Unit Test Review Updated 4/24/2012.

FAMOUS BRIDGES Bridge NameLocationImportance Brooklyn Bridge Brooklyn – Manhattan, NYC crosses East River Designer: John Roebling; completed in 1883 Used caissons to build piers (caisson disease) Uses cable-stayed AND main cable designs George Washington Manhattan, NYC – Fort Lee, NJ crosses Hudson River First modern suspension bridge built after collapse of Quebec Bridge during construction, proved strength and safety of suspension bridges for very long crossings Golden Gate Bridge San Francisco – Marin County, CA; crosses Golden Gate National icon Oakland Bay Oakland – San Francisco crosses Oakland Bay Collapsed in earthquake in 1989 Two bridges combined: suspension & beam Two bridges combined: suspension & beam On-ramp section melted in truck fire in 2007 Sunshine Skyway Bradenton – St. Petersburg, FL crosses Tampa Bay Freighter hit it in 1980 Rebuilt with cable-stayed design Uses damage-sensing monitors (smart bridge), dolphins Tacoma Narrows (“Galloping Gertie”) Tacoma – Gig Harbor, WA crosses Tacoma Narrows Collapsed in 1940, ignored effect of constant 40 mph wind Rebuilt in 1950 using flexible, open design Parallel bridge completed in 2007 Verrazano Narrows Brooklyn – Staten Island, NYC crosses Verrazano Narrows Longest suspension span in the United States Akashi Kaikyo Kobe – Awaji Island, Japan crosses Akashi Straight Longest suspension span in the world, built across a fault line

PURPOSE of BRIDGES  Bridges cross barriers (water, chasms, low areas, roads, other bridges)  Primary purpose: get people and their goods to the other side of barriers  Roman bridges 1. Move armies/troops to conquer land 2. Move goods (trade) throughout empire  Form & function: balance the beauty (shape) of a bridge with its purpose (usefulness, strength)  Commerce: carry trade and services between cities

Main type Roadbed support Sub-typeExample Beam straight pieces triangles TrussUsher Park bridge Trestle GirderRR bridge over Spring Brook DrawChicago River draw bridges King PostMorton Arboretum ped bridges Arch curves Roman curved deckIrving Park ped. bridge Through Half-through Deck Suspension suspended from cables Main (anchored) cable Golden Gate Akashi Kaikyo Verrazano Narrows Cable-stayed Sunshine Skyway Brooklyn Bridge TYPES of BRIDGES

Beam Bridge Types Triangle TrussTrestle Draw Bridge King Post

Beam Bridges Firth of Forth Rail Bridge New Zealand trestle bridge box beam Chicago draw bridges girder bridge, Itasca

Arch Bridge Types THROUGH ARCH HALF-THROUGH ARCH DECK ARCH ROADBED ROMAN ARCH

Arch Bridges on the California Hwy. aqueduct, Segovia, Spain Rialto Bridge, Venice Eads Bridge, St. Louis

Suspension Bridge Types ROADBED MAIN (ANCHORED) CABLE PIERS (TOWERS) CABLE-STAYED

Suspension Bridges Millau Viaduct, France Mackinac Bridge, Michigan Zakim Bridge, Boston Clifton Bridge, Bristol, England Capilano Bridge, Vancouver

OTHER BRIDGES  aqueduct: bridge that carries water  cantilever: bridge with middle section supported by counterweights  pontoon: bridge that floats

PARTS of a BRIDGE Length Span  Roadbed: carries the traffic  Superstructure: part of bridge above the roadbed  Substructure: part of bridge below the roadbed  Pier: primary vertical support  Length: distance from one end of bridge to the other, including access roadways  Span  Arch/beam: distance from edge to edge of area crossed  Suspension: distance from one pier/tower to the other

PARTS of a BRIDGE  Caisson: pier construction method where sections are sunk as the river bottom is dug out inside  Dolphin: “bumper” that protects bridge piers from boat traffic

JOINTSJOINTS  Butt: end of one piece attached to side of another at right angles  Miter: end of one piece attached to side at an angle, often 45 degrees  Notch: both pieces cut halfway through and joined, like Lincoln logs  Lap: end of one piece is “hung” over the side of another  Lamination: full length of two sides are attached to each other

NATURAL MATERIALS  No tools yet  hanging vines  piles of stones, rocks moved by water  fallen trees

FIRST BRIDGES  Tools were needed  woven vines, ropes  stepping stones placed by humans  wood

MODERN MATERIALS  Modern (since Roman times)  stone (Roman arch)  wood (covered bridges)  iron (early railroad, cracked easily)  steel (requires painting to prevent rust)  steel-reinforced concrete

STRESSES and FORCES  compression: squeezing or pressing together  tension: stretching or pulling apart  neutral axis: point in a beam where compression and tension are equal  torsion: torque or twisting motion  oscillation: bending or swinging back and forth in an even rhythm  shear: two parallel and opposing compression forces (think scissors) Compression Tension

APPLYING STRESS  shapes  triangle: strongest shape for resisting bridge forces  racking: collapse of a rectangle to a parallelogram; corrected by bracing  loads  dead: the weight of the bridge load itself  live: the weight of loads that change, e.g., traffic, wind, ice, snow

BRIDGE SAFETY  civil engineer: a design engineer who builds municipal infrastructure, i.e., bridges, roads, power plants, etc.  bridge failures: about 150 to 200 bridges, partially or totally each year in the U.S.  inspections: U.S. bridges over 20 feet require inspections every 2 years  “smart” bridges: use computer sensors to warn of damage before it gets serious