Exploration Of Methods For Obtaining Bridge Dynamic Response Parameters Based On Video

The dynamic behavior of the bridge is an important reference for evaluating the safety status of the structure.The existing technology usually obtain the dynamic characteristic parameters of the bridge based on the data of the finite point contact sensor.This method cannot obtain holographic information of the structure.This paper relies on the National Natural Science Foundation’s project of China,which is hosted by the instructor,“Exploration of the method for deducting bridge holographic deformation and structural state based on image contour line overlap analysis(51778094)”,Based on this project,the exploration of acquiring holographic dynamic behavior data of bridge structures based on non-contact high-speed cameras was carried out.The main research work is as follows:(1)For the model of Self-anchored suspension bridge,a high-speed camera was used to obtain the dynamic response video of the bridge;the principles and implementation steps of the existing image magnification technology were summarized.Based on the characteristics of small deformation of the bridge’s dynamic response,the image magnification algorithm and visual measurement theory are used to analyze and process the captured video to realize the micro-motion zoom visualization of the bridge’s dynamic response.(2)Aiming at the dynamic response video of the motion-enlarged suspension bridge,Canny edge operator was used to extract the edge contour line of the image of the beam,This paper proposes a video-based structural dynamic response information acquisition method: by fixing the edge selection area in the time dimension,averaging and overlapping the gray values of the area to obtain the gray value-time curve,and applying Fourier change to acquisition the information of Structure frequency.This method is based on the assumption that the image noise is consistent in a short period of time,and performs noise reduction processing by overlapping and averaging.Finally,the relevant code is written to realize the calculation of the structural dynamic response parameters based on video.Compared with the traditional test results,the validity of the method is verified.(3)The theoretical derivation of the vibration form of the simply supported beam was carried out,and the experimental research on the dynamic response of the simply supported beam under various excitations was carried out.Acceleration sensors and highspeed cameras are used to collect dynamic response test data of the simply supported beam.The frequency values obtained from the three methods of theoretical calculation,measurement point acceleration,and image processing are compared with vibration shapes,which verifies the feasibility and rationality of the method in this paper.Finally,a camera was set about 500 meters away from Dongshuimen Yangtze River Bridge in Chongqing City,And the photogrammetry of the cable of the bridge was carried out.The cable frequency value obtained by image processing is consistent with the measured value of radar.It further confirmed the applicability of this method in actual engineering.