april 2016 structural design... · 2016-10-26 · nepal: structural design criteria for school...

Structural Design Criteria for School Buildings Nepal: Post earthquake Reconstruction of Schools

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DepartmentofEducation(DOE)MinistryofEducationGovernmentofNepal

April2016


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Acknowledgement

This document has been prepared by the Asian Development Bank (ADB) and Japan International Cooperation Agency (JICA).

The document is intended to be the official guidelines to the Department of Education (DOE), for structural aspects of planning and design of new schools consistent with the Design Guidelines for Type Design of School Buildings which sets out architectural and planning requirements.


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ListofFigures...................................................................................................................................6

ListofTables....................................................................................................................................7

Chapter 1Introduction................................................................................................................9

1.1 Introduction...................................................................................................................9

1.2 ScopeandPurpose.........................................................................................................9

1.3 StructuralSystem...........................................................................................................9

1.4 StructuralComponents................................................................................................10

1.5 Codes,StandardsandReferences................................................................................12

Chapter 2DesignPhilosophyandApproach..............................................................................14

2.1 Introduction.................................................................................................................14

2.2 Definitions....................................................................................................................14

2.3 OverallDesignProcedure.............................................................................................14

2.3.1 DesignProcedure1....................................................................................................14

2.3.2 DesignProcedure2....................................................................................................16

Chapter 3BasicMaterials..........................................................................................................17

3.1 Introduction.................................................................................................................17

3.2 Concrete.......................................................................................................................17

3.3 ReinforcingSteel..........................................................................................................17

3.4 StructuralSteel.............................................................................................................17

3.5 Cold-formedSteel........................................................................................................17

3.6 Masonry.......................................................................................................................18

3.7 Timber..........................................................................................................................18

Chapter 4Loads.........................................................................................................................19

4.1 Introduction.................................................................................................................19

4.2 GravityLoad.................................................................................................................19

4.3 WindLoad....................................................................................................................19

4.4 SeismicLoad.................................................................................................................19

4.5 LoadCombinations.......................................................................................................21

Contents


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4.5.1 Code-basedDesign....................................................................................................21

4.5.2 PerformanceEvaluation............................................................................................22

Chapter 5StructuralSystems....................................................................................................23

5.1 Introduction.................................................................................................................23

5.2 DifferentStructuralSystems........................................................................................23

5.2.1 OrdinaryReinforcedConcreteMomentResistingFramesandMasonryInfillWalls23

5.2.2 SpecialSteelMomentResistingFrames....................................................................24

5.2.3 ReinforcedInterlockingBearingWalls.......................................................................25

5.2.4 SpecialReinforcedConcreteMomentResistingFrame............................................26

5.2.5 Cold-FormedSteelOrdinaryMomentFrame............................................................27

5.2.6 Hot-RolledSteelOrdinaryMomentFrame................................................................27

5.2.7 TimberStructure........................................................................................................27

Chapter 6Code-basedDesign....................................................................................................28

6.1 Introduction.................................................................................................................28

6.2 ModelingofStructuralSystem.....................................................................................28

6.2.1 Beams........................................................................................................................30

6.2.2 RoofTruss..................................................................................................................30

6.2.3 Columns.....................................................................................................................30

6.2.4 Footings.....................................................................................................................30

6.2.5 MasonryInfillWalls...................................................................................................31

6.2.6 ReinforcedInterlockingBearingWalls.......................................................................31

6.2.7 Damping....................................................................................................................31

6.3 AnalysisProcedures.....................................................................................................31

6.3.1 ModalAnalysis...........................................................................................................32

6.3.2 LinearStaticProcedure(LSP).....................................................................................32

6.3.3 ResponseSpectrumAnalysis(RS)..............................................................................32

6.4 ComponentandMemberDesign.................................................................................32

Chapter 7SeismicPerformance-basedEvaluation....................................................................36

7.1 Introduction.................................................................................................................36

7.2 ModelingofStructuralSystem.....................................................................................36

7.2.1 Beams........................................................................................................................38

7.2.2 Columns.....................................................................................................................38

7.2.3 MasonryInfillWallsandReinforcedInterlockingBearingWalls...............................38

7.2.4 Damping....................................................................................................................38


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7.3 AnalysisProcedures.....................................................................................................39

7.3.1 NonlinearStaticProcedureforGravityLoad(NSP)...................................................39

7.3.2 NonlinearTimeHistoryAnalysis(NLTHA)..................................................................39

7.3.3 PushoverAnalysis......................................................................................................39

7.4 PerformanceCriteria....................................................................................................40

7.4.1 ExpectedandLower-BoundStrengthusedinPerformanceEvaluation....................40

7.4.2 PerformanceCriteriaforDesignProcedure1............................................................40

7.4.3 PerformanceCriteriaforDesignProcedure2............................................................45


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ListofFigures

Figure2-1:OverallDesignProcedure1..........................................................................................15

Figure2-2:OverallDesignProcedure2..........................................................................................16

Figure4-1:ResponseSpectraforEarthquakeswithDifferentReturnPeriodsforSoilTypeII(MediumSoilSites)(Ref:Figure7.1b,HazardSpectraforKathmandu(KawashimaAttenuationModel,GC2,5%Damping,NBC400V2.RV8-1994)........................................................................21

Figure5-1:DesignProcedureforOrdinaryReinforcedConcreteMomentResistingFrameswithMasonryInfillWalls.........................................................................................................................24

Figure5-2:DesignProcedureforSpecialSteelMomentResistingFrames....................................25

Figure5-3:DesignProcedureforReinforcedInterlockingBearingWalls.......................................26

Figure5-4:DesignProcedureforReinforcedConcreteSpecialMomentResistingFrame............27

Figure7-1:CapacityCurvefromPushoverAnalysis.......................................................................45


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ListofTables

Table1-1:TypicalStructuralMemberandComponents 10

Table3-1:CompressiveStrengthofconcrete 17

Table3-2:YieldStrengthofReinforcingsteel 17

Table3-3:YieldStrengthofStructuralSteel 17

Table3-4:YieldStrengthofCold-formedSteel 18

Table3-5:StrengthofMasonryPrism 18

Table4-1:LiveLoadandSuperimposedDeadLoad 19

Table4-2:ParametersforWindLoading 19

Table4-3:ParametersforSeismicLoading 20

Table4-4:UltimateStrengthDesignLoadCombinationsusedinCode-basedDesign 21

Table4-5:AllowableStressDesignLoadCombinationsusedinCode-basedDesign 22

Table6-1:ModelingofStructuralSystemforCode-basedDesign 28

Table6-2:AnalysisProceduresusedinCode-basedDesign 31

Table6-3:ComponentandMemberDesign 32

Table7-1:ModelingofStructuralSystemforPerformance-basedEvaluation 36

Table7-2:DampingRatios 39

Table7-3:AnalysisProceduresusedinPerformance-basedEvaluation 39

Table7-4:FactorstoTranslateLower-BoundMaterialPropertiestoExpectedStrengthMaterialProperties 40

Table7-5:AcceptanceCriteriaforGlobalResponseofSchoolBuildings 41

Table7-6:ClassificationofActionsandAcceptanceCriteria 42


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ListofAbbreviations

ACI AmericanConcreteInstitute

ADB AsianDevelopmentBank

ASCE AmericanSocietyofCivilEngineers

DBE DesignBasisEarthquake

DOE DepartmentofEducation

DUDBC DepartmentofUrbanDevelopmentandBuildingConstruction

GON GovernmentofNepal

IBC InternationalBuildingCodes

IS IndianStandard

MCE MaximumConsideredEarthquake

NBC NepalNationalBuildingCode

NEHRP NationalEarthquakeHazardsReductionProgram

NIST NationalInstituteofStandardsandTechnology

NLTHA NonlinearTimeHistoryAnalysis

PDNA PostDisasterNeedsAssessments

PEER PacificEarthquakeEngineeringResearchCenter

PGMD PEERGroundMotionDatabase

RC ReinforcedConcrete

RS ResponseSpectrumAnalysis

UBC UniformBuildingCode


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Chapter 1 Introduction

1.1 IntroductionAmajorearthquakeofshallowdepthmeasuring7.6ontheRichterscalestruckcentralNepalonApril 25th causingwidespread destruction. There have been several aftershocks, including a bigonemeasuring6.8onMay12causingfurthercausalitiesanddamage

The Government of Nepal (GON), and several development partners have developed acomprehensivePostDisasterNeedAssessment(PDNA)document.OneofthesectorconsideredintheoverallPDNAisEducation,whichidentitiestheneedsforrehabilitationandreconstructionofeffected infrastructure foreducation sector, including the schoolbuildingsand facilities. Adraftstrategywaspreparedforreconstructionafterthisdisaster,addressingbothshorttermandlong-termreconstruction,inlinewiththeoverallframeworkof“BuildBackBetter”.

