Recently, there have been constructed a lot of plate girder bridges with a few main girders, which have usually thicker flanges. In this kind of bridge, flange vertical buckling of compressive flange indicated by Basler may occur, because the web cannot support thick flange enough. Therefore, bending tests and FEM analyses were conducted in this paper. And the following conclusions were obtained: 1) plate girder with thick flanges collapsed according to flange vertical buckling after yielding of cpmpressive flange, even though the width-thickness ratio of web satisfied the limit of JSHB. 2) After flange vertical buckling, bending strength decrease significantly. 3) If the web has reasonable width-thickness ratio, plate girder with thick flange will have enough plastic rotation capacity
