闭口肋轻型组合桥面板疲劳性能研究

以洞庭湖二桥闭口肋轻型组合桥面板为对象，研究了焊接疲劳开裂细节，并引入热点应力法计算得到其应力幅值。对比分析后发现，与横梁相关的疲劳细节仍然有较高的应力幅值。针对国内外规范中典型横梁闭口肋开孔形式以及不同横梁厚度，开展有限元分析，从而进一步优化各疲劳细节的受力状态。数值分析结果表明：与传统钢桥面板相比，闭口肋轻型组合桥面板能大大降低各典型疲劳细节的应力幅值，降幅可达23.2%~86.1%|Eourcode3规范推荐的铁路桥梁孔型较优|横梁厚度的变化能大大改善横梁处相关疲劳细节的应力水平。足尺模型疲劳试验表明，洞庭湖二桥横梁圆弧过渡处疲劳细节强度满足设计要求|通过对STC层与钢顶板之间三种不同黏结方式的分析表明，界面黏结性的增强能改善轻型组合结构的受力性能。

Study on fatigue performance of lightweight composite bridge deck with closed ribs

Taking the Second Dongting Lake Bridge (a suspension bridge with a lightweight composite bridge deck) as an example, hot spot stress approach is used to study the fatigue-cracking details of welds and calculate the stress ranges. Comparative analyses show that the stress ranges of fatigue details related to diaphragms are still very high. In order to optimize the mechanical behavior of fatigue details, parameter analyses are performed to investigate the typical cutout types of closed ribs of diaphragms which are adopted in domestic and foreign codes and the thicknesses of various diaphragms based on finite element analysis. The results reveal that, compared with traditional steel bridge deck, the stress ranges of fatigue details of lightweight composite bridge deck with closed ribs can be reduced by 21.7%~85.7%| the type of cutout adopted in railway bridge recommended by Eourcode3 is better than others| changing the thickness of diaphragm can significantly decrease the stress level of fatigue details around diaphragms. Additionally, the full-scale model fatigue test indicates that, the fatigue performance of circular-arc transition on diaphragms of the Second Dongting Lake Bridge can meet the design requirements| the study on 3 different bonding modes between the layer of STC and steel top plate implies that, strengthening the interface bond can improve the mechanical behavior of lightweight composite structure.