| Summary: | 博士 === 國立臺灣大學 === 土木工程學研究所 === 100 === Almost all transmission installations are designed for overhead transmission, and transmission lines are linked by steel towers as their supports. Once a tower on the line is damaged or becomes unstable, a large-scale power failure will occur, and consequently huge economic losses may occur. Therefore the safety of steel towers strongly influences the reliability of power supply in transmission lines. In this paper, two different types of tower in Taiwan Power Company (TPC) will be studied and discussed, those are composed of suspension towers (Type B5), and strain towers (Type E5). Their dynamic characteristics, non-linear behavior, and ultimate capacity under wind force will be well studied.
The firstly, cable models based on loading and sag condition analysis will be established, and the dynamic characteristics and reactions for cables under wind disturbance will be investigated. According to the specifications of TPC Standard Code, the applied loads on tower in the transverse, longitudinal, and vertical directions will be determined. The secondary, the towers will be analyzed linearly and nonlinearly by using Pseudo-elastic method and nonlinear static pushover analysis associated with SAP program. Finally, the ultimate lateral force, and ultimate drift can be determined. The results presented in this paper for the ultimate capacity of the towers with acceptable accuracy.
In addition, our approach is based on the new techniques of Hilbert-Huang Transform (HHT), such as the Ensemble Empirical Mode Decomposition (EEMD), the Ensemble Hilbert Spectrum (EHSP), and the two-station HHT spectral ratio approach. This study is intended to identify the dynamic characteristics from the measured ambient vibration data for the tower, and from which the tower can be assessed to be sound, damaged or unstable from the spectrum appearance after analysis.
The new techniques of HHT and nonlinear analysis method associated with pseudo-elastic approach and nonlinear static pushover analysis could be applied to carry out the dynamic characteristics and the ultimate capacity of the towers with acceptable accuracy. The results of this study would be valuable references for the advanced studies in improving design, safety assessment and health monitoring of the transmission towers in Taiwan.
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