Abstract：A unified analytical beam model and a finite nodal-line method are employed to analyze the dynamic properties of a single-box three-cell girder, for the purpose of computing the first three order vibration frequencies and vibration modes and the investigation into the vibration characteristics of the girder, with the help of the diagrams of top flange vibration modes.Computational results show that the vibration in the non-symmetricaxis direction of the girder are coupled together with the torsional vibration of the cross section.

Keyword：box girder;single-box three-cell girder;unified analytical beam;finite nodal-line method;torsional vibration;