Sensitivity Analysis of Geometrical Parameters on the Aerodynamic Performance of Closed-Box Girder Bridges

In this study, the influence of two critical geometrical parameters (i.e., angles of wind fairing, a; and lower inclined web, beta) in the aerodynamic performance of closed-box girder bridges was systematically investigated through conducting a theoretical analysis and wind tunnel testing using laser displacement sensors. The results show that, for a particular inclined web angle beta, a closed-box girder with a sharper wind fairing angle of alpha = 50 degrees has better flutter and vortex-induced vibration (VIV) performance than that with alpha = 60 degrees, while an inclined web angle of beta = 14 degrees produces the best VIV performance. In addition, the results from particle image velocimetry (PIV) tests indicate that a wind fairing angle of alpha = 50 degrees produces a better flutter performance by inducing a single vortex structure and a balanced distribution of the strength of vorticity in both upper and lower parts of the wake region. Furthermore, two-dimensional three-degrees-of-freedom (2D-3DOF) analysis results demonstrate that the absolute values of Part A (with a reference of flutter derivative A(2)*) and Part D (with a reference of A(1) H-3*) generally decrease with the increase of beta, while the change of the participation level of heaving degrees of freedom (DOF) in torsion-dominated coupled flutter initially increases, reaches its peak, and then decreases with the increase of beta.