Different bridge models were subjected to earthquake motions to evaluate the influence of cross frames on the seismic performance of steel I-girder bridges. The maximum lateral displacement of the bottom flange, the maximum moment developed in the web, and the maximum total base shear for different conditions were obtained from the linear dynamic time history analyses by adding the horizontal reactions at the supports. The addition of cross braces at midspan or quarter points reduced the horizontal displacement of the bottom flange and the total base shear for cases where cross braces are provided over supports was less than the others without the cross frames.
