Vibration Analysis Of Steel Truss Beam Based On 3D Digital Image Detection Technology

With the development of society,the construction of bridges has continued to develop with large spans and light weights.Therefore,bridge safety detection technology should also be improved.Since the traditional dynamic load test needs to place the sensor at the position to be measured,the position and quantity of the measurement point are limited by the sensor.A small number of sensors easily leads to incomplete measurement and large errors,and a large number of sensors will cause a substantial increase in workload.The digital image detection technology has the advantages of non-contact,unlimited measuring points,no equipment loss,and so on.It can owns hundreds of measuring points on a beam at one time.Not only the result is more accurate,but also the high degree of automation saves time and effort.In order to demonstrate the reliability of three-dimensional digital image detection technology in the vibration analysis of steel truss girders,this paper details the principle and flow of digital image method.Furthermore,it adopts finite element method,traditional detection method,and digital image method to subjecte the vibration modal analysis and parameter identification of an self assembled steel truss beam.The finite element method was used as the theoretical benchmark to compare the accuracy of the traditional detection method with the digital image method.The main work contents and results are as follows:(1)Two video recording equipments are used to record the vibration of steel truss beams from the vertical direction and the horizontal direction,and the images are cropped and grayed by MATLAB.After the whole pixel edge is obtained by Canny operator,two-dimensional orthogonal polynomial fitting method is used to obtain the sub-edges.Theresult of time-history analysis is imported into the DASP system to obtain the first three natural frequencies and spatial modes.(2)Midas Civil is used to establish the finite element model of the steel truss girder basing on the parameters of the steel truss girder.The result of the static load test and sensitivity analysis shows that the main source of error comes from the definition of the bolt connection.Therefore,the stiffness coefficient of the bolt needs to be identified and determined.The first three natural frequencies and mode results obtained from the modified model are used to be the theoretical basis for comparison between the traditional detection method and the digital image method.(3)After placing the acceleration sensors on the top and side of the beam respectively,the vibration signal of the steel truss beam is collected by the signal acquisition instrument.Then the transmission response,generation structure,and real-mode multi-degree-of-freedom fitting are analyzed by the DASP software.The first three natural frequencies and modes were obtained as a comparison between the traditional test method and the digital image method.