Aspartoftherebuildingstrategy,guidelineshavebeendevelopedforthedesignofnewschools1.Thisdocumentisdevelopedtosupportthestructuraldesignoftheschoolbuildingstobedesignedbasedontheguidelines.Itisimportanttocarryoutproperstructuraldesignofthetypedesignforvarioushazards,aswellasforcosteffectiveness.

Thisdocumentpresents thedesigncriteriaandoverallmethodology tobeused in thestructuraldesignofnewschoolbuildingsinNepal.Thecriteriapresentedincludesspecificinformationonthedescription of the building and its structural system, codes, standards and references, loadingcriteria,materials,modeling,andtheproposedanalysisanddesignprocedures.ThisdocumentwillbeconsideredasanInterimGuidelines,untiltheNBCisrevisedoradditionalhazardmappingandassessmentisavailable.

1.2 ScopeandPurposeThisdocument is intended toprovideaunifiedandconsistent criterion for carryingoutdetailedstructuraldesignofschoolbuildingsinNepal,forresistancetotheeffectsofearthquakesandothernaturalhazards.ThedocumentisparticularlyapplicabletotheTypeDesignofnewschoolbuildingsforthepost-earthquakereconstructioninthe14mosteffecteddistricts.

However,thedocumentmayalsobeusedforstructuraldesignofschoolbuildingsingeneralintheentirecountryonceapprovedandadoptedby theDepartmentofEducation inconsultationwithandagreementofDUDBC.Schoolbuildingscoveredbythedocumentmaybesingleormulti-storybuildings2.ThebuildingsmaybelocatedanywhereinNepal,eitherinmountains,hillsorplains.

1.3 StructuralSystemFivetypesofbasicstructuralsystemsconsideredinthisdocumentwithanobjectivetoachievethegoodperformanceandcosteffectiveness.Thestructuralsystemstobedevelopedareasbelow.

1) Sys-1:Ordinaryreinforcedconcretemomentframewithunreinforcedmasonryinfillwalls

2) Sys-2:Specialsteelmomentresistingframe

1GuidelinesforDevelopingTypeDesignsforSchoolBuildingsinNepal,February2016.

2Foralltypedesign,itshouldbeapprovedbyDOEandDUDBC,andalsomeetcodeprovisionslikefireexitandlift.


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3) Sys-3:Reinforcedinterlockingblockbearingwallsystem(forexample,Habitechsystem)

4) Sys-4:Specialreinforcedconcretemomentframe

5) Sys-5:Cold-formedsteelordinarymomentframe

6) Sys-6:Hold-rolledsteelordinarymomentframe

7) Sys-7:Timberstructure

Isolated and strip footings may be used to transfer the load of the building to supporting soil,dependingon the soil conditionsat site. Steel trussorRC slabmaybeused to support the roofsystem,whereas intermediate floorsmayeitherbeofRCslabonRCframeorcompositeslabonsteelframe.

1.4 StructuralComponentsThecomponentsofstructuralsystemsaresummarizedinthefollowingtable.

Table 1-1 : Typical Structural Member and Components

StructuralSystem Element TypicalComponentTypes

Sys-1:OrdinaryRCmomentframewithmasonryinfillwalls

Foundation RCisolatedfootingforcolumnorRCstripfootingforcolumnandwall

Column RCcolumn

Masonrywall Burnt-brick in c/s mortar (1:6), tied to RCframe

Beam RCbeam

Slabongrade Generallynotrequired

Plinthbeams RCbeam

Lintels RCbeam

Intermediatefloors RCslab

Walls Unreinforcedmasonrywallsfullcontactwithboundingframes

Roofsystem SteeltrussorRCslab

Sys-2:Specialsteelmomentresistingframe

Foundation RCisolatedfootingforcolumnRCstripfootingforcolumn

Column SteelhollowboxorH,IorWshapes,orbuiltupsections

Beam Steel hollow box or I sections, or built upsections


Plinthbeams RCbeam

Lintels RCbeam

Intermediatefloors Compositeslab

Walls Unreinforced masonry walls, Light weightpartitions(non-loadbearingwalls)

Roofsystem Steeltrussorcompositeslab

Sys-3:Reinforcedinterlockingbearingwall(Habitechsystem)

FoundationBrickorstoneRC strip footing for wall reinforced stonemasonryinC/Cmortar

Bearingwall Compressed interlocking blocks, reinforcedwithrebars


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Plinthbeams RCbeam,blocksreinforcedwithrebars

Lintels RCbeam,blocksreinforcedwithrebars

Intermediatefloors RCslab,Habitechwaistslaborsimilar


Sys-4:Specialreinforcedconcretemomentframe


Column RCcolumn

Beam RCbeam


Plinthbeams RCbeam

Lintels RCbeam

Intermediatefloors RCslab



Sys-5:Cold-formedsteelordinarymomentframe


Column Cold-formedchannelsections

Beam Cold-formedchannelsections


Plinthbeams RCbeam

Lintels RCbeam

Intermediatefloors Notpermitted.


Roofsystem Cold-formedsteelchanneltruss

Sys-6: Hot-rolled steel ordinarymomentframe


Column SteelhollowboxorH,IorWshapessections

Beam SteelhollowboxorIsections


Plinthbeams RCbeam

Lintels RCbeam

Intermediatefloors Compositeslab


Roofsystem Steeltrussorcompositeslab

Sys-7:Timberstructure


Column Timbercolumn

Beam Timberbeam


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Plinthbeams RCbeam

Intermediatefloors Timberfloor

Roofsystem Timbertruss

1.5 Codes,StandardsandReferencesThebasicbuilding codes tobe referredare listedbelow.However, specific applicationsof thosecodeprovisionsarediscussedinthecorrespondingsections.

BuildingCodes

• Seismic Design of Buildings in Nepal, Nepal National Building Code, NBC 105: 1994, orlatereditions,asapplicable

• WindLoad,NepalNationalBuildingCode,NBC104:1994,orlatereditions,asapplicable

• CriteriaforEarthquakeResistantDesignofStructures,IndianStandard,IS:1893(Part1)-2002

• InternationalBuildingCode,IBC2012,InternationalCodeCouncil,Inc.

• UniformBuildingCode,UBC97,InternationalCodeCouncil,Inc.

MaterialCodes

• Steel:NepalNationalBuildingCode,NBC111:1994,orequivalent

• Plain and Reinforced Concrete: Nepal National Building Code, NBC 110: 1994, orequivalent

• Masonry:Unreinforced:NepalNationalBuildingCode,NBC109:1994,orequivalent

• Mandatory Rules of Thumb Concrete Buildings with Masonry Infill, Nepal NationalBuildingCode,NBC201:1994

• MandatoryRulesofThumbReinforcedConcreteBuildingswithoutMasonry Infill,NepalNationalBuildingCode,NBC205:1994

• Timber,NepalNationalBuildingCode,NBC112:1994

• ColdFormedLightGaugeStructuralSteelSection,IS811(1987),orequivalent

• DesignofStructuralTimberinBuilding-CodeofPractice,IS883(1994),orequivalent

• CodeofPracticeforUseofColdFormedLightGaugeSteelStructuralMembersinGeneralBuildingConstruction,IS801(1975),orequivalent

• Reinforced Concrete: Building Code Requirements for Structural Concrete andCommentary,ACI318M-08,AmericanConcreteInstitute

• Building CodeRequirements and Specification forMasonry Structures, TMS 402-13/ACI530-13/ASCE5-13,AmericanConcreteInstitute

• Special Design Provisions for Wind and Seismic - 2015, ANSI / AWC SDPWS-2015,AmericanWoodCouncil

• MandatoryRulesofThumbReinforcedConcreteBuildingswithoutMasonry Infill,NepalNationalBuildingCode,NBC205:1994


