CE FinalReport

7/29/2019 CE FinalReport

1/29

SeismicEvaluation&Design:SpecialMomentResistingFrameStructure

SanFranciscoStateUniversity,CanadaCollegeandNASASponsoredCollaboration

FinalPaper2011August,15

By:AndrewChan,JohnPaulino,MoisesQuiroz,andJoseValdovinos

Advisor:Dr.ChengChen

StudentAdvisor:QiMingZeng


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TableofContentsIntroduction.................................................................................................................................................. 3

DesignChallenge........................................................................................................................................... 4

ProblemStatement................................................................................................................................... 4

GeneralProcedure.................................................................................................................................... 5

Execution....................................................................................................................................................... 5

LocalBuckling................................................................................................................................................ 5

LocalBucklingResults............................................................................................................................... 6

ColumnsFlangeCheck.......................................................................................................................... 6

ColumnsWebCheck............................................................................................................................. 7

BeamFlangeCheck............................................................................................................................... 7

BeamWebCheck.................................................................................................................................. 8

LocalBucklingConclusion......................................................................................................................... 8

DesignofBeamsandRequirements............................................................................................................. 9

BeamNominalMomentCheck................................................................................................................. 9

BeamDeflectionCheck........................................................................................................................... 10

ShearStrengthofBeam.......................................................................................................................... 11

DesignofColumnRequirements................................................................................................................ 12

EffectiveLengthandSlendernessRatioLimitations............................................................................... 12

CompressiveStrengthforFlexuralBuckling........................................................................................... 13

AnalysisTechnique...................................................................................................................................... 14

StructuralDesignMethods..................................................................................................................... 15

EquivalentLateralForceProcedure.................................................................................................... 15

SeismicResponseCoefficient.............................................................................................................. 15

ResponseModification

Factor............................................................................................................. 15

ImportanceFactor............................................................................................................................... 15

TimeHistoryAnalysis.............................................................................................................................. 16

AnalysisImplementation............................................................................................................................ 16

ASCE70512.8.1EquivalentLateralForceProcedure........................................................................... 16

TimeHistoryAnalysis:............................................................................................................................. 17


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Results:........................................................................................................................................................ 18

SeismicSystemResearch............................................................................................................................ 22

MomentFrameVsEccentricallyBracedFrame...................................................................................... 23

ConclusionsonTypesofFrames............................................................................................................. 24

Conclusions................................................................................................................................................. 24

References.................................................................................................................................................. 25

Appendix..................................................................................................................................................... 26

LocalBucklingConstants......................................................................................................................... 26

BeamConstants...................................................................................................................................... 26

ColumnCalculations............................................................................................................................... 27

EquivalentLateralForceProcedureWork.............................................................................................. 28


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Introduction

Civilengineeringisconsideredtobetheclassicalfieldofengineering.Butbytheturnofthe20th

centurynewmaterialsandmethodsofconnectingthemhadbecomereadilyavailable. Andsomankind

createdaneedforitselftopushfortaller,safer,stronger,andcheaperbuildings.

Forourproject,weweretaskedwithdesigninga3storyofficebuildinginanearthquakeprone

area. WeincorporatedourselvesintothestyleofconservativethinkingthatisreflectedintheAISCSteel

ManualandASCE705MinimumDesignLoadsforBuildings. A requirementwasthatourstructure

shouldconsistofspecialsteelmomentresistingframes. Andthatwouldincorporatethemostviewing

areafortheinteriorofthestructurebutalsoprovidethestrengthtowithstandearthquakesthathave

historicallyoccurredintheWalnutCreekarea.

Accomplishingthedesignandmodelingphasewouldbeahugestepforwardforusaswehave

hadnopriordesignexperience. Ourplanwastohaveeverymemberdesigntheirownstructure. But

witheveryonecontributingtheirworktotheoverallreport. Inthisapproach,ourhopewasthatforeveryonetohavegainedthemostunderstandingoftheconcepts. Thissortofdoeverythingapproach

stemmedfromourinitialapprehensionofpouringthroughpagesoftwosteeldesigntextbooks,the

ASCE705designprocedurecodesandAISCSteelmanualdesigncodes. Ourthoughtswerethatifwe

weretojustcoveronesectionandnotunderstandwhatwasoccurringwiththeothersection,thenwe

wouldmissalotofconnections. Untilweallkneweverypartwell,wewouldnotbeabletodesigna

singlebuildingtogether.

Thelayoutofthisreportfollowsachronologicalorder. Webeginbypresentingtheproblem

statement,ourplanofapproachandthenadesignphase. Thedesignphaseconsistedofdetermining

thebeamsandcolumnsbucklingrequirements. Thenactuallytestingfortheloadrequirementsforthebeamsandthencolumns. Eachofcoursehavingdifferentrequirements. Lastlywefinalizeandimprove

uponourdesignsbasedonearthquakeloadsthatwesubjectontothestructure. Thisanalysisconsists

oftwomethods,anEquivalentLateralForceandaperformancebasedtimehistory.


