Long-span bridges service under long-term transportation loads, strength degradation of structure materials because of fatigue cumulative damage is key factor of durability.

• 大型钢桥是在交通载荷作用下长期工作的,疲劳累积损伤引起结构材料强度逐渐退化,成为大型钢桥耐久性的关键因素。