International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 12 Issue: 12 | Dec 2025 www.irjet.net p-ISSN: 2395-0072
A REVIEW OF TIME HISTORY ANALYSIS OF HIGH-RISE BUILDINGS WITH OUTRIGGER AND BELT TRUSS SYSTEMS
Ajeet Kumar Yadav1, Mr. Ushendra Kumar2
1Master of Technology, Civil Engineering, Lucknow Institute of Technology, Lucknow, India
2Head of Department, Department of Civil Engineering, Lucknow Institute of Technology, Lucknow, India
Abstract - The rapid vertical expansion of urban environments has made high-rise buildings a dominant featureofmodernskylines,buttheirstructuralstabilityunder seismic and wind-induced lateral loads remains a critical engineering challenge. Outrigger and belt truss systems have emergedashighlyefficientstructuralmechanismstoenhance lateral stiffness, minimize inter-story drift, and control overturning moments in tall buildings. This review paper synthesizes existing experimental and numerical research, with a particular focus on time history analysis, which offers detailed insights into the nonlinear and dynamic behavior of high-rise structures. The discussion covers fundamental concepts of outrigger and belt truss systems, their individual and integrated contributions, and comparative performance under seismic loading. Special emphasis is given to the influenceofoutriggerplacement,belttrussconfiguration,and combined system optimization on structural response. Findingsindicatethatintegratedoutrigger–belttrusssystems consistently outperform outrigger-only or belt truss-only systems, particularly in reducing seismic vulnerability. However, challenges related to construction complexity, modeling limitations, and context-specific performance outcomes highlight the need for further research. The paper concludesbyidentifyingpotentialfuturedirections,including hybrid materials, damped and virtual outriggers, soil–structure interaction studies, and performance-based design frameworks, to achieve safer and more sustainable high-rise structures.
Key Words: High-rise buildings; Outrigger system; Belt truss system; Time history analysis; Lateral load resistance; Seismic performance; Structural optimization; Drift control; Performance-based design
1. INTRODUCTION
1.1 Background on the Rapid Growth of High-Rise Buildings and Challenges in Structural Stability
Thecontinuousurbanizationandpopulationgrowth inmetropolitancitieshaveledtoasteepriseinthedemand forhigh-risestructures.Tallbuildingsnotonlyoptimizeland usage but also symbolize technological advancement and economic development. However, with the increase in height, these structures encounter several engineering challengesrelatedtostructuralstabilityandserviceability. The major concerns include lateral displacements, interstory drifts, and vibrations induced by seismic and wind
loads.ResearcherssuchasTaranath(2016)emphasizethat as the height of a building increases, the lateral stiffness becomesagoverningparameterinstructuraldesign,often taking precedence over strength requirements. This necessitates the development of efficient lateral loadresisting systems to ensure both safety and occupant comfort.
1.2 Importance of Lateral Load Resistance (Earthquake and Wind Loads)
Tallbuildingsfacealotofstressfromnaturalforces, especially earthquakes and strong winds. When an earthquake strikes, the shaking of the ground pushes powerful sideways forcesintothebuilding’sstructure. On the other hand, wind doesn’t hit all at once it creates a steadyswayingmotionthatcanweardownthebuildingover time and even make the occupants feel uncomfortable. As Chopra(2012)pointsout,abuilding’sabilitytoresistthese sideways, or lateral, forces is one of the most important factorsinhowwellitperformsduringanearthquake.Ifthe buildingisn’tstiffenoughorcan’tabsorbandreleaseenergy effectively, the risk of serious damage or even collapse increases.Similarly,studiesinwindtunnelshaveshownthat asbuildingsgettaller,windeffectslikevortexsheddingand sudden gusts become more intense (Kareem & Gurley, 1996).Becauseofthis,engineersareconstantlyworkingon smarterdesignsthatkeepbuildingsstrongandstablewhile avoidingtheneedforhugeamountsofextramaterial.
