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Output-only modal analysis for non-synchronous data using stochastic sub-space identification
Engineering Structures ( IF 5.5 ) Pub Date : 2021-01-02 , DOI: 10.1016/j.engstruct.2020.111702
Lin-Jun Lu , Hua-Fei Zhou , Yi-Qing Ni , Fei Dai

The stochastic subspace identification (SSI) method has been recognized as the most dominant and popular system identification technique in the time domain. Nevertheless, it cannot cope with the non-synchronicity of dynamic response measurements that happens sometimes in structural health monitoring practice. To overcome this, this study proposes a strategy for the SSI algorithm to realize system identification from non-synchronous dynamic response measurements. The modal identification is carried out in a pairwise manner by pairing a time-shifted signal with a common reference signal. The state space model is employed to fit the pair of reference and time-shifted signals and the SSI algorithm is exploited to extract the modal parameters. The core of the strategy is the tactical usage of the mean phase deviation (MPD) of the mode for seeking out the actual time lag as well as the actual mode shape components simultaneously. By so doing, the strategy fulfills integrated time lag estimation and modal extraction for non-synchronous dynamic response measurements. Furthermore, the strategy also overcomes the difficulty to determine the model order with the use of the stabilization diagram and reduces the computational cost substantially with the help of the periodicity of the MPD. To examine the performance of the strategy, intensive validations are conducted by making use of the non-synchronous acceleration measurements of the Jiangyin Bridge subjected to a ship collision and the artificially misaligned acceleration measurements of the Canton Tower struck by an earthquake. Both the time lags and the mode shapes identified by the strategy can be well validated, indicating that the proposed strategy is competent for modal identification of non-synchronous dynamic response measurements.



中文翻译:

使用随机子空间识别的非同步数据的仅输出模态分析

随机子空间识别(SSI)方法已被公认为是时域中最主要和最受欢迎的系统识别技术。然而,它不能应付结构健康监测实践中有时发生的动态响应测量的非同步性。为了克服这个问题,本研究提出了一种用于SSI算法的策略,该策略可从非同步动态响应测量中实现系统识别。通过将时移信号与公共参考信号配对,以成对方式执行模态识别。使用状态空间模型来拟合参考信号和时移信号对,并利用SSI算法提取模态参数。该策略的核心是战术的平均相位偏差(MPD)在战术上的使用,以便同时找出实际的时间滞后以及实际的模式形状分量。通过这样做,该策略实现了针对非同步动态响应测量的集成时滞估计和模态提取。此外,该策略还克服了使用稳定图确定模型阶数的困难,并借助MPD的周期性显着降低了计算成本。为了检验该策略的性能,通过使用江阴大桥遭受船体碰撞的非同步加速度测量值以及地震造成的广州塔的人为失准加速度测量值,进行了深入的验证。

更新日期:2021-01-02
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