NON-CONTACT DYNAMIC DISPLACEMENT MEASUREMENT FOR STAY CABLES BASED ON VIDEOGRAMMETRY TECHNIQUE

摘要

Dynamic displacement response measurement for stay cables is the basis for cable force measurement, performance evaluation and vibration control. However, no mature technique is available until now. In this paper, a non-contact dynamic displacement measurement method based on videogrammetry technique is proposed. Relying on the instant digitized image acquisition using a digital video recorder and image processing based on the digital close-range photogrammetry theory, the dynamic deformation of the stay cables can be captured by the video recorder, extracted from the digital image and then computed according to the collinearity relation between image plane and object space. To demo the process of this measurement technique and validate its accuracy, a dynamic test on a scaled stay cable is conducted in the lab. Following the procedures of video recorder calibration, video acquisition and deformation calculation, cable dynamic response at given target point can be obtained. Compared with the results obtained from the traditional LVDT based technique, the proposed method is feasible and of enough precision for dynamic displacement measurement for stay cables.