Performance of Rib-to-deck weld joint of an orthotropic steel deck through structural stress method

The rib-to-deck welded connections in orthotropic steel decks (OSDs) used for railway and highway bridges are highly susceptible to experiencing fatigue cracks. The fatigue life, crack initiation position, and steel requirement in these bridges are influenced by the rib shape, size, and wheel load. A parametric study of an OSD was presented in this paper, considering different geometries of U- and V-ribs, deck plate thickness, weld penetration, and patch load. The structural stress (SS) method was employed to determine stresses and fatigue life related to the weld joints, with the analysis conducted using finite element(FE) software. The results indicate that variations in the depths of U- and V-ribs significantly impact the SS in rib-to-deck weld joints. However, the variation in the bottom width of the U-rib has a negligible effect on the SS along the weld line. Increasing the deck plate thickness leads to a reduction in stress within the weld joint. The location of the maximum stress remains substantially away from the ends of the deck and remains unaffected by the depth, bottom width of the rib, and deck plate thickness. However, a rib with a smaller depth exhibits a shorter fatigue life for the deck system. The stresses responsible for failure modes in the toe-deck and deck-root welds show negligible changes as the weld penetration increases. A comparison was made between U- and V-ribs of equal perimeter and equal depth. The conclusions emphasize that for optimal performance of an OSD, the depths of U- and V-ribs should fall within the range of 250-300 mm, and the bottom width of the U-rib should be in the range of 100-125 mm. Excessive depth and bottom width can lead to an uneconomical design. Additionally, it is shown that V-ribs are preferable over U-ribs in the construction of an OSD.