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DesignChallenge

TheproceduretookthroughoutthisinternshiphasbeentofollowwhatDr.Chenandour

graduatestudentQiMinglaidoutforus. Partofthechallengewasthatresourcesweredifficultto

procureandassowereliedheavilyonourgraduatestudentsknowledge. Butslowlywegotusedtothe

laborious2100+pagesPDFonlinereferencematerialsalongwithmanualotherPDFreferencemanuals

thatweprocured.

ProblemStatement

DesignathreestorybuildingintheWalnutCreekarea.Thebuildingwillbeanofficebuildingin

anearthquakepronearea. Weweretousethestandard50[psf]orlbspersquareftasaliveloadfor

eachfloor. Theroof,3rd

floor,and2nd

floorweredesignedtohold95[psf],90[psf],and92[psf]

respectively. Thesquarefootageforeachfloorwastobe11250sqft. Andthecolumnsfromthebase

tothetopfloorwere13ft,11ftand11ft. ThisbuildinghadtobedesignedaccordingtoAISCscodeand

ASCEsequilateralforceprocedures. Theequilateralforceprocedureincludesequivalentearthquakeforcesmeanttoimitatehistoricalearthquakeloads. Andfinallywedesignedandmodeledthestructure

inSAP2000repeatingthedesignphaseasnecessary.


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GeneralProcedure

1. UtilizetheEquivalentLateralForceProcedureinASCE072. UnderstandtheSteelDesignandtheStructuralAnalysisbookonbeamsandcolumnsalongwith

typesofconnectionsandblockshear.

3. FollowedtheEquivalentLateralForceProcedureanalysistechniqueaslaidoutintheASCE7manual.

4. DesignedthebeammembersforeachflooraccordingtoAISCcodesfromtheLRFDSteelDesignbook,inexcel.

5. DesignedthecolumnmembersforeachflooraccordingtoAISCcodesfromtheLRFDSteelDesignbook,inexcel.

6. Modeledthebeamsandcolumnsalongwiththebaseshear,liveloads,anddeadloadsintoSAP2000. Rananalysis.

7. UtilizeSAP2000sstorydeflectionbyelasticanalysistoaidinthestorydriftdeterminationundertheASCE07EquivalentLateralForceProcedure.

8. RedesignedthebuildinginaccordancewithASCE07EquivalentLateralForceProcedures12.8.6StoryDriftDetermination.

9. Assesandanalyzefourearthquakestoeachbuildingthroughatimehistoryanalysis.Execution

Beingfreshnewengineeringstudentswetooktoanyandalladvicethatourgradstudent,Qi

Ming,instructed. WewererecommendedtofollowtheAISCSteelmanual. Atfirstweweredauntedby

howvastandconfusingitinitiallywas. ButafterspendingmuchqualitytimewiththePDFversionofthe

book,wegrewtorelyonitseverystepsandrequirements. Thebookaidedinourunderstandingofwhy

andhowtoanalysisstructures. Thesearetheresultsfromourworkdesigningeachmembersection.Alsoanappendixisattachedthatincludesthecalculationsandconstantsforeachresult.

Webeganwiththelocalbucklingcheckforourbeamsandcolumns;thisrequirementensures

thatthesectionmemberswepick,fromtheAISCdatabase,willconformresistcertainbuckling

requirements.

LocalBuckling

Allbeamsandcolumnmembershavetopassawebandflangethicknessratiotest. Thisisalso

referredtoasLocalBucklingreferencingtosectionB4ChapterBintheAISCSteelManual.Classificationofsectionsforbucklingisnecessarytopreventlocalbuckling.

ChapterBsectionB4.requiresthatwecheckthebeamsandcolumnsofthemembersfor

compact,noncompact,andslenderness. Forourpurposeswerequiredthatthebeamsandcolumnsbe

compactandnonslender. Thiswasespeciallyimportantforourcolumnsectionsaselementsthatare

tooslendernesswillcausebuckling.


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Theclassificationforeachsectionbreaksdownintotwobasicelements,stiffenedand

unstiffenedelements. ForanIBeamorWsection,thebeamcontainsacentralwebsandwiched

betweenatopflangeandbottomflange. Generallywewantcompactsectionsforourbeams,thisis

becausecompactbeamstendtobucklelessandsoitisadesiredtraitinbeams. Butforourcolumns,

becausetheyholdverticalloads,wedesireanoncompactshape. Noncompactshapesallowforplastic

andelasticbucklingbehaviorandaredesiredforearthquakeresistantframessincethecolumnswillbe

allowedtosway.

Figure4.9illustratesatypicallyWsectionforcolumnsections. Wearerequiredtocheckthat

theratiobetweentheflangeelementsthicknessandwidthconformtotheAISCcode. Itisalso

necessaryfortocheckthewebfortheheightandwebthickness.Thewebisconsideredthestiffened

elementandtheunstiffenedelementsarethetopandbottomflanges.

