变速车辆作用下拱桥吊杆的动态内力分析

ANALYSIS OF THE DYNAMIC STRESS RESPONSE OF THE HANGERS IN ARCH BRIDGE UNDER SPEED-VARYING VEHICLE

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 hangers of arch bridge are important bearing components and also the components which are easily destroyed. The main reason of hanger failure is the fatigue damage under the alternating stress caused by the dynamic coupling of vehicles and bridge structure. The vehicle-bridge coupling simulation is conducted for a large-scale concrete-filled steel tube arch bridge by considering the road roughness, 3-D characteristics and speed-varying of the vehicle. The axial forces, bending moment and nouniformity of the alternating stress over hanger sections are discussed. The results show that the acceleration of the vehicle will significantly increase the vehicle impact on the bridge, and the bending moment in hanger section is obviously influenced by vehicle speed, acceleration, and road roughness, while the lateral bending moment is usually larger than the longitudinal bending moment. The dynamic stress over the hanger section shows significant nonuniformity, with the maximum value being about twice the minimum, while the percentage of the bending stress is about 30% of the total stress. These factors should be considered in design, maintenance, monitoring and evaluation for this kind of bridge.