PERFORMANCE BASED ANALYSIS OF TALL BUILDING WITH OUTRIGGER STRUCTURAL SYSTEM IN HIGH SEISMIC ZONES

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 06 | Jun 2025 www.irjet.net p-ISSN: 2395-0072

PERFORMANCE BASED ANALYSIS OF TALL BUILDING WITH OUTRIGGER STRUCTURAL SYSTEM IN HIGH SEISMIC ZONES

Sevanthi S1, L. Govindaraju2 ,

1Post Graduate Student Department of Civil Engineering, UVCE College (University), Banalore 2Professor, Department of Civil Engineering, UVCE College (University), Karnataka, India 560056

Abstract - This study presents a performance based analysisofa40-storeyhigh-risebuildingwithandwithout outrigger systems, focusing on its seismic performance in ZonesIVandVasperIS1893(Part1):2016.Theobjectiveis toevaluatetheeffectivenessofoutriggersinreducinglateral displacement and inter-storey drift under seismic loading conditions. The building is modeled and analyzed using ETABSandSAP2000software,considering irregularplan configurations.Keyparameterssuchasstoreydisplacement and drift are compared for models with and without outriggersusingtheEquivalentStaticMethodandResponse Spectrum Method. Further, advanced seismic analysis techniques such as Pushover Analysis and Time History Analysis are performed to understand the building's nonlinear behavior and dynamic response to actual earthquake records. The influence of Soil-Structure Interaction(SSI)isalsoincorporatedtoassesshowdifferent soil conditions affect structural performance. The results indicate a significant reduction in both displacement and drift when outriggers are used, especially in Zone V. The additionofoutriggersgreatlyenhancesthelateralstiffness and stability of the structure. The study concludes that outriggers are a highly effective structural solution for improvingtheseismicperformanceoftallbuildingsinhighriskseismiczones.

Key Words: Outrigger System, High-Rise Building, Seismic Analysis, Story Drift, ETABS, SAP2000, SoilStructure Interaction, Performance-Based Design.

1. INTRODUCTION

Tallbuildingsareincreasinglycommoninurbanareasdue to the growing demand for vertical expansion in densely populatedregions.Thesestructuresfacesubstantiallateral forcesgeneratedbywindandseismicactivity,necessitating advancedstructuralsystemstoensuresafetyandstability. Theoutriggerstructuralsystemhasemergedasaprominent solution, effectively linking a building's central core to its perimeter columns to distribute lateral loads more efficiently. This configuration significantly improves the building'slateral stiffnessandminimizessway,enhancing occupantcomfortandstructuralintegrity.

In high seismic zones, where the risk of ground motion is considerable, such reinforcement becomes even more critical.Theintegrationofoutriggersystemshelpscontrol

inter-storeydriftandreducestheoveralldeformationofthe structure during seismic events. This paper explores the performance of various outrigger configurations and evaluatestheireffectivenessusingcomputationalmodeling andrealseismicdata.Additionally,thestudyincorporates theimpactofSoil-StructureInteraction(SSI),acknowledging thatfoundationflexibilitycanalterthedynamicresponseof tallbuildings.Byaddressingthesefactors,theresearchaims toprovidevaluableinsightsintooptimizingstructuraldesign for earthquake resilience, ultimately contributing to the development of safer and more sustainable urban infrastructure.

2. LITERATURE REVIEW

Numerous studies have underscored the benefits of outriggersystemsintallstructures.Fawzia&Fatima(2010) demonstrated substantial reductions in lateral deflection withmulti-leveloutriggers.Changetal.(2013)introduced semi-activedampedoutriggersusingMRdampers,showing enhanced seismic control. Chopra (2017) emphasized the roleofpushoveranalysisincapturingnon-linearbehavior. Otherresearchers,suchasKogilgeri&Shanthapriya(2015), examined the effect of varying outrigger depths and concluded that full-height outriggers provide optimal performance.Despitethesefindings,researchgapsremainin understandingvirtualoutriggers,soil-structureinteraction, and the response of irregular building geometries under actualseismicconditions.

3. OBJECTIVES AND METHODOLOGY

2.1

Objectives Of The Study

Theprimaryobjectiveofthisstudyistoevaluatetheseismic performanceoftallbuildingwithandwithoutoutrigger

1. To compare the lateral displacements (story displacement) and story drifts of a building structurewithandwithoutanoutriggersystem.

