The present study is based on performing 3D vibrations studies of large structures using digital image correlation (DIC) technique. A 3D-DIC setup is developed for measuring in-plane and out-of-plane 3D displacements as well as natural frequencies of a vibrating structures (small to large scale). The DIC setup is first validated with laboratory experiments. The first indoor lab experiment is based on the application of the developed DIC setup in measuring pure in-plane and out-of-plane displacements. The in-plane and out-of-plane translations have been carried using a micrometer and a Vernier caliper, respectively. The developed DIC setup is able to accurately measure these in-plane and out-of-plane static displacements. With this success, in another indoor experiment, the developed DIC setup is used for performing vibration study of a PVC pipe (length 1m, inner diameter 56.6mm, outer diameter 60.6mm). The DIC setup is able to measure the dynamic displacements of the pipe in all three axes. Apart from this, the natural frequency measurement is also accurate. The first fundamental frequency of the pipe is 4.167 Hz. After successful validation and application in the indoor experiments, the developed DIC method is used for a field experiment. In the field experiment, the DIC technique is applied to perform vibration study of a light pole (length 3m, diameter 75.5mm, made of iron). The cameras are placed at a distance of 14.6m from the pole, whereas the distance between the cameras is 8.5m. A large size calibration board is fabricated and used for calibrating the stereovision system. The developed DIC method is able to produce 3D displacements of the vibrating pole as well as accurately measure its natural frequency. The fundamental natural frequency of the light pole is 4.9Hz. An accelerometer was also used during the field experiment for the validation of the developed DIC-based non-contact 3D vibration testing method.
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