基于强震观测和ARMAV模型的混凝土坝模态识别

摘要

采用混凝土坝的实测振动响应识别结构模态参数是进行结构动力特性研究的一种可行的方式.基于混凝土坝的强震观测数据,提出采用矢量自回归滑动平均模型(Auto-Regressive Moving Average Vector,ARMAV)和稳态图法来进行混凝土坝结构模态参数识别.研究了结构实测振动响应时间序列的ARMAV模型表达形式,并通过引入辅助变量(Instrumental Variable,Ⅳ)技术,来求解模型中的未知系数;通过研究ARMAV模型系数矩阵与结构系统矩阵的关系,以便为结构模态识别提供理论依据;根据综合了各测点观测信息的平均标准化功率谱(Average Normalized Power Spectrum Density,ANPSD)来对传统的稳态图法进行改进,以实现强震激励下混凝土坝的系统定阶和虚假模态剔除.通过一个数值算例和一个工程实例,验证了提出的基于强震观测和ARMAV模型的结构模态参数识别方法的精度、有效性和工程适用性.%It is a feasible way to study the dynamic properties of concrete hydraulic structures through modal identification using the vibration measurement of structures.In this paper,an auto-regressive moving average vector (ARMAV) model and stabilization diagram method was adopted to perform modal identification using the strong-motion observation of concrete dams.The vibration response time series were expressed by the ARMAV model at first,and the instrumental variable (Ⅳ) technique was adopted to improve estimation accuracy of unknown model coefficients.Then the relationship between the ARMAV model coefficient matrix and structural state space matrix was studied to provide theoretical basis for modal identification.The stabilization diagram was improved by the average normalized power spectrum density function,which integrated the modal information of all the measurement channels,to the determine system order and remove spurious modes.A numerical example and a practical engineering application were used to verify the accuracy,effectiveness and applicability of the proposed modal identification method based on strong-motion observation and the ARMAV model.