DYNAMIC ANALYSIS OF HIGH RISE STRUCTURE WITH RC …...provides significant drift control for tall...

DOI : 10.23883/IJRTER.2018.4394.FUQ 1

DYNAMIC ANALYSIS OF HIGH RISE STRUCTURE WITH RC

SHEAR WALL AND OUTRIGGER

Vinay B. Dandagalkar1, Usha K N

2

1P G Student Department of Civil Engineering, EWIT, Karnataka, India 2 Assistant Professor, Department of Civil Engineering, EWIT, Karnataka, India

Abstract— Tall building development has been rapidly increasing worldwide introducing new challenges. In tall

structures high lateral forces develops due to wind load and earthquake load are crucial. Thus the effect of lateral loads

need consideration for strength and stability of the structures. The Outrigger in structures provides lateral stiffness that

provides significant drift control for tall buildings. The study includes Rigid Frame, Shear Wall/Central Core, Wall

Frame Interaction and Outrigger effect on tall structures. The objective of this study is to know the performance of

outrigger structural system in high-rise building subjected to wind load and seismic load as per Indian standards. In this

comparative study mainly the bare frame will be compared with Steel outrigger with core for the structural efficiency. In

this comparative study, the static and dynamic behaviour of the composite structure for different models such as steel

bare frame, steel frame with outrigger, steel frame with shear wall, steel frame with shear wall and outrigger, steel frame

with shear wall openings, and Steel frame with shear wall openings and outrigger will be compared for the structural

response of a 40 storey composite building frame situated in earthquake zone-II and zone-V using ETABS software.

Keywords— Shear Wall, Outrigger.

I. INTRODUCTION

TallvBuilding hasvalways beenva visionvof dreamsvand technicalvadvancement leadingvto

thevprogress ofvthe world. Presently,vwith thevrapidly increasing urbanization, tallvbuilding

hasvbecome avmore convenientvoption forvoffice andvresidential housing. Tallvbuildings

arevusually designedvfor Residential,voffice orvcommercial use. Theyvare primarilyva reactionvto

the rapidvgrowth ofvthe urbanvpopulation andvthe demandvby businessvactivities tovbe asvclose

toveach othervas possible. Avlarge portionvof Indiavis susceptiblevto damagingvlevels ofvseismic

hazards. Hence,vit isvnecessary tovconsider thevseismic loadvfor thevdesign ofvhigh-risevstructure.

Thevdifferent lateralvload resistingvsystems arevused invhigh-risevbuilding asvthe lateralvloads

duevto earthquake areva mattervof concern. Thesevlateral forcesvcan producevcritical stressesvin the

structure,vinducing undesirablevstresses invthe structure,vand undesirablevvibrations or

causevexcessive lateralvsway ofvthevstructure.

Invthe pastvyears, structuralvmembers werevassumed tovcarry primarilyvthe gravityvloads.

Today,vhowever, byvthe advancesvin structuralvdesign/systemsvand high strengthvmaterials,

buildingvweight hasvreduced, invturn increasingvthe slenderness, whichvnecessitates takingvinto

accountvmajorly thevlateral loadsvsuch asvwind and earthquake. Specificallyvfor thevtall buildings,

asvthe slenderness, andvflexibility increases, buildingsvare severelyvaffected fromvthe lateralvloads

resultingvfrom windvand earthquake. Hence,vit becomesvmore necessaryvto identifyvthe proper

structuralvsystem forvresisting thevlateral loadsvdepending uponvthe heightvof the building.

Therevare many structuralvsystems thatvcan bevused forvthe lateralvresistance ofvtallvbuildings.

