Motion tracking of scaled bridge induced by wind force

In wind tunnel test, laser displacement transducer is widely used to extract displacement of scaled bridge induced by wind force. But, laser displacement transducer is not appropriate to measure multipoint displacements and it has a restriction that mounted location cannot be movable. Furthermore, it need to keep a certain distance from each other in order to avoid the error caused by the electrical interference. In this study, the motion tracking technique is proposed to overcome these shortcomings of the conventional measurement. The motion tracking technique is the method to extract the displacement from images which have regular time intervals sequentially. And according to improve on measurement method, the motion tracking technique reduces the errors which are occurred by having no consideration for lateral degree of freedom (DOF) and by mounting the location of laser. As a Fast Fourier transform (FFT) analysis result, displacement from images extract the frequencies by own degree of freedom effect, whereas the displacement from laser. And the time history analysis represents that displacement from images is more exact to extract vertical displacement compared with displacement of laser.