LocalBucklingResults

ColumnsFlangeCheck

Columns

DesignStep1:AISC

B4.Classificationof

SectionsforLocal

Buckling,Flange Upperlimit

Width

Thickness

Ratiosof

Members,

Flange

LocalStabilityCheckfor

UnstiffenedElements,Flange

Members

AISC13thEd.LRFD

Formula r=0.56*(E/Fy)1/2

=bf/(2*tf) r=0.56*(E/Fy)1/2> =bf/(2*tf)

W18X65 Roof 13.49 5.06 Okay

W18X71 3rd 13.49 4.71 Okay

W18X97 2nd

13.49 6.41 Okay


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ColumnsWebCheck

Columns

DesignStep1:AISC

B4.Classificationof

SectionsforLocal

Buckling,Web Upperlimit

Width

Thickness

Ratiosof

Members,Web

LocalStabilityCheckfor

StiffenedElements,Web

Members

AISC13thEd.LRFD

Formula r=1.49*(E/Fy)1/2

=h/(tw) r=1.49*(E/Fy)1/2

> =h/(tw)

W18X65 Roof 35.88 35.70 Okay

W18X71 3rd

35.88 32.40 Okay

W18X97 2nd

35.88 30.00 Okay

BeamFlangeCheck

TransMember

Check:

Flange

Check

Member

Properties

Compact

Checker

NonCompact

Checker

Slender

Checker

CheckFlange

Overall Formula =bf/(2*tf) p p< r > r

W21X68 Roof 6.04 Yes,Compact No,Compact NotSlender

W21X68 3rd 6.04 Yes,Compact No,Compact NotSlender

W21X68 2nd 6.04 Yes,Compact No,Compact NotSlender

LongMember

Check:

Flange

Check

Member

Properties

Compact

Checker

NonCompact

Checker

Slender

Checker

CheckFlangeOverall Formula =bf/(2*tf) p p< r > r




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BeamWebCheck

TransMember

Check:

Web

Check

Member

Properties

Compact

Checker

NonCompact

Checker

Slender

Checker

CheckWeb

Overall Formula =h/(tw) p p< r > r




LongMember

Check:

Web

Check

Member

Properties

Compact

Checker

NonCompact

Checker

Slender

Checker

CheckWeb

Overall Formula =h/(tw) p p< r > r




LocalBucklingConclusion

Fromthedatabasetablesabove,wewereabletopickeachbeamandcolumnandtheyreflect

therequirementsthatwerestatedabove. Forourcolumns,werequiredthemtobelessthantheupper

limit rmeaningthatourcolumnmemberswerenoncompact. Thisisgoodnewsaswewillseelater

thatnoncompactcolumnstendtoallowforelasticandplasticbucklingbehavior. Iftheyweretotally

inelastictheywouldneverpassinanearthquakeasthecolumnswouldbeunabletoreformtheir

originalshape.

Forbeamswewereabletoachievecompactnessintheflangeandwebsections. Thisallowsfor

minimalbucklingofourbeams. Thisisgoodnewsasforbeams;theyrequirethatthefloorshave


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minimalbuckling. Iftheywerenotthen,forexamplesomeonebringsinheavyequipmentorthereisa

largegatheringofpeople,thefloorwouldnoticeablebuckle! Soacompactbeamisthemostfavorable

sectionforourbeamselections.

Designof

Beams

and

Requirements

Forthebeamsdesign,wehadtwotypesperfloor. Onetypeisa30ftlonginthetransverse

directionofthebuildingandthenextisa25ftlongbeaminthelongitudinaldirection. Thereareatotal

of18beamsinthetransversedirectionand20beamsinthelongitudinaldirection. Andforeachfloor

therewasadifferentdeadloadrequirementalongwiththeliveloadandtheearthquakeload,story

force,distributedtoeachfloor.

WefirststartedoutwithAISCChapterF,F1andF2. FromsectionF2.1wewereabletoassume

thatthenominalmomentwouldbeequaltotheplasticmoment. Thisassumptionisokaybecauseour

beamspassedthischeck;Zx/Sx


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CHECK:

Floor

AISCSteelDesign

Requirements Mubeam Murequired

MubeamvsMu

required

Roof W21X55 5670 1669.090 Okay

3rd W21X55 5670 1617.266 Okay

2nd W21X55 5670 1637.996 Okay

BeamDeflectionCheck

Abeamwilldeflectnomatterwhatloadyouplaceonit. Eventhebeamsownweightaddsto

thedeflections. Butthisisthemostimportantanddeterminingfactorforourdecisionsindeciding

whichbeamsectiontoselect.

TRANS

MEMBER

CHECK:

Maximum

PermissibleLive

LoadDeflection MaterialProperty

Formula

Constant

[inch] Check

Floor

AISCSteel

Design

Requirements =(5/384)*((wL*L4)/(E*Ix)) L/360 =(5/384)*((wL*L4)/(E*Ix))


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2nd W21X55 0.697 0.833 Okay

ShearStrengthofBeam

Thewebsectionofthebeamgenerallyhastohandletheshearforcesfromtheloadsaboveit.