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• StructuralSteel:SpecificationforStructuralSteelBuildings,ANSI/AISC360-10,AmericanInstituteofSteelConstruction

• SeismicProvisionsforStructuralSteelBuildings,ANSI/AISC341-10,AmericanInstituteofSteelConstruction

• North American Specification for the Design of Cold-formed Steel StructuralMembers,AISIStandard

OtherReferences

• SeismicEvaluationandRetrofitofExistingBuildings,ASCE/SEI41-13,AmericanSocietyofCivilEngineers

• Minimum Design Loads for Buildings and Other Structures, ASCE/SEI 7-10, AmericanSocietyofCivilEngineers

• Assessment of First Generation Performance-based Seismic Design Methods for NewSteelBuildings,Volume1:SpecialMomentFrames,NISTTechnicalNote1863-1,NationalInstituteofStandardsandTechnology

• NEHRP Seismic Design Technical Brief No. 1, Seismic Design of Reinforced ConcreteSpecial Moment Frames, NIST GCR 8-917-1, National Institute of Standards andTechnology

• NEHRP Seismic Design Technical Brief No. 2, Seismic Design of Steel Special MomentFrames,NISTGCR09-917-3,NationalInstituteofStandardsandTechnology

• NEHRP Seismic Design Technical Brief No. 9, Seismic Design of Special ReinforcedMasonry Shear Walls, NIST GCR 14-917-31, National Institute of Standards andTechnology

• Seismic Hazard Mapping and Risk Assessment for Nepal 1994, NBC 400-V2. RV8, 18November1994

• Relatedresearchpapersandreports


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Chapter 2 DesignPhilosophyandApproach

2.1 IntroductionThischapterpresentsthedesignphilosophyandapproachestobeusedinstructuraldesignofnewschoolbuildings.

2.2 DefinitionsThissectiondescribesthedefinitionsofthetermsusedineachbuilding.

Remain elastic:Responseofstructuralcomponentupto firstyield.Whenthe force isapplied tothecomponentitstoresstrainenergy,andwhentheforceisremovedthisenergyisrecovered.

Gravity loads:Weightof structuralcomponents,partition, floor finishing, serviceequipmentandliveload.

Inelastic behavior: Response of structural component, in which some of thework done on thecomponent as it deforms is dissipated, as plasticwork, friction, facture energy, etc. An inelasticbehaviorwillalwaysbenonlinear.

DBE: Design Basis Earthquake. This earthquake is generally used in design, based on codeprocedures.

MCE:MaximumConsideredEarthquake

Capacity design: A design process in which it is decided which components within a structuralsystemwillbepermittedtoyield(ductilecomponents)andwhichcomponentswillremainelastic(brittlecomponents).Thecomponentsaredesignedinsuchawaythatplastichingescanformonlyin predetermined positions and in predetermined sequences. The concept of this method is toavoidbrittlemodeoffailure.

Responsespectrum:Spectrumpresentsthemaximumaccelerationresponseofthebuildingduetogroundshakingwithrespecttonaturalperiods.

2.3 OverallDesignProcedureTwo methods are mentioned that the structural designer would select in consultation withDoE/DUDBC.

2.3.1 DesignProcedure1

Analysisanddesignoftheschoolbuildingsshallbeperformedaccordingtothefollowingstepsforeachstructuralsystem.

1) Develop the structural system/concept for each structural system. Use the basicstructuralsystemsdescribedinTable1.1asaguideline.

2) Create the finite element model with varying complexity and refinement suitable fordeveloping understanding the response. Carry out different types of analysis todeterminetheresponseofthebuildingundergravityandlateralloadings.

3) Design the structural components to remain elastic under gravity and wind loads andprovidewell-definedinelasticbehaviorwherenonlinearresponseoccursunderDBElevelearthquake, as appropriate. Capacity design approachwill be used for the response ofmemberstoremainelasticunderDBElevelearthquake,asappropriate.Linear,responsespectrumanalysisshouldbeconductedforDBElevelearthquakewithresponsereduction


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factortodeterminetheresponseofthebuilding.Designiscarriedoutinaccordancewiththerelevantprovisionsofthelatestnationalbuildingcodeprovisions.

4) As design would be typical schools which will be replicated for several sites, theperformanceofthebuildingshouldbeevaluatedaftersubstantialcompletionofdesigninaccordancewithcodeproceduresmentionedinstep3.PerformanceofthebuildingshallbeevaluatedwithanobjectivetoprovideLifeSafetyperformancelevelunder1000-yearreturn period earthquakes. Optionally, Collapse Prevention performance level under2000-year return period earthquake may be checked. Pushover analysis shall beconductedasminimumrequirements.Overallresponse,suchastransientdrifts,residualdrifts,anddeformationandstrengthcapacityrequirementsofcomponentsarechecked.

5) If the performance based on global building and local component responses does notmeettheacceptancecriteria,carryoutstep1to4toenhancethestructuralperformanceofthebuilding.

6) If the performance based on global building and local component responsesmeet theacceptancecriteria,structuraldesigndrawingsshallbepreparedforconstruction.

Regarding“DesignProcedure1”, to refer to theChapter3,4,5,6, and7.1 to7.4.2 isrequired.

Architectural design

Step 1: Structural system development

Step 2: Modeling and analysis

Step 3: Structural design in accordance with

building codes

Step 5: Is performance acceptable?

Step 4: Verification of design using

performance-based approaches for seismic

loading

Step 6: Preparation of structural drawings

YES

NO

Figure 2-1 : Overall Design Procedure 1


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2.3.2 DesignProcedure2

Analysisanddesignoftheschoolbuildingsshallbeperformedaccordingtothefollowingstepsforeachstructuralsystem.

1) Develop the structural system/concept for each structural system. Use the basicstructuralsystemsdescribedinTable1.1asaguideline.

2) Create the finite element model with varying complexity and refinement suitable fordeveloping understanding the response. Carry out different types of analysis todeterminetheresponseofthebuildingundergravityandlateralloadings.

3) Design the structural components under gravity, seismic loads and wind loads. Designshall be carried out in accordance with both Nepal National Building Code (NBC) andlatestIndianStandards(IS),andshallsatisfybothcodes.

4) After designing in accordance with NBC and IS, it is preferable to evaluate theperformanceofthebuildingbypushoveranalysis.Pushoveranalysiswillbeconductedtodetermine the displacement ductility factor “µ”. Response reduction factor, R will becalculatedbasedonductility factor “µ”.HereR factor basedon IS (code-baseddesign)canbedefinedas“Rc”andalsobasedonperformance-basedcanbedefinedas“Rp”.

5) IftheresultofRandKare

Rc＞Rp,calculatecode-baseddesignagainbyusingRp.

Incase,Rc≤Rp,itisnotnecessarytoredothecode-baseddesign.

6) Structuraldesigndrawingsshallbepreparedforconstruction.

Regarding“DesignProcedure2”,it’snecessarytorefertotheChapter7.4.3.Inaddition,thesentence relating to theoriginalNBCand IS inChapter3,4,5,and6needs tobetakenintoaccount.

Figure 2-2 : Overall Design Procedure 2


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Chapter 3 BasicMaterials

3.1 IntroductionThischapterpresentsthestrengthofmaterialsusedinthedesignofstructuralcomponents.

3.2 ConcreteThe minimum compressive strength measured at 28 days, for the cylinder specimen used indifferent typesof structuralcomponentsareshown in the following table.Highervaluesmaybeusedbasedonthediscretionoftheengineer.

