What It Means
A suspension bridge is a long-span structure in which the deck is supported by vertical hanger cables descending from a main cable that is draped in a catenary curve between two towers and anchored in massive gravity or tunnel anchorages at each end. The main cable carries the deck dead load and live load in pure tension, transferring the load to the towers (which act as compression members) and ultimately to the anchorages. Suspension bridges are the longest-span bridge form available, with main spans ranging from 1,000 feet to over 6,500 feet, and are typically used for major river or harbor crossings where intermediate piers are impractical. Iconic U.S. suspension bridges include the Brooklyn Bridge (New York, 1883, 1,595-foot main span, one of the earliest steel-wire suspension bridges), the Golden Gate Bridge (California, 1937, 4,200-foot main span), the Mackinac Bridge (Michigan, 1957, 3,800-foot main span), and the Verrazzano-Narrows Bridge (New York, 1964, 4,260-foot main span). Suspension bridges represent a tiny fraction of the NBI inventory (fewer than 100 structures) but carry some of the heaviest traffic volumes and have immense iconic and economic value. Inspection focuses on main cable wire condition (internal corrosion inspection via wedging and sampling), suspender cable condition, saddle condition at tower tops, anchorage integrity, tower coating and structural condition, and deck stiffening truss condition. Main cable dehumidification systems, pioneered in Japan and now retrofitted on bridges like the Mid-Hudson Bridge and Newburgh-Beacon Bridge in New York, extend cable life by keeping the interior dry and preventing wire corrosion.
Frequently Asked Questions
What does "Suspension Bridge" mean?
A long-span bridge supported by a main cable draped between towers, with vertical hangers suspending the deck below.
Why does Suspension Bridge matter for bridge safety?
A suspension bridge is a long-span structure in which the deck is supported by vertical hanger cables descending from a main cable that is draped in a catenary curve between two towers and anchored in massive gravity or tunnel anchorages at each end. The main cable carries the deck dead load and liv...