随机车流对梁式桥模态参数识别的影响研究

现有的桥梁模态参数识别中,将随机车流视为一部分环境激励,忽略了车辆附加质量的影响,桥梁由于损伤导致的模态参数变化会被随机车流所引起的变化掩盖,从而影响后续损伤识别的正确性。文章利用元胞自动机模型模拟作用在桥梁上的随机车流的具体位置,将车流信息加入有限元模型,计算桥梁的动力响应;以简支梁和连续梁为例,应用随机子空间法识别模态参数,并比较车-桥系统、局部损伤桥梁和无损桥梁的模态参数差异;对比分析采用随机车流、单个移动车辆和静置车辆3种方式模拟车流时对频率与振型识别结果的影响。结果表明,桥梁局部损伤和随机车流均会导致识别的频率减小和振型改变,环境激励下的模态参数识别中必须考虑随机车流的作用并剔除其影响。

In the existing bridge modal parameter identification, the stochastic traffic flow is regarded as a part of the ambient excitation, and the influence of additional mass of vehicles is ignored. The damage induced changes in modal parameters will be masked by the changes induced by stochastic traffic flow, thus affecting the accuracy of subsequent damage detection. In this paper, the cellular automaton model is used to simulate the specific position of stochastic traffic flow on the bridge. The traffic flow information is loaded into finite element model to calculate the dynamic response of the bridge. Then, taking simply supported beams and continuous beams as examples, the stochastic subspace identification method is used to identify the modal parameters, and the differences in the vehicle-bridge system, bridge with local damage, and the undamaged bridge are compared. The influences of stochastic traffic flow, parked vehicle and single moving vehicle on the identification results of frequencies and mode shapes are investigated. The results indicate that both local damage and stochastic traffic flow will reduce the identified frequencies and change the mode shapes, so it is essential to consider the influence of stochastic traffic flow and eliminate its effects in modal parameter identification under ambient excitation.