Conventional sensors, such as the accelerometers and velocimeters, have been generally adopted to conduct the vibration measurements of stay cables for the identification of their dynamic parameters. Even though these contact sensors are able to obtain accurate measurements, the installation of such devices may require substantial efforts. A simple digital videogrammetric technique without using any artificial target is developed in this study to perform the ambient vibration measurements of stay cables for the subsequent identification of cable frequencies. This method significantly simplifies the image processing procedures by exploiting the straight boundary of cable to determine the midpoint of its edge line for serving as a convenient pseudo target. Demonstrated by the on-site measurements for three different cables selected from Chi-Lu Bridge, it is shown that this nontarget technique equipped with a customer grade camcorder and an ordinary tripod placed on the bridge deck can attain the same order of accuracy for cable frequency identification as that of high-resolution velocimeters. Both the vertical and transverse displacements of cable were measured under the ambient vibration amplitudes in the order of 0.5 mm and 0.2 mm, respectively. Based on this study, it is proved that the practical application of a nontarget videogrammetric technique to the cables of long-span cable-stayed bridges is not only feasible but also advantageous in many aspects.
All Science Journal Classification (ASJC) codes
- Civil and Structural Engineering
- Building and Construction