Which deck type is described as a steel deck stiffened longitudinally and transversely using open or closed ribs and floor beams?

• A. Overlay
• B. Orthotropic Deck
• C. Overdriving
• D. On the Overpass

Answer: (B)

A steel deck stiffened in both directions by ribs and floor beams is an orthotropic deck. In this arrangement a steel plate forms the flat deck and is reinforced with longitudinal stiffeners along the span and transverse ribs across the width, often connected to floor beams. This creates a deck that has different stiffness and strength when loaded along the length versus across the width—hence the term orthotropic, meaning direction-dependent properties. The open or closed ribs provide the necessary stiffening geometry, while the floor beams tie the deck into the girders and enable efficient load transfer to the bridge structure. This design yields a lighter yet stiff deck suitable for steel bridges with long spans and high fatigue demands. The other terms describe surface overlays or unrelated concepts, not a deck type with this bidirectional stiffening.