随机实测车辆荷载下大跨径斜拉桥钢箱梁的动力响应特征

Dynamic response characteristics of steel box girder under randomly measured vehicle loads in long-span cable-stayed bridge

依据南京长江第三大桥的实测交通流统计数据，结合等效疲劳损伤原理建立随机状态下的车辆荷载谱，基于有限元数值仿真程序进行全桥动力响应分析。通过计算大桥在实测车流作用下主梁不同位置位移和内力的动力响应时程曲线，分析车辆运营时程内主梁截面内力变化及动力放大系数。结果表明：随机车流作用下大桥主梁塔根处弯矩及轴力绝对值最大，跨中处弯矩及轴力变化幅值最大，而在1/4跨位移动力响应最大。跨中、1/4跨和塔根附近截面在时程内的最大应力幅值处，动力放大系数在1.00-1.03之间，动力放大系数比单考虑弯矩或轴力时稳定，且动应力放大系数与国内现行规范的动力放大系数较为吻合。

According to measured traffic flow statistics from the Nanjing Third Yangtze River Bridge, in Jiangsu Province, a vehicle load spectrum in a random state was developed based on the theory of fatigue damage equivalence, and a full-bridge dynamic response analysis was conducted using finite element numerical simulation. Through calculation of the displacements and vibration response time-history curves of internal forces in different sections of the main beam of the bridge under the influence of measured vehicle flow, the changes of internal forces and dynamic magnification factors were analyzed. The results show that, under the influence of random traffic, the absolute values of the bending moment and axial force were at their maximum at the bottom of the tower of the main beam. The mid-span bending moment and axial force changed most significantly. At one quarter of the span, the displacement vibration was most intense. The dynamic magnification factor ranged from 1. 00 to 1. 03 at the maximum stress amplitude at mid-span, one quarter of the span, and near the tower bottom. The dynamic magnification factor was more stable than in the case considering only the bending moment or the axial force, and was consistent with that of the current specifications in China.