Table 3-1 : Compressive Strength of concrete

Standard Member f'c(Nominal)(MPa)

f'c(Expected)(MPa)

NBC205:1994 Footings 16 20.8

NBC205:1994 Beams 16 20.8

NBC205:1994 Columns 16 20.8

3.3 ReinforcingSteelMinimum yield strength of reinforcing steel to be used in the design is shown in the followingtable.

Table 3-2 : Yield Strength of Reinforcing steel

Standard Diameter fy(Nominal)(MPa)

fy(Expected)(MPa)

NBC205:1994 12mmandabove 415 518

NBC205:1994 10mmandbelow 250 313

3.4 StructuralSteelYieldstrengthofstructuralsteelusedinthedesignisshowninthefollowingtable.

Table 3-3 : Yield Strength of Structural Steel

Standard SectionFy

(Nominal)(MPa)

Fu(Nominal)(MPa)

Fy(Expected)(MPa)

Fu(Expected)(MPa)

IS800:1984 Wideflangeshapes

250 410 275 451

IS800:1984 Angleandchannelsections

250 410 275 451

IS800:1984 Miscellaneousplatesandconnectionmaterials

250 410 275 451

3.5 Cold-formedSteelMinimumyieldstrengthofcold-formedsteelusedinthedesignisshowninthefollowingtable.


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Table 3-4 : Yield Strength of Cold-formed Steel

Standard SectionFy

(Nominal)(MPa)

Fu(Nominal)(MPa)

Fy(Expected)(MPa)

Fu(Expected)(MPa)

IS:801-1975 Channel 250 410 275 451

3.6 MasonryMinimumstrengthofmasonryusedinthedesignisshowninthefollowingtable.

Table 3-5 : Strength of Masonry Prism

Element StrengthNominal(MPa)

Expected(MPa)

Burntclaybricks Compressivestrength 2.07 2.7

Compressedsoilcementblocks

Compressivestrength 2.71 2.71

3.7 TimberMaterialpropertiesshallbeinaccordancewithNBC112:1994orIS883-1994.


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Chapter 4 Loads

4.1 IntroductionThischapterpresentsthedesignloadsconsideredinthestructuraldesign,includinggravityloads,seismicloadsandwindloads.

4.2 GravityLoadSelf-weightofthestructureisconsideredasdeadloadandfinishesandpartitionsareconsideredas superimposed dead load. Live load is determined in accordance with occupancy or use. Thefollowing loads are in addition to the self-weight of the structure. The minimum loadingrequirementsshallbetakenfromIS875(Part2)-1987orequivalent.

Table 4-1 : Live Load and Superimposed Dead Load

OccupancyorUse LiveLoad SuperimposedDeadLoad

Classrooms 3.0kPa Tobecomputedforactualfinishesandpartitions

Corridors 4.0kPa Tobecomputedforactualfinishesandpartitions

Roof 0.75kPa

4.3 WindLoadWindspeedshallbedeterminedinaccordancewithNBC104-1994.Thecountryisdividedintotworegions:a) the lowerplainsandhillsand,b) themountains.The firstzonegenerally includesthesouthern plains of the Terai, the Kathmandu Valley and those regions of the country generallybelowanelevationof3000meters.Thesecondzonecoversallareasabove3000meters.FortheNepaleseplainscontinuouswiththeIndianplanes,abasicvelocityof47m/sshallbeused.Inthehigherhills,abasicwindvelocityof55meterspersecondshallbeused.

Table 4-2 : Parameters for Wind Loading

Parameter Value

Basicwindspeed Tobedeterminedbasedonbuildinglocation

Terraincategory Tobedeterminedbasedonbuildinglocation

4.4 SeismicLoadFor design procedure 1, the basic seismic input shall be determined fromNBC. 500-year returnperiod earthquake shall be used as Design Basis Earthquake in code-based design. Theperformance shall be checked for Life Safety performance level under 1000-year return periodearthquake,andoptionallyCollapsePreventionperformancelevelunder2000-yearreturnperiodearthquake.

For design procedure 2, the seismic input used in code-based design shall be Design BasisEarthquakementionedinlatestNBCandIS.


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Table 4-3 : Parameters for Seismic Loading

Parameter Value

Zonefactor,Z(NBC105-1994)Zonefactor,Z(IS1893-2002)

10.36

Importancefactor 1.5

Soiltype II(Needstobedeterminedbasedonbuildinglocation)

Structuralperformancefactor,K • System1=2• System2=1• System3=4• System4=1• System5=4• System6=4• System7=4

Responsereductionfactor,R • System1=1.5**• System2=5• System3=3• System4=5• System5=3**• System6=3**• System7=1.5**

Ca* • 500-yr=0.36• 1000-yr=0.46• 2000-yr=0.58

Cv* • 500-yr=0.45• 1000-yr=0.58• 2000-yr=0.73

*Usedindesignprocedure1.

**AssumedRvaluesincethevaluesarenotavailableinIS1893-2002.


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Figure 4-1 : Response Spectra for Earthquakes with Different Return Periods for Soil Type II (Medium Soil Sites) (Ref: Figure 7.1b, Hazard Spectra for Kathmandu (Kawashima

Attenuation Model, GC 2, 5% Damping, NBC 400 V2.RV8-1994)

Note:Importancefactorof1isusedinthefigureforcomparison.

ResponsespectrumcurveforNBC105-1994isbasedonK=4.

4.5 LoadCombinations

4.5.1 Code-basedDesign

4.5.1.1 UltimateStrengthDesign

Ultimatestrengthdesignloadcombinationsusedincode-baseddesignareshowninthefollowingtable.(Ref:NBC105:1994,NBC110:1994,IS875-1987)

Table 4-4 : Ultimate Strength Design Load Combinations used in Code-based Design

No. LoadCombination

1 1.4D+1.5L

2 1.0D+1.25W

3 1.0D+1.3L+1.25W

4 1.0D+1.25W

5 1.0D+1.3L+1.25E

6 0.9D+1.25E

Where: D=Deadload

L=Liveload

E=EffectsofforcesatDBElevel

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

0 0.5 1 1.5 2 2.5 3

SpectralAcceleral

on(Sa)

NaturalPeriod(sec)

ElaslcResponseSpectra-5%ofcrilcaldamping

500-yr

1000-yr

2000-yr

NBC105-1994

IS1893-2002

2.5Ca

Ca

Cv/T


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W=Windload

Liveloadisnotincludedinthemasscalculations.

Verticalseismic loadeffectshallbeconsidered,takenastwo-thirdsofdesignhorizontalresponsespectrum.

4.5.1.2 AllowableStressDesign

Allowablestressdesign loadcombinationsused incode-baseddesignareshown in the followingtable.(Ref:NBC105:1994,NBC110:1994,IS875-1987)

Table 4-5 : Allowable Stress Design Load Combinations used in Code-based Design

No. LoadCombination

1 D

2 D+L

3 D+L+W

4 0.7D+W

5 D+L+E

6 0.7D+E

4.5.2 PerformanceEvaluation

Loadcombinationsusedinperformanceevaluationareshowninthefollowingtable.

No. LoadCombination

1 1.0D+0.25L±1.0E

Where: D=Deadload

L=Liveload

E=Earthquakeload

Liveloadisnotincludedinthemasscalculations.


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Chapter 5 StructuralSystems

5.1 IntroductionThischapterpresentsthebasicstructuralsystemstobeusedindesignofschoolbuildings.

5.2 DifferentStructuralSystems

5.2.1 OrdinaryReinforcedConcreteMomentResistingFramesandMasonryInfillWalls

Masonry infill walls shall be considered as primary seismic force resisting system and momentframewill be act as backup system for ductility. The frames and infillwalls shall resist the totallateralforceinaccordancewiththeirrelativerigidities,consideringtheinteractionoftheinfillwallsand frames. Referring to Table 16-N, UBC-97, overstrength factor, R for ordinary reinforcedconcretemomentresistingframeis3.5,inwhicheffectofmasonryinfillwallsarenotconsidered.InNBC-105, structural performance factor, K for ductilemoment resisting frame is 1 and framewithmasonryinfills is2.Responsereductionfactor is2timesdifferencebetweenmomentframewithmasonry infillsandmoment framewithoutmasonry infills.Hence,overstrength factor,Rof1.5wouldbeusedforordinaryreinforcedconcretemomentresistingframewithmasonryinfillsforseismicloadinginaccordancewithUBC-97.

Unreinforcedmasonry infill walls shall be designed as shear infill panels to act as seismic forceresisting system. Shear infill panels shall be in full contact with the frame elements on all foursides.RefertoTMS402-13/ACI530-13/ASCE5-13,AppendixB,theinfillwallshallbedesignedasparticipating infills. The infills shall be supported out-of-plane by connectors attached to thebounding frame. Infills shall be designed for in-plane shear forces and out-of-plane flexuraldemand.