II. RELATED WORK

Po Seng Kiran and Frits Torang Siahaan (2001) [1]: have workedVon the ideaVto increase

the stiffnessVand make the structureVproficient under windVas well as seismicVload by

introducingVoutrigger and beltVtruss system connectingVcore to exteriorVcolumn. In this

researchVwork authors have studiedVthe application of diagonalVoutrigger and beltVtruss with

differentVconfigurations. They haveVcarried out the analysisVon a 40 storied 2-

dimensionalVmodels subjectedVto wind load byVintroducing outrigger andVbelt truss systems

withVeight different configurationsVby varying theVlocations of outriggerVas per the

International Journal of Recent Trends in Engineering & Research (IJRTER)

Volume 04, Issue 11; November - 2018 [ISSN: 2455-1457]

@IJRTER-2017, All Rights Reserved 2

BritishVstandard. SimilarlyV60 storied 3-dimensionalVmodels subjected to earthquakeVload by

incorporatingVoutrigger and beltVtruss system with 5Vdifferent configurations byVvarying

Locations, Vnumbers and heightVof diagonal outriggerVbeam and belt truss. AVcomparative study

hasVbeen carried outVto examine theVreduction in lateral displacement. VResearchers have

alsoVfocused on to determineVthe optimum locationVof outrigger. Investigation Vof this

researchVpaper have foundVthat 65% maximum reductionVin displacementVis attained in the

40Vstoried 2 -dimensionalVmodels subjected to windVload by providing twoVoutriggers. The

firstVoutrigger is assignedVat the topVand second at theVmid height ofVthe structure. Further,

Vabout 18% maximumVreduction in displacementVis attained in 60Vstoried 3-dimensionalVmodel

subjectedVto earthquake load byVproviding optimumVlocation of outriggerVtruss at theVtop and

33rdVlevel.

N. Herath et al. (2009) [2]: carriedVout the researchVbased on theVunderstanding that

earthquakeVground motion canVoccur anywhere inVthe world and theVrisk associated with

tallVbuildings, especiallyVunder severe earthquakes, Vshould be givenVspecial attention, sinceVtall

buildings oftenVaccommodate thousandsVof occupants. VWhen the height of buildingVincreases,

the considerationVof stiffness is veryVimportant in tallVbuilding. In such caseVoutrigger beam is

proposedVto be providedVin between theVshear wall andVexterna l columns toVimprove

satisfactory lateralVstiffness to theVstructure. The mainVintention of thisVresearch was toVoptimize

the locationVof Outrigger forVsafety againstVEarthquakes and EconomyVin design. ForVthis

purpose, researchersVhave consider 9Vprevious earthquakeVrecords and basedVon acceleration

toVvelocity ratios (A/VVRatio) namely, VPark field (28VJune 1966), VFriuli (6Vmay 1976), Patras

(V29 Jan 1974), VGazli (17Vmay 1976), ElVCentro (18 MayV1940), Spitak (7VDec 1988),

MexicoVCity (19 Sep 1985), VTabas (13VSep 1978), San FernandoV (9 Feb 1971). The

performanceVof high rise buildingVhas been examinedVby studyingVdifferent

configurationsVof outriggerVstructuralVsystem. A model of 50 storiesVwas analyzed forVthree

different ratios ofVpeak ground accelerationVto peak groundVvelocity. In each categoryVof

earthquake recordsVwere incorporated in Vthis research study toVprovide aVconsistent level

ofVapproach. Response spectrumVanalysis was conductedVto determine behaviourVof the

buildingVconsidering parametersVsuch as lateralVdisp lacement and interVstorey drift. It was

provedVfrom this studyVthat the structureVis optimized whenVthe outrigger isVplaced between

22V-24 levels. ThereforeVit can be concludedVthat the optimumVlocation of the structureVis

between 0.44-0.48 timesVits height (takenVfrom the bottomVof the building).

Kiran Kamath et al. (2012) [3]: fulfilled theVstudy of efficientVOutrigger Structural

SystemVin high riseVreinforced concreteVbuilding. The basicVthought behind thisVresearch

studyVwas to increaseVthe stiffness and makeVthe structural formVefficient under the lateralVload

acting onVthe structure dueVto wind loadVas well asVearthquake loads. TheirVresearch

examined theVbehaviour of reinforcedVconcrete structureVwith central core wallVwith various

configurationsVof outrigger systemVby varyingVrelative flexural rigidity. VIn this paper

authorsVhad also focusedVon optimum locationVof outrigger systemVin tall buildingsVby

considering theVrelative height ofVoutrigger beamVi.e. (ratio of height ofVoutrigger to totalVheight

of building).

