Vibration Research Of Parabolic Arch Structure Based On Video Image Detection Technology

The vibration characteristics of the structure is one of the important indicators to determine the bearing capacity and operating state of the structure.Based on the modern bridge industry is in a period of vigorous development,it is particularly important to carry out safety assessment and health monitoring of the bridge.Most of the current structural detection methods are based on traditional methods.The shortcomings of this method are as follows:First,contact measurement;Second,the number of measuring points is limited,and it can not meet all the deformation requirements of long-span bridges;last but not least,the process of measuring points is cumbersome and time-consuming consumables are labor-intensive.There fore,it is necessary to find a non-contact,full-scale measurement,convenient work and other methods,and it is necessary to meet the real-time automatic recording structure deformation and processing of continuous measurement data.In this paper,the parabolic arch structure test model is used to record the in-plane and out-of-plane vibration video of the parabolic arch structure separately,and then the vibration video is decomposed into digital image sequences by frame,and each image is sub-pixel by two-dimensional orthogonal polynomial fitting method.The edge recognition detection obtains the position of each point of the parabolic arch edge at each moment.The edge data of the vibration process of the entire parabolic arch structure is identified by Matlab program.Finally,the vibration time displacement response of each point on the edge of the arch structure is obtained.The above data was imported into the modal analyzer for modal analysis,and the first three-order vibration frequency and vibration mode of the parabolic arch structure were obtained.In this paper,the video image method test results are compared with the theoretical calculation solution,the traditional detection technology and the finite element calculation model.The error is within the reasonable range and can meet the engineering detection application.The main work and research results of this paper are as follows:(1)Combining the theoretical formulas in the book "Vibration and Stability of Bridge Structures",the approximate solution method is used to calculate the theoretical value of the in-plane vibration of the parabolic arch structure.Based on this theoretical value,this paper verifies and compares the following tests.(2)Apply the vibration sensor calibrator to the coefficient calibration of the sensor used in the test,connect the sensor to the modal analyzer,and record the maximum and minimum values of each sensor in three directions through the amplitude field statistical processing in the basic analysis.Value and amplitude,based on one of the sensors,coefficient correction for other sensors.(3)Using the finite element software to simulate and analyze the parabolic arch structure model,the first three natural frequencies and vibration modes of the simulated parabolic arch structure are obtained.Comparing the calculation results of the theoretical calculation values,the correctness of the finite element modeling can be inferred.(4)Record the vibration video of the arch structure with a suitable video format,and combine the Matlab software to perform video decomposition,image preprocessing,edge calculation,and data post-processing.Based on the modal analysis system,the signal analysis of the measuring point is completed,the modal parameters of the arch structure model are identified,and the theoretical calculation values are compared.The accuracy and reliability of the health monitoring and safety assessment of the structural vibration characteristics of the video image detection technology are demonstrated.(5)In the process of collecting the out-of-plane vibration of the parabolic arch structure,due to the limited experimental conditions,the shooting angle of the single position is not up to standard.It is necessary to simultaneously shoot two positions and propose time calibration using the peak of the sound,which solves many problems.The time synchronization problem of the edge stitching of the aircraft.In the case of simple and accurate operation,the multi-angle and multi-angle is used to identify the lateral vibration of the parabolic arch structure vibration,which shows the superiority of the video detection method.