Eachboundingcolumnshallbedesignedtoresisttheshearandmomentdemandequalnottolessthan1.1multipliedbytheresultsfromtheequivalentstrutframeanalysis,andforaxialforcenotless than the results from thatanalysis. Inaddition, thedesign shearateachendof the columnshall be increasedby thehorizontal componentof the equivalent strut force actingon that endunderdesignloads.Eachboundbeamshallbedesignedtoresisttheshearandmomentequaltoatleast1.1multipliedby theresults fromtheequivalentstrut frameanalysisand foranaxial forcenotlessthantheresultsfromthatanalysis.Inadditionalthedesignshearateachendofthebeamshallbeincreasedbytheverticalcomponentoftheequivalentstrutforceactingonthatendunderdesignloads.


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Determine member demand forces

Design beams for flexural demand and columns for

axial and flexural demands

Design beam and column shear to resist the shear demand from analysis

Reinforcement detailing

Determine out-of-plane and in-plane demand

forces

Design mechanical connections between infill

and bounding frame

Design for out-of-plane flexural and in-plane shear

demand

Design check for bounding columns and

beams (moment and shear)

Figure 5-1 : Design Procedure for Ordinary Reinforced Concrete Moment Resisting Frames with Masonry Infill Walls

5.2.2 SpecialSteelMomentResistingFrames

Beams,columns,andbeam-columnconnectionsinspecialsteelmomentframesareproportionedanddetailed to resist flexural,axial,andshearingactions that resultasabuildingsways throughmultiple inelastic displacement cycles during strong earthquake ground shaking. Specialproportioning and detailing requirements are therefore essential in resisting strong earthquakeshakingwithsubstantialinelasticbehavior.Threemainobjectivesofspecialsteelmomentresistingframeare:

1) Toachieveastrong-column/weak-beamconditionthatdistributesinelasticresponseoverseveralstories

2) ToavoidP-deltainstabilityundergravityloadsandanticipatedlateralseismicdrifts

3) Toincorporatedetailsthatenableductileflexuralresponseinyieldingregions.

It is importanttoavoidearlyformationof inelasticresponsewhich isdominatedbyformationofplastic hinges at the tops and bottoms of columns within a single story. When such storymechanisms form, itwould result very largeP-delta effects at those locations. Inorder to avoidthis,formationofsideswaymechanismsdominatedbyhingingofbeamsispreferable,asopposedtocolumnhinging.

Inasevereearthquake,framestructureshavethepotentialtocollapseinasideswaymodeduetoP-delta effects. These effects are caused by vertical gravity loads acting on the deformedconfigurationofthestructure.SecondorderanalysisshallbeconductedtoconsiderP-deltaeffects.


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Capacity design for members and panel zones

Verify design story drift

Analyze the model considering P-delta effects

Figure 5-2 : Design Procedure for Special Steel Moment Resisting Frames

5.2.3 ReinforcedInterlockingBearingWalls

Reinforced interlocking bearing wall system shall be designed to resist the lateral loading andgravityloads.Areinforcedinterlockingbearingwallsystemiscomposedofwallsegments,eachofwhich can be categorized as either flexure-dominated or shear-dominated. A flexure-dominatedwall segment is one whose inelastic response is dominated by deformations resulting from thetensile yielding of flexural reinforcement. A shear-dominated segment is one whose inelasticresponse is dominated by diagonal shear (tension) cracks. It can be checked whether a wallsegmentisflexure-dominatedorshear-dominatedbycomparingitsflexuralcapacitywithitsshearcapacity. A flexure-dominated segment has a lower flexural capacity than shear capacity; for ashear-dominatedsegment,theoppositeistrue.

The ductility capacity of flexure-dominated walls depends on the aspect ratio, the flexuralreinforcementpercentage,and theaxial load. Flexure-dominatedelementsaregenerallyductile.Shear-dominated elements are generally brittle, with failure characterized by diagonal shearcracks.

When a reinforced interlockingwall has a shear-span-to-depth ratioMu/(Vudv) greater than onewith a well-designed plastic hinge zone, these requirements plus the required capacity-baseddesign for shear generally result in flexure-dominated, ductile behavior. However, when areinforcedinterlockingwallhasashear-span-to-depthratiolessthanoneorahighaxialload,thesamecombinationofprescriptive requirementsmaystill result inawall that is shear-dominatedandbrittle.

To protect a reinforced interlocking wall against shear failure caused by possible flexural overstrength, the design shear strength, ΦVn , should exceed the shear corresponding to thedevelopmentofthenominalmomentcapacitybyafactorofatleast1.25.


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Determine out-of-plane and in-plane demand

forces

Design for out-of-plane flexural and axial demand

forces

Design for in-plane flexural and axial demand forces

Design for in-plane shear forces

(capacity-based design)

Check for sliding shear

Figure 5-3 : Design Procedure for Reinforced Interlocking Bearing Walls

5.2.4 SpecialReinforcedConcreteMomentResistingFrame

Specialreinforcedconcretemomentresistingframesshallbeproportionedanddetailedinsuchaway that the frame undergo safely extensive inelastic deformations that are anticipated underearthquakes.

Threemainobjectivesofspecialreinforcedconcretemomentresistingframeare:

1) To achieve a strong-column/weak-beam design that spreads inelastic response overseveralstories

2) Toavoidshearfailure

3) Toprovidedetailsthatenableductileflexuralresponseinyieldingregions.

Whenthebuildingswaysduringanearthquake,thedistributionofdamageoverheightdependsonthedistributionoflateraldrift.Ifthebuildinghasweakcolumns,drifttendstoconcentrateinoneorafewstories,andmayexceedthedriftcapacityofcolumns.Additionally,thecolumnsinagivenstory support the weight of the entire building above those columns, whereas the beams onlysupportthegravityloadsofthefloorofwhichtheyformapart;therefore,failureofacolumnisofgreaterconsequencethanfailureofabeam.

Ductileresponserequiresthatmembersyield inflexure,andthatshearfailurebeavoided.Shearfailure,especiallyincolumns,isrelativelybrittleandcanleadtorapidlossoflateralstrengthandaxial load-carryingcapacity.Flexuralyieldingregionsshallbedesignedforcode-requiredmomentstrengths, and then calculate design shears based on equilibrium assuming the flexural yieldingregionsdevelopprobablemomentstrengths.Hoopstypicallyareprovidedattheendsofcolumns,


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aswellasthroughbeam-columnjoints,andattheendsofbeamsinordertoimprovetheductilebehavior.


Design beams for flexural demand and columns for

axial and flexural demands

Design beam and column shear based on capacity based design procedures

Check for joint shear

Check strong column/weak beam requirements

Reinforcement detailing

Figure 5-4 : Design Procedure for Reinforced Concrete Special Moment Resisting Frame

5.2.5 Cold-FormedSteelOrdinaryMomentFrame

Cold-formedsteelordinarymomentresistingframesshallbeproportionedanddetailedinsuchawaythattheframewillremainessentiallyelasticordesignthehigherstrengthtoreducethehighductilitydemandsunderearthquakes.Asthemassofstructuralsystemissmall,thedesignwillbeprimarilygovernedbywindloading.

5.2.6 Hot-RolledSteelOrdinaryMomentFrame

Hot-rolled steel ordinary moment resisting frames shall be designed and detailed for higherstrengthtoreducethehighductilitydemands.

5.2.7 TimberStructure

Wood-frameshearwallssheathedwithshearpanelsofparticleboard,structuralfiberboard,andgypsumwall boardareused to resist the seismic forces.Bearingwall systemcategorywouldbeapplicablebecause shearwalls used for seismic force resistance also function to support gravityloadsofabuilding.


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Chapter 6 Code-basedDesign

6.1 IntroductionThis chapterpresents the finiteelementmodeling, analysisanddesignprocedures tobeused inthecode-baseddesignofschoolbuildings.

6.2 ModelingofStructuralSystemA complete, three-dimensional elastic models are created, representing the structure’s spatialdistribution of the mass and stiffness to an extent that is adequate for the calculation of thesignificantfeaturesofthebuilding’selasticresponse.SAP2000isusedasanalysistool.Theelasticmodelsareusedforgravity,windandDBElevelearthquakeanalysis.Nominalmaterialpropertiesare used in modeling of structural components. The models include footings, columns, beams,walls, and roof truss. Recommended element types and stiffness modifiers to be used in themodelingofdifferenttypesofcomponentsaresummarizedinthefollowingtable.

