View
240
Download
0
Category
Preview:
Citation preview
7/29/2019 CE FinalReport
1/29
SeismicEvaluation&Design:SpecialMomentResistingFrameStructure
SanFranciscoStateUniversity,CanadaCollegeandNASASponsoredCollaboration
FinalPaper2011August,15
By:AndrewChan,JohnPaulino,MoisesQuiroz,andJoseValdovinos
Advisor:Dr.ChengChen
StudentAdvisor:QiMingZeng
7/29/2019 CE FinalReport
2/29
1|P a g e
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
7/29/2019 CE FinalReport
3/29
2|P a g e
Results:........................................................................................................................................................ 18
SeismicSystemResearch............................................................................................................................ 22
MomentFrameVsEccentricallyBracedFrame...................................................................................... 23
ConclusionsonTypesofFrames............................................................................................................. 24
Conclusions................................................................................................................................................. 24
References.................................................................................................................................................. 25
Appendix..................................................................................................................................................... 26
LocalBucklingConstants......................................................................................................................... 26
BeamConstants...................................................................................................................................... 26
ColumnCalculations............................................................................................................................... 27
EquivalentLateralForceProcedureWork.............................................................................................. 28
7/29/2019 CE FinalReport
4/29
3|P a g e
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.
7/29/2019 CE FinalReport
5/29
4|P a g e
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.
7/29/2019 CE FinalReport
6/29
5|P a g e
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.
7/29/2019 CE FinalReport
7/29
6|P a g e
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
7/29/2019 CE FinalReport
8/29
7|P a g e
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
W21X55 Roof 7.87 Yes,Compact No,Compact NotSlender
W21X55 3rd 7.87 Yes,Compact No,Compact NotSlender
7/29/2019 CE FinalReport
9/29
8|P a g e
W21X55 2nd 7.87 Yes,Compact No,Compact NotSlender
BeamWebCheck
TransMember
Check:
Web
Check
Member
Properties
Compact
Checker
NonCompact
Checker
Slender
Checker
CheckWeb
Overall Formula =h/(tw) p p< r > r
W21X68 Roof 43.60 Yes,Compact No,Compact NotSlender
W21X68 3rd 43.60 Yes,Compact No,Compact NotSlender
W21X68 2nd 43.60 Yes,Compact No,Compact NotSlender
LongMember
Check:
Web
Check
Member
Properties
Compact
Checker
NonCompact
Checker
Slender
Checker
CheckWeb
Overall Formula =h/(tw) p p< r > r
W21X55 Roof 50.00 Yes,Compact No,Compact NotSlender
W21X55 3rd 50.00 Yes,Compact No,Compact NotSlender
W21X55 2nd 50.00 Yes,Compact No,Compact NotSlender
LocalBucklingConclusion
Fromthedatabasetablesabove,wewereabletopickeachbeamandcolumnandtheyreflect
therequirementsthatwerestatedabove. Forourcolumns,werequiredthemtobelessthantheupper
limit rmeaningthatourcolumnmemberswerenoncompact. Thisisgoodnewsaswewillseelater
thatnoncompactcolumnstendtoallowforelasticandplasticbucklingbehavior. Iftheyweretotally
inelastictheywouldneverpassinanearthquakeasthecolumnswouldbeunabletoreformtheir
originalshape.
Forbeamswewereabletoachievecompactnessintheflangeandwebsections. Thisallowsfor
minimalbucklingofourbeams. Thisisgoodnewsasforbeams;theyrequirethatthefloorshave
7/29/2019 CE FinalReport
10/29
9|P a g e
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
7/29/2019 CE FinalReport
11/29
10|P a g e
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))
7/29/2019 CE FinalReport
12/29
11|P a g e
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
7/29/2019 CE FinalReport
13/29
12|P a g e
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.
7/29/2019 CE FinalReport
14/29
13|P a g e
Columns AISC13thEd.LRFDFormula
SlendernessRatio,
ChapterE2.
AISCChapterE
SectionE2.
Check
Status
Floors
ChapterE2.SlendernessLimitations
andEffectiveLength (KL/ry)
Donotexceed
200
(KL/ry)
7/29/2019 CE FinalReport
15/29
14|P a g e
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.
7/29/2019 CE FinalReport
16/29
15|P a g e
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.
7/29/2019 CE FinalReport
17/29
16|P a g e
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.
7/29/2019 CE FinalReport
18/29
17|P a g e
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
7/29/2019 CE FinalReport
19/29
18|P a g e
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
7/29/2019 CE FinalReport
20/29
19|P a g e
2nd W21X68 Okay W21X55 Okay
Columns ColumnSelection
FloorLevels Columns OverallStatusCheck
Roof W18X65 Okay
3rd W18X71 Okay
2nd W18X97 Okay
SAP2000sbeamandcolumnindividualmembercheckforstress/capacity.Allmemberspassed.
7/29/2019 CE FinalReport
21/29
20|P a g e
Ahigherresolutionvisualqualitycheckofthebuildinganddesign.
BelowisaCompressionanalysisoneachcolumnmember. Thecolumnsontherightofthebuildingare
experiencingmorecompressionbecausetheearthquakeforcewasdirectedfromlefttoright.And
becauseofthatthecolumnsontheleftofthebuildingareexperiencinglesscompressiveforce. Thisis
goodbecausethecolumnsexperiencingthemostcompressiveforcesareabletostillpasstheminimum
designchecks.
7/29/2019 CE FinalReport
22/29
21|P a g e
BelowisathestorydriftsimulationinSAP2000.Weinputedeachforceoneachleveltoachievea
uniformdriftandthusasimulatedearthquake,abietinonedirectiononlyfornow.
Thispicturedisplayshowweappliedourdeadloads. Similarlytheliveloadsandotherloadswere
appliedinthisfashionaswell. Weuseddistributedloadsastheybestsimulatedrealworldloads.
7/29/2019 CE FinalReport
23/29
22|P a g e
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.
7/29/2019 CE FinalReport
24/29
23|P a g e
MomentFrameVsEccentricallyBracedFrame
We havecreated2DmodelsofmomentandbracedframesonSAP2000.Theyareof
equallengthandheight.Theyalsousethesametypeofcrosssectionbeams.Wethenapplied
deadandearthquakeloadsontotheframesandranasimulationonSAP.
Afterthesimulation,wediscoveredthattheMomentResistingFrame(MRF)hada
largerdeflectionthantheEccentricallyBracedFrame(EBF).Also,therearelessshear,axial
force,andbendingmomentactingontheEBFthantheMRF.
7/29/2019 CE FinalReport
25/29
24|P a g e
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.
7/29/2019 CE FinalReport
26/29
25|P a g e
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
7/29/2019 CE FinalReport
27/29
26|P a g e
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=
7/29/2019 CE FinalReport
28/29
27|P a g e
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
7/29/2019 CE FinalReport
29/29
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
Recommended