Usuallyhowevertheshearstrengthofthebeamismuchgreaterthantherequiredshearstrengthfrom

theprovidedloads. Belowareourresultsfromtheshearstrengthcheck.

Anexampleofshearisprovided:

TRANS

MEMBER

CHECK:

Step3,CheckShear

Strength MaximumShear

VurequiredTransverseShear

perMember[kipsft] CheckShear

Floor

AISCSteelDesign

Requirements v*Vn,[kips] Vurequired=(1/2)*wu*L v*Vn>Vu

Roof W21X68 244.971 34.912 Okay

3rd W21X68 244.971 33.876 Okay

2nd W21X68 244.971 34.290 Okay

LONG

MEMBER

CHECK:

Step3,CheckShear

Strength MaximumShear

VurequiredLongitudinalShear

perMember[kips] CheckShear

Floor

AISCSteelDesign

Requirements v*Vn,[kips] Vurequired=(1/2)*wu*L v*Vn>Vu

Roof W21X55 210.6 33.382 Okay

3rd W21X55 210.6 32.345 Okay

2nd W21X55 210.6 32.760 Okay


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DesignofColumnRequirements

Whilethedesignofthebeamsisimportantforeachfloor,itisthecolumnsthathavetosupport

theweightoftheentirebuilding. Soitisthecolumnsthatwehavetopaythemostattentionto. After

checkingthelocalstabilityabove,wenowhavecolumnsthatareabletohandleplasticandelastic

bucklingconditions. UnderAISCChapterE,DesignforCompressionMembers,itstatesthatwemust

checktheeffectivelengthandslendernessratiosofourcolumnmembers. Thisisimportantasthereisa

limitthatourcolumnmustnotexceedintermsofitseffectivelength. Onceitexceedsthislimitour

columnswouldbegreatlysusceptibletobuckling. Bucklingisbad,butwealsowanttotakein

considerationhighceilings. Generallyclientsortheownerswouldwanttoincludehighceilingsandthus

highcolumnsastheyallowforamoreappealingaestheticfeeltotheenvironment.

EffectiveLength

and

Slenderness

Ratio

Limitations

Thereisaneffectivelengththateachcolumnprovides. Iftheeffectivelengthislowthenthere

willbesomeminoraxisbuckling,asshowninFig(a)above. Butiftheeffectivelengthishighthenthere

willbesomemajoraxisbuckling,asshowninFig(b)above. Soitisimportanttocheckforthislimitation.

Wealsocheckedourmembersslendernessratioasthispertainstoeffectivelengths. Asbucklingisa

majorandrealconcernallofourchosenmemberspassedthetests.


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Columns AISC13thEd.LRFDFormula

SlendernessRatio,

ChapterE2.

AISCChapterE

SectionE2.

Check

Status

Floors

ChapterE2.SlendernessLimitations

andEffectiveLength (KL/ry)

Donotexceed

200

(KL/ry)


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W18X65 Roof

InelasticColumns,

Fcr 32.01 611.34

W18X71 3rd

InelasticColumns,

Fcr 32.18 669.24

W18X97 2nd

InelasticColumns,

Fcr 38.81 1106.04

Columns

DesignStep1:AISCE1.

GeneralProvisions

Sumof

FactoredLoads

Design

Compressive

Strength

Relationshipbetween

LoadandStrength

Members

AISC13thEd.LRFD

Formula

Purequired=

1.2*D+1.6*L c*Pn Pu c*Pn

W18X65 Roof 95.04 550.20 Okay

W18X71 3rd 188.12 602.32 Okay

W18X97 2nd 282.40 995.44 Okay

Andfinallywecheckthatourcolumnmeetsthecompressivestrengthrequiredbyourfactored

loads. Noticethatweexceedtherequiredloadsbyalargefactor. Thisisbecausethecolumns

determiningfactorisinthestorydriftcalculation. Thestorydriftincludesthestoryforcesand

earthquakeloadsintoconsideration,andisamuchstrictercode.

AnalysisTechnique

Thejobofacivilengineeristoensurethatthebuildingswecreatearebuilttowithstandthe

testsoftimeandnature. Andbecauseofsuch,ithasbeenprovennecessarytoperformanumberof

analysistechniquesinourbuildingdesigns. Suchtwotechniquesaretimehistoryanalysis,a

performancebasedanalysistechnique,andASCE705sequivalentlateralforceprocedure. Thelatteris

aprocedurethatisdesignedtomimicrealloadscausedbyearthquakes,whiletheformerismeanttotestthebuildingperformanceagainstanactualearthquake. Ourthreestorywillbedesignedaccording

tobothmethods. Ourgoalistodeterminewhichmethodwillproducethebestresultswiththemost

minimaldesignspecifications.