2. To analyze the behavior and performance of the structure when subjected to seismic forces, particularlyinhighseismiczones

3. To evaluate the overall performance of the structure, focusing on how the outrigger system enhances the building’s ability to resist lateral forces.

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 06 | Jun 2025 www.irjet.net p-ISSN: 2395-0072

4. Toassessthestructure’sperformanceundermore realistic conditions, such as actual earthquake records,ratherthansimplifiedloadmodels.

5. Toinvestigatetheeffectofsoil-structureinteraction (SSI) on the performance of the building with an outriggersystem.

2.2 Methodology

Seismic analysis included Equivalent Static Method, ResponseSpectrumAnalysis,PushoverAnalysisandTime HistoryAnalysisusingrealearthquakedata(Bhuj2010).For SSI analysis, modeled using springs with defined stiffness values were evaluated to determine their impact on structuralperformance.

ANALYSIS METHODS:

1. Equivalentstaticanalysis(ESA)

2. Responsespectrumanalysis(RSA)

3. Lineardynamicmodalanalysis

4. Nonlineardynamictimehistory

5. NonlinearStaticPushoverAnalysis(NSPA)

6. Soil-StructureInteraction(SSI)

3. MODELS CONSIDERED FOR ANALYSIS

A 40-storey, 30x30m reinforced concrete building was modelled using ETABS and SAP2000. The analysis considered two main configurations: with and without outriggersystems.Thebuildingwassubjectedtogravityand seismicloadsaccordingtoIS1893(Part1):2016andIS875 (Part3).

InPresentstudy,fourmodelsareconsideredforanalysisas follows:

MODEL1- In model 1 40-story without outriggers is consideredandanalyzedforsoftsoilinzoneIV&zoneV.

MODEL 2-Inmodel140-storywithoutriggersisconsidered andanalyzedforsoftsoilinzoneIV&zoneV

3.1 Geometry of the Model Considered

Table -1: Geometryofthemodelconsidered

No. of storey’ s G+39

No. of bays in X-direction 5

No. of bays in Y- direction 5 X-direction bay width 6m Y-direction bay width 6m

Height of bottom storey 3.2m

Height of storey 3.2m

3.2 Section Properties

Table -2: SectionProperties

PARAMETERS BUILDING CONFIGURATION

LengthinX-direction 30m

LengthinY-direction 30m

No.ofstoreys G+39

Beam

B=400X700mm,M40grade concrete

Column C=800X1200mm,M40grade concrete

Slab 150mmM25gradeconcrete

Bracing 600X600X30Steelhollowsection

3.3 Loads considered

Table -3: Loadsconsidered Load Type

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3.4 Seismic Parameters

Table -4: seismicparameters

Structure type RC building with special moment resisting frame (SMRF)

Typeofsoil SOFT,TYPEIII

Zone IV&V

Damping

Importance

4 RESULTS AND DISCUSSION

4.1 RESPONSE SPECTRUM ANALYSIS

4.1.1 STOREY DISPLACEMENT

Themaximumstoreydisplacementofthestructureisin Y-direction. Hence the results are taken in Y-direction for zoneIV&zoneVwithsoftsoilcondition.Storeydisplacement variations are shown in chart below. The inclusion of fullheightoutriggersresultedinan80%reductionintop-story displacement. Structures without outriggers exhibited excessivelateralmovement,makingthemvulnerableduring earthquakes.

Chart -1:Comparisonofdisplacementwith&without Outriggers(RSY)forZ4

Chart -2:Comparisonofdisplacementwith&without Outriggers(RSY)forZ5

4.1.2 STOREY DRIFT

The maximum drift of the structure is in Y-direction. HencetheresultsaretakeninY-directionforzoneIV&zone Vwithsoftsoilcondition.Storeydriftvariationsareshownin chartbelow.Driftvaluesweresignificantlylowerinmodels withoutriggers.Amaximumreductionofapproximately45% was observed Y directions under seismic loading. This indicatesbettercontroloverrelativefloormovements,which iscrucialforoccupantsafetyandnon-structuralcomponent stability.

