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EVOLUTION CHARACTERISTIC AND WORKING MECHANISM ANALYSIS OF ROTATING THIN-WALLED STRUCTURES IN POST-CRITICAL TURBULENT INTERVAL BASED ON FIELD MEASUREMENT
Wang Hao, Ke Shitang
Chinese Journal of Theoretical and Applied Mechanics    2019, 51 (1): 111-123.   DOI: 10.6052/0459-1879-18-125
Abstract   （217 HTML2 PDF（pc） （15937KB）（284）

Recent study found that the time-varying characteristic of the load may have a significant effect on the vibrational strength and energy mechanism. The most important structures in fire/nuclear power plants (such as cooling towers, chimneys, etc.) are all typical rotating thin-walled structures. To reveal the vibration evolution characteristic and working mechanism of thin-walled structures in post-critical turbulent interval, the vibration responses of eight typical rotating thin-walled structures of high Reynolds number flow ($Re \ge$3.5$\times$10$^6$) are measured. Firstly, non-stationary identifications of signals with different time intervals are performed after depressing and filtering noise. The time-varying mean and extreme estimation of response are studied based on non-stationary analysis model. Besides, the frequency domain evolution characteristics are studied based on evolution spectrum method. On this basis, proportion of resonance component in wind-induced response and its effect are discussed. Then, self-resonant frequency and damping ratio of the structures are identified, and the damping mechanism of different rotating thin-walled structures is studied. The evolution characteristic and working mechanism are revealed as follows. (1) The wind-induced vibration response of the rotating thin-shell structure in post-critical turbulent interval is characterized by stable frequency evolution characteristics and non-stationary evolution characteristics in intensity aspect; (2) The wind-induced vibration problem of rotating thin-walled structures in post-critical turbulent interval should be studied as quasi-static and resonance excitation points separately. The vibration energy distributions of resonance excitation points at different regions of the cooling tower were similar, but the PSD functions of quasi-static points were dramatically different from each other; (3) Vibration energy distribution of the resonant excitation points showed a phased trend, and the proposed resonance spectral expression takes three variation stages of responses into account and achieves high prediction accuracy; (4) With the concept of equivalent damping ratio proposed in this paper, the damping ratio prediction formula is proposed. More importantly, these analysis results show that resonance effects and non-stationary effects on wind-induced effects of rotating thin-walled structures in post-critical turbulent interval are generally notable, and the irrationality of 5% damping ratio value commonly used in the current project for this type of rotating thin-walled structure has been demonstrated.

A B C D E F G H
year of construction 2015 1989 2015 2014 2013 2006 2015 2015
tower arrangement five towers five towers single towers single tower three towers three towers two towers single tower
height/m 182.0 150.0 179.0 180.0 126.7 80.0 190.0 180.0
thickness/m 0.22 ?1.20 0.21 ?0.74 0.26 ?1.85 0.34 ?1.85 0.19 ?1.50 0.15 ?0.55 0.28 ?1.40 0.35?2.30
throat diameter/m 78.0 66.0 98.6 109.6 58.6 34.4 84.0 102.0
concrete grade C35 C30 C40 C40 C40 C30 C45 C40
reference wind pressure/(kN.m-2) 0.35 0.35 0.35 0.55 0.55 0.55 0.45 0.55
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Table 1 Main parameters of 8 measured targets
Extracts from the Article