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StructuralDesignMethods

SafetyandUsabilityarethemajorthingsEngineerstakeintoconsiderationwhendesigninga

structure.Thereareseveralapproachestodesigningstructuresthatmustwithstandseismic,wind,snow,

andotherloads.Oneapproachistocreatemodelsthataregoodapproximatesoftheactualstructure

andobservehowthesemodelsrespondtothedifferentloadsappliedtothem.Theotherapproachis

thedetailedanalysisofthestructure.Detailedanalysiscanalsohavevariousapproaches,suchasthe

EquivalentLateralForceProcedureandTimeHistoryAnalysis.

EquivalentLateralForceProcedure

TheEquivalentLateralForceProcedureinvolvesapplyingstaticforcesonthestructureand

analyzinghowitreactstotheseforces.Also,theforcesareusuallyappliedatthejointsofthemembers,

whichmakesthecrosssectionalmembersactliketwoforcemembers.Themostimportantforceinthis

procedureisthebaseshear,orthesumofallthelateralforcesaffectingthestructure.Thestrengthor

capacityofthemembersmustbeabletowithstandthebaseshear.Tofindoutiftheappropriatemembersareselected,engineersperformthestorydriftcheck.Otherfactors,suchastheseismic

responsecoefficient,responsemodificationfactorandimportantfactormustbetakenintoaccount

whenfollowingthisprocedure.ASCE7section12.8carefullyenumeratestheequationsandconditions

thatmustbesatisfiedwhenfollowingtheEquivalentLateralForceProcedure.

SeismicResponseCoefficientTheSeismicResponseCoefficient,Cs,isusedtodeterminethebaseshearofthestructure.

AccordingtoASCE7,thebaseshearcanbeobtainedbymultiplyingtheResponseCoefficientbythe

structureseffectiveweight.Theeffectiveweightofthebuildingincludesthedeadloadandotherloads,

suchasliveandsnowloads.

ResponseModificationFactorWhenengineersdesignastructure,theyexpectthebuildingtosustainpermanentdamage.

Eventhebestdesignedbuildingsaresusceptibletoinelasticdeformation.Withthisismind,thegoalof

theengineeristodesignabuildingthatwillnotcollapse.TheResponseModificationFactor,R,accounts

fortheabilityofthestructuretoabsorbenergywithoutcollapsingoritsenergydissipationcapacity.This

modificationfactordependsonthetypeofstructurebeingexamined.Themoreductilethestructureis,

thehigheritsmodificationfactor.Aductilestructuremeansithastheabilitytochangeshapeunder

stressbeforeitbreaks.

ImportanceFactorTheImportanceFactor,I,dependsontheuseofthebuilding.Itcanbedeterminedbyreferring

toASCE7table11.51,whichincludesdifferentOccupancyCategoriesforbuildings.Facilitiessuchas

hospitalsandschoolshaveahighImportanceFactor.Facilitieslikestoragebuildingsareassignedwith

loweraImportanceFactor.


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TimeHistoryAnalysis

Itisveryimportanttounderstandhowbuildingsmovebefore,during,andafteranearthquake.

TimeHistorygraphsallowengineerstostudythestructuresbehavioroveraspecifiedamountoftime.

ThemaindifferencebetweenEquivalentLateralForceProcedure(ELFP)andTimeHistoryAnalysis(THA)

isthetypeofloadusedtosimulateanearthquake.InELFP,thebaseshearisthemainload,andtheanalysisisstatic.InTHA,simulationsaredonebyincorporatingrealearthquakesrecordedinthepast.

ThefirststepinperformingaTimeHistoryAnalysisistodecidewhataccelerogramtouse.

Accelerogramsaregraphsthatshowgroundaccelerationoveraperiodoftime.ThePacificEarthquake

EngineeringResearchconductstherecordingoftheseaccelerogramsandallowsthepublictodownload

earthquakedatafromtheirwebsite.

Theseaccelerogramsarethenuploadedontostructuralanalysisprograms,suchasSAP2000.

Theuploadedearthquakemustbeamplifiedtomimictheeffectsofthebaseshear.Designersapplythe

earthquakedataasaloadcombinationandrunthesimulation.Checkingthestorydriftisdifferentfrom

thestorydriftcheckinstaticanalysis.Thehighestjointisusuallychosentobeexaminedbecausethe

totaldeflectioncanbeseenthere.Mostprogramshavefeaturesthatletthedesigneranalyzethe

displacementhistoryofthatjoint.Thelargestdisplacementmustnotexceedtheallowable

displacementdeterminedbythebuildingcode.

AnalysisImplementation

ASCE70512.8.1EquivalentLateralForceProcedure

TheEquivalentLateralForceProcedurewasthelaststepinourdesignprocess. Thisincludescalculatingthestoryforcesforeachindividuallevel,assigningitinSAP2000andrunningthesimulation

togetourdeflectionbyelasticitytestresult. Oncethisresulthasbeenobtained,weareabletotestif

ourbuildingwillpassASCE705srequirementformaxallowablestorydrift. Belowisatabulationofour

resultsafterithasbeenrunthroughSAP2000sanalysisprogram.

