Abstract
Recently, it is reported that horizontal cracks have been found in web plates just under the vertical stiffeners which are placed in the crossings of the intermediate floor beams and outside stringers of a steel truss bridge. This cause is investigated by focusing on the occurrence of out-of-plane secondary stress due to the difference of axial thrust between the stringers using the numerical analysis, and it is pointed out that a present rehabilitated case for this damage probably can not prevent the relapse of fatigue crack. Finally, some suggestions to decrease the out-of-plane secondary stress in the web plate of floor beam are described.
