结构设计外文文献翻译.docx

结构设计AugustineJoFredrich摘要:结构设计是选择材料和构件类型,大小和形状以安全有用的样式承担荷载。一般说来，结构设计暗指结构物如建筑物和桥或是可移动但有刚性外壳如船体和飞机框架的工厂稳定性。设计的移动时彼此相连的设备(连接件)，一般被安排在机械设计领域。关键词：结构设计结构分析结构方案工程要求Abstract：Structuredesignistheselectionofmaterialsandmembertype,size,andconfigurationtocarryloadsinasafeandserviceablefashion.Ingeneral»structuraldesignimpliestheengineeringofstationaryobjectssuchasbuildingsandbridges,orobjectsthatmaybemobilebuthavearigidshapesuchasshiphullsandaircraftframes.DeviceswithpartsplannedtomovewithrelationtoeachOther(Iinkages)aregenerallyassignedtotheareaofmechanical.Keywords:StructureDesignStructuralanalysisstructuralschemeProjectrequirementsStructureDesignStructuraldesigninvolvedatleastfivedistinctphasesofwork:projectrequirements,materials,structuralscheme,analysis,anddesign0Forunusualstructuresormaterialsasixphase,testing,shouldbeincluded.Thesephasesdonotproceedinarigidprogression,sincedifferentmaterialscanbemosteffectiveindifferentschemes,testingcanresultinchangetoadesign,andafinaldesignisoftenreachedbystartingwitharoughestimateddesign,thenloopingthroughseveralcyclesofanalysisandredesign.Often,severalalternativedesignswillprovequitecloseincost,strength,andServiceability0Thestructuralengineer,owner,orenduserwouldthenmakeaselectionbasedonotherconsiderationsoProjectrequirementSoBeforestartingdesign,thestructuralengineermustdeterminethecriteriaforacceptableperformance.TheloadsorforcestoberesistedmustbeprovidedoForspecializedstructures,thismaybegivendirectly,aswhensupportingaknownpieceofmachinery,oracraneofknowncapacity.Forconventionalbuildings,buildingscodesadoptedonamunicipal,county,or,statelevelprovideminimumdesignrequirementsforliveloads(occupantsandfurnishings,snowonroofs,andsoon).Theengineerwillcalculatedeadloads(structuralandknown,permanentinstallations)duringthedesignprocess0Forthestructuraltobeserviceableoruseful,deflectionsmustalsobekeptwithinlimits,sinceitispossibleforsafestructuraltobeuncomfortable“bounce“Verytightdeflectionlimitsaresetonsupportsformachinery,sincebeamsagcancausedriveshaftstobend,bearingtoburnout,partstomisalign,andoverheadcranestostall0Limitationsofsaglessthanspan/1000(1/1000ofthebeamlength)arenotuncommon.Inconventionalbuildings,beamssupportingceilingsoftenhavesaglimitsofspan/360toavoidplastercracking,orspan/240toavoidoccupantconcern(keepvisualperceptionlimited)0Beamstiffnessalsoaffectsfloorbounciness,“whichcanbeannoyingifnotcontrolledoInaddition,lateraldeflection,sway,ordriftoftallbuildingsisoftenheldwithinapproximatelyheight/500(1/500ofthebuildingheight)tominimizethelikelihoodofmotiondiscomfortinoccupantsofupperfloorsonwindydays0Membersizelimitationsoftenhaveamajoreffectonthestructuraldesign.Forexample,acertaintypeofbridgemaybeunacceptablebecauseofinsufficientunderclearanceforrivertraffic,orexcessiveheightendangeringaircraftoInbuildingdesign,ceilingheightsandfloor一to一floorheightsaffectthechoiceoffloorframing。Wallthicknessesandcolumnsizesandspacingmayalsoaffecttheserviceabilityofvariousframingschemes.Materialsselection.Technologicaladvanceshavecreatedmanynovelmaterialssuchascarbonfiberandboronfiber-reinforcedcomposites,whichhaveexcellentstrength,stiffness,andStrength-to-weightproperties.However,becauseofthehighcostanddifficultorunusualfabricationtechniquesrequired,theyareusedonlyinverylimitedandspecializedapplications.Glassreinforcedcompositessuchasfiberglassaremorecommon,butarelimitedtolightlyloadedappIicationsoThemainmaterialsusedinstructuraldesignaremoreprosaicandincludesteel,aluminum,reinforcedconcrete,wood,andmasonry.Structuralschemes.Inanactualstructural,variousforcesareexperiencedbystructuralmembers,includingtension,compression,flexure(bending),shear,andtorsion(twist).However,thestructuralschemeselectedwillinfluencewhichoftheseforcesoccursmostfrequently,andthiswillinfluencetheprocessofmaterialsSelection0Tensionisthemostefficientwaytoresistappliedloads,sincetheentiremembercrosssectionisactingtofullcapacityandbuckingisnotaconcernoAnytensionschememustalsoincludedanchoragesforthetensionmembers.Inasuspensionbridge,forexample,theanchoragesareusuallymassivedeadweightsattheendsofthemaincables.Toavoidundesirablechangesingeometryundermovingorvaryingloads,tensionschemesalsogenerallyrequirestiffeningbeamsortrusses0CompressionisthenextmostefficientmethodforcarryingloadsoThefullmembercrosssectionisused,butmustbedesignedtoavoidbucking,eitherbymakingthememberstockyorbyaddingsupplementarybracing.Domedandarchedbuildings,archbridgesandcolumnsinbuildingsframesarecommonschemes.Archescreatelateraloutwardthrustswhichmustberesisted0Thiscanbedonebydesigningappropriatefoundationsor,wherethearchoccursabovetheroadwayorfloorline,byusingtensionmembersalongtheroadwaytotiethearchendstogether,keepingthemfromspreading0Compressionmembersweakendrasticallywhenloadsarenotappliedalongthememberaxis,somoving,variable,andunbalancedloadsmustbecarefullyConsidered0Schemesbasedonflexurearelessefficientthantensionandcompression,sincetheflexureorbendingisresistedbyonesideofthememberactingintensionwhileth