigue experiments of steel deck considering the effect of initial stress in directions of parallel and vertical to the weld were carried out. In combination of theoretical analysis, the influence of macroscopic initial stress on the fatigue behavior was studied.Second, the fatigue experiment of the steel deck with local initial stress was launched to study the influence of local initial stress on fatigue behavior in consideration of the change of residual stress. Third, the law of fatigue crack growth of the steel deck as well as the fatigue strength under the initial stress was studied according to the experiment and theoretical analysis. Finally, a reasonable assessment principle of fatigue failure was set up based on the current theories and modified for the influence of initial stress to develop the assessment principle of fatigue failure considering the initial stress. The research conclusion can serve as references for the accurate assessment of the fatigue behavior of the steel bridge deck.

正交异性钢桥面板广泛应用于桥梁工程，由于自身构造原因，疲劳损伤难以避免，一旦疲劳开裂将直接威胁桥梁运营安全。目前，裂纹失效判定方法众多，且未充分考虑初始应力的影响，评估结果与实际存在偏差。本研究通过疲劳试验和理论分析，针对初始应力作用下的钢桥面板疲劳失效准则进行研究。首先，考虑平行和垂直于焊缝方向的两种宏观初始应力，进行钢桥面板疲劳试验，结合理论分析，研究宏观初始应力对疲劳性能的影响。其次，考虑局部初始应力进行钢桥面板疲劳试验，通过改变残余应力分布，研究局部初始应力对疲劳性能的影响。再次，根据试验和理论分析结果，研究初始应力作用下的钢桥面板疲劳扩展规律和疲劳强度。最后，基于现有理论，建立合理的疲劳失效判断准则，并针对初始应力影响进行修正，建立考虑初始应力影响的疲劳失效判断准则。研究结论可为钢桥面板疲劳性能精确评估提供理论参考。

钢桥面板因其轻质、高强、经济等优点广泛应用于国内外各类桥梁中，然而钢桥面板构造复杂，疲劳影响因素众多，钢桥面板焊缝连接位置在成桥以后往往处于复杂受力状态，存在多种初始应力作用。现有疲劳设计和评估中未充分考虑初始应力的影响，导致疲劳设计与评估的受力条件与实桥情况有所差异，从而影响桥梁的运营安全。失效准则是钢桥面板疲劳设计与评估的基础，现有的疲劳失效理论及失效状态的定义众多，导致对疲劳失效的认识缺乏统一的失效准则。.为研究初始应力作用下钢桥面板顶板焊缝的疲劳特征及评估方法，本研究结合疲劳试验和数值模拟开展了系统研究。采用振动型疲劳试验机和初始应力加载装置对近70个试件施加疲劳荷载和初始应力。利用目视检查法、指示法和显微镜法等手段研究了疲劳裂纹萌生位置、扩展路径和断面形状。利用应变仪记录初始应力和关键测点应力在加载过程中的变化。通过对比疲劳弧线、疲劳沟线、瞬断区等断口特征，揭示了初始应力下疲劳开裂及裂纹扩展机理。在此基础上，考虑初始应力对顶板焊缝疲劳性能影响的量化方法，提出了顶板疲劳断裂的评估指标，并建立了钢桥面板顶板焊缝疲劳裂纹的数学模型。通过初始应力大小、板厚、焊接类型等参数对比分析了不同参数下的疲劳寿命，评估了现有疲劳评估方法在实际应用中的准确性和适用性。结合有限元模拟，对已有钢桥面板疲劳失效准则进行初始应力修正，提出考虑初始应力影响的钢桥面板疲劳失效准则。研究成果可为钢桥面板疲劳性能精确评估提供理论参考。