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中下承式拱桥的吊杆是重要的承重构件,同时也是最易发生破坏的构件。车辆荷载与桥梁结构的动力耦合作用,使吊杆在交变应力作用下发生疲劳损伤是吊杆破坏的重要原因。基于大型钢管混凝土拱桥结构,考虑路面不平度影响,采用三维多自由度车辆模型,进行变速车辆的车桥耦合模拟。重点针对变速车辆荷载对吊杆产生的轴向和弯曲作用进行了分析,讨论了吊杆截面不均匀分布的交变应力情况。结果表明,车辆的加速度将显著增大车辆对桥梁的冲击作用;短吊杆截面弯矩受车辆速度、加速度和路面不平度影响明显,通常横向弯矩大于纵向弯矩;车辆荷载导致的吊杆截面内动态应力分布具有显著的不均匀性,最大应力是最小应力的2倍,弯曲应力占比近30%。这些因素在这类桥梁的设计、维护、监测与评价中应予重视。
The middle and the bottom of the arch bridge boom is an important load-bearing components, but also the most prone to damage components. The dynamic coupling between vehicle load and bridge structure causes the fatigue damage of the boom under alternating stress, which is an important reason for the destruction of the boom. Based on the structure of large-scale CFST arch bridge and considering the influence of road roughness, a three-dimensional multi-freedom vehicle model is used to simulate the vehicle-bridge coupling of variable speed vehicles. Focusing on the axial and bending effects of the variable speed vehicle load on the boom, the alternating stress distribution with uneven distribution of boom section is discussed. The results show that the acceleration of the vehicle will significantly increase the impact of the vehicle on the bridge. The moment of short boom section is significantly affected by the vehicle speed, acceleration and road roughness, usually the transverse bending moment is greater than the longitudinal bending moment. The distribution of dynamic stress in the cross-section has significant inhomogeneity, the maximum stress is 2 times the minimum stress, and the bending stress accounts for nearly 30%. These factors should be emphasized in the design, maintenance, monitoring and evaluation of such bridges.