Aerostatic Performance Improvement Based on a Novel Aerodynamic Countermeasure: Simulation and Wind Tunnel Test.

Flexible civil structures are prone to aerodynamic instabilities, such as long-span bridges and high-rise buildings, and wind-induced vibration is harmful to structural life-span and users' comfort. To address this issue, this study proposes a new aerodynamic countermeasure that is designed to improve the structural aerodynamic performance, i.e., adding a strip seam cover device (SSCD) on the surface of a structure, and the influence of the device on the aerostatic performance of the main structure is presented. Taking the box girder of long-span bridges, for example, the effectiveness and influence factors of the proposed device are investigated in detail. First, the proposed device is introduced and three aerostatic force coefficients are selected as the evaluation indices for the SSCD's effectiveness. Second, the typical streamlined box-girder sectional model of bridges with and without the additional device is compared respectively based on the two-dimensional (2D) computational fluid dynamics (CFD) simulation technique. Results show the bridge girder's pitch moment coefficients can be decreased efficiently. In addition, influences of gap distance (i.e., 30 cm, 60 cm, 90 cm, and 120 cm) between the device and the bridge girder, effective width (i.e., 50 cm, 60 cm, 90 cm, and 180 cm), and void ratio (i.e., 1∶5 , 1∶3 , 1∶2 , 1∶1 , 2∶1 , and 5∶1) of seams are investigated based on wind tunnel tests. Results of the same cases based on the experiment and CFD simulation are very close, showing the accuracy of the simulation and experiment. Experimental results show that the gap distance is recommended to be 60 to 90 cm, the effective width is 90 cm, and the void ratio is recommended to be a value larger than 1∶1. In this case, the pitch moment value and the slope of the curve for the pitch moment coefficient versus wind attack angle are efficiently reduced, which is beneficial for improving the critical wind speed of aerostatic torsional divergence and aerostatic stability. The proposed device can be used to improve the aerostatic and aerodynamic performances of buildings, bridges, and some other structures; moreover, its potential application in the control of vortex-induced vibration is found preliminarily, which will be reported in further study. [ABSTRACT FROM AUTHOR]