Full-scale measurements of wind structure and dynamic behaviour of a transmission tower during a typhoon

This article reports on a detailed study of the wind characteristics and dynamic behaviour of a transmission tower, based on field monitoring during the passage of Typhoon Haima. It was found that the wind direction at the eye of the storm has an approximately 180? turn, and the mean wind speed shows an apparent M-shaped variation during the passage of the typhoon. The turbulence intensity and gust factor show significant decreasing trends with the mean wind speed. The turbulence integral scale increases with the mean wind speed at the landfall phase, while the tendency at the after-landfall phase is somewhat opposite. Compared with the empirical spectrum, the proposed normalised power spectrum agrees well with the measured wind spectrum. The identified fundamental frequency of the transmission tower decreases with the mean wind speed while the damping ratio increases due to the aerodynamic damping contribution, and their percentages could be very considerable at high wind speed. The structural damping ratio of the investigated transmission tower is close to the recommended amount of 1 percent in regional structural codes.