Influence of Wearing Surfacing on Performance of Orthotropic Steel Plate Decks

The AASHTO Bridge Design Specifications first incorporated provisions for the design of orthotropic steel plate deck bridges in 1973. This and subsequent editions as well as the technical literature provided few requirements or guidelines for the design of the wearing surface. Little information is available in the United States today to help bridge designers find suitable materials and design methods for orthotropic deck wearing surfacings. An orthotropic steel deck plate requires a wearing surfacing for skid resistance, for smooth riding, and for corrosion protection. The wearing surfacing is subjected to the heavy impact of loaded truck wheels imposed by the passage of millions of trucks during the several decades of its service life. The performance of the wearing surfacings on orthotropic decks in the United States varies from excellent to poor, depending largely on deck plate flexibility, volume of heavy-truck traffic using the bridge, and, in particular, the type and thickness of the surfacing. Influences of the thickness and modulus of wearing surfacings on the performance of orthotropic steel plate decks are presented. Graphs using AASHTO truck wheel loading are presented; they show the wheel loading demand on the wearing surfacing as a function of thickness and the n value, which is the ratio of the wearing surface modulus to the steel modulus. A successful surfacing material must have properties that meet these demands initially, as well as many millions of wheel load applications during many years of service. Laboratory testing may be required to determine the durability properties of the surfacing.