CantileverTrussBridges

RobertCotton

GabrielGehenio

ClaytonMiller

LessonOverview

Definitions DeterminingFactors CantileverTrussBridgeFactors TypesofCantilevertrussbridges Advantages/Disadvantages Forces ExamplesofCantilevertrussbridges

Definitions

Bridge Astructurebuilttospanagorge,valley,road,railroadtrack,river,bodyofwater,oranyotherphysicalobstacle.

Truss Astructuralformwhichisusedinthesamewayasabeam,butbecauseitismadeofanweblikeassemblyofsmallermembersitcanbemadelonger,deeper,andtherefore,strongerthanabeamorgirderwhilebeinglighterthanabeamofsimilardimensions.

Span Thehorizontalspacebetweentwosupportsofastructure.Alsoreferstothestructureitself.

Definitions Cantilever

Astructuralmemberwhichprojectsbeyondasupportingcolumnorwallandiscounterbalancedand/orsupportedatonlyoneend.

CantileverTrussBridge

Abridgethatisformedbytwoormorecantileversplacedbacktoback.Thecantileversaresupportedinthecenterofthebridgeatthepiers.

DeterminingFactors

Therearefourfactorscommonlyusedtoclassifydifferenttypesofbridges.

TypeofSpan MaterialsUsed TravelSurfacePlacement Form

TypeofSpan

Therearethreecommontypesofspans ACantileverTrussBridgehasaCantileverspan

TherearetwodifferenttypesofCantileverSpans

TheSuspendedSpan

MostCantileverTrussBridgeshavemorethanonesetofcantileversandthearmsofthetwocantileversinthemiddledonotnormallytouch.Thisformsabasictrussbridgesuspendedinthecenterofthebridge.

MaterialsUsed

Throughouthistorybridgeshavebeenconstructedusingmanydifferentmaterials.TodayCantileverTrussBridgesmainlyonlyusetwotypesofmaterials.

StructuralSteelPrestressedConcrete

TravelSurfacePlacement

Therearethreemaintypesoftravelsurfaceplacementsinrelationtothestructureofthebridge.DependingonthetypeofCantileverTrussBridge,therecanbetwotypesoftravelsurfacesonthesetypesofbridges.

DeckThrough

TravelSurfacePlacement

BridgeForm

ACantileverTrussBridgeusesatrussformratherthanabeamorgirderconstructiondesign.

CantileverTrussBridgescanusemanytypesoftrusstypes.Usingmanydifferentanglesandtriangles.

TypesofCantileverTrussBridges

Superstructure

Substructure

Symmetrical

CounterbalanceandAnchorArms

Throughouthistory,engineershavefoundwaystomakeCantileverTrussBridgesstronger.Thebestwaytheyhavefoundtomakethebridgestrongeriscounterbalancing.

ForcesontheBridge

Tension Theuppermembersofthebridgesupporttheforceoftensionanddistributetheforcethroughtheanchorarms.

Compression Commonlythelowermembersofthebridgeareusedagainstthecompressionforce.Thecompressioniscarriedtothelowerfoundationsofthebridge.

CantileverTrussBridge

Advantage Canachievelongspans

Disadvantage Notmadeforsevere

weather

The newest suspension bridge in the United States is the orthotropic Alfred Zampa Memorial Bridge in northern California (foreground), recently built to replace a narrow, aging cantilever truss bridge built in 1927.

Sources

http://en.wikipedia.org/wiki/Cantilever_bridge

http://pghbridges.com/termsBrg.htm http://www.pghbridges.com/basics.htm http://www.tfhrc.gov/pubrds/05mar/06.htm

Cantilever Truss BridgesLesson OverviewDefinitionsDefinitionsCantilever Truss BridgeDetermining FactorsType of SpanThe Suspended SpanMaterials UsedTravel Surface PlacementTravel Surface Placement Bridge FormTypes of Cantilever Truss BridgesCounterbalance and Anchor ArmsForces on the BridgeCantilever Truss BridgeSources