This study is focused on reaction forces at bridge bearings which may be relatively easy to access among other bridge members, and is aiming at estimating the damage state of a steel bridge and evaluating its structural integrity by measuring reaction forces at bridge bearings. In this paper, finite element analysis was performed on a 3D FE model of a steel I girder bridge. Results showed that when some main girders are corroded, reaction force at the support of the corroded girder decreased and reaction force at the support of sound girder next to the corroded girder increased, and that the horizontal reaction force caused by the deflection difference affects the vertical reaction force because the bridge is indeterminate structure.