1.3 Significance of Structural Systems like Outriggers and Belt Trusses
When it comes to helping tall buildings resist sideways forces, one of the most effective systems is the outrigger and belt truss setup. Think of the outrigger as a stronghorizontalarmthatlinksthebuilding’scentralcoreto theoutercolumns.Thisconnectionletstheoutsidecolumns sharethejobofresistingthetippingoroverturningforces that happen during wind or earthquakes. The belt truss worksalongsideitbytyingtheoutercolumnstogether,so instead of acting separately, they behave like a single, stronger unit. Together, these systems make the whole buildingmorestableandbetterabletohandlelateralloads. StudiesbySmithandCoull(1991)andlaterbyMoon(2010) havedemonstratedthattheincorporationofoutriggerand belt truss systems significantly reduces lateral deflections andoptimizesmaterialusage,makingthemhighlypreferred
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Volume: 12 Issue: 12 | Dec 2025 www.irjet.net p-ISSN: 2395-0072
in super-tall building design. Their strategic placement at different building heights has shown to be effective in redistributing forces and controlling seismic and wind responses.
1.4 Purpose of Time History Analysis in Dynamic Structural Evaluation
Dynamic analysis forms the backbone of seismic design, and time history analysis is considered one of the most accurate methods for evaluating the response of structures under real earthquake excitations. Unlike equivalent static or response spectrum methods, time historyanalysisincorporatestheactualvariationofground motionwithtime,therebyprovidingrealisticinsightsinto structural performance (Chopra, 2012). For high-rise buildings with complex structural systems like outriggers and belt trusses, this method enables the evaluation of nonlinear behavior, inter-story drift, acceleration profiles, andoverallenergydissipation.Ithelpsengineersassessthe effectiveness of different configurations of outrigger-belt trusssystemsinmitigatingseismicresponses.Therefore,it serves as a crucial tool in advancing performance-based seismicdesign.
2. FUNDAMENTALS OF OUTRIGGER AND BELT TRUSS SYSTEMS
2.1 Outrigger System
2.1.1
Concept and Working Mechanism
Theoutriggersystemisconsideredoneofthemost effectiveapproachesintallbuildingdesign.Itsmainpurpose is to connect the building’s central core usually made of reinforcedconcreteshearwallsorabracedframe tothe outer columns with stiff horizontal members known as outriggers. When wind or earthquake forces act on the structure,thecoretendstobend,whichcausesrotationatits edges.Theoutriggerscounterthiseffectbylinkingthecore to the exterior columns, which then take on tension and compressionmuchliketheflangesofabeam.Thismakesthe entirebuildingbehavelikealarge,deepbeam,reducingthe riskoftippingandlimitingside-to-sidesway.Asexplained by Smith and Coull (1991), this cooperation between the core and the perimeter columns increases the overall stiffnessofthebuildingwithoutrequiringamajorincrease inmaterialuse.
2.1.2 Evolution of Outrigger Systems in Tall Buildings
The idea of using outriggers in tall buildings has grownandimprovedalotoverthepastfewdecades.Backin the 1960s, the first examples appeared in steel-framed skyscrapers,wheresimpleoutriggertrussesconnectedthe central core to the outer columns. As time went on,
engineers realized they could get better results by adding morethanonelevelofoutriggersatcarefullychosenheights in the building. Today, it is common to see two or more outriggersystemsplacedatspotslikemid-heightandnear thetop,whichhelpscontrolsidewaysmovementandkeeps thestructurebalanced.Morerecently,designershavealso started combining outriggers with other systems, such as mega-bracesordampers,toimprovehowbuildingsrespond toearthquakes.AccordingtoMoon(2010),thebiggestshift hasbeenmovingawayfromtrial-and-errormethodstoward adesignapproachthatfocusesonstiffness.Thischangehas made outrigger systems both more effective and more economical.
