Bridge Expansion Joint for Bridges with Orthotropic Steel Decks

Orthotropic steel decks are used on long-span bridges where the weight of a concrete deck would be excessive. The expansion joint at an orthotropic steel deck bridge must be designed for the fatigue loading from the direct traffic loading on the steel deck, which is more severe than for concrete deck bridges. Fatigue loading on orthotropic steel deck expansion joints is caused by the repeated bending of the deck plate under traffic loading. The deck plate is thin (typically 12-16 mm) and flexible, so it deflects significantly under wheel loads. This deflection creates high stress cycles in the deck-joint interface, requiring careful fatigue design. Edge beam connection to the orthotropic deck must be designed for the fatigue loading. The connection must transfer the traffic loads from the deck to the edge beam without creating stress concentrations that could initiate fatigue cracks. Continuous fillet welds are preferred over intermittent welds for fatigue resistance. The weld quality must be verified by non-destructive testing. Deck plate continuity at the joint location requires careful detailing to prevent fatigue cracking. The deck plate must be terminated at the edge beam with a smooth transition that minimizes stress concentrations. Any abrupt changes in cross-section or stiffness at the joint location must be avoided. Wearing surface on orthotropic steel decks is typically a thin layer of mastic asphalt or epoxy asphalt, 40-60 mm thick. The wearing surface must be terminated at the expansion joint and sealed to prevent water infiltration. The seal must be flexible enough to accommodate the movement of the joint without cracking. Inspection of orthotropic steel deck expansion joints requires close attention to the deck-joint interface. Fatigue cracks typically initiate at stress concentrations in the deck plate or the edge beam connection. Magnetic particle testing or dye penetrant testing should be used to detect any cracks that are not visible to the naked eye.