Bridges: Past, Present, and Future Dr. Lisa Spainhour Dept. of Civil and Environmental Eng. FAMU-FSU College of Engineering

What Defines a Bridge? Four main factors define a bridge Span (simple, continuous, cantilever) Travel surface (deck, pony, through) Form (beam, arch, truss, etc.) Material (timber, concrete, steel)

Bridge Basics—Span Types

Bridge Basics—Travel Surface

Bridge Basics—Types Five main types of bridges Beam bridge Truss bridge Arch bridge Cable-stayed bridge Suspension bridge Bridges may combine different types

Beam Bridges Simple span: top surface in compression, bottom in tension Cantilever span: top in tension, bottom in compression Best for spans < 1000’, requires many supports to cross a long distance

Beam Bridges—Types

Beam Bridges—Examples Pony plate girder bridge Stone footbridges

Beam Bridges—Examples I-540/I-70 Interchange, NC Lincove Viaduct, NC I-44, 16th St. Overpass, OK

Truss Bridges Simple truss Cantilever truss 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’.

Truss Bridges—Types

Truss Bridges—Examples Stillwater Bridge, MN Baihe Bridge, China Bridge No. 1482, MN Smithfield Street Bridge, PA

Covered Truss Bridges Stone Mt. Covered Bridge, GA Germantown Covered Bridge, OH Inverted bowstring truss (1870’s) Town lattice truss (1830’s)

Cantilever Truss Bridges Kingston-Rhinecliff Bridge, NY Firth of Forth, Scotland (1890)

Arch Bridges Under load, ends try to move outward, require strong abutments or ties to resist spreading When supported at ends, arch is in compression Best for spans of 1000’ to 2000’.

Arch Bridges—Types

Arch Bridges—Examples 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 Bridges—Construction New River Bridge, WV Natchez Trace Arch, TN

Tied Arch Bridges—Examples Bayonne Bridge, NJ Willamette River Bridge, OR I-64 Ohio River Bridge, IN

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 Bridges—Examples Menai Suspension Bridge, United Kingdom (1826), Removed from service in 1940 Luding Iron-chain Bridge, Over Dadu River, China (1705-06)

Suspension Bridges—Examples Humber Bridge, England Brooklyn Bridge, NY Golden Gate Bridge,CA

Tacoma Narrows Bridge Failure “Galloping Gertie” After Failure Approach Span, After Failure Replacement Bridge

Cable-Stayed Bridges Cables under tension                                                                                                                                                                                           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 Bridges—Examples                                                                    Sunshine Skyway, FL Clark Bridge, IL Puente del V Centerario Seville, Spain Normandy Bridge, France

Cable-Stayed Bridges—Examples Footbridge, Aarhus, Denmark Santarem-Almeirim Bridge, Portugal Salzburg, Austria

Cable-Stayed Bridges—Examples                                                                    Leonard P. Zakim Bunker Hill Bridge, Over Charles River Boston, MA

Bridge Basics—Materials Past Stone Timber* Iron Present Steel* Steel-Reinforced Concrete Prestressed Concrete* Future Those with asterisks Fiber-Reinforced Polymers (FRP’s) ???

Bridge Materials—FRP Wickwire Run Bridge, West Virginia “No-Name Creek” Bridge, Kansas

Footbridges—Entirely FRP Fiberline Bridge, Denmark Parson’s Bridge, Wales Aberfeldy Footbridge, Scotland

Modern Timber Bridges Gluelam Beams & Arches Short lengths of treated wood bonded with epoxy Stiff, strong components Custom designed off-site Natural, aesthetic appearance Keystone Wye Bridge, South Dakota, 1968 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?