Application of analytical mode decomposition method to separate temperature effectfrom dynamic strain measurements

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Journal of Vibration and Shock ›› 2012, Vol. 31 ›› Issue (21) : 6-10.

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Application of analytical mode decomposition method to separate temperature effectfrom dynamic strain measurements

Li Miao1, Ren Wei-xin1, Hu Yi-ding1,2, Wang Ning-bo1

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Abstract

Under temperature load, structure stress of long-span bridge changed and strain of structure was affected remarkably. For proper assessment of bridge operation condition, it’s highly necessary to remove the effect of varying temperature on strain data and get the structure strain induced by dynamic load on bridge. Dynamic strains of the active strain gauges fixed on chord of steel truss at mid span of suspension bridge and inactive strain gauges, that didn’t sense mechanical surface strains but temperature variation induced strains, were analyzed. According to normalized PSD (power spectral density) ratio, the information in strain data of the active gauges were separated into two parts in frequency domain which were respectively dominated by varying temperature and dynamic load using the value of dividing frequency. After nalytial mode decomposition method being applied to the strain data, the slow-varying component and fast-varying component are obtained. The fact that fast-varying component did not fluctuate periodically showed the slow-varying component including strain of gauges and stress-induce strain of structure under temperature variation is effectively eliminated from strain data of the active strain gauges. Through test analysis with rain-flow counting method, strain amplitude information of fast-varying component and original data from active gauges are similar. It’s concluded that fast-varying component properly retained the information of dynamic load produced strain and is of some practical engineering value.

Key words

suspension bridge / health monitoring / analytial mode decomposition method / temperature variation / strain / signal separation

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Li Miao;Ren Wei-xin;Hu Yi-ding;Wang Ning-bo. Application of analytical mode decomposition method to separate temperature effectfrom dynamic strain measurements[J]. Journal of Vibration and Shock, 2012, 31(21): 6-10