Beam BridgesExamples Pony plate girder bridge Stone footbridges
Beam BridgesExamples I-44, 16 th St. Overpass, OK I-540/I-70 Interchange, NC Lincove Viaduct, NC
Truss Bridges Overall behavior like a beam with less material in the middle Each member either in tension (e.g. bottom chord) or compression (e.g. top chord) Rigid because bar ends pinned into triangles Best for spans < 2000. Simple truss Cantilever truss
Arch BridgesExamples The Pont du Gard Aqueduct, France (Ca. 100 AD) Thomas Aqueduct, MD (1835) Rio Cobre Bridge, Jamaica (1800) Wrought-Iron Ties, Cast-Iron Deck
Arch BridgesConstruction New River Bridge, WV Natchez Trace Arch, TN
Tied Arch BridgesExamples Bayonne Bridge, NJ I-64 Ohio River Bridge, IN Willamette River Bridge, OR
Suspension Bridges Cables (thousands of steel wires) under tension Towers under compression Require anchorages at ends to resist span deflection, bending of towers Best for spans of > 3000.
Suspension BridgesExamples Luding Iron-chain Bridge, Over Dadu River, China (1705-06) Menai Suspension Bridge, United Kingdom (1826), Removed from service in 1940
Suspension BridgesExamples Humber Bridge, England Golden Gate Bridge,CA Brooklyn Bridge, NY
Tacoma Narrows Bridge Failure After Failure Galloping Gertie Approach Span, After Failure Replacement Bridge
Cable-Stayed Bridges Cables under tension Towers, deck under compression (w/post- tensioning) No end anchorages, require less cable, and are faster to build than suspension bridges Best for spans of 1000 to 3000.
Cable-Stayed BridgesExamples Clark Bridge, ILSunshine Skyway, FL Normandy Bridge, France Puente del V Centerario Seville, Spain
Cable-Stayed BridgesExamples Footbridge, Aarhus, Denmark Salzburg, Austria Santarem-Almeirim Bridge, Portugal
Cable-Stayed BridgesExamples Leonard P. Zakim Bunker Hill Bridge, Over Charles River Boston, MA
Bridge BasicsMaterials Past Stone Timber* Iron Present Steel* Steel-Reinforced Concrete Prestressed Concrete* Future Those with asterisks Fiber-Reinforced Polymers (FRPs) ???
Bridge MaterialsFRP Wickwire Run Bridge, West Virginia No-Name Creek Bridge, Kansas
Modern Timber Bridges Keystone Wye Bridge, South Dakota, 1968 Gluelam Beams & Arches Short lengths of treated wood bonded with epoxy –Stiff, strong components –Custom designed off-site –Natural, aesthetic appearance Unknown
Modern Timber Bridges Stress-Laminated Bridge Decks Short lengths of treated wood run lengthwise Steel or FRP rods crosswise through holes in deck Stressing the rods puts steel in tension, timber in compression. Creates strong, stiff deck. Wisconsin River Bridge Steel rod anchorage
Summary/Questions Four main factors define a bridge Span (simple, continuous, cantilever) Travel surface (deck, pony, through) Form (beam, arch, truss, etc.) Material (timber, concrete, steel) Each is suitable for different sites/conditions What factors affect the selection/design of a bridge?