Floors

DeflectionbyElastic

TestU1,xe

Deflectionof

Levelx,x

MaxAllowable

Drift a

DriftCheck,

2 1 [units] Check

Roof 1.940 10.669 3.3 1.576 [inch] Okay

3rd

1.653 9.093 3.3 2.823 [inch] Okay

2nd 1.140 6.270 3.9 1.140 [inch] Okay

Fromthetableabove,itisclearthatourbuildinghaspassedthedriftcheck. Atthemostextremeend,

themaxallowabledriftforthe3rd

flooris3.3inches. Ourbuildingmanagedareasonable2.82inchdrift.


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Soatourmostextremeendwewereabletoallowupto85%ofallowabledrift. Thistellsmethatwe

didnotexceedtherequirementanddidnotoverperformtherequirement. Thussavingintotalweight

ofourbuildingmaterialandofcoursecosts.

Abovedisplaysthestoryforcesappliedatthecenterofeachlevelforour3DmodelinSAP2000.

TimeHistory

Analysis:

OurgoalistoanalyzetheperformanceoftheASCE705procedurewithversustimehistory

analysisandmodeltheperformanceina3storystructure. Theframewillbecomposedentirelyof

specialmomentresistingframes. Wewillfirstapplytheequivalentlateralforceprocedure,andthen

pickourbeamsandcolumns,runananalysistest,andfinallydetermineifthebeamswechosewould

passthestorydriftcheck;repeatasnecessaryuntilthestorydriftconditionssatisfy. Theprocedure

remainsthetrueforthetimehistoryanalysis. ThedifferencebetweenthetwomethodsisthattheELFP

reliesonamaximumcomputedbasesheartodistributethelateralforcesforallstories. ThatisELFPwill

testthebuildingforthemaximumpredictedearthquakethatASCE7determinedasallowable. This

processfordeterminingthemaximumbaseshearforourbuildingwasdevelopedthroughresearchinto

earthquakecoderequirementspertainingtocertainearthquakeproneareas. Whilethetimehistory

analysismethodwillpitourdesignelementinaperformancebasedtestbasedonactualearthquake

data.

Howthebuildingdriftsperflooristhebeamandcolumnrestrictivefactorforinourdesigns.

Buildingspriortothesecodesdidnotdriftuniformlyandassuch,structuresofthepastwouldcrumble


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duringanearthquake. Butabuildingthathassomeallowabledriftisbetterabletodissipatetheenergy

fromanearthquakethroughouttotherestofthestructure.

Results:

Inourpreviousfindings,ourresultshaveindicatedthatspecialmomentresistingframesutilize

heavierbuildingmaterials,buttheyoffersuperiorexpansiveviewsandmoreflexibleestheticdesigns.

Stilltheyaremuchmoreaffordableandsimplertoimplementthanbaseisolateddampeningsystems.

Inourprocedureswetestedframesystemafterframesystem,eachtimeanalyzingthedrift

betweeneachfloorlevels,takingnoteofthechangeseachtime.Ourgeneralfindingsindicatedthatthe

3rdfloorbeamsincurredthelargestdrifts. Furthertestingindicatedthatifweincreasedthebeamsize

forthe3rdfloorbeams,weincurredlessdrift. The3rdfloorsystemwasthedeterminingfactorin

controllingtheamountofdriftforourbuildingsystem. Thiswastrueforbothlateralandlongitudinal

directionalearthquakeforces. Ifwewerenottoconsiderfortheeaseofconstruction,itwouldbe

possibletojustbeefupthe3rd

floorbeamsinordertolightenupthecolumnsfortherestofthebuilding.

Asitwere,thecolumnsmorethanexceededtherequireddeadandliveloadsandsoourdesigncould

benefitfromalighterdesign.

OnoneoccasionwhendesigningourstructureaccordingtoASCE705wewereabletoreach

lessthan1%oftheallowabledrift. Thisdevelopedsomeinterestingperformanceachievements.

Notably,ouraveragedifferenceuntilreachingthemaxlimitwas26.37%forall4performanceinduced

earthquakes. Performancewise,thisisgoodnewsasitiswellwithinASCE7designrequirements. And

since3outof4oftheearthquakesoccurredinCalifornia,ourdesignswouldsavelives. Howevertaking

intoaccountthe1995KobeearthquakethatstruckJapan,causingthemostdamageintermsoflivesin

thisproject,weobservedratherclosestorydriftsdeveloping. Theclosestbeing6.95%tothemax

allowabledrift. Despitethisfinding,itisstillwithintheallowableranges.

AftermuchcalculationandlearningofthecodesandhowtoutilizeitinourSAP2000student

editionsoftware,wewereabletopresenta3Dmodelofourdesign! Thebeamsthatwehavepicked

arerepresentedinthetablesbelow.BelowthemareresultsfromSAP2000sbeamandcolumnanalysis

checks.

