正交异性钢桥面板中RD焊缝的疲劳强度评估和加固方法研究

Due to the advantages such as light-weight and shorter construction time compared with concrete decks, orthotropic steel bridge decks are widely used in long span bridges and urban viaducts. However, many fatigue cracks were observed around rib-to-deck (RD) weld joints of orthotropic steel bridge decks recently, which may undermine the service life and safety of the decks. Since the stress situation around RD joints is very complicated and the type of fatigue cracks is various, Up to now, the fatigue resistance of RD joints has not been confirmed yet. In this project, numerical simulation, theoretical analysis and experimental study will be conducted to study the fatigue life evaluation of RD joint and strengthening methods for RD joints. The research contents include: (1) Experimental study on the fatigue resistance of the RD joints in service by using the high frequency and low cost fatigue test system developed by the applicant; (2) Analysis on the fatigue crack propagation rate and route Based on fracture mechanics and extended finite element method; (3) Investigating the influence of high ratio of reweld penetration and double side welding on the fatigue resistance of RD joints. The expected outcomes of the project are to achieve the design methodology and key techniques for improving the service life and decreasing the lifecycle maintenance cost of orthotropic steel deck bridges.

正交异性钢桥面板具有自重轻和建设工期短等优势，被广泛的应用于大跨径桥梁和城市立交桥中。但是近年来在很多现役钢桥面板的纵肋和钢顶板的焊缝处(RD焊缝)处发现了大量的疲劳裂缝，严重影响着钢桥面板的耐久性与行车安全性。由于RD焊缝处应力状态复杂和裂缝多样性，目前关于此类焊缝的疲劳强度评估和补强方法还不够完善。本项目拟采用数值模拟、理论分析和实验研究相结合的研究方法，对RD焊缝的疲劳寿命评估以及加固补强方法开展系列研究。研究内容包括：(1) 运用申请人攻读博士期间开发的高效低成本疲劳实验系统对多组现役类型的RD焊缝试件展开疲劳实验研究；(2) 综合运用断裂力学理论和扩展有限单元数值模型计算分析疲劳裂缝的生长速度和路径；(3) 研究提高既有RD焊缝的焊透率和新型双面焊接形式对其的疲劳强度提升效果。 本项目的完成将为提高正交异性钢桥面板桥梁的使用寿命和降低维护费用提供实用技术方案。

正交异性钢桥面板单元有着自重轻，建设工期短等优点，因此被广泛应用于大跨径桥梁，城市立交桥以及可开合桥梁中。正交异性钢桥面板单元一般由桥面钢顶板，纵肋以及横隔板等组件焊接拼装而成。在我国，绝大多数大跨径桥梁均采用此类桥面板单元组成桥面体系但是近年来，在一些现役正交异性钢桥面板单元中发现了大量的疲劳裂缝。其中U型纵肋和钢顶板焊接缝处的疲劳裂缝会造成钢箱梁漏水，钢结构腐蚀和桥面铺装破坏进而对交通安全造成严重的影响。本研究通过数字图像相关法光学手段研究了焊接钢板背面散斑图像的残余应变分布形式，为光学仪器在测量应变分布上提供了一定的试验基础，也为改善钢板对接焊温度场和残余应力场提供了一定的理论基础。此外本项目对提高焊透率后的RD焊缝的疲劳强度更进行了相关的研究，从而确定多种类型的RD焊缝疲劳强度，为研究者和工程师计算评估钢桥面板中的RD焊缝的疲劳寿命提供相关依据。