结构设计外文翻译

结构设计AugustineJ.Fredrich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(linkages)aregenerallyassignedtotheareaofmechanical.Keywords:StructureDesignStructuralanalysisstructuralschemeProjectrequirementsStructureDesignStructuraldesigninvolvedatleastfivedistinctphasesofwork:projectrequirements,materials,structuralscheme,analysis,anddesign.Forunusualstructuresormaterialsasixphase,testing,shouldbeincluded.Thesephasesdonotproceedinarigidprogression,sincedifferentmaterialscanbemosteffectiveindifferentschemes,testingcanresultinchangetoadesign,andafinaldesignisoftenreachedbystartingwitharoughestimateddesign,thenloopingthroughseveralcyclesofanalysisandredesign.Often,severalalternativedesignswillprovequitecloseincost,strength,andserviceability.Thestructuralengineer,owner,orenduserwouldthenmakeaselectionbasedonotherconsiderations.Projectrequirements.Beforestartingdesign,thestructuralengineermustdeterminethecriteriaforacceptableperformance.Theloadsorforcestoberesistedmustbeprovided.Forspecializedstructures,thismaybegivendirectly,aswhensupportingaknownpieceofmachinery,oracraneofknowncapacity.Forconventionalbuildings,buildingscodesadoptedonamunicipal,county,or,statelevelprovideminimumdesignrequirementsforliveloads(occupantsandfurnishings,snowonroofs,andsoon).Theengineerwillcalculatedeadloads(structuralandknown,permanentinstallations)duringthedesignprocess.Forthestructuraltobeserviceableoruseful,deflectionsmustalsobekeptwithinlimits,sinceitispossibleforsafestructuraltobeuncomfortable“bounce”Verytightdeflectionlimitsaresetonsupportsformachinery,sincebeamsagcancausedriveshaftstobend,bearingtoburnout,partstomisalign,andoverheadcranestostall.Limitationsofsaglessthanspan/1000(1/1000ofthebeamlength)arenotuncommon.Inconventionalbuildings,beamssupportingceilingsoftenhavesaglimitsofspan/360toavoidplastercracking,orspan/240toavoidoccupantconcern(keepvisualperceptionlimited).Beamstiffnessalsoaffectsfloor“bounciness,”whichcanbeannoyingifnotcontrolled.Inaddition,lateraldeflection,sway,ordriftoftallbuildingsisoftenheldwithinapproximatelyheight/500(1/500ofthebuildingheight)tominimizethelikelihoodofmotiondiscomfortinoccupantsofupperfloorsonwindydays.Membersizelimitationsoftenhaveamajoreffectonthestructuraldesign.Forexample,acertaintypeofbridgemaybeunacceptablebecauseofinsufficientunderclearanceforrivertraffic,orexcessiveheightendangeringaircraft.Inbuildingdesign,ceilingheightsandfloor-to-floorheightsaffectthechoiceoffloorframing.Wallthicknessesandcolumnsizesandspacingmayalsoaffecttheserviceabilityofvariousframingschemes.Materialsselection.Technologicaladvanceshavecreatedmanynovelmaterialssuchascarbonfiberandboronfiber-reinforcedcomposites,whichhaveexcellentstrength,stiffness,andstrength-to-weightproperties.However,becauseofthehighcostanddifficultorunusualfabricationtechniquesrequired,theyareusedonlyinverylimitedandspecializedapplications.Glass-reinforcedcompositessuchasfiberglassaremorecommon,butarelimitedtolightlyloadedapplications.Themainmaterialsusedinstructuraldesignaremoreprosaicandincludesteel,aluminum,reinforcedconcrete,wood,andmasonry.Structuralschemes.Inanactualstructural,variousforcesareexperiencedbystructuralmembers,includingtension,compression,flexure(bending),shear,andtorsion(twist).However,thestructuralschemeselectedwillinfluencewhichoftheseforcesoccursmostfrequently,andthiswillinfluencetheprocessofmaterialsselection.Tensionisthemostefficientwaytoresistappliedloads,sincetheentiremembercrosssectionisactingtofullcapacityandbuckingisnotaconcern.Anytensionschememustalsoincludedanchoragesforthetensionmembers.Inasuspensionbridge,forexample,theanchoragesareusuallymassivedeadweightsattheendsofthemaincables.Toavoidundesirablechangesingeometryundermovingorvaryingloads,tensionschemesalsogenerallyrequirestiffeningbeamsortrusses.Compressionisthenextmostefficientmethodforcarryingloads.Thefullmembercrosssectionisused,butmustbedesignedtoavoidbucking,eitherbymakingthememberstockyorbyaddingsupplementarybracing.Domedandarchedbuildings,archbridgesandcolumnsinbuildingsframesarecommonschemes.Archescreatelateraloutwardthrustswhichmustberesisted.Thiscanbedonebydesigningappropriatefoundationsor,wherethearchoccursabovetheroadwayorfloorline,byusingtensionmembersalongtheroadwaytotiethearchendstogether,keepingthemfromspreading.Compressionmembersweakendrasticallywhenloadsarenotappliedalongthememberaxis,somoving,variable,andunbalancedloadsmustbecarefullyconsidered.Schemesbasedonflexurearelessefficientthantensionandcompression,sincetheflexureorbendingisresistedbyonesideofthememberactingintensionwhiletheothersideactsincompression.Flexur