Elimination of moving vehicles effects on modal identification of beam type bridges

The modal parameters identified under operation conditions are normally employed for bridge damage detection. However, the moving vehicles are usually deemed as part of the operation conditions without considering their mass property. Thus, the identified modal parameters belong to the vehicle-bridge system rather than the bridge itself, which would affect the effectiveness of subsequent damage detection. In this paper, the effects of moving vehicles on the identified frequencies and mode shapes under operation conditions are investigated via finite element model. The necessary of considering the moving vehicle effects is demonstrated by comparing the modal parameters variations induced by the moving vehicle and bridge damage. Then the empirical formulas to eliminate the moving vehicle effects considering the vehicle mass, velocity, bridge span and relative position are established by using the orthogonal test and least square method. Finally, examples are conducted to verify of the effectiveness of the proposed empirical formulas.