Flutter and buffeting performances of Third Nanjing Bridge over Yangtze River under yaw wind via aeroelastic model test

Abstract

Third Nanjing Bridge over Yangtze River in China is a long-span steel cable-stayed bridge with a main span of 648 m and a closed streamline cross-section of single box. The flutter and buffeting performances of the bridge under yaw winds were investigated via a wind tunnel test of full bridge aeroelastic model at a geometric scale of 1:120. The service state and three key construction states including the longest single-cantilever state, the longest double-cantilever state with a temporary pier, and the longest double-cantilever state without any temporary pier, were considered in the test. The test was conducted in both smooth and simulated boundary layer wind fields with various combinations of wind yaw angle and inclination angle. The model was elaborately designed and manufactured, and the modal properties of the service-state model were checked before the test. The natural frequencies and mode shapes were identified automatically using a self-developed special software from the acceleration signals recorded in an ambient vibration test, where an “artificial” turbulent wind with lower mean speed of 1 m/s was used as a major ambient excitation addition to the “natural” one from the slight ground trembling. The modal damping ratios were checked using free-decay vibration approach. The testing results show that the bridge has enough aerodynamic stability for all structural states and wind directions concerned, and the most unfavorable buffeting responses often occur in yaw wind case with a yaw angle between 5° and 30°.