Orthotropic steel bridge deck has lighter self-weight,faster fabrication in bridge factory and erection during construction.It is applied widely in steel bridges both in China and Japan.However,fatigue cracks have been detected in the welded joints of some steel bridges,within the range of their designed service life.In this paper,stress of the trough-deck welded joint is analyzed with FEA (finite element analysis),and fatigue strength is investigated.Firstly,both shell and solid finite element models are compared with different mesh sizes.Secondly,hot spot stress is discussed at two points,one is bottom of the deck plate near the toe-weld and the other is trough-rib near the toe-weld.Finally,stress under the moving unit wheel load is studied.Fatigue damages,under the truck load,are evaluated based on the hot spot stress method.Fatigue damage reduction due to distribution of transverse location of a vehicle is discussed.