Table 6-1 : Modeling of Structural System for Code-based Design

StructuralSystem Component

ElementtobeUsed Wind DBE

System1

RCbeams FrameFlexural–1.0IgShear–1.0Ag

Flexural–0.35IgShear–1.0Ag

RCcolumns Frame Flexural–1.0IgShear–1.0Ag


Masonryinfillwalls

Shellorframe(tomodelstrut)

In-planeFlexural–1.0IgShear–1.0AgOut-of-planeFlexural–1.0IgShear–1.0Ag


Footing Shell



Rooftruss FrameAxial–1.0AgFlexural–1.0IgShear–1.0Ag

Axial–1.0AgFlexural–1.0IgShear–1.0Ag

System2

Steelbeams Frame Flexural–1.0IgShear–1.0Ag


Steelcolumns Frame Flexural–1.0IgShear–1.0Ag


Footing Shell





System3 Reinforcedinterlocking Layeredshell In-plane

Flexural–1.0IgIn-planeFlexural–0.15Ig


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bearingwalls Shear–1.0AgOut-of-planeFlexural–1.0IgShear–1.0Ag

Shear–0.35AgOut-of-planeFlexural–0.1IgShear–0.2Ag

Footing Shell





System4

RCbeams Frame Flexural–1.0IgShear–1.0Ag


RCcolumns FrameFlexural–1.0IgShear–1.0Ag


Footing Shell





System5

Cold-formedsteelbeams Frame



Cold-formedsteelcolumns

Frame Flexural–1.0IgShear–1.0Ag


Footing Shell





System6

Hot-rolledsteelbeams Frame Flexural–1.0Ig

Shear–1.0AgFlexural–1.0IgShear–1.0Ag

Hot-rolledsteelcolumns Frame



Footing Shell





System7 Timberbeams FrameFlexural–1.0IgShear–1.0Ag



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Timbercolumns Frame Flexural–1.0IgShear–1.0Ag


Shearpanels Shell



Footing Shell





6.2.1 Beams

Frame elements are used inmodeling of beams,which includes the effects of bending, torsion,axialdeformation,andsheardeformations.Insertionpointsandendoffsetsareappliedtoaccountfor the finite size of beam and column intersections, if required. The end offsetsmay bemadepartiallyorfullyrigidbasedonengineeringjudgmenttomodelthestiffeningeffectthatcanoccurwhentheendsofanelementareembeddedinbeamandcolumnintersections.Endreleasesareappliedtomodeldifferentfixityconditionsattheendsoftheelementinaccordancewiththetypeofdetailing.

6.2.2 RoofTruss

Frameelementsareused inmodelingof truss.End releasesareapplied tomodeldifferent fixityconditionsattheendsoftheelementinaccordancewiththetypeofdetailing.

6.2.3 Columns

Frameelements areused inmodelingof columns,which includes the effects of biaxial bending,torsion, axial deformation, and biaxial shear deformations. Insertion points and end offsets areappliedtoaccountforthefinitesizeofbeamandcolumnintersections,ifrequired.Theendoffsetsmaybemadepartiallyorfullyrigidbasedonengineeringjudgmenttomodelthestiffeningeffectthatcanoccurwhentheendsofanelementareembeddedinbeamandcolumnintersections.Endreleasesareappliedtomodeldifferentfixityconditionsattheendsoftheelementinaccordancewiththetypeofdetailing.

6.2.4 Footings

Shell elements are used in modeling of footings. The effect of soil structure interaction isconsidered for the buildings inwhich an increase in fundamental period due to soil effectswillresult in an increase in spectral accelerations. Vertical springs and lateral springs are assignedrespectively in order to consider the interaction effect of soil. The spring stiffness values arecalculated based on the sub-grade modulus values from geotechnical report if available.Approximate sub-grade modulus values can be estimated based on the empirical formulasmentionedbelow.


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K=3Es forcohesionlesssoil

K=1.6Es forcohesivesoil

Vertical spring stiffness may be determined based on the allowable bearing capacity as below.Horizontalspringstiffnessmaybeassumed50%ofverticalspringstiffness.

Kv=AllowablebearingcapacityxSafetyfactorx40

6.2.5 MasonryInfillWalls

Masonryinfillwallscanbemodeledintwooptionsasbelow.

1) UsingShellElement

Shell elements shall be used inmodeling of unreinforcedmasonry infillwalls,which include themembraneandplatebendingbehavior.Thewallelementsaremeshedhorizontallyandverticallyinadequatenumbers.Theorientationoflocalaxisoftheshearwallelementsshallbeconsistentinentirewall. Unreinforcedmasonrywallsmay be checked to resist out-of-plane inertial forces asisolated components spanning between floor levels, and/or spanning horizontally betweencolumnsandpilasters.

2) UsingStrutElement

Equivalent strutmodel, capable of resisting compression only, can be used. The section size ofequivalent strut shall be determined in accordance with TMS 402-13/ACI 530-13/ASCE 5-13,Section B.3.4.1. Strut element shall be released at each end for moments about 2 and 3 axes.Tension limitshallbesettozeroforthestrutelements.Nonlinearanalysisshallbeconductedtoconsiderthecompressiononlystrut.

6.2.6 ReinforcedInterlockingBearingWalls

Layered shell elements areused inmodelingof reinforced interlockingbearingwalls. The entirecrosssectionofthewallisdiscretizedintoindividuallayers.Theselayersarelocatedbyaspecificdistance from the reference surfaceandwith the specified thickness. Thematerial propertiesofeachlayerarespecifiedbythepropertiesofeachmaterial.Theelementsaremeshedhorizontallyandverticallyinadequatenumbers.Theorientationoflocalaxisoftheshearwallelementsshallbeconsistent inentirewall. In layeredelement,massandweightarecomputed formembraneandshelllayers,notforplatelayers.

6.2.7 Damping

5%constantmodaldampingisusedinseismicanalysisatDBElevel.

6.3 AnalysisProceduresAnalysisprocedurestobeusedforcode-baseddesignarepresentedinthefollowingsections.

Table 6-2 : Analysis Procedures used in Code-based Design

LoadCase Analysis

Gravityandwind Linearstaticanalysis

Earthquake Responsespectrumanalysis


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6.3.1 ModalAnalysis

Modalanalysisiscarriedouttodeterminethemodalpropertiesofthebuilding.100%ofdeadload,superimposed dead load and 25%of live load are considered asmass source inmodal analysis.EitherEigenanalysisorRitzanalysisshallbeused.Sufficientnumberofvibrationmodesshallbeconsideredtoachieveatleast90%ofparticipatingmassofthebuilding.

6.3.2 LinearStaticProcedure(LSP)

Linearstaticanalysisiscarriedoutforgravityandwindloadings.Windloadmaybeappliedtotheexposurefromwallsandroofsintheanalysismodel.

6.3.3 ResponseSpectrumAnalysis(RS)

Responsespectrumanalysis iscarriedoutusing linearlyelastic responsespectra.At least90%oftheparticipatingmassofthebuildingisconsideredineachoftwoorthogonalprincipaldirectionsofthebuilding.CompleteQuadraticCombination(CQC)ruleisusedforcombinationofresponsesfromeachmode.Orthogonaleffectsareconsideredbydesigningelementsfor100percentoftheprescribeddesignseismicforcesinonedirectionplus30percentoftheprescribeddesignseismicforcesintheperpendiculardirection.5%constantmodaldampingisconsideredintheanalysis.

6.4 ComponentandMemberDesignThe structural components are designed to satisfy the strength and ductility requirements.Strength capacity for different types of actions considered in the design are summarized in thetablebelow.