2.1.3 Types of Outriggers (Concrete, Steel, Hybrid)
Outriggerscanbedesignedusingdifferentmaterials depending on structural requirements and architectural constraints.Reinforcedconcreteoutriggersarewidelyused incompositetallbuildings,particularlywhentheyarecast monolithicallywiththecore.Steeloutriggers,ontheother hand,arefavoredfortheirhighstrength-to-weightratioand easeofprefabrication,makingthemsuitablefortall steelframedstructures.Hybridoutriggers,whichcombinesteel and concrete, have gained popularity for providing both stiffnessandconstructionflexibility.AccordingtoTaranath (2016),hybridsystemsareespeciallyeffectiveinsupertall buildings as they allow designers to balance rigidity, constructability,andarchitecturalspaceutilization.
2.2 Belt Truss System
2.2.1
Function and Integration with Outriggers
Thebelttrusssystemworkshandinhandwiththe outriggertomaketallbuildingsstrongeragainstsideways forces. A belt truss is a horizontal framework that wraps aroundtheoutsideofthebuildingatthesamelevelasthe outrigger.Itsmainjobistolinktheexteriorcolumnssothat theyworktogetherinsteadofseparatelywhenresistingthe overturningforcespassedonbytheoutrigger.Indoingso,it creates a stiff belt around the structure, allowing more columns to share the load and improving how the whole building responds. As Smith and Coull (1991) explain, the belttrussisespeciallyvaluablebecauseitspreadsoutthe forcesefficiently;makingsuretheoutrigger’ssupportisfully used.
2.2.2 Structural Behaviour under Lateral Loads
When tall buildings face strong winds or earthquakes,belttrussesplayanimportantroleinkeeping thestructuresafeandstable.Theyspreadoutthesideways, orshear,forcesamongtheoutercolumnssothatnosingle column takes on too much stress. By doing this, they also reducedifferencesinhowmuchindividualcolumnsmove, whichhelpsprotectthebuilding’sfaçadefromdistortion.Ali andMoon(2007)pointoutthatbelttrussesareespecially
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effectivewhenpairedwithoutriggersystems,sincetogether they cut down inter-story drift and improve how well the structure absorbs and releases energy. Because of these benefits,belttrussesareoftenseenasavaluablefeaturein modernseismicdesignfortallbuildings.
2.2.3 Typical Configurations in Practice
Inreal-worldprojects,belttrussesareusuallymade of steel because the material is light and very effective at transferring loads. They are often built as diagonal truss membersalongthefaçade,creatingastiffframethatwraps aroundthebuilding.Thetypicalapproachistoplaceonebelt truss at the same level as each outrigger, but in some advanced designs, multiple belt trusses are added at differentheightstogiveextrastability.Inmanycases,these trussesarealsoblendedwiththebuilding’sfaçade,allowing themtoservebothasstructuralsupportandaspartofthe architecturallook.Well-knownexamplesincludetheJinMao TowerinShanghaiandTaipei101, wherethe belttrusses arenotonlyfunctionalbutalsocontributetothebuildings’ distinctivedesigns(Taranath,2016).
2.3 Combined Role of Outriggers and Belt Trusses
2.3.1
HowThey EnhanceStiffnessandControlDrift
Whenusedincombination,theoutriggerandbelt trusssystemsprovideasynergisticeffectthatsignificantly improves the performance of tall buildings under lateral loading.Outriggerstransferoverturningmomentsfromthe core to the outer columns, while belt trusses ensure that these forces are evenly distributed across the building’s perimeter. This combined action enhances the structural stiffness, reduces overall drift, and minimizes inter-story displacements. Studies by Moon (2010) have shown that buildings with integrated outrigger-belt truss systems exhibit superior seismic performance compared to those withisolatedlateralload-resistingsystems.
2.3.2
Comparative Advantage over Other Lateral Load-Resisting Systems
Compared to alternative lateral load-resisting systems such as braced frames, shear walls, or tubular systems, the outrigger–belt truss combination offers a unique balance of efficiency and architectural flexibility. Whileshearwallsandbracedframesoftenconsumelarge amounts of usable floor space, outrigger systems require minimal intrusion into the interior layout, making them more favorable for high-rise residential and commercial projects. Additionally, tubular systems, although efficient, arebestsuitedforverytallanduniformbuildings,whereas outrigger-belttrusssystemscanbeappliedtoawiderange ofstructuralgeometries.AliandMoon(2007)pointoutthat this adaptability makes outrigger-belt truss systems the preferred choice for modern skyscrapers seeking both structuralresilienceandfunctionalversatility.
