Influence of Asphalt Surfacing on Fatigue Evaluation of Rib-to-Deck Joints in Orthotropic Steel Bridge Decks

Abstract

Numerous fatigue cracks were observed recently in orthotropic steel bridge decks that have been in service for a long period of time. A fatigue crack initiating from the rib-to-deck (RD) joint may especially produce asphalt surfacing damage, and hence have an impact on traffic safety. In fatigue evaluation of RD joints, in most current design specifications the asphalt surfacing is just treated as a layer dispersing wheel loads, in which the wheel loads are uniformly distributed on the deck plate and the effect of the composite stiffness of the deck plate and asphalt surfacing is neglected. In this study, comprehensive finite-element and load models were used to investigate the asphalt surfacing influence on the wheel load dispersal and composite stiffness. The analysis result shows that wheel loads are not uniformly distributed on deck plates but are concentrated on the weld joints, the asphalt surfacing could significantly decrease the stress magnitude around the RD joints, and this decrease may mainly result from composite stiffness rather than load dispersal. The effective stresses of RD joints, and their fatigue evaluation indicate that the fatigue life of RD joints could be drastically improved by asphalt surfacing. However, on the other hand, the fatigue life is shortened considerably by the effects of temperature. Moreover, the type of fatigue crack initiating from the weld root may also be influenced by the asphalt surfacing.