Optimization of Design Details in Orthotropic Steel Decks Subjected to Static and Fatigue Loads

Abstract

In recent decades, orthotropic steel decks (OSDs) have been routinely incorporated into long-span bridges. The most widely used method to reduce stress concentration, improve fatigue performance, and control crack propagation is to cut out the diaphragms (or subfloor beams) into which the OSDs frame. However, the capital cost of cutout fabrication in the United States is high and may not be economically feasible. Study is required of cost-effective modified design details without cutouts as well as comparisons with their corresponding flexural and fatigue performance against current design details that use cutouts. Alternative design details (e.g., deck ribs welded directly to the transverse diaphragms using full-penetration welds) with thicker deck plates, but without cutouts, were investigated for potential improvements in fatigue resistance and capital cost. A parametric study was conducted with calibrated finite element models of a portion of the Bronx–Whitestone Bridge in New York City to study the effects of cutouts, deck plate thickness, and other important parameters on fatigue performance. Various traffic load combinations and truck types were considered with the use of an elaborate weigh-in-motion database. Results detail the equivalent stress ranges at critical locations in the OSDs that were calculated to quantitatively estimate fatigue lives for two OSD models: one with cutouts and one without. On the basis of these comparisons, recommendations related to overall structural performance were made to ensure a safe and rational design for various OSD options in long-span bridges.