Table 6-3 : Component and Member Design

StructuralSystem

Component DesignApproach/Consideration CodeReference

System1 RCbeams Flexural,Shear ACI318-08

Chapter10,11and21

RCcolumns PMM,Shear ACI318-08

Chapter10,11and21

Masonryinfillwalls Out-of-planeflexuralandin-planeshear

ACI530-13,AppendixB

Footings Bearingcapacityofsoil

Flexural,shear

ACI318-08

Chapter15

Steeltruss AISC360-10

ChapterDandE

Steelconnections AISC360-10

ChapterJ

System2 Steelbeams Flexuralresponse

• Flexuralyielding

• Lateral-torsionalbuckling

• Flangelocalbuckling

• Weblocalbuckling

AISC360-10

ChapterFandG


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StructuralSystem


Shear

Steelcolumns Compression

• Flexuralbuckling

• Torsionalandflexural-torsionalbuckling

Flexure





Shear

AISC360-10

ChapterEandH


Flexural,shear

ACI318-08

Chapter15

Steeltruss Compression



Tension

AISC360-10

ChapterDandE

Steelconnections Momentconnections

Shearconnections

AISC360-10

ChapterJ

System3 Reinforcedinterlockingbearingwalls

Bearing,axialcompression

In-planeflexuralandshear

Out-of-planeflexural

ACI530-13asappropriateandtestresults


Flexural,shear

ACI318-08

Chapter15




Tension

AISC360-10

ChapterDandE


Shearconnections

AISC360-10

ChapterJ

System4 RCbeams Flexural,Shear ACI318-08

Chapter10,11and21

RCcolumns PMM,Shear ACI318-08

Chapter10,11and21


Flexural,shear

ACI318-08

Chapter15

Steeltruss Compression AISC360-10


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StructuralSystem




Tension

ChapterDandE


Shearconnections

AISC360-10

ChapterJ

System5 Cold-formedsteelbeams

Flexuralresponse

Shear

AISI-Commentary

ChapterC


Compression

Flexure

Shear

AISI-Commentary

ChapterC


Flexural,shear

ACI318-08

Chapter15


Tension

AISI-Commentary

ChapterC


Shearconnections

AISC360-10

ChapterJ

System6 Steelbeams Flexuralresponse





Shear

AISC360-10

ChapterFandG

Steelcolumns Compression



Flexure





Shear

AISC360-10

ChapterEandH


Flexural,shear

ACI318-08

Chapter15




AISC360-10

ChapterDandE


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StructuralSystem


Tension


Shearconnections

AISC360-10

ChapterJ

System7 Timberbeams Flexural,Shear ANSI/AWCSDPWS-2015,NBC112:1994,IS-883:1994

Timbercolumns PMM,Shear ANSI/AWCSDPWS-2015,NBC112:1994,IS-883:1994

Shearpanels Out-of-planeflexuralandin-planeshear

ANSI/AWCSDPWS-2015,NBC112:1994,IS-883:1994


Flexural,shear

ACI318-08

Chapter15

Timbertruss ANSI/AWCSDPWS-2015,NBC112:1994,IS-883:1994

Connections ANSI/AWCSDPWS-2015,NBC112:1994,IS-883:1994


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Chapter 7 SeismicPerformance-basedEvaluation

7.1 IntroductionThis chapter presents the modeling, analysis and evaluation procedures used in seismicperformance-basedevaluationofschoolbuildings.Fordesignprocedure1,structuralperformanceof the building shall be evaluated under 1000-year return period and 2000-year return period(optional) earthquakes. For design procedure 2, response reduction factor, R factor will bedeterminedbasedonthefunctionofductilityfactor,µ,regardlessofseismicdemandlevel.

7.2 ModelingofStructuralSystemFor seismic performance-based evaluation, nonlinear verification models are used, in whichdeformation-controlled actions are modeled as nonlinear while force-controlled actions aremodeledaslinear.

Themodelincludesinelasticpropertiesforcomponentsthatareanticipatedtobeloadedbeyondtheir elastic limits. These include flexural response of beams, columns, in-plane response ofunreinforced masonry infills and reinforced interlocking walls. Elements that are assumed toremain elastic are modeled with elastic member properties. These include shear response ofbeamsandcolumns,flexuralandshearresponseoffootings.

In design procedure 2, it is important to note that all force-controlled actions shall bemodeledwith force-controlled hinges. Force-controlled hinges shall lose the load carrying capacity whenmaximumforce is reached. Indeformation-controlledhinges,post-yieldingstiffnessandstrengthlossshallbeproperlydefined.

Table 7-1 : Modeling of Structural System for Performance-based Evaluation


ElementtobeUsed 1000-year 2000-year

System1 RCbeams Framewithflexuralhinges



RCcolumns FramewithPMMhinges



Masonryinfillwalls

Nonlinearlayeredshell



Footing Shell In-planeFlexural–1.0IgShear–1.0AgOut-of-planeFlexural–1.0IgShear–1.0Ag


Rooftruss Frame Axial–1.0AgFlexural–1.0IgShear–1.0Ag


System2 Steelbeams Framewithflexuralhinges



Steelcolumns FramewithPMMhinges



Footing Shell In-plane In-plane


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Flexural–1.0IgShear–1.0AgOut-of-planeFlexural–1.0IgShear–1.0Ag

Flexural–1.0IgShear–1.0AgOut-of-planeFlexural–1.0IgShear–1.0Ag




Nonlinearlayeredshell







System4 RCbeams Framewithflexuralhinges



RCcolumns FramewithPMMhinges







System5 Cold-formedsteelbeams

Framewithflexuralhinges




FramewithPMMhinges







System6 Hot-rolledbeams

Framewithflexuralhinges



Hot-rolledcolumns

FramewithPMMhinges




page 38 of 46







7.2.1 Beams

Frame elements are used inmodeling of beams,which includes the effects of bending, torsion,axialdeformation,andsheardeformations.Nonlinear flexuralhingesareassignedat theendsofbeamstorepresentthenonlinearflexuralresponsewhileshearresponseismodeledaslinear.

7.2.2 Columns

Frameelements areused inmodelingof columns,which includes theeffects of biaxial bending,torsion, axial deformation, and biaxial shear deformations. Fiber P-M2-M3 hinges are used tomodelthenonlinearbehaviorofcoupledaxialforceandbi-axialbending.Fiberhingesareassignedbothendsofthecolumn.User-definedfiberhingesareused,bygeneratingthefiber layoutfromSection Designer. In reinforced concrete columns, rebar fibers are lumpedwhile generating thefiber layout to reduce the analysis time. Plastic hinge length of reinforced concrete columns isdeterminedbasedonthefollowingequation.

Lp=0.08L+0.022fyedbl≥0.044fyedbl(MPa)

Where

Lp =plastichingelength

H =sectiondepth

L =criticaldistancefromthecriticalsectionofplastichingetothepointofcontraflexure

fye =expectedyieldstrengthoflongitudinalreinforcement

dbl =diameteroflongitudinalreinforcement

7.2.3 MasonryInfillWallsandReinforcedInterlockingBearingWalls

Nonlinear layered shell elements are used in nonlinear modeling of masonry infill walls andreinforced interlocking bearing walls. The procedure is same as linear modeling of reinforcedinterlocking bearing walls, except for considering nonlinear material behavior for concrete andreinforcementinin-planeresponse.

7.2.4 Damping

Rayleighdampingmodelisused.Thedampingratiosareprovidedasfollows.


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Table 7-2 : Damping Ratios

PeriodratioT/T1 DampingRatio

0.2 3%

0.9 2%

Where,T1isfirstmodenaturalperiod.

7.3 AnalysisProceduresAnalysis procedures to be used for seismic performance-based evaluation are presented in thefollowingsections.

Table 7-3 : Analysis Procedures used in Performance-based Evaluation

LoadCase Analysis

Gravity Nonlinearstaticanalysis

Earthquake Nonlineartimehistoryanalysis(fordesignprocedure1)

Pushoveranalysis(Nonlinearstatic,fordesignprocedure2)

7.3.1 NonlinearStaticProcedureforGravityLoad(NSP)

Nonlinearstaticanalysiswillbeconductedforgravity loading,priorto lateral loadanalysis,using“Full Load” control application. In nonlinear static procedure, monotonically increasing gravityloadingisappliedonthebuilding.P-∆effectsshallbeconsideredintheanalysis.

7.3.2 NonlinearTimeHistoryAnalysis(NLTHA)

Nonlinear time history analysis is carried out using pairs of ground motion records, analyzingsimultaneously along each principal direction of the building. If fewer than seven time historyanalyses are performed, the maximum response is used for evaluation. If seven or more timehistory analyses are performed the average value of response is used. Nonlinear time historyanalysisiscontinuedfromthestateendofgravityloadcase.Rayleighdampingmodelwith2-3%ofcriticaldampingisused(Specifydampingbyperiod).P-∆effectsareconsideredintheanalysis.