In thisVresearch article researchersVhave considered 40Vstorey three dimensionalVmodels of 6

differentVconfigurations of outriggerVof varying Hs/H ratioVand varying relative

flexuralVrigidity betweenV0.25 to 2 forVmodelling of structure. VFor static behaviour

purposeVequivalent staticVanalysis wasVperformed as wellVas for dynamicVbehaviour purpose

Time historyVanalysis by consideringVthe previous earthquakeVdata of peak

groundVacceleration ofVCalifornia region as perVIndian standard codesVwas carri ed out. A

comparativeVstudy for the investigationVof various parameters, Vsuch as lateral deflection, Vpeak

acceleration andVinter story driftVhas been performed. VFrom the whole investigationVit is




observedVthat by consideringVthe criteria forVreduction inVtop displacement, optimumVposition

of outriggerVis at mid heightVof the building withVrelative flexural rigidityVof 0.25 by staticVand

dynamicVanalysis. Further, accordingVto the authors, in timeVhistory analysis theVresponse of

structureVdoes not show anyVparticular trend with peakVacceleration, though forVall earthquake

historiesVof California regionVthe top lateral displacementVwas least forVoutrigger structureVwith

relative heightVof 0.5.

Thejaswini R. M. and Rashmi A. R. (2015) [4]: haveVcarried outVa comparative

studyVandVanalysisVofVdifferentVlateralVloadVresistingVstructuralVystems to understand

theVrealisticVperformanceVof theVbuildingVduringVearthquakeVandVunderVthe excessive wind

pressureVas wellVas to selectVstructural system ofVtall building toVstay in goodVcondition

withVeffect ofVgravity, live loadVand externalVlateral load, Vmoment, shear force andVtorque

with acceptableVstrength and stiffness.V

For thisVresearch workVthey haveVmodelled a geometricallyVirregular 14 storeyVRCC high

rise buildingVwith different formsVof structural system, Vsuch as Rigid frameVstructure, Core

wallVstructure, and ShearVwall structure withVdifferent configurations ofVshear wall location,

TubeVstructure and outrigger structure. VResults of theVanalysis reveal thatVthe values

ofVdisplacement were less inVtube structure andVoutrigger structural system. VThe authors

haveValso stated thatVin geometrically irregularVstructure; stability ofVstructure will boostVand

the columns swayVcan be reduced by implementingVL-shaped shearVwall along the cornersVof the

structure. VOne importantVconclusion that theVresearchers haveVdrawn from this studyVis that

when outriggerVstructural system isVprovided at aVstory which has maximumVdrift, it

canVperform as aVmaximum drift controller.

Alpana L. Gawate and J. P. Bhusari (2015) [5]: have publishedVtheir paperVwhich focused

onVenhancement the lateralVstiffness of tallVbuildings, because asVthe height ofVthe building

increasesVthe core alone isVnot adequate toVkeep the drift withinVpermi ssible limit.

ThereforeVsome other structuralVelement is toVbe added inVthat building toVtake care of drift.

VOutriggers are theVstructural system, whichVhelp in reducingVthe lateral drift increasingVthe

stiffness ofVthe structureVby hugeVamount.

In this paper, Vthe optimum locationVof the outriggerVis found byVconsidering few

constraintVconditions. The parametersVon which the conclusionsVmade are the lateralVdrift and

formationVof soft storey. VA softVstorey is oneVin which theVlateral stiffnessVis less than 70

percentVof that in theVstorey above orVless than 80 percentVof the averageVlateral stiffness ofVthe

threeVstoreys above. It alsoVtakes into accountVthe change in resultsVdue to changes inVsizes of

crossVsections of columnsVand shearVwalls. For the analysisVof this problem researchersVhave

chosen a 30Vstoried three dimensionalVmodel withVvarious configurations ofVoutrigger such

asVsystem with singleVand double outriggerVby changing crossVsectional dimensionsVof columns

andVthickness of shearVwall. The saidVmodel was analyzedVby response spectrumVanalysis as

perVIndian standard codesVand following conclusionVhas beenVdrawn. When thereVwas provision

ofVonly one outrigger, Vthe system was notVeffective as concerningVof drift. There wasVa

remarkable changeVobserved in the driftVprofile when twoVoutriggers wereVprovided. One

importaVnt conclusion figuredVout from thisVresearch is noVstory was foundVas soft story

forVall 9 trials madeVin model with twoVoutriggers with changes Vin cross section alVdimensions

of columnsVand thickness of shearVwall.

