Investigation and Control of VIVs with Multi-Lock-in Regions on Wide Flat Box Girders

Abstract

On the preliminary designing of a wide flat box girder with the slenderness ratio 12, vertical and torsional vortex-induced vibrations (VIV) are observed in wind tunnel tests. More than one lock-in region, which are defined as "multi-lock-in regions," are recorded. Therefore, suspicions should be aroused regarding the viewpoint that wide box girders are aerodynamic friendly. As the three nascent vortexes originating at the pedestrian guardrails and inspection rails shed to near-wake through different pathways with different frequencies, the mechanisms of VIVs and multi-lock-in regions are analyzed to be determined by the inappropriate subsidiary structures. A hybrid method combining Large Eddy Simulation (LES) with experimental results is introduced to study the flow-structure interactions (FSI) when undergoing VIVs; the vortex mode of torsional VIV on wide flat box girders is defined as "4/2S," which is different from any other known ones. Based on the mechanism of VIV, a new approach by increasing ventilation rate of the pedestrian guardrails is proved to be effective in suppressing vertical and torsional VIVs, and it is more feasible than other control schemes. Then, the control mechanisms are deeper investigated by analyzing the evolution of vortex mode and FSI using Hybrid-LES method.

Refined Time‐Domain Buffeting Analysis of a Long‐Span Suspension Bridge in Mountainous Urban Terrain

“…According to existing literature [23,27], geometrical optimizations of the girder are effective measures in suppressing the wind-induced vibrations on bridges while not significantly increasing the construction budget. is section introduces several minor modifications to the originally designed girder (Case 1) and studies their influences on the buffeting responses of a long-span suspension bridge.…”

“…Taken together, the control countermeasures should be designed by synthetically considering the efficiency and budget. According to [23,27], the flow field around a bridge structure can be substantially changed by modifying its geometrical shape. Of particular attention is that the overall dimensions of the bridge have been established before evaluating its aerodynamic behavior.…”