钢桥面板顶板与纵肋连接焊根位置疲劳损伤特征
Fatigue damage characteristics of rib-to-deck weld root on orthotropic steel bridge deck

针对闭口肋正交异性钢桥面板顶板焊根处疲劳裂纹处于纵肋内部,不易发现与危害大等问题,根据所处位置的不同,将顶板焊根疲劳细节分为横隔板节间内(RD细节)和跨横隔板截面(RDF细节)2种类型,采用有限元方法分析了2种细节的应力影响面,考虑了轮迹横向概率分布、多轴轮载作用以及铺装与桥面板相互作用等影响,研究了2种细节的疲劳损伤特征。分析结果表明:当轮载作用于目标细节正上方时为最不利状态,纵桥向轮载中心移至目标细节前后0.6 m范围内应力较大,横桥向2种细节的轮载影响均在1.0 m范围内; 考虑轮迹横向分布影响,简化计算时,RD、RDF细节的等效应力幅横向折减系数可以分别取0.92、0.96; 在双、三联轴作用下,RD细节的损伤度分别是单轴荷载的2.10、3.21倍,若近似采用单轴叠加,所得损伤度可能偏于不安全,建议寿命评估时考虑车辆类型影响; 计入铺装与桥面板相互作用后,细节处应力幅明显降低,顶板厚度为12 mm的铺装模型焊根处应力幅几乎与16 mm厚的钢桥面板相当,且降低程度随铺装弹性模量的增大而增大; 对于45°扩散角简化铺装扩散模型,当顶板厚度不小于16 mm时,其应力幅小于同时考虑铺装扩散作用与铺装刚度贡献的实体模型,且差值随顶板厚度的增加而增大,简化时需要考虑其适用范围,否则会偏于不安全; 当顶板厚度为18 mm且考虑铺装作用时,2种细节疲劳寿命满足设计使用寿命要求,RDF细节疲劳寿命约为RD细节的67%,较为不利。
For the problems that the root-deck fatigue cracks of orthotropic steel decks with closed ribs located inside ribs were invisible and greatly harmful, the deck root welding fatigue details were divided into RD details(rib-to-deck details)and RDF details(rib-to-deck details crossing floor beams)according to the connected locations of longitudinal ribs and deck, and the finite element method was applied to study the stress influence surfaces of two fatigue details. The transverse frequency distribution of wheelmark, multiaxial loads and pavement-deck interaction were considered, and the damage characteristics of two fatigue details were analyzed. Analysis result shows that the target details are in the most unfavorable condition when the wheel is right above each of them. In the longitudinal direction, the stress is relatively higher when the distances of wheel load and target details are no more than 0.6 m. In the transverse direction, the wheel load influence ranges of two details are within 1.0 m. When the transverse distribution of wheelmark is considered, the transverse reduction coefficients of equivalent stress ranges of two details in simplified computation are 0.92 and 0.96, respectively. Under the dual-axle and tri-axle loads, the damages of RD details are 2.10 times and 3.21 times of the damage under single-axle load, respectively. It is unsafe to compute the damage by approximately adding the damage of each axis load, so it is suggested to consider vehicle type while assessing the fatigue life. The stress range of each detail obviously reduces when the pavement-deck interaction is considered, and the change will increase with the increase of elastic modulus of pavement. The stress range of deck with 12 mm thickness considering pavement is almost equal to the range of bare deck with 16 mm thickness at the welding root. For the simplified diffusion model of pavement with 45° dispersion angle, when the thickness of deck is no