scholarly journals CLARIFICATION OF THE AMPLITUDE DEPENDENCY OF NATURAL FREQUENCIES OF TRADITIONAL TIMBER FRAME STRUCTURES FOR UTILIZATION OF AMBIENT VIBRATION MEASUREMENTS

2021 ◽  
Vol 86 (784) ◽  
pp. 957-966
Author(s):  
Yuta KIMOTO ◽  
Jimpei NEZAKI ◽  
Mina SUGINO ◽  
Yasuhiro HAYASHI
Keyword(s):  
Natural Frequencies ◽  
Ambient Vibration ◽  
Frame Structures ◽  
Vibration Measurements ◽  
Timber Frame ◽  
Ambient Vibration Measurements ◽  
Amplitude Dependency

scholarly journals Bridge Scour Identification and Field Application Based on Ambient Vibration Measurements of Superstructures

2019 ◽  
Vol 7 (5) ◽  
pp. 121 ◽  
Author(s):  
Wen Xiong ◽  
C.S. Cai ◽  
Bo Kong ◽  
Xuefeng Zhang ◽  
Pingbo Tang
Keyword(s):  
Natural Frequencies ◽  
Model Updating ◽  
Ambient Vibration ◽  
Hangzhou Bay ◽  
Scour Depth ◽  
Fe Model ◽  
Bridge Scour ◽  
Vibration Measurements ◽  
Ambient Vibration Measurements ◽  
Best Fit

A scour identification method was developed based on the ambient vibration measurements of superstructures. The Hangzhou Bay Bridge, a cable-stayed bridge with high scour potential, was selected to illustrate the application of this method. Firstly, two ambient vibration measurements were conducted in 2013 and 2016 by installing the acceleration sensors on the girders and pylon. By modal analysis, the natural frequencies of the superstructures were calculated with respect to different mode shapes. Then, by tracing the change of dynamic features between two measurements in 2013 and 2016, the discrepancies of the support boundary conditions, i.e., at the foundation of the Hangzhou Bay Bridge, were detected, which, in turn, qualitatively identified the existence of bridge foundation scour. Secondly, an FE model of the bridge considering soil-pile interaction was established to further quantify the scour depth in two steps. (1) The stiffness of the soil springs representing the support boundary of the bridge was initially identified by the model updating method. In this step, the principle for a successful identification is to make the simulation results best fit the measured natural frequencies of those modes insensitive to the scour. (2) Then, using the updated FE model, the scour depth was identified by updating the depth of supporting soils. In this step, the principle of model updating is to make the simulation results best fit the measured natural frequency changes of those modes sensitive to the scour. Finally, a comparison to the underwater terrain map of the Hangzhou Bay Bridge was carried out to verify the accuracy of the predicted scour depth. Based on the study in this paper, it shows that the proposed method for identifying bridge scour based on the ambient vibration measurements of superstructures is effective and convenient. It is feasible to quickly assess scour conditions for a large number of bridges without underwater devices and operations.

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