Multi-camera DIC Method In Shaking Table Experiment Application And Error Analysis

With the advancement and development of science and technology,various new building structures continue to emerge,and structural testing methods such as earthquake simulation shaking table tests are usually required to verify the seismic performance of the structure.The motion parameters of the measured structure can be obtained through various measurement methods,which can be divided into two types:contact type and non-contact type according to contact conditions.As one of the non-contact measurement methods,the multi-camera Digital Image Correlation method has gained tremendous development in technology since it was put forward,and has gradually been widely used in engineering dynamic measurement.At present,some attempts have been made to apply DIC to the measurement of dynamic motion,and the feasibility of using the DIC method for dynamic measurement has been confirmed.However,because the vibration table will vibrate the nearby site during the vibration process,it is still impossible to compare the vibration of the site environment.The influence of camera DIC measurement is judged.This article first explores the feasibility and measurement error of the multi-camera DIC method for engineering measurement.Two sets of IDS cameras are used to form two sets of binocular systems to conduct four-point bending experiments on four BFRP beams respectively.The calculated images of the two sets of measurement systems are used to complete image stitching based on the coordinate unified method of coded marker points.After the calculation results are spliced,the data changes in the whole field can be visually monitored,including the monitoring of deflection changes and crack development.The deflection measurement error of the beam when it is not loaded to failure is within 0.2mm.On the basis of the above experiments,the multi-camera DIC method can be applied to the measurement of subsequent experiments.The shaking table test was carried out with the multi-camera DIC method.Similarly,the structure was measured in 21 working conditions by using two sets of cameras,and the displacement measurement data was compared with the data of the displacement meter and the laser displacement meter.In the measurement results,the data measured by the displacement meter was recorded for a shorter period of time during the measurement;The difference from the four-point bending experiment is that the experiment has changed from static measurement to dynamic measurement.In the experiment,the shaking table will cause vibration to the site.In view of this,a high-speed camera is placed near the shaking table to analyze the camera shake while measuring the structure.Interference to the measurement.The results show that vibration does have an impact on the camera.Although the impact on the measured amplitude of the high-speed camera is not much different(0.08mm)and has no direct correlation with the measured value at rest(the correlation coefficient is less than 0.3),the seismic wave intensity is obviously positively correlated with the degree of vibration of the measured value.This paper studies the application of the multi-camera DIC method in shaking table experiments,and explores the errors caused by environmental vibration.According to the experiment,it can be known that the multi-camera DIC method is feasible to measure the displacement of the shaking table,and the vibration intensity is positively correlated with the degree of interference to the camera measurement.This article provides valuable experience for follow-up research work.