3. TIME HISTORY ANALYSIS IN STRUCTURAL ENGINEERING
3.1 Overview of Dynamic Analysis Methods
3.1.1
Response Spectrum Method vs. Time History Method
Dynamicanalysisisanessentialpartofearthquake engineering because it allows engineers to assess how structures behave under seismic excitations. Among the commonlyusedapproaches,theresponsespectrummethod andthetimehistorymethodarethemostprominent.The response spectrum method provides an estimate of peak responses of a structure by using a predefined spectrum derivedfromseismiccodesorrecordedgroundmotions.Itis computationallyefficientandwidelyappliedinpreliminary seismic design (Chopra, 2012). However, it only gives maximumresponseswithoutaccountingforthesequenceof loading or cyclic behavior. On the other hand, the time history method involves the direct integration of the structure’sequationsofmotionusingrecordedorartificially generated ground motion data. This method captures the entire time-dependent response, including displacements, velocities,accelerations,andinternalforces,makingitmore accurateforevaluatingtallandcomplexbuildings(Kunnath, 2004).Thus,whiletheresponsespectrummethodisoften used for code compliance, the time history approach is regarded as more reliable for performance-based seismic design.
3.2 Significance of Time History Analysis for Seismic Evaluation
Theprimaryadvantageoftimehistoryanalysislies initsabilitytosimulatetheactualseismicdemandimposed onastructure.Unlikesimplifiedmethods,itincorporatesthe duration,frequencycontent, andamplitude of earthquake groundmotions,offeringarealisticassessmentofstructural performance.Forhigh-risebuildingsequippedwithcomplex systems such as outriggers and belt trusses, this becomes particularly significant, as their nonlinear behavior and interaction between structural components can only be captured through detailed dynamic simulations (Boore, 2003). Furthermore, performance-based seismic design frameworks, which emphasize serviceability, damage control,andcollapseprevention,relyheavilyontimehistory analysis to evaluate building performance under varying seismicintensities.Thisensures thatthedesignisnotjust safeagainstcollapsebutalsomeetsfunctionalrequirements aftermajorseismicevents.
3.3 Selection Criteria for Ground Motion Records
Acrucialstepintimehistoryanalysisisthecareful selection of ground motion records. The chosen records mustberepresentativeoftheseismichazardatthesitein
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termsofmagnitude,distance,soilconditions,andfrequency content.AccordingtoguidelinesprovidedinFEMAP-1051 (2017)andEurocode8,groundmotionsshouldbescaledto matchthetargetresponsespectrumfortheregiontoensure consistency with local seismicity. Additionally, both historicalearthquakedataandartificialgroundmotionscan beemployed,dependingonavailability.Researcherssuchas BakerandCornell(2006)emphasizetheimportanceofusing multiple ground motions to capture variability and uncertainty in seismic demand. For high-rise buildings, particular attention must be given to long-period ground motions, as these tend to resonate with the fundamental modesoftallstructures,amplifyingdisplacementsanddrifts.
3.4 Modeling Considerations for High-Rise Structures
Accuratemodelingiscriticalforthesuccessoftime historyanalysisintallbuildings.Thestructuralmodelmust incorporate realistic material properties, geometric nonlinearity,anddampingcharacteristics.Forbuildingswith outriggerandbelttrusssystems,theconnectivitybetween thecoreandperimetercolumnsneedsspecialattention,as theefficiencyofloadtransfersignificantlyinfluencesresults. Chopra (2012) notes that modal damping ratios are often assumed in practice, but more advanced models may use energy-based damping approaches to simulate real structural behavior. Additionally, the inclusion of soilstructure interaction (SSI) is vital for very tall buildings, since flexible soil conditions can alter dynamic responses. Simplifications such as lumped mass models may be sufficientforpreliminarystudies,butdetailedfiniteelement models are recommended for performance-based evaluations(Kunnath,2004).
