Numerical Research On The Aerodynamic Performance Of The Hangers Of The Bridge

The stability and security of the bridge are impacted by not only the self-effects and the structural design but also the wind load. The wind load is a very important load for the bridge. It is very necessary for us to consider the wind load in the design of the bridge structure. There are two kinds of wind effects on the bridge. One is static, the other is dynamic. The vortex-induced vibration is one of the most common dynamic effects in the wind effects on the bridge. Although vortex-induced vibrations may not cause catastrophic damage, it can lead to the fatigue damage on the structure because it occurs at the low wind speed and it occurs frequently. Vortex-induced vibrations normally occur in the slender structure which has smaller damping. Because of all these above, nowadays, the engineers pay more and more attentions on the question of vortex-induced vibration.Nanjing Dashengguan Yangtze River Bridge is the transportation hub planned by the Ministry of Railways, whose main bridge contains six-span continuous steel truss arch bridges with three load-bearing truss structures. The length of the longest hangers of the bridge is over 50 meters. With the high flexibility, the vortex-induced vibration would highly probably occur in the slender hanger. The main task of this thesis is to study the 2D statistic aerodynamic performance of the hangers of the bridge by numerical simulation, and do the preliminary work for the vortex-induced vibration of the hangers of the bridge, in order to provide the basis for the following dynamic analysis. In this thesis, we used the computational fluid dynamics software ANSYS CFX to simulate the hanger which was in three kinds of cross-section shape. The 2D model foundation and grid partition were achieved in the special pre-processor software ICEM-CFD. We mainly researched the aerodynamic performance of the three kinds of cross-section shape including rectangular, corner rectangular and rounded rectangular, and finally determined the optimal cross-section in order to restrict the vibration.On the basis of the above work, we did further study on the hanger with corner rectangular cross-section shape. Taking the actual situation into account, we should consider the wind angle of attack. In this thesis, we calculated the flow field with both single hanger and double hangers in the different kinds of wind angle of attack and also compared the results of the two cases. At last, we got the range of the most harmful wind angle of attack and the value of the angle of attack at which the two hangers had no mutual interference.