AbdulvKarim Mullavand ShrinivasvB.N (2015) [6]: hadvcarried outvresearch invregular as

wellvas verticallyvirregular structurevto increasevaxial stiffnessvwith exteriorvcolumns to resistvthe

overturningvmoment byvintroducing Outriggervstructural systemvwith steel bracing.

Irregularvstructure hasvdiscontinuity invmass, stiffnessvand geometryvof the structure.

Accordingvto authorvthe majorvreason ofvearthquake wasvvertical irregularities thoughvit can




bevavoided byvproviding outriggervto increasevlateral stiffness. Invthis article researchersvhave

performedvthe comparativevanalysis of 3 dimensionalvregular and verticallyvirregular

shapedvsymmetrical plan 20 storeyvstructures withvand without providingvoutrigger

beamvsubjected tovearthquake load. Thevanalysis ofvstructure wasvdone by equivalentvstatic

methodvand responsevspectrum methodvas pervthe Indian standardvcode practice. Tovmeasure

thevefficiency ofvthe structurevauthors havevconsidered parametersvsuch asvlateral displacement,

storyvdrift, basevshear andvfundamental natural period. Onvthe samevline authorsvhave

alsovexamined thevresponse ofvthe structurevwith varyingvseismic zonesvas wellvas thevbehaviour

ofvoutrigger byvequivalent staticvand responsevspectrum methodvby incorporatingvconcrete

andvsteel outrigger. Furthervthey havevalso focusedvon thevdetermination ofvoptimum locationvof

outriggervbeam tovlower thevlateral displacement. Itvwas observedvthrough thisvresearch

thatvthere isvconsiderable reductionvin Timevperiod whenvoutrigger wasvintroduced invregular

andvirregular building structurevwhich willvimprove thevoverall stiffnessvof thevstructure.

Basevshear willvreduce andvminimize thevinter storyvdrift byvincorporating outrigger.

Geometricvvertical irregularityvwas moreveffective duevto reductionvof selfvweight comparedvto

regular buildingvand Concretevoutrigger arevmore effectivevthan steelvoutrigger withvX bracing

typevin reducingvlateral storyvdisplacement.

VijayavKumari GowdavM Rvand ManoharvB C (2015) [7]: havevworked onvlateral load

resistingvstructural systemvby introducingvbelt trussvat topvand midvheight ofvbuilding.

Thisvproved tovbe costveffective tovimprove thevperformance ofvbuilding subjectedvto

earthquakevload. Basicallyvbelt trussvis thevtruss whichvis providedvalong thevperipheral

columnsvof structurevat certainvheight ofvbuilding tovimprove thevstiffness andvfirmness

againstvlateral loads. Invthis researchvwork researchersvhave carriedvout avcomparative studyvby

usingvdifferent typesvof beltvtruss whichvincludes X, V, invertedvV diagonalvetc. forvdifferent

seismicvzone criteriavto understandvthe importancevof beltvtruss. Tovexecute thisvstudy

researchersvhave modelledv 30 vstoried 3- d imensional modelsvby implementing differentvtypes

ofvbelt trussvand analyzedvthe modelvby equivalentvstatic analysisvand responsevspectrum

methodvas pervthe IndianvStandard codes. Avcomparative studyvhas beenvperformed basedvon

percentagevreduction ofvdisplacement andvstory driftvat the differentvseismic zones. Itvis

foundvfrom thevstudy thatvfor reducingvlateral displacement andvstory drift, Concretevbelt trussvis

morevefficient comparedvto structuralvsteel beltvtruss asvit givesvnegligible results. Eachvtype

ofvtrusses givesvdifferent resultsvfor different seismicvzones, thereforevbased onveconomical

conditionsvresearchers havevconcluded that invertedvV-type ofvbelt trussvis one ofvthe bestvtype

