资源描述:
《Bridge engineering handbook桥梁工程手册-20木桥.pdf》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、20*TimberBridges20.1IntroductionTimberasaBridgeMaterial•Past,Present,andFutureofTimberBridges20.2PropertiesofWoodandWoodProductsPhysicalPropertiesofWood•MechanicalPropertiesofWood•WoodandWood-BasedMaterialsforBridgeConstruction•PreservationandProtection20.3Typeso
2、fTimberBridgesSuperstructures•TimberDecks•Substructures20.4BasicDesignConceptsSpecificationsandStandards•DesignValues•KennethJ.FridleyAdjustmentofDesignValues•BeamDesign•WashingtonStateUniversityAxiallyLoadedMembers•Connections20.1IntroductionWoodisoneoftheearlies
3、tbuildingmaterials,andassuchoftenitsusehasbeenbasedmoreontraditionthanonprinciplesofengineering.However,thestructuraluseofwoodandwood-basedmaterialshasincreasedsteadilyinrecenttimes,includingarenewedinterestintheuseoftimberasabridgematerial.Supportingthisrenewedi
4、nteresthasbeenanevolutionofourunderstandingofwoodasastructuralmaterialandourabilitytoanalyzeanddesignsafe,durable,andfunctionaltimberbridgestructures.Anaccurateandcompleteunderstandingofanymaterialiskeytoitsproperuseinstructuralapplications,andstructuraltimberand
5、otherwood-basedmaterialsarenoexceptiontothisrequire-ment.Thischapterfocusesonintroducingthefundamentalmechanicalandphysicalpropertiesofwoodthatgovernitsstructuraluseinbridges.Followingthisintroductionofbasicmaterialprop-erties,apresentationofcommontimberbridgetyp
6、eswillbemade,alongwithadiscussionoffundamentalconsiderationsforthedesignoftimberbridges.20.1.1TimberasaBridgeMaterialWoodhasbeenwidelyusedforshort-andmedium-spanbridges.Althoughwoodhasthereputationofbeingamaterialthatprovidesonlylimitedservicelife,woodcanprovidel
7、ong-standingandserviceablebridgestructureswhenproperlyprotectedfrommoisture.Forexample,manycoveredbridgesfromtheearly19thcenturystillexistandareinuse.Today,ratherthanprotectingwood*PartsofthischapterwerepreviouslypublishedbyCRCPressinHandbookofStructuralEngineeri
8、ng,W.F.Chen,Ed.,1997.©2000byCRCPressLLCbyaprotectiveshelteraswiththecoveredbridgeofyesteryear,woodpreservativeswhichinhibitmoistureandbiologicalattackhavebeenu