Modal Parameter Identification Of Steel Truss Structure

Modal parameter identification of vibration system is the way and means expressed structural dynamic characteristics. It is not the ultimate goal. Its purpose is solving some relating problem generated from structural dynamic using the result of parameter identification, such as vibration system's diagnosis; modify structural design; vibtation control, dynamic response analysis and so on.Experimental modal parameter identification is an important part of vibration signal processing. Its main assignment is determining the modal parameters of system which contained modal natural frequency,modal damp ratio,modal shape,modal mass and modal stiffness through the vibration signal data obtained from testing. As far, there exists three common methods of modal parameter identification:time domain method,frequency domain menthod and time-frequency joint analysis.This article adopts traditional method of modal parameter identification, eatablished the single-input multiple-output model of vibration system. This method compared to ambient vibration measurements get more exact data regardless input response and output respose. Based on the basic theory of frequency domain method and time domain method, select some algorithms that be focused on and write programs. Set up a 9-story steel truss frame structure on vibration table for verificating the above algorithm in earthquake engineering laboratory of dalian university of technology. Select white noise and threee seismic waves from different venues.as excitation. Through accerlemeter sensors deployed on the structure achieve data's acquisition. This approach described details on all experiment contained programs,seismic wave exciation and data's acquisition, others can use the data more convenient.Establish three-dimensional finite element model to modal analysis. Also, verify a new method about restoring force participated modal parameter identification based on the accerlation data under the white noise exciation. Compared the modal frequency,normalized modal shape and damp ratio from several methods contained levy method,orthogonal polynomials method and Ibrahim method, reach conclusion advantage and disadvantage of every method. Also verify the method of retoring force participation, this method is useful for modal parameter identification.