The Modal Parameters Identification Of Xi’an Bell Tower Based On Wavelet And Singular Value Theory

With the continuous development of society,the influence of the environment on the ancient wood structure is increasing.The health monitoring based on the environmental excitation has gradually become an important issue in the study of ancient wood structure.In this paper,modal parameters were identified by vibration monitoring of the national key cultural relics protection unit Xi’an bell tower under environment excitation that has strong noise,a series of data preprocessing such as wavelet threshold denoising is used to apply the method based on wavelet and singular value theory to the data obtained through monitoring;Compare and analyze the measured values of the Xi’an bell tower’s modal parameters identified by the different methods and the value by calculating according to the specifications and the modal parameters obtained from the modal analysis of the three-dimensional finite element model.Thereby analyze and demonstrate the feasibility of modal parameter identification methods based on singular value and wavelet theory.The main research contents include:In this paper,the wavelet threshold denoising is performed on the monitored vibration signal,and the denoising effects of various wavelet functions are compared and analyzed.Finally,the haar wavelet is selected as the optimal denoising wavelet function.Based on the natural excitation technique,the cross-correlation function is used in place of the impulse response function,and the modal parameters of the bell tower wood structure are identified based on wavelet and singular value theory.The modal parameters obtained are compared with the results of recognition obtained by the ITDmethod.According to the structural characteristics of the bell tower,an ANSYS finite element model of the bell tower wood structure is built and modal analysis is performed to obtain the modal parameters of the bell tower.It found that modal parameters are consistent with the results of the identification by ITD.Calculate the modal parameters of the wood structure according to the 《Technical Specifications for Vibration of Ancient Buildings against Industrial Vibrations》 and compare the simulated values obtained from the modal analysis of the finite element model,the values calculated according to the 《Technical Specifications for Vibration of Ancient Buildings against Industrial Vibrations 》 and values based on the modal parameters identified by the wavelet and singular value theory,it is concluded that the modal parameter identification method based on wavelet and singular value theory is feasible and can be applied to modal parameter identification of ancient wood structure under strong noise environment.