ofvbelt trussvin allvseismic zonesvto increasevthe efficiencyvof thevbuilding

ShivshankarvK etval. (2015) [8]: presentedvresearch involvingvinvestigation ofvthe actionvof

outriggervstructural systemvin Tallvvertical irregularityvstructure. Verticalvgeometric

irregularityvshall bevconsidered tovexist wherevthe horizontalvdimension ofvthe lateralvforce

resistingvsystem invany storeyvis morevthan 150 percentvof thatvin itsvadjacent storey. Invthis

study, 30 storeyvmodels havingvvertical irregularityvwere taken. Thevbuilding planvchanges at 11th

and 21st vstory. Thesevmodels werevanalysed withvonly barevframe andvbare framevwith

onevoutrigger andvbelt trussvfor 6 configurationvof outriggervbeam byvchanging theirvposition.

Similarlyvbare frame withvtwo outriggervand beltvtruss for 5 differentvconfigurations andvthe

responsevof thevstructure wasvevaluated undervthe differentvparameters i.e. Lateralvdisplacement,

buildingvdrift, maximumvstory shearvand axialvload ofvdifferent columns. Tovexamine

thevbehaviour ofvvertical irregularityvof outriggervstructural system, linearvstatic analysisvhas

beenvcarried outvas per thevIndian standard. Itvwas recognizedvthrough thisvresearch thatvaround

28.58% vand 27% lateralvdeflection andvbuilding driftvwas restrainvby providingvoutrigger

structural systemvin highvrise verticalvirregularity structurevwhen it isvprovided at 0.67 timesvits

heightvcompare tovbare framevas wellvas 37.7% and 36.11% ofvthe Deflectionvand driftvis




controlledvby providingvoutrigger withvbelt trussvat 0.67 timesvits heightvand 0.5 timesvit’s

whenvcompared withvbare frame. Thisvstudy concludedvthat thevoptimum locationvof

outriggervwas between 0.5 timesvits heightvin tallvvertical irregularityvstructure.

III. OBJECTIVES

1. To understand the behavior of the highvrisvsteel structures subjectedvtov earthquakevloads.

2. Tovstudy theveffect ofvcombined shearvwall/core wall and outriggervin highvrise

steelvstructures.

3. To study the effect of the openings on the behavior of the reinforced concrete shear walls.

4. Here the totalvsix modelsvare analyzed.vi.e., steelvframe, steelvframe with outrigger,vsteel

framevwith shearvwall, steelvframe withvshear wallvand outrigger,vsteel framevwith

shearvwall withvopenings, andvsteel framevwithvshear wallvwith openingsvandvoutrigger.

5. Efficiencyvof highvrise steelvstructures withvrespect tovthe storeyvlateral

displacement,vstorey drift,vbase shearvand timevperiod arevfound outvfor allvsix models.

IV. METHODOLOGY

1. Onvthis studyvhigh risevsteel structurevof 40 storiesvsubjected to lateral earthquake loads is

considered.

2. Analysisvis carriedvout using equivalentvstatic methodvand dynamicvresponse spectrum

analysisvmethod usingvIS 1893:2002 forvhigh seismicvzone (V)& for zone (II) byvusing

ETABSvsoftware.

3. Efficiencyvof highvrise steelvstructures withvrespect tovthe storeyvdisplacement,

storeyvdrift, basevshear andvtime periodvare foundvout forvall typevofvmodels.

4. Furthervanalysis isvextended withvthe incorporationvof outriggervand RCvshear

wallvseparately andvresponses ofvthe steelvstructure isvextracted.

5. Locationvof shearvwall isvselected atvthe corevof thevbuilding.

6. Hencevtotal sixvmodels arevanalyzed.

vModel -1: Steelvframe.

vModel -2: Steelvframe withvOutrigger.

vModel -3: Steel framevwith shearvwall.

vModel -4: Steel framevwith shearvwall andvoutrigger.

vModel -5: Steel framevwith shearvwallvopenings.

vModel -6: Steel framevwith shearvwall openingsvandvoutrigger.

