One of the typical bridge deteriorations is bearing restraint due to corrosion or other damages. If the bearings are unexpectedly restrained, fatigue cracks may occur around the sole plate. Therefore, it is crucial to evaluate the bridge bearings' conditions quantitatively. In this study, the inverse problem with the influence line as observation information is discussed to estimate the rotational spring constants and bending stiffness of the bridge. In addition, an index about rotational resistance of bearing is proposed, which is calculated from the deflection angle at the girder end. The estimation results of spring constants and the index showed the possibility of evaluating the soundness of the bridge bearing.
