Video Measurement Method Development to Modal Identification of 3D Sandwich Panels

Operational modal analysis typically requires the physical attachment of a sensor to measure the structure vibration. As a non-contact method, digital cameras are relatively inexpensive, fast, and providing high spatial resolution results. The aim of this study is to identify the dynamic parameters of structures (frequency and damping ratio) by using video measurement (output only) based on the phase. For this purpose, it was only used mobile smartphones to identify modal parameters. The accelerometer sensor in the 3 attached smartphones was used to extract vibrational information. Video recorded by another mobile smartphone simultaneously identifies the dynamic parameters. In video measurement, the steerable pyramid transform is applied to frames that were extracted from the video to identify the local phases encoded in the image. After that, blind source separation (complexity pursuit) and single value decomposition techniques were applied to the image phase. Frequencies and damping ratios are extracted by the Fourier transform and logarithmic reduction technique. Thus, to validate the proposed method, two samples of 3D wall sandwiches panel, including a concrete sample and a straw sample that were already loaded and their stiffness was reduced by an average of 90%, were used. The results showed that the proposed method was able to extract the frequencies and damping ratios of the panels with an error of less than 2%.