Which movable bridge design involves girders and deck swinging about a vertical support ring at the middle piers?

• A. Lift Bridges
• B. Swing Bridges
• C. Bascule Bridges
• D. Drawbridges

Answer: (B)

Movable bridges that open by rotating the entire span around a vertical axis are designed to swing the deck away from the water. The key feature is a central pivot provided by a vertical ring bearing or similar support in the middle piers, which lets the girders and deck swing horizontally like a door on hinges. This rotation about a vertical axis distinguishes it from other movable types that lift or tilt the deck, or that are described by a general term rather than a specific motion. So the design described—girders and deck swinging about a vertical support ring at the middle piers—fits a swing bridge.