Beam

Selection

TransBeam

Selection

LongBeam

Selection

Floor

Levels TransverseBeam StatusCheck

Longitudinal

Beam StatusCheck

Roof W21X68 Okay W21X55 Okay

3rd W21X68 Okay W21X55 Okay


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2nd W21X68 Okay W21X55 Okay

Columns ColumnSelection

FloorLevels Columns OverallStatusCheck

Roof W18X65 Okay

3rd W18X71 Okay

2nd W18X97 Okay

SAP2000sbeamandcolumnindividualmembercheckforstress/capacity.Allmemberspassed.


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Ahigherresolutionvisualqualitycheckofthebuildinganddesign.

BelowisaCompressionanalysisoneachcolumnmember. Thecolumnsontherightofthebuildingare

experiencingmorecompressionbecausetheearthquakeforcewasdirectedfromlefttoright.And

becauseofthatthecolumnsontheleftofthebuildingareexperiencinglesscompressiveforce. Thisis

goodbecausethecolumnsexperiencingthemostcompressiveforcesareabletostillpasstheminimum

designchecks.


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BelowisathestorydriftsimulationinSAP2000.Weinputedeachforceoneachleveltoachievea

uniformdriftandthusasimulatedearthquake,abietinonedirectiononlyfornow.

Thispicturedisplayshowweappliedourdeadloads. Similarlytheliveloadsandotherloadswere

appliedinthisfashionaswell. Weuseddistributedloadsastheybestsimulatedrealworldloads.


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SeismicSystemResearch

Choosingtheappropriateframeforabuildingiscrucialinprovidingasafeandstable

environmentforthebuilding.Buildingsaresusceptibletocollapseifthewrongtypeofframeischosen.

Itisveryimportanttoacknowledgeandunderstandwhatthebuildingwillbeusedfor,whowilloccupy

thebuilding,whenthebuildingisexpectedtobecompleted,whatkindofseismicactivityispresentin

thearea,andhowmuchfundingwilltheprojectreceive.Itisalsoimportanttounderstandwhattypes

ofseismicframesorsystemsareavailableinthemarket.

TwoofthemostcommonlyusedframesintheengineeringindustryareMomentResisting

Frames(MRF)andBracedFrames.MomentResistingFramesareusuallymadeofsteelandtheycan

resistloadsinthelateraldirectionsuchaswindsorearthquakeloads.Theyareintendedtoremain

elasticandexhibitductilebehavior,meaningtheystretchbeforebreakingapart,duringamajor

earthquake(propertyrisk.com).EccentricallyBracedFrames (EBF)areatypeofbracedframethathas

highelasticstiffnessandsuperiorinelasticperformancecharacteristics(tufts.edu).Muchlikeatruss,

EBFsworkintensionandcompression,unlikeMRFs,wherebendingmomentaffectsthemembers.

Toimprovetheperformanceoftheseismicframe,engineersutilizevariousseismicorenergy

dissipationsystems.OnesuchsystemistheDampingsystem.Asitsnamesuggests,thissystem

dampenstheseismicenergyabsorbedbytheframes.Thissystemhasachambercontaining

incompressiblefluidthattransfersbetweenthechamber,thusconvertingkineticenergyintoheat

energy.Thisheatenergyissafelydissipatedintotheenvironment(akirawada.com).Anotherseismic

systemthatreducesthedamagedonebyearthquakesisbaseisolation.Baseisolatedstructuresabsorb

lessshearforcesacrosstheirisolationsurfacethanstructuresthatarenotisolatedfromthebase.

Althoughthemainstructureisisolatedfromthebase,itdoesnotmeanthatthebuildingisearthquake

proof(Berkeley.edu).

TodeterminewhichSeismicFrameperformsbetterundervarioustypesofloads,wehave

createdmodelsonSAP2000toexamineandcomparethebehaviorofMRFsandEBFs.


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MomentFrameVsEccentricallyBracedFrame

We havecreated2DmodelsofmomentandbracedframesonSAP2000.Theyareof

equallengthandheight.Theyalsousethesametypeofcrosssectionbeams.Wethenapplied

deadandearthquakeloadsontotheframesandranasimulationonSAP.

Afterthesimulation,wediscoveredthattheMomentResistingFrame(MRF)hada

largerdeflectionthantheEccentricallyBracedFrame(EBF).Also,therearelessshear,axial

force,andbendingmomentactingontheEBFthantheMRF.


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ConclusionsonTypesofFrames

EccentricallyBracedFramesworkbetterthanMomentResistingFrames,buttheyare

hardertobuildandcostmore.TheDampingSystemcanbeincorporatedintoeitherframeto

improvetheframesperformance.Anotherwayofimprovingtheperformanceofaframeisto

incorporatebaseisolation.Iftheownerofthebuildingwantstouseaneconomicandreliable

frame,anMRFwithisolatedbaseishischoice.Butifbudgetisnotanissueandhewantsavery

strongframe,anEBFwithdampingsystemsishischoice.