Chart -3:Comparisonofdisplacementwith&without Outriggers(RSY)forZ4

Chart 4:Comparisonofdriftwith&withoutOutriggers (RSY)forZ5

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 06 | Jun 2025 www.irjet.net p-ISSN: 2395-0072

4.2 TIME HISTORY ANALYSIS

Non-linear time history analysis is a dynamic analysis method used to evaluate the seismic performance of structures under real earthquake ground motions. Bhuj Groundmotionisconsideredforanalysis.

4.2.1

STOREY DISPLACEMENT

Themaximumstoreydisplacementoccursattopstoreyof thebuilding.

WhencomparedtoEquivalentstaticandresponsespectrum analysis, in non-linear time history analysis the storey displacementdecreasesandtheresultsobtainedarewithin thelimitsi.e.,H/250aspercoderecommendation.

4.2.2

STOREY DRIFT

Theresultsaretakenformodel1andmodel2inzoneIV&V withsoftsoilcondition.

 Formodel1zoneIVwithoutbracingsthemaximum storey drift occurs at Storey 7 with a value of 3.318mm.

 Formodel1zoneVwithoutbracingsthemaximum storey drift occurs at Storey 7 with a value of 4.963mm.

 For model 2 zone IV with bracings the maximum storey drift occurs at Storey 28 with a value of 1.1mm

 For model 2 zone V with bracings the maximum storey drift occurs at Storey 25 with a value of 1.733mm

4.3 PUSHOVER ANALYSIS

Pushover analysis is done for G+39 building with and without Outrigger in zone IV and Zone V with soft soil condition.

 ResultsaretakenforModel1andModel2 inZone IV&ZoneVwithand withoutoutrigger,eachmodel

exhibits different displacement at performance pointindicatingvaryingstructuralcapacities.

 The pushover analysis results provided critical insightsintothenonlinearbehaviorofthestructure under increasing lateral loads. Buildings without outriggersreachedtheiryieldandultimatecapacity much earlier, showing a steep decline in strength post-yield. In contrast, buildings with outrigger systems demonstrated greater displacement tolerance before failure. The pushover curves indicatedenhancedductilityandenergydissipation, reflectingtheimprovedseismicperformancedueto thepresenceofoutriggers.Plastichingeformation wasmoreevenlydistributedinoutrigger-equipped structures, reducing the likelihood of localized failures.

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 06 | Jun 2025 www.irjet.net p-ISSN: 2395-0072

4.4 SOIL-STRUCTURE INTERACTION (SSI)

TheanalysiswascarriedoutforaG+39storeybuildingwith andwithoutoutriggers,locatedinSeismicZonesIVandV, knownfortheirhighseismic activity.Thestructureswere supportedonsoftsoilwithabearingcapacityof150kN/m² andadepthof30meters.A5-meter-deepmatfoundation was used to transfer loads from the superstructure to the underlyingsoil.Thebaseofthesoilwasassumedtobefixed, andsurfacespringswereincorporatedatthebaseofthemat foundation to simulate soil-structure interaction. These springs represented the soil's stiffness and damping characteristics,enablinga morepreciseassessmentofthe building'sseismicresponse.

4.4.1 STOREY DISPLACEMENT

Themaximumstoreydisplacementofthestructureisinboth Xand Y-direction.HencetheresultsaretakeninbothXand Y-direction for zone IV & zone V with soft soil condition. Storey displacement variations are shown in chart below. From chart 6 it can be conclude that the model without outriggers in zone V is showing maximum storey displacementandstructurewithoutriggersshowsminimum displacement.

4.4.2 STOREY DRIFT

The drift of the structure is taken in both X and Ydirection.HencetheresultsinbothXandY-directionforzone IV&zoneVwithsoftsoilcondition.Storeydrift variations are shown in chart below. From chart 15 & 16 it can be concludethatthemodelwithoutriggersinzoneIVreduces 35%iny-directionandinzoneV40%inx-direction. This improvementminimizestheriskofnon-structuraldamage.