3.5 Advantages and Limitations of Time History Analysis
Timehistoryanalysisoffersseveraladvantagesover other dynamic methods. It provides a complete representationofstructuralresponseovertime,allowsfor the consideration of nonlinearities, and enables detailed evaluation of critical response parameters such as interstory drift, residual displacement, and energy dissipation. This makes it indispensable for tall buildings where the complexityofstructuralsystemsdemandsrigorousanalysis. However, it also has notable limitations. The method is computationally demanding and requires high-quality groundmotionrecords,whichmaynotalwaysbeavailable. Moreover, the variability of earthquake ground motions means that multiple analyses with different records are necessary to obtain reliable results, thereby increasing computationaleffort.Chopra(2012)andBoore(2003)both highlight that while time history analysis is the most accurate tool available, its effective use requires careful selectionofinputmotions,realisticmodelingassumptions, and significant computational resources. Despite these challenges, it remains the preferred method for advanced seismicevaluationofhigh-risebuildings.
4. REVIEW OF LITERATURE
4.1 Studies on Outrigger Systems
4.1.1 Summary of past research on outrigger effectiveness
Researchoverthepastfewdecadeshasconsistently shown that outrigger systems are an effective and economicalwaytoincreasethelateralstiffnessandreduce overturning of tall buildings. Early analytical and design treatises established the basic mechanics: by tying the central core to the perimeter columns through stiff horizontalmembers,outriggersmobilizeexteriorcolumnsas flanges of a large cantilever, markedly increasing the structure’s moment arm and reducing story drifts. More recentnumericalandparametricstudieshaverefinedand quantified this effect for a wide range of building heights, plan shapes and load cases. Parametric investigations employing detailed finite-element and multi-degree-offreedom models demonstrate that single- and multi-level outrigger schemes can reduce peak lateral displacements, inter-story drifts and base overturning moments when compared to identical buildings without outriggers; these benefits hold for both wind- and earthquake-induced loadings,thoughthedegreeofimprovementdependsonthe outriggerstiffness,thecore-to-perimeterstiffnessratio,and overall building height. Contemporary reviews and comparative analyses also note that properly designed outriggerscanachievetheseperformancegainswhileoften loweringoverallmaterialandcostwhencomparedtoother high-stiffnesssolutions.
4.1.2 Findings related to location, number, and material of outriggers
Alargebodyofworkhasfocusedonwheretoplace outriggers,howmanylevelstouse,andwhatmaterialsor configurations yield the best trade-offs between stiffness, ductilityandconstructability.Multiplestudiesconvergeon twopracticalobservations:(a)asingleoutriggerlevelplaced nearthemid-heightofatallbuildingoftenproducesalarge portionoftheattainablestiffnessgainforthatbuilding,and (b)forverytallstructures,twoormoreoutriggerlevels typicallyspacedsuchthatoneliesroughlyaroundone-third and another near two-thirds of the height (or equidistant spacing depending on the objective) provide superior controlofdriftandmodalcontributionsthanasinglelevel. Optimization and sensitivity studies also show that the incrementalbenefitofeachadditionaloutriggerdiminishes beyond a certain number, so designers must balance performance gains with added complexity and cost. Regarding materials and layout, reinforced-concrete outriggers provide high stiffness but can be heavy and introduceconstructionsequencingissues;steeloutriggers are lighter and easier to prefabricate and often provide better ductility; hybrid or composite outriggers (steel
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elements integrated with concrete cores or slabs) are an activeresearchareabecausetheyaimtocombineconcrete’s stiffness with steel’s ductility and constructability. Recent comparative studies both analytical and experimental have examined hybrid configurations and novel infill concepts, finding that hybrid solutions can approach the stiffness of concrete outriggers while improving constructability, although their effectiveness depends strongly on details of connection design and stiffness distribution.Finally,severalinvestigatorshaveemphasized thatoptimaloutriggerdesignisproblem-specific:the“best” location, number and material depend on the target performance metric (e.g., minimizing peak drift, reducing differentialaxialshortening,orcontrollingaccelerationfor occupant comfort) and on site-specific factors such as seismicityandsoil-structureinteraction.
