Long-term structural vibration monitoring of the tpc meteorological mast – the synchronicity of the tide and the third natural frequency of the structure

In this study, we use the monitoring data from the Taiwan Power Company (TPC) meteorology mast (Lu et al., 2020) to present relationships between the dynamic characteristics of the structure and the site environmental characteristics using a multi-physics survey. First, we compare the modal frequency of the structure and the modal shape with other environmental phenomena. Then, we discuss these relationships and the synchronous variations in the modal frequency of the structure and the tidal height. In particular, we found that the third natural frequency of the structure was obviously synchronous with the tidal height curve. However, there were some other unknown effects. We used the frequency domain decomposition (FDD) method to extract the natural frequencies from the monitored structural vibration responses and to compare the data with records of the environmental conditions. Our results show that we can feasibly use observations from structural dynamics to detect environmental characteristics. However, further studies are required to understand the relationship in detail. The platform for this research is ready for implementation and can be used to satisfy specific needs by adding monitoring items according to survey requirements. This concept can be applied to the operation and maintenance of offshore wind farms, providing a specific and accurate method for engineering judgments and a clarification on the practical strategy. From the results, the synchronicity between the structural natural frequency and a curve of the tidal height was observed. These findings are presented and the data processing steps are introduced. A new chronological FDD was successfully implemented to extract the time-dependent structural frequency and verified using a short-time Fourier transform (STFT).