Fatigue cracks which initiated from the root of welded joints between deck plate and U-rib and propagated toward the surface of the weld bead (bead-through cracks) have been reported in Orthotropic Steel decks, but the fatigue strength evaluation method is not established. In this study, field investigations and FE-analysis were conducted for the bridge which bead-through cracks were found. And crack initiation point of bead-through crack was confirmed to be the same position as deck-through crack (initiates from the root of the weld and propagates through the thickness of the deck plate). In addition, fatigue damage of bead-through cracks was calculated using reference strain which proposed for deck-through crack.
