Modal response identification of a highway bridge under traffic loads using frequency domain decomposition (FDD)

Özet

In this study, a four-span, 224m long, post-tensioned concrete box girder bridge sup-ported on single column piers was subject to a series of controlled vehicle tests. Bridge acceleration response datasets were used to study the effect of truck speed and a sudden stop, on the modal identification of the bridge structure. Natural fre-quencies and mode shapes of the bridge were determined using the frequency do-main decomposition technique for all datasets. The passing of the truck rendered dif-ficult to identify the first bridge frequency. Conversely, the vehicle tests improved the identification of higher vibration modes. This is because the truck preferentially ex-cites the bridge vertical response, which is associated with higher modes of vibra-tions, especially when a sudden stop of the vehicle occurs. Thus, carefully conducted vehicle-crossing tests provide detailed information about the bridge structure dy-namics in the vertical direction. However, to identify lower modes, no vehicle on the bridge is preferred.