Automatic welding robots cannot be applied to welding horizontal stiffeners to the web panel of curved steel box girder bridges due to the manufacturing cost increase. Elimination or reduction of the number of horizontal stiffeners without increasing the web thickness is desirable. In the present study, the influence of the horizontal stiffeners on the ultimate capacity and the collapse process were clarified by FE analysis considering the design sectional forces. From the obtained results, it was concluded that, even if the horizontal stiffeners are eliminated, the ultimate capacity decrease is little since the compression flange of box girders restrains bending buckling of the web panel.