4.5 PUSHOVER ANALYSIS FOR SSI

Pushoveranalysisisanonlinearstaticanalysismethodused toevaluatetheseismicperformanceofstructures,including soil-structureinteraction(SSI)effects.Thisanalysisaccounts fornonlinearbehaviourofstructuralelements,foundations, and soil, and applies a lateral load pattern to simulate seismic forces. By considering SSI effects, including soil nonlinearity,foundationflexibility,andstructure-foundation interaction, pushover analysis provides valuable insights intoastructure'sseismicperformance.Theanalysisinvolves creatingadetailedmodelofthestructure,foundation,and soil, applying a lateral load pattern, and performing a nonlinear static analysis to determine the structure's response.Theresultscanbeusedtoevaluatethestructure's performance,includingdeformation,damage,andpotential failuremodes.Pushoveranalysiscanhelpidentifypotential

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 06 | Jun 2025 www.irjet.net p-ISSN: 2395-0072

weaknessesinthestructure,foundation,orsoil,andinform retrofitting or design decisions to improve seismic resistance.Theresultscanbeconcludedas;

Models

SpectralDisplacement (mm) x y

Modelwithoutoutriggers(Z4) 200 199

Modelwithoutriggers(Z4) 65 65

Modelwithoutoutriggers(Z5) 250 260

Modelwithoutoutriggers(Z5) 133 144

Chart 7:Comparisonofspectraldisplacementofwithand withoutoutriggerfrompushoveranalysis(SSI)

3. CONCLUSIONS

 This research aimed to enhance the seismic performanceofa40-storeyhigh-risebuildingthrough theimplementationofoutriggersystems.

 The inclusion of outriggers significantly improved structuralstabilitybylinkingthebuildingcorewith perimetercolumns,therebyallowingthestructureto functionasacohesivelateralload-resistingsystem.

 the use of outriggers contributed to substantial displacementreductions,withZoneIVexperiencing anapproximate67%decrease

 Decreaseinstorydriftwasobserved,witharounda 35% reduction recorded in Zone IV and approximatelya40%reductioninZoneV

 When considering Soil-Structure Interaction (SSI):Displacement reductions remained effective, rangingfrom33–37%inZoneIVand35–37%inZone V,confirmingthefunctionalityofoutriggersonsoft claysoils.

 Pushover Analysis showed enhanced post-yield performance;buildingswithoutriggerscouldendure higherloadsanddemonstratedsuperiorductilityand energyabsorption.

 Pushover Analysis showed enhanced post-yield performance;buildingswithoutriggerscouldendure higherloadsanddemonstratedsuperiorductilityand energyabsorption.

REFERENCES

[1]IS:875(Part1)–1987Codeofpracticefordesignloads (otherthanearthquake)forbuildingsandstructures.

[2]IS:875(Part2)–1987Codeofpracticefordesignloads (otherthanearthquake)forbuildingsandstructures.

[3]IS1893(Part1):2002CriteriaforEarthquakeResistant designofstructures:Generalprovisionsandbuildings.

[4] Deflection control in composite building by using belt trussandoutriggerssystem.S.FawziaandT.Fatima(2010).

[5]Semi-activedampedoutriggersforseismicprotectionof high-rise buildings Chia-Ming Chang, Zhihao Wang. et al.(2013).

[6].Astudyonbehaviourofoutriggersystemonhighrise steel structure by varying outrigger depth. Srinivas Suresh Kogilgeri , Berly Shanthapriya(2015).

[7].Optimizeduseofmulti-outriggerssystemtostiffentall buildings.Z.Bayati,M.Mahdikhani,A.Rahaei(2018).

[8].StabilityEnhancementofOptimumOutriggersandBelt TrussStructuralSystem.ArchitDangi,SagarJamle(2019).

[9].Analysisofhigh-risebuildingwithoutriggerusingnondimensional parameter Varsha Virde, Dr .R. Singh et al.(2020).

2025, IRJET | Impact Factor value: 8.315 | ISO 9001:2008

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056

Volume: 12 Issue: 06 | Jun 2025 www.irjet.net p-ISSN: 2395-0072

[10].AComprehensiveintroductiontooutriggersandbelttrusssysteminskyscrapers.WaelAlhaddad,YahiaHalabiet al.(2020).

[11].Assessmentofwind-inducedvibrationmitigationina tallbuildingwithdampedoutriggersusingreal-timehybrid simulations. Safwan Al-Subaihawi, Chinmoy Kolay. et al.(2020).

[12]..Seismicperformanceandoptimizationofmultistoryed building by outrigger along belt truss structure Shriya Shetye,S.N.Tande(2021).

[13] .Dynamic analysis of composite structures with outrigger system using response spectrum method. GurkiratSingh,S.K.Singh(2022).

BIOGRAPHIES

SEVANTHIS M.TECH,EARTHQUAKE ENGINEERING

UVCE,BANGALORE,KARNATAKA