7. Basedvon thevresults extractedvfrom sixvmodels, discussionsvwill bevmade and

conclusionsvwill bevmade byvindicating theveffect ofvshear wallvand outriggervin highvrise

steelvstructures.

V. STRUCTURAL MODLING AND LOAD

The structure is a G+39 story steel structure. The structure is 120m tall, and its length

and width is 35m. The story height is 3m. Depth of deck slab is 200mm, thickness of glass is

25mm, type of support is pinned, thickness of shear wall is 300mm, floor finish load is

1.5kN/mm2, live load is 4 kN/mm

2 glazing load is 1.59 kN/mm

2, poison’s ratio is 0.2.

Earthquake zones used for the analysis is zone II and zone V. The soil type is Medium soil.

Importance factor is 1.5, response reduction factor is 5, damping ratio is 5%, wind speed for

zone II is 33m/s and wind speed for zone V is 50m/s, terrain category is 4, structure class is

C.




Fig. 5.1 Plan View and Three Dimensional view of SteelvFrame

Fig. 5.2 Plan View and Three Dimensional view of SteelvFrame with Shear Wall




Fig. 5.3 Three Dimensional view of Steel Frame with Shear Wall openings with and without outriggers.




Fig. 5.4 Three Dimensional view of Steel Frame with Shear Wall with outrigger and bare frame with outriggers.

VI. RESULTS AND DISCUSSIONS

Thevbehaviour ofveach modelvis capturedvand thevresultsvare tabulated. Thevvariation

ofvsystematic parametersvlike storyvlateral displacement, storeyvdrift, natural time periodvand base

shear hasvbeen studiedvfor EquivalentvStatic methodvand Response Spectrumvmethod. Thevresults

ofvall thevmodels arevobserved and thevmost suitablevmodel isvselected byvcomparing thevresults

ofveachvmodel.

6.1 STOREY DISPLACEMENT:

Fig. 6.1 Variationvof Storey Displacementvvs No. ofvstorey forvEquivalent Staticvmethod

alongvX and Y directionv (Zone II)

Fig. 6.2 Variation of Storey Displacement vs No. of storeyvfor EquivalentvStatic methodvalong

X and Y - directionv (Zone V)




Fig. 6.3 Variationvof Storey Displacementvvs No. ofvstorey forvResponsevSpectrum

methodvalong X andY - vdirection (Zone II)

Fig. 6.4 Variation of Storey Displacement vs No. of storey for Response Spectrum method

along X and Y-direction (Zone V)

By comparing their values in fig 6.1 to 6.4, Outvof allvthe consideredvmodels, steelvframe

withvshear wallvand outriggervgives thevgood resultvin thevreduction ofvdisplacement. Steelvframe

withvshear wallvand outriggervgives 33% vto 43% ofvreduction invlateral displacementvwhen

comparevto steel barevframe. We can see that the displacement increases as the storey height

increases. Comparevto steelvbare frame,vsteel framevwith thevoutrigger givesv 10% vto 22%

ofvreduction in displacement for equivalent static method and when compare to steel frame with the

outrigger, steel bare frame gives 10% to 22% for response spectrum method along X-direction and

Y-direction. Similarly,vas comparevto steelvframe withvshear wall,vsteel framevwith shearvwall

and outrigger gives the 15% to 26% of reduction in displacement for equivalent static method and

15% to 25% for response spectrum method along X-direction and Y-direction. Similarlyvas

comparevto steelvframe withvshear wallvwith thevopenings, vsteel framevwith shearvwall

openingsvand outriggervgives the 16% to 26% ofvreduction invdisplacement forvequivalent

staticvmethod and 25% to 35% forvresponse spectrumvmethod alongvX - directionvand Y -

direction. Thevdisplacement along Y-direction willvbe greater when compare to displacement in X-

direction. Outvof allvthe consideredvmodels, steelvframe withvshear wallvand outriggervgives

thevgood resultvin thevreduction ofvdisplacement.