4.2 Studies on Belt Truss Systems
4.2.1
Research Findings on Belt Truss Efficiency and Drift Reduction
Over the years, a number of studies have been conducted to assess how belt trusses improve the lateral stiffnessoftallbuildingsandreducedrift(bothinter‐story drift and overall displacement). For example, The Use of Outrigger and Belt Truss System for High-Rise Concrete BuildingsbyPoSengKian(2004)analyzed40-storeytwodimensionalmodelsunderwindload,and60-storeythreedimensional models under earthquake loads. In the 40‐storeycase,thestudyreportedupto65%reductionin maximum displacement when the belt truss (along with outriggers)wasplacedoptimally(onenearthetop,another mid-height).Inthe60‐storeyearthquakemodel,about18% reductioninmaximumlateraldisplacementwasobserved withoptimalbelttrussandoutriggerarrangement.
Another noteworthy study is Comparative Study on ConventionalandVirtualOutriggerswithBeltTrussSystems inHighriseStructures(2024)byYaminiLakshmi&Venkat Rao,wherea40-storeybuildingismodeledusingoutriggers + belt trusses at ½ and 2/3 heights plus a cap truss. The findings there show that maximum displacement and maximumstorydriftarelowestwhenthebelttrussisplaced atmid‐height(≈the20thstory)andatthe2/3height(≈the 26thstory)alongwithacaptrussatthetop.Thisconfirms that belt trusses have a substantial effect on drift reduction especiallywhentheirelevationisalignedwith criticalmodeshapesorwherethebuildingwouldotherwise swaymost.
In another study, A seismic behavior of RCC high rise structurewithandwithoutoutriggerandbelttrusssystem fordifferentearthquakezonesandtypeofsoil(Nigdikar& Shingade, 2023), researchers modeled a 40-storey RCC building in different seismic zones (II, III, IV, V) and soil types.Theresultsshowedthatthecombinationofbelttruss plusoutriggerprovidedlowerstorydisplacementanddrift
comparedtobuildingswithoutthesesystems.Particularly,in more severe earthquake zones and softer soils, the belt truss’scontributionbecamemorepronounced.
Yet another paper, Research and Optimization of the Belt TrussLocationinHigh-RiseRCCStructure(Shravan,Mantri, Hi was, 2019) considered a G+24 irregular residential buildinginearthquakezoneIVonhardrock.Byplacingbelt truss(s) (shear wall, hollow steel sections, or X-braced sections)inmid-floors(13-14thfloor)theyachievedabout 22% reduction in lateral deflection compared to same buildingwithoutbelttruss.Thisshowsagainthatbelttruss positionedaroundmid-heightcanbeveryeffective.
4.2.2 Comparative Studies with and without Belt Truss
Comparativestudieshelpdelineatethequantitative advantageofincludingbelttrusses(oftenwithoutriggers) relative tostructures withoutthem.Inmany of the works mentionedabove,thebaselinemodelisaconventionalframe or frame + core, without belt truss. For example, in the Nigdikar&Shingade(2023)study,thebuildingwithoutbelt truss or outrigger had substantially higher story displacement and drift under seismic zones; adding belt truss+outriggersreducedthosemetricssignificantly.
In the fragility-curves study (Iran), two models were considered: a moment frame vs a frame with belt truss + outrigger.Underseveralgroundmotionrecords,themodel withbelttrussshowedaconsistentreductioninmaximum inter-storydrift(≈12-28%)andnodedisplacements,across threshold damage states (e.g. Immediate Occupancy, Life Safety,CollapsePrevention).Thisdemonstratesnotonlythat belt truss helps under a variety of seismic intensities, but thatthebenefitisnotjustinpeakdriftbutinprobabilistic, performance-baseddesign.
