Effects of maintenance vehicle track-like attachments on the vortex-induced vibration of a flat box bridge girder

Maintenance vehicle tracks induce local flow separations that frequently result in vortex-induced vibration (VIV) of flat box bridge girders. The effects of maintenance vehicle track-like attachments on the VIV responses and flow dynamics of a flat box girder were investigated using laser displacement sensors, particle image velocimetry, pressure scanners, and individual pressure transducers. The attachments were h = 0.1 D in height (where D is the characteristic length of the girder). A girder without attachments ( h = 0 D ) was also examined for comparison. The results show that maintenance vehicle track-like attachments change the VIV features of a flat box bridge girder. The maximum amplitude decreased from 0.030 D to 0.005 D , and the lock-in region shrank from a reduced velocity U r = [5.41, 7.09] to U r = [5.53, 6.72]. These VIV changes are attributable mainly to distorted von Kármán vortex shedding produced by reattachment and merging of the leading-edge vortex (LEV) with upper trailing-edge vortices ( u -TEV) and subsequent interaction with lower trailing-edge vortices ( l -TEV), in contrast to classical von Kármán vortex shedding produced by the meeting of u -TEV and l -TEV in the near wake of a bridge girder. The LEV performs negative work just before it reaches the trailing-edge fairing, although it does positive work over the whole VIV process, resulting in a decrease in the positive work fraction from 80.52% ( h/D = 0) to 54.55% ( h/D = 0.1) and an increase in the negative work fraction from 19.48% to 45.45%. Modal analysis revealed distinct dominant flow modes: an asymmetric vortex shedding mode for h/D = 0 with an energy contribution of 61.44, versus a distorted asymmetric mode (30.98%) for h/D = 0.1.