Abstract
This paper investigates changes in modal properties of a steel plate gider bridge due to artificial damages at the girder end. The modal properties are identified from vehicle-induced vibration data measured during the damage experiment on the bridge. Stochastic subsupace identification (SSI) is adopted to identify modal properties of the bridge, and dominant modes are extracted by means of stabilization diagram (SD). Observation demonstrates feasibility of damage detection from changes in modal properties. In order to examine the mechanism of the change, eigenvalue analysis utilizing finite element model with artificial damages is carried out. The mechanism of increasing frequency for the first bending mode is discussed by means of sesnsitivity analysis. Observations showed that the first bending mode is more greatly affected by changes in boundary condition due to damage than those changes in stiffness due to the damage. It is noted that in vibration-based bridge health monitoring it needs to consider the influence of change in boundary conditions at the supports.