Conclusions

TheconclusionwemadefromtheseresultstellusthatformostUSbasedstructuresandseismic

activity,theASCE705EquivalentLateralForceProcedureperformswithintheacceptablelimits. Our

buildingdesignscouldhavebeenloweredtosaveweightinmaterialcosts.

Inthetenweeksleadinguptothefinalizationofourproject,wewouldliketothankallofthe

SanFranciscoStatestructuralengineeringgraduatesstudentsforlendingustheirknowledgeand

allowingustopartakeintheirstudyspace. Ofnote,weareespeciallygreatfullandindebtedtoour

graduatestudentQiMingZeng. WithoutQiMingZengstirelesscommitmentsandoffhourshelp,we

wouldhavehadagreatdisconnectinregardstoretainpassionandknowledgeinthefieldofcivil

engineering. AndofcoursewithoutthehelpofourfacultyadvisorsDr.ChengChenandDr.Amelito

Enriqueztherewouldbenothing! Thankyou.


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References

AISCSteelConstructionManual,13theditioncopyright2005

ISBN156424055X

ASCE/SEI705MinimumDesignLoadsforBuildingsandOtherStructurescopyright2006

ISBN0784408319

SteelDesign4thEdition,Segui,T.Williamcopyright2007

ISBN10:0495244716

http://www.akirawada.com/paper/conference/state.pdf

http://engineering.tufts.edu/cee/people/hines/HinesJacobOrlando2010.pdf

http://www.propertyrisk.com/refcentr/steelside.htm

http://nisee.berkeley.edu/lessons/kelly.html

http://home.iitk.ac.in/~vinaykg/Iset443.pdf

http://www.inrisk.ubc.ca/process.php?file=TIMBER_STRUCTURES/Seismic_Design.pdf

http://www.spsu.edu/architecture/classes/3212Kaufman/Lateral%20Force1.pdf

ABeginnersGuideToASCE705,www.bgstructuralengineering.com


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Appendix

LocalBucklingConstants

GlobalFlange

MemberProperties

CheckAgainst[Lower

Limit] CheckAgainst[UpperLimit]

Formula p=0.38*(E/Fy)^(1/2) r=1.0*(E/Fy)^(1/2)

MemberProperties 9.15 24.08

GlobalWebMember

Properties

CheckAgainst[Lower

Limit] CheckAgainst[UpperLimit]

Formula p=3.76*(E/Fy)^(1/2) r=5.70*(E/Fy)^(1/2)

MemberProperties 90.55 137.27

BeamConstants

TRANS

MEMBER

PROPERTIES

ReferenceBoxA:Wu

ReferenceCalculations,

forTransMember

liveloadper

transverse30ft,L

deadloadper

transverse30ft,D

FloorLevels #numberftperfloor #totalrate[kips/ft]

#numberftper

floor #totalrate[kips/ft]

Roof 14.8 0.493 28.1 0.938

3rd 14.8 0.493 26.6 0.888

2nd 14.8 0.493 27.2 0.908

TRANS

MEMBER

PROPERTIES

Step1&2,Design

Strength

FactoredUniform

Load,Wu

Transverse

[12.4.2.3]

Mumax=

Transverse[kips

ft]

MumaxTransverse

[kipsinch]

FloorAISCSteelDesign

Wu=(1.2+

0.2*SDS)*D+ *QE+ Mumax= Mumax=


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Requirements 1*L+0.2*S (1/12)*Wu*L2 (1/12)*Wu*L

2

Roof W21X68 2.327 174.562 2094.741

3rd W21X68 2.258 169.379 2032.553

2nd W21X68 2.286 171.452 2057.428

TRANS

MEMBERPROPERTIES Step3,ShearStrength

FactoredUniformLoad,WuTransverse[12.4.2.3]

MaximumNominalShear

Floor

AISCSteelDesign

Requirements

Wu=(1.2+0.2*SDS)*D+ *QE

+1*L+0.2*S

Vnmax=0.6*Fy*Aw,

[kips]

Roof W21X68 2.327 272.19

3rd W21X68 2.258 272.19

2nd W21X68 2.286 272.19

ColumnCalculations

Columns

AISC13thEd.

LRFDFormula

Sumof

Factored

Loads ElasticCriticalBucklingStress[ksi]

Slenderness

Parameter, c

Floors AISCConstants

Purequired=

1.2*D+1.6*L Fe=(2*E)/(K*L/ry)

2

c=

(K*L/r*)*(Fy/E)1/2

Roof W18X65 95.04 46.92 1.03

3rd W18X71 188.12 47.47 1.03

2nd W18X97 282.40 82.59 0.78


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EquivalentLateralForceProcedureWorkReferenceBox3

VerticalDistribution

Factor

Level [kips] [ft] [kft]

[kips] SumV[kips]

Roof 1068.75 35 90338.54 0.534 259.27 0.00

3rd 1012.50 24 53443.96 0.316 153.38 259.27

2nd

1035.00

13 25418.02 0.150 72.95

412.65

Total 3116.25 169200.52 1.000 485.60 485.60

CE FinalReport

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