The Contrastive Research On The Modal Analysis Method About Ancient Timber Structure

Modal analysis technology is the core and foundation of vibration engineering theory,especially the application in the field of civil engineering which is more and more widely.But because the constraints are more complex and many engineering structures,which leads to the difficulty in measuring and extracting actual vibration signals.Therefore,choosing the appropriate method of structure modal parameter identification of excitation encourage the scientists to explore and find more effective methods.As a valuable cultural heritage of China,the ancient wooden structure occupies a very important position in the long history of Chinese civilization.But with the progress of society,people's life changed greatly,especially the rapidly development of traffic.It brings convenience to people's lives,at the same time,the influence of traffic micro vibration on ancient architecture is more obvious.In order to protect the ancient buildings in a better state,the effective modal analysis method is used to accurately identify the modal parameters of the structure,which provides the theoretical support for the safety monitoring and damage identification of the ancient wooden structure.Based on Liaocheng Guangyue tower as an example,using environment excitation method had the experimental modal analysis of the wooden structure of Guangyue tower.Compared time domain method and frequency domain method with the results of experimental modal analysis determined the modal analysis method for ancient wooden structures.The main contents are as follows:(1)Guangyue tower vibration testUsing the system of TST dynamic signal test obtain the time history curve of each measuring point by determining the test plan,setting up monitoring of parameters,and the arrangement of measuring points.Meanwhile,to gain the measured vibration semaphore to flatness,removing the trend of processing,we need take some correlation process by removing direct current,smoothing,and eliminating the trend of processing.(2)By using The TST modal analysis software of Guangyue tower take experimental modal analysis to attain the natural frequency,formation,damping ratio.At the same time,according to the formula of “Technical specifications for aegis of historic architectures against man-made vibration”,the results of the test modal analysis are verified.(3)Comparison of modal analysis methodsBased on MATLAB software algorithm programming selected reference points,using the method of NExT,ITD,PREC,ERA and PEAK identified modal parameters.The identification results of TST experimental modal and modal analysis method were compared to determine the modal analysis method for ancient wooden structures.