Dynamic performance of ultra-long stay cable in small-scale extreme winds

Abstract

The wind-induced vibration and its mitigation of ultra-long stay cables are critical to the safety of long-span bridges. Remarkable progress has been made in understanding and mitigating the vibration of stay cables in normal wind, while the cable response in small-scale extreme winds such as downbursts and tornadoes remains unclear. This study compares the dynamic performance of an ultra-long stay cable in a downburst and a tornado. Firstly, a downburst and its induced vibration of an ultra-long stay cable of a kilometer-level cable-stayed bridge are introduced based on the data recorded by the structural health monitoring system (SHMS). A tornado with the same intensity as the measured downburst is then simulated analytically at the bridge site. The tornado-induced vibration of the stay cable is obtained based on the finite element method. The dynamic performance of the cable under the downburst and the tornado, including the acceleration characteristics, displacement characteristics, and frequency characteristics, are investigated and compared. The result shows that large-amplitude cable vibration is found during the two extreme winds and the out-of-plane acceleration is larger than the in-plane acceleration. For the same wind intensity in this study, the acceleration of the cable caused by the downburst is much larger than that caused by the tornado. During the tornado, the in-plane displacement of the cable is much larger than the out-of-plane displacement, which is the opposite during the downburst. The frequency range of the cable vibration induced by the small-scale extreme winds is similar and it is about 2.5 ∼ 6 Hz, and the mode order is from the 10th to the 25th.