正交异性钢桥面板横隔板弧形切口疲劳评价的热点应力法

借助有限元分析和随机车流下构造细节应力现场监测数据获取了某正交异性钢桥面板横隔板弧形切口疲劳细节一定宽度范围内的应力时程, 分析了应力峰值分布; 基于国际焊接学会和挪威船级社推荐的热点应力外插公式评价了横隔板弧形切口疲劳寿命, 研究了适用于横隔板弧形切口热点应力的外插公式。研究结果表明: 在桥面车辆通行下, 横隔板弧形切口响应为压应力, 且应力峰值大; 横隔板弧形切口不仅产生了显著的应力集中, 且应力沿构造细节最小净截面一定范围呈显著的非线性分布; 因应力插值点位于横隔板弧形切口应力分布的非线性区, 采用国际焊接学会和挪威船级社提出的热点应力插值公式得到的热点应力偏大, 评价的疲劳寿命均偏保守; 提出的两点线性外插公式和三点二次外插公式的应力插值点均位于构造细节应力的线性分布区, 且第1个插值点均距横隔板弧形切口自由边1倍横隔板厚度, 依此方法评价的横隔板弧形切口疲劳寿命与实桥该构造细节的开裂寿命较为一致。正交异性钢桥面板横隔板弧形切口的疲劳性能评价若基于热点应力法开展, 可采用疲劳等级FAT90和建议的三点二次外插公式。 

Fatigue assessment of floorbeam cutout in orthotropic steel bridge deck based on hot-spot stress method

Based on finite element analysis and stress monitoring data at fatigue details under random traffic flows, stress time histories for an area close to a floorbeam cutout of orthotropic steel bridge deck were obtained to analyze the peak stress distribution.Fatigue assessment at a floorbeam cutout was carried out based on the hot-spot stress obtained through the extrapolation formulas specified by the International Institute of Welding and the Det Norske Veritas, respectively.Suitable extrapolation formulas for hot-spot stress at floorbeam cutout were also investigated.Research result shows that under the passage of vehicles on deck, stress responses at floorbeam cutout are compressive, and the peak stress is high. A significant stressconcentration occurs at the free edge of floorbeam cutout, and an obviously nonlinear stress distribution appears in a small range along the critical section of floorbeam cutout.When using the hot-spot extrapolation formulas provided by the International Institute of Welding and the Det Norske Veritas, the hot-spot stress is overestimated and the estimated fatigue life is conservative due to their stress extrapolation points falling into the nonlinear distribution zone.All the stress extrapolation points of the proposed two-point linear extrapolation formula and three-point quadratic extrapolation formula are located on the linear distribution zone of the construction details stress.The first extrapolation point is located on one thickness of floorbeam away from the free edge of the cutout.The fatigue life at floorbeam cutout evaluated by this method agrees well with the observed cracking life of floorbeam cutout on a real bridge.When the hot-spot stress is employed to evaluate the fatigue life of floorbeam cutout of orthotropic steel bridge deck, the fatigue category of FAT90 and the proposed three points quadratic extrapolation formula are suggested.