Classification of longitudinal welds in an aluminum bridge deck

An aluminum bridge deck (called ALUMADECK) has been developed by Reynolds Metal Company and is made of extruded aluminum sections welded together at the sides to form a bridge deck. The longitudinal welds used to connect the extrusions do not match any of the fatigue category details in the AASHTO LRFD Bridge Specifications. In order to classify these welds, two fatigue tests were performed on a two-span ALUMADECK section fabricated over "simulated" bridge girders. Certain locations on the longitudinal welds were tested at a constant amplitude fatigue stress of at least 13.8 MPa (equivalent to the 1994 AASHTO LRFD Bridge Specification Category C Detail) to determine if the welds could be conservatively classified as a detail category C. The ALUMADECK was subjected to 10,000,000 cycles of fatigue loading. There was no sign of fatigue crack initiation during this loading. Once the fatigue loading was complete a residual strength test was performed. The residual strength of the ALUMADECK after fatigue loading was 33% greater than the ultimate strength of an earlier generation of the ALUMADECK. From the data collected and observations made during the fatigue loading the longitudinal welds in the ALUMADECK can be conservatively classified as an AASHTO detail category C.