Stress analyses and fatigue evaluation of rib-to-deck joints in steel orthotropic decks

The transverse distribution of wheel loads in orthotropic decks generates significant out-of-plane bending moments in the deck plate and rib wall at the rib-to-deck joint. Due to the relatively small thickness of both the deck plate and rib wall, the out-of-plane bending moments result in high local flexural stresses causing fatigue cracks to develop at the joint. In this study, the transverse stresses within the joint region that arise under the action of wheel loads are investigated with finite element analyses. Based on the stress results and the basic theories of linear elastic fracture mechanics, the design fatigue strength is determined for the joint. Factors affecting the stress range are also studied. The analyses show that the surface stresses in the deck plate are much larger than those in the rib wall in the case of 75% weld penetration into the rib wall, indicating that the fatigue strength of the joint is governed by the fatigue cracks propagating into the thickness of deck plate. It is also shown with finite element analyses that increasing the distribution area of wheel load or the thickness of deck plate can reduce the stress range of the deck plate and increase significantly the fatigue life of the joint. (C) 2007 Elsevier Ltd. All rights reserved.