Aerodynamic Stabilization Mechanism of a Twin Box Girder with Various Slot Widths

Five representative girder cross sections with various slot widths are utilized to analyze the effects of center slots on their aerodynamic performance, based on wind-tunnel tests and theoretical analyses. It is shown that the favorable aerodynamic effects of the center slot on bridge decks depend on the aerodynamic shape of the box girders and on the slot widths rather than unconditionally improving the aeroelastic stability. Further investigation of a streamlined box girder with various slot widths results in a modified Selberg formula to calculate the critical flutter wind speed for design purposes, wherein the Lorentz peak-value function is utilized. The flutter mechanism is illustrated utilizing a two-dimensional three-degrees-of-freedom (2D-3DOF) analysis scheme. The results indicate that the center slot changes the participation level of the heaving motion at the flutter onset, which is highly correlated with the critical flutter wind speed. In addition, particle image velocimetry (PIV) and proper orthogonal decomposition (POD) techniques are employed to assist in revealing the aerodynamic stabilization mechanism of the center slotting of box girders.