Study On Parameter Identification Of Model Structure In Shaking Table Test

Structural modal parameter identification is the basis and premise of the study of structural dynamic characteristics,structural damage diagnosis and structural safety assessment.It has been widely concerned and studied in mechanical engineering,aeronautical engineering and civil engineering.In the field of seismic engineering,the structural parameters from the response data measured in the actual earthquake are identified as the hot research items.Many modal parameter identification methods and improved algorithms are proposed and applied.In this paper,through numerical simulation and shaking table test measured ground motion response records,a variety of modal parameter identification methods were compared,the main research work and conclusions are as follows:1.This paper discusses the development and current situation of modal parameter identification methods at home and abroad.In this paper,the theoretical basis of the modal parameters is introduced in detail,including the mutual conversion of physical coordinates and modal coordinates,the concept of the frequency response function and the impulse response function,correlation function and its application.2.The feasibility of the time domain signal preprocessing method is verified by a three-layer plane frame model.The method uses the cross-correlation function of the structure under white noise excitation to replace the free attenuation signal of the structure and It is pointed out that in the process of calculating the correlation function,some original input data length is needed to reduce the influence of randomness of white noise.Secondly,a reasonable free attenuation signal length is set to reduce the influence of signal-to-noise ratio.3.The three modal parameter identification methods of ITD,STD and ARX are studied emphatically.The numerical results show that: 1)These three methods can accurately identify the structural frequency when the structural seismic response is input data,The STD method is more accurate than the ITD method,and the calculation speed is faster.2)The STD method and the ITD method are affected by the smoothness of the white noise,and the signal length is required to reduce the error.The ARX method directly uses the structural response and the input data,the stability is higher.4.Based on the shaking table test data of a three-layer RC frame model,the STD method and the ARX method were used to identify the experimental model after the different working conditions respectively.The results were compared with theexperimental phenomena.The results showed that: 1)When the structure is in good or minor damage,the two methods of the frequency of the identification results are closer,further illustrates the two methods and the reliability of the calculation program.2)As the structural damage deepens,the frequency of the structure decreases gradually,and the damping ratio increases.At the same time,the two methods lose the true mode when the order is low,and get false mode when the order is high,and the damping recognition effect is poor,the accuracy of the method need to be improved...