Mechanical Behavior of Steel Bridge Deformed by Collision

A bridge over a highway is damaged by a truck running underneath occasionally. Typical collision damages observed in a steel girder bridge are as follows: a lower flange is deformed in the vertical direction and/or in the horizontal direction; a web plate is bent; a transverse stiffener is buckled; and a transverse stiffener is partly separated from the web. The influence of the damage on the safety of the bridge has to be judged right away. Nevertheless, it is not an easy task, since the mechanical behavior of a deformed girder has not been studied well. The first author has been involved in the evaluation of a steel girder bridge damaged by collision. Based on the data obtained from this bridge, the mechanical behavior of the deformed girder is studied numerically in the present study. To be specific, the deformation of the main girder due to collision is reproduced by the finite element analysis and the deformed steel girder is loaded to investigate its mechanical behavior. The result indicates that the damage influences the mechanical behavior of the girder, yet as far as the damage is confined to the deformation of the girder, the collision does not threaten the safety of the bridge even when the deformation is quite large. It is also clarified that the influence is mostly attributable to the configuration change and that the residual stress plays a relatively small role.