土木工程类外文文献翻译.docx
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土木工程类外文文献翻译
毕业设计(外文文献翻译)
题目:
新余学院学生实习楼
系别:
土木与建筑学院
专业:
2012级建工方向
姓名:
汪楠
学号:
2012102745
指导教师:
李新猷
外文翻译
Abstract:
Tostudytheapplicationofcontinuumstructuraltopologyoptimizationmethodstorealengineeringstructures,anoptimizationmethodforanoptimaltopologydesignofmultistorysteelframebracingsystemsispresented.Onasensitivityanalysis,anelementremovalcriterionforcontinuumstructureswithstressandmulti-displacementconstraintsundermultiplelateralloadingconditionsisproposed.Aconceptofmeanthicknessofadesigndomainisprovidedtoensurethereasonablenessofoptimalresults.Intheproposedoptimizationmethod,theoptimaldesignofanunbracedsteelframewithoutdisplacementconstraintsisperformedfirstly,andthentheoptimaltopologyofabracingsystemforthemultistorysteelframeconsideringdisplacementconstraintsisobtainedbyusingevolutionarystructuraloptimizationandthegivenremovalcriterion,andfinallytheoptimalayoutofthebracingsystemisinterpretedasbracingmembers.Anexampleof3-bay12-storyplanesteelframeshowsthatitiseffectiveforthegivenoptimizationmethodintheoptimaldesignofbracingsystemsformultistorysteelframes.
Keywords:
steelframe;bracingsystem;continuum;topologyoptimization;evolutionarystructuraloptimization
2.1ReinforcedConcrete
Plainconcreteisformedfromahardenedmixtureofcement,water,fineaggregate,coarseaggregate(crushedstoneorgravel),air,andoftenotheradmixtures.Theplasticmixisplacedandconsolidatedintheformwork,thencuredtofacilitatetheaccelerationofthechemicalhydrationreactionlfthecement/watermix,resultinginhardenedconcrete.Thefinishedproducthashighcompressivestrength,andlowresistancetotension,suchthatitstensilestrengthisapproximatelyonetenthlfitscompressivestrength.Consequently,tensileandshearreinforcementinthetensileregionsofsectionshastobeprovidedtocompensatefortheweaktensionregionsinthereinforcedconcreteelement.
Itisthisdeviationinthecompositionofareinforcesconcretesectionfromthehomogeneityofstandardwoodorsteelsectionsthatrequiresamodifiedapproachtothebasicprinciplesofstructuraldesign.Thetwocomponentsoftheheterogeneousreinforcedconcretesectionaretobesoarrangedandproportionedthatoptimaluseismadeofthematerialsinvolved.Thisispossiblebecauseconcretecaneasilybegivenanydesiredshapebyplacingandcompactingthewetmixtureoftheconstituentingredientsareproperlyproportioned,thefinishedproductbecomesstrong,durable,and,incombinationwiththereinforcingbars,adaptableforuseasmainmembersofanystructuralsystem.
Thetechniquesnecessaryforplacingconcretedependonthetypeofmembertobecast:
thatis,whetheritisacolumn,abean,awall,aslab,afoundation.amasscolumns,oranextensionofpreviouslyplacedandhardenedconcrete.Forbeams,columns,andwalls,theformsshouldbewelloiledaftercleaningthem,andthereinforcementshouldbeclearedofrustandotherharmfulmaterials.Infoundations,theearthshouldbecompactedandthoroughlymoistenedtoabout6in.indepthtoavoidabsorptionofthemoisturepresentinthewetconcrete.Concreteshouldalwaysbeplacedinhorizontallayerswhicharecompactedbymeansofhighfrequencypower-drivenvibratorsofeithertheimmersionorexternaltype,asthecaserequires,unlessitisplacedbypumping.Itmustbekeptinmind,however,thatovervibrationcanbeharmfulsinceitcouldcausesegregationoftheaggregateandbleedingoftheconcrete.
Hydrationofthecementtakesplaceinthepresenceofmoistureattemperaturesabove50°F.Itisnecessarytomaintainsuchaconditioninorderthatthechemicalhydrationreactioncantakeplace.Ifdryingistoorapid,surfacecrackingtakesplace.Thiswouldresultinreductionofconcretestrengthduetocrackingaswellasthefailuretoattainfullchemicalhydration.
Itisclearthatalargenumberofparametershavetobedealtwithinproportioningareinforcedconcreteelement,suchasgeometricalwidth,depth,areaofreinforcement,steelstrain,concretestrain,steelstress,andsoon.Consequently,trialandadjustmentisnecessaryinthechoiceofconcretesections,withassumptionsbasedonconditionsatsite,availabilityoftheconstituentmaterials,particulardemandsoftheowners,architecturalandheadroomrequirements,theapplicablecodes,andenvironmentalreinforcedconcreteisoftenasite-constructedcomposite,incontrasttothestandardmill-fabricatedbeamandcolumnsectionsinsteelstructures.
Atrialsectionhastobechosenforeachcriticallocationinastructuralsystem.Thetrialsectionhastobeanalyzedtodetermineifitsnominalresistingstrengthisadequatetocarrytheappliedfactoredload.Sincemorethanonetrialisoftennecessary