复杂交通环境激励下西安城墙模态参数识别与分析

Modal parameter identification and analysis of Xi'an City Wall under complex traffic environment

结构的模态参数识别一直是结构健康监测的基础和重点,其能评估结构状态、识别结构损伤,对结构的后续维护具有重要意义,对古建筑结构亦是如此。西安城墙属于中国第一批重点文物保护单位,其模态参数识别更是需要重视。在西安城墙瓮城处城墙布设速度与加速度动力特性监测系统,通过现场动力测试试验,获取复杂交通环境激励下城墙振动响应数据;通过特征系统实现算法(ERA)、随机子空间法(SSI)和峰值法(PP)3种模态识别方法相结合,对响应数据进行结构模态参数识别,获取该区域城墙模态参数;结合城墙数值有限元模型,对比3种方法所得的模态参数,建立有效的结构动力模型。结果表明:3种方法均可以在环境激励下有效识别结构的模态频率并最终得出振型,验证了该3种模态识别方法对古城墙模态参数识别的可行性。

Structural modal parameter identification is generally the foundation and emphasis of structural health monitoring.It can evaluate the structural state and identify structural damage,which is of great significance to the subsequent maintenance of the structure,as well as the ancient building structure.Xi'an city wall belongs to the first batch of key cultural relic protection units in China,and its modal parameter identification needs more attention.Based on the monitoring system of velocity and acceleration dynamic characteristics of the wall at the Wengcheng of Xi'an urban wall,the vibration response data of the urban wall under the excitation of complex traffic environment were obtained through the field dynamic test.The structural modal parameters of the response data were identified by the combination of the three modal identification methods of the feature system realization algorithm(ERA),the random subspace method(SSI)and the peak value method(PP)to obtain the modal parameters of the urban wall in the region.Combined with the numerical finite element model,the modal parameters obtained by the three methods were compared to establish an effective structural dynamic model.The results show that these three methods can effectively identify the modal frequency of the structure under environmental excitation and finally obtain the vibration mode,which verifies the feasibility of the three modal identification methods for the modal parameter identification of the ancient city wall.