4A Balancing Act Support its own weight. All forces must be in balance or bridge will fall.Two major forces act on the parts of the bridge.Compression – pushes on or squeezes bridge parts.Tension – pulls on or stretches bridge parts.
6Suspension BridgeA bridge with overhead cables supporting its roadway.One of the oldest of engineering forms, suspension bridges were constructed by primitive peoples using vines for cables and mounting the roadway directly on the cables.
7Suspension BridgeGolden Gate Bridge, San Francisco
8Suspension BridgeGeorge Washington Bridge over the Hudson River.
9Suspension BridgeSuspension bridge across the Ohio River at South Shore, KY.
12Cable-Stayed Bridge Follows the cantilever method The tower is built, one cable and a section of the deck are constructed in each direction.The process is repeated until the deck section meet in the middle where they are connected.The ends are anchored at the abutments.
20Truss BridgeA Truss is a structural member usually fabricated from straight pieces of metal or timber to form a series of triangles lying in a single plane. (A triangle cannot be distorted by stress)
21Truss BridgeAstoria Bridge over the Columbia River, Oregon.
22Truss Bridge13th Street Bridge over Ohio River at Ashland, KY.
23Steel I-Beam BridgeKY 32 Bridge over Little Sandy River in Elliott Co.
28Covered BridgeA timber-truss structure carrying a roadway over a river or other obstacle, popular in folklore and art but also of major significance in engineering history.The function of the roof and siding, which in most covered bridges create an almost complete enclosure, is to protect the wooden structural members from the weather.