6.2 STORY DRIFT :

Fig. 6.5 Variation of Storey Drift vs No. of storey for Equivalent Static method along

X and Y-direction (Zone II)

Fig. 6.6 Variation of Storey Drift vs No. of storey forvEquivalent Staticvmethod along

X and Y - vdirection (Zone V)

Fig. 6.7 Variation of Storey Drift vs No. of storey for Response Spectrum method along




X and Y-direction (Zone II)

Fig. 6.8 Variation of Storey Drift vs No. of storey for Response Spectrum method along

X and Y-direction (Zone V)

By comparing their values in fig 6.5 to 6.8. out of all the considered models. It can be

observed that the storey drift reduces more at the location of outrigger where it is placed. We can see

that the story drift increases as the storey height increases. Compare to steel bare frame, steel frame

with the outrigger gives the 5% to 30% of reduction in storey drift for equivalent static method and

when compared to steel frame with the outrigger, steel bare frame gives 25% to 50% of reduction in

storey drift for response spectrum method along X – direction and Y – direction. Similarly, as

compare to steel frame with shear wall, steel frame with shear wall and outrigger gives 3% to 21% of

reduction in storey drift for equivalent static method and 6.5% to 25% for response spectrum method

along X – direction and Y – direction. Similarly, as compare to steel frame ith shear wall with the

openings, steel frame with shear wall openings and outrigger gives 24% to 32% of reduction in

storey drift for equivalent static method and 24% to 32% for response spectrum method along X –

direction and Y – direction.

6.3 BASE SHEAR:

Fig. 6.9 Variation of Base Shear (Zone II and ZONE V)

From Fig. 6.9 it can be observed that the steel frame structure has lower base shear values

when compared to the steel frame with shear wall and outrigger structure. Steel frame structure with

shear wall and outrigger is having 4% to 22% more base shear hen compared to bare steel frame. It is




also observed that the base shear will be same for both X – direction as well as Y – direction for both

equivalent static method and response spectrum method.

6.4 MODAL TIME PERIOD:

Fig. 6.10 Variation of Time Period for different modes

It is observed that the time period is significant higher for steel frame with outrigger system

when compared to all other models. If we consider the for the first three of the modes, the time

period is increased by 30% to 33% for bare steel frame hen compared to steel frame with shear walls

and outrigger.

VII. CONCLUSION

The present study is to compare the behaviour of steel structure with and without outriggers

by using shear walls subjected to lateral loads. The significant parameters considered for study are

storey displacement, storey drift, base shear and time period. To analyse the seismic behaviour of

structure models are subjected to seismic load as per IS:1893 (part I):2002 for zone II and zone V.

Similarly, the structure as subjected to wind load as per IS:800 part III. Following conclusions are

made for different cases considered in the steel structures. By considering the obtained results, the

steel frame with shear wall and outrigger gives the better result when compare to all other models.

The steel frame with shear wall and outrigger gives 33% to 43% of reduction in storey displacement

when compared with bare frame. The steel frame with shear wall and outrigger gives 35% to 50% of

reduction in storey drift when compared with bare frame for 20th

storey where the outrigger has been

placed. The steel frame structure with shear wall and outriggers is having 4% to 22% more base

shear when compared to bare steel frame. The time period is increased by 30% to 33% for bare steel

frame when compare to steel frame with shear walls and outrigger by considering first 3 modes.

Introduction of shear wall greatly reduces lateral displacements as well as storeys drift and shear wall

also results in the increase of stiffness to the structures. The most proficient structure is the structure

having steel outrigger along ith shear wall core for both wind and earthquake loading. Proving the

outrigger along with shear wall/core wall increases the strength as well as stiffness of the building

against wind and earthquake loads. There is considerable reduction in the lateral defection, storey

drift while adding an outrigger system in the structure. The outrigger structure systems not only

control the top displacements but also helps in reducing the inter storey drift. By providing the

outriggers at different levels, the more reduction in inter storey drift can be achieved. Maximum base

shear at the base of the building increase with the increase in number of stories. Hence it can be

concluding that base shear depends mainly on seismic weight of the building.




REFERENCES

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building”, International Journal of Modern Trends in Engineering & Research, e-ISSN

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Structure with Belt Truss Systems for Different Seismic Zones”, International Journal of

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Volume 12, Issue 2 Ver. II (Mar - Apr. 2015), PP 54-63

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