Vibrational measurements play an important role for structural health monitoring, e.g., modal extraction and damage diagnosis. Moreover, conditions of civil structures can be mostly assessed by displacement responses. However, installing displacement transducers between the ground and floors in real-world buildings is unrealistic due to lack of reference points and structural scales and complexity. Alternatively, structural displacements can be acquired using computer vision-based motion extraction techniques. These extracted motions not only provide vibrational responses but are also useful for identifying the modal properties. In this study, three methods, including the optical flow with the Lucas–Kanade method, the digital image correlation (DIC) with bilinear interpolation, and the in-plane phase-based motion magnification using the Riesz pyramid, are introduced and experimentally verified using a four-story steel-frame building with a commercially available camera. First, the three displacement acquiring methods are introduced in detail. Next, the displacements are experimentally obtained from these methods and compared to those sensed from linear variable displacement transducers. Moreover, these displacement responses are converted into modal properties by system identification. As seen in the experimental results, the DIC method has the lowest average root mean squared error (RMSE) of 1.2371 mm among these three methods. Although the phase-based motion magnification method has a larger RMSE of 1.4132 mm due to variations in edge detection, this method is capable of providing full-field mode shapes over the building.

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比较研究

振动测量在结构健康监测中发挥着重要作用，例如模态提取和损伤诊断。此外，土木结构的状况主要可以通过位移响应来评估。然而，由于缺乏参考点、结构尺度和复杂性，在现实世界建筑的地面和楼层之间安装位移传感器是不现实的。或者，可以使用基于计算机视觉的运动提取技术获取结构位移。这些提取的运动不仅提供振动响应，而且对于识别模态属性也很有用。在这项研究中，三种方法，包括 Lucas-Kanade 方法的光流，双线性插值的数字图像相关（DIC），和使用 Riesz 金字塔的基于平面相位的运动放大，使用带有商用相机的四层钢框架建筑进行介绍和实验验证。首先，详细介绍了三种位移获取方式。接下来，位移是从这些方法中通过实验获得的，并与从线性可变位移传感器感测到的位移进行比较。此外，这些位移响应通过系统识别转换为模态特性。从实验结果可以看出，在这三种方法中，DIC 方法的平均均方根误差 (RMSE) 最低，为 1.2371 mm。尽管由于边缘检测的变化，基于相位的运动放大方法的 RMSE 较大，为 1.4132 mm，