The selected ground motion records for time history analysis should have magnitude, faultdistances, and source mechanisms that are consistent with those that control the designearthquake groundmotions for each seismic demand level. For each set of groundmotion, thesquarerootofsumofthesquares(SRSS)ofthe5%-dampedresponsespectraofthescaledgroundmotioncomponent shallbeconstructed.Thesetsofgroundmotion records shallbescaledsuchthattheaveragevalueoftheSRSSspectradoesnotfallbelow1.3timesthe5%-dampedspectrumforthedesignearthquakeforperiodsbetween0.2Tand1.5T(whereTisthefundamentalperiodofthebuilding).

ThePEERGroundMotionDatabase (PGMD)web-based tool (PEER,2011)maybeused for linearscaling and selecting groundmotions tomatchwith the design response spectrum of particularseismicleveltobechecked.Thelinearscalingfactorforeachgroundmotionshouldnotbegreaterthan8.

7.3.3 PushoverAnalysis

Firstly, nonlinear static analysis shall be performed for gravity loads using “Full Load” controlapplication.Nonlinear static analysis for lateral loading shall be continued from the stateendof


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gravityloadcase,usingmodaldeformationloadpattern,with“DisplacementControl”application.P-∆effectsshallbeconsideredinbothgravityandlateralloadcases.

7.4 PerformanceCriteriaThissectionpresentstheperformancecriteriatobeusedinseismicperformance-basedevaluationofschoolbuildings.

7.4.1 ExpectedandLower-BoundStrengthusedinPerformanceEvaluation

Whereevaluatingthebehaviorofdeformation-controlledactions,theexpectedstrength,QCE,shallbeused.Whereevaluatingthebehaviorofforce-controlledactions,alower-boundestimateofthecomponentstrength,QCL,shallbeused.

ExpectedStrength

Expectedmaterialpropertiesshallbeusedtocalculatethedesignstrengthsinaccordancewiththecodebasedprocedures,exceptstrengthreductionfactor,Φshallbetakenequaltounity.Expectedmaterialpropertiesmaybecalculatedbymultiplyinglower-boundvaluesbyappropriatefactors.

Table 7-4 : Factors to Translate Lower-Bound Material Properties to Expected Strength Material Properties

MaterialProperty Factor

Concretecompressivestrength 1.3

Reinforcingsteeltensileandyieldstrength 1.25

Masonrycompressivestrength 1.3

Masonryflexuraltensilestrength 1.3

Masonryshearstrength 1.3

Structuralsteelyieldstrength 1.1

Note:Factorof1.3isusedforconcretecompressivestrengthinlieuoffactorof1.5,mentionedinTable10-1,ASCE41-13.

Lower-boundStrength

Lower-boundmaterialpropertiesshallbeusedtocalculatethedesignstrengthsinaccordancewiththe code based procedures, except strength reduction factor, Φ shall be taken equal to unity.Nominalmaterialpropertiesareusedaslower-boundstrength.

7.4.2 PerformanceCriteriaforDesignProcedure1

Structural performance shall be satisfied for “Life Safety” performance level under 1000-yearreturn period earthquakes and “Collapse Prevention” performance level under 2000-year returnperiodearthquakes.

7.4.2.1 GlobalResponseAcceptanceCriteria

Inlieuofotherlimits,theacceptancecriteriaforglobalresponseofthebuildingisasbelow.


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Table 7-5 : Acceptance Criteria for Global Response of School Buildings

Type SeismicLevel

DBE MCE

Storydrift• System1• System2• System3• System4• System5

0.5%1.5%0.6%1.5%1.5%

0.6%3%1.5%3%3%

Foundation• Totalsettlement• Differentialsettlementin30ft• Sliding• Overturning

6in.0.5in.FS≥1.5FS≥1.5

Majorsettlementand

tiltingFS≥1.5FS≥1.5

7.4.2.2 ComponentResponseAcceptanceCriteria

Actions in all lateral load resisting elements are categorized as either force-controlled ordeformation-controlled actions. Following table summarizes the classification of componentactions.

Deformation-ControlledActions

The response of the components under deformation-controlled actions shall be checked inaccordancewith theacceptancecriteria fornonlinearproceduresmentionedthroughChapters8through11ofASCE41-13.

Force-ControlledActions

Theresponseofthecomponentsunderforce-controlledactionsshallbecheckedusingthelower-boundstrengthswhichshallnotbe less thanmaximumdesign forcesormaximumdesign forcesdevelopedaslimitedbythenonlinearresponseofthecomponent.


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Table 7-6 : Classification of Actions and Acceptance Criteria

StructuralSystem

ComponentDeformation-Controlled Force-Controlled

ReferenceAction NLResponse Action

System1 RCbeams • Moment • Hingerotation

• Shear ASCE41-13,Table10-7

RCcolumns • PMM • Hingerotation

• Axialcompression

• Shear

ASCE41-13,Table10-8

Masonryinfillwalls3

• In-planeshear

• In-planerotation(Drift)

• Columnshearadjacenttoinfillpanels

• Beamshearadjacenttoinfillpanels

ASCE41-13,Table11-9,11-10

Footing - - Bearingcapacityofsoil

Flexural,shear

ACI318-08

Chapter15




Tension

AISC360-10

ChapterDandE

Steelconnections

Momentconnections

Shearconnections

AISC360-10

ChapterJ

System2 Steelbeams • Moment • Hingerotation


Steelcolumns • PMM • Hingerotation



Flexural,shear

ACI318-08

Chapter15

Steeltruss Compression AISC360-10

3Masonryinfillwallsshallbeprovidedwithhorizontalreinforcedconcrete(RC)bandsthroughthewallataboutone-thirdandtwo-thirdsoftheirheightabovethefloorineachstorey.WallopeningsshallbeframedbyRCframingcomponentsasperNBC201:1994Clause8.


page 43 of 46

StructuralSystem





Tension

ChapterDandE

Steelconnections

Momentconnections

Shearconnections

AISC360-10

ChapterJ


• In-planeflexureandshear

• Drift • Axialcompression

ASCE41-13,Table11-7asappropriateandtestresults


Flexural,shear

ACI318-08

Chapter15




Tension

AISC360-10

ChapterDandE

Steelconnections

Momentconnections

Shearconnections

AISC360-10

ChapterJ

System4 RCbeams • Moment • Hingerotation


RCcolumns • PMM • Hingerotation

• Axialcompression

• Shear

ASCE41-13,Table10-8


Flexural,shear

ACI318-08

Chapter15



• Torsionalandflexural-

AISC360-10

ChapterDandE


page 44 of 46

StructuralSystem



torsionalbuckling

Tension

Steelconnections

Momentconnections

Shearconnections

AISC360-10

ChapterJ

System5 Cold-formedSteelbeams

• Moment,Shear

AISI-Commentary

ChapterC

Cold-formedSteelcolumns

• Axial,moment,Shear

AISI-Commentary

ChapterC


Flexural,shear

ACI318-08

Chapter15

Cold-formedSteeltruss

Compression

Tension

AISI-Commentary

ChapterC

Steelconnections

Momentconnections

Shearconnections

AISC360-10

ChapterJ

System6 Hot-rolledsteelbeams

Moment Hingerotation

Shear ASCE41-13,Table9-6

Hot-rolledsteelcolumns

PMM Hingerotation

Shear ASCE41-13,Table9-6


Flexural,shear

ACI318-08

Chapter15




Tension

AISC360-10

ChapterDandE

Steelconnections

Momentconnections

Shearconnections

AISC360-10

ChapterJ

System7 Notapplicable


page 45 of 46

7.4.3 PerformanceCriteriaforDesignProcedure2

Theductilityfactor:“μ”, isdeterminedbytheratiobetweenthemaximumdisplacementandthedisplacementatfirstyield.

Figure 7-1 : Capacity Curve from Pushover Analysis

Responsereductionfactor,R,shallbedeterminedfromfollowingequationsasbelow.

R=μ(forstructuralperiodsgreaterthanapproximately0.7sec)

R= 2𝜇 − 1(forstructuralperiodslessthanapproximately0.3sec)

If R factor in code-based design is less than R factor determined from performance-basedevaluation, code-based design will be carried out using R factor from performance-basedevaluation.

DepartmentofEducation(DOE)MinistryofEducationGovernmentofNepal

april 2016 structural design... · 2016-10-26 · nepal: structural design criteria for school...

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