ThestudyComparativeStudyonConventionalandVirtual OutriggerswithBeltTrussSystemslikewisecompares“with belttruss”vs“without”andshowsthatmidandupperbelt trusspositioning(withcaptrussattop)yieldslowerdrift and displacements than baseline models (no belt truss or outrigger) or models with only outriggers or belt truss in suboptimallocation.
Another comparison is in Po Seng Kian (2004), where models without belt truss + outrigger were compared to models with them under wind and earthquake. In the 40storey wind loaded models, the displacement reduction (with both systems) was large (~65%) compared to base models.Intheearthquakeloaded60-storeymodel,though the%reductionwaslower(~18%),itwasstillsignificant.
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4.3 Integrated Outrigger–Belt Truss Systems
4.3.1
Key Contributions Highlighting Combined Systems
Thecombinationofoutriggersandbelttrusseshas emerged as one of the most efficient lateral load-resisting strategiesfortallbuildings.Individually,outriggersconnect thecentralcoretoexteriorcolumnstoincreasethemoment arm and reduce overturning, while belt trusses distribute theseforcesalongtheperimeter. Together,theycreate an integrated structural action where the outrigger system mobilizesperipheralcolumnsandthebelttrussensuresthat allcolumnsatagivenlevelsharetheinducedforces.
Research studies consistently demonstrate the superior efficiency of combined systems. For instance, Kian (2004) analyzed 40- and 60-storey buildings and found that integrated outrigger–belt truss systems reduced displacementsbynearly65%inwindloadcasesand18%in seismic cases, compared to conventional frames without these systems. The inclusion of belt trusses enhanced the action of outriggers by ensuring that stiffness is not concentratedinonlyafewexteriorcolumnsbutdistributed acrosstheperimeter.
More recent studies by Nigdikar and Shingade (2023) examined the performance of RCC high-rise structures across various seismic zones in India. Their findings highlighted that when outriggers and belt trusses were integrated, story displacement and inter-story drift were significantlyreducedunderZoneVearthquakeconditions, demonstratingthatthecombinedsystemprovidesresilience even in the most severe seismic demands (Nigdikar & Shingade,2023).
Similarly, Lakshmi and Rao (2024) reported that placing dual outriggers with belt trusses and a cap truss in a 40storey building resulted in minimum drift compared to systemswithoutriggersalone.Thisfindingreinforcesthat belt trusses complement the outrigger mechanism by improvingthestiffnessdistributionandreducingdifferential deformations along the building height (Lakshmi & Rao, 2024).
4.3.2
Optimization of Location and Configuration
Theefficiencyofanintegratedoutrigger–belttruss systemdependsnotonlyontheirpresencebutalsoontheir placement and configuration. Research indicates that the bestperformanceisusuallyachievedwhenoutriggersand belttrussesarelocatedatmid-heightandnearthetopoftall buildings. Placing them only at the top may reduce overturningmomentsbutdoesnotadequatelyaddressinterstorydriftatintermediatelevels.
Shravanetal.(2019)studiedaG+24storeyRCCbuildingand demonstratedthatpositioningbelttrussesandoutriggersat the 13th and 14th floors (mid-height) resulted in a 22%
reduction in lateral deflection compared to top-only placements. Their research emphasized that a multi-level arrangement,combiningmid-heightandupper-leveltrusses, optimizesbothstrengthandstiffness(Shravanetal.,2019).
PatilandMujawar(2023)furtherexploreddifferentbracing configurationsinintegratedsystems.Theirstudyconcluded thatX-typebracinginbelttrusses,combinedwithoutriggers, offers greater reduction in drift compared to V-type or unbracedconfigurations.Thishighlightsthatconfiguration choices suchasthetypeoftrussbracingandthestructural materialused playacrucialroleinmaximizingefficiency (Patil&Mujawar,2023).
4.4 Time History Analysis on High-Rise Structures
4.4.1 Review of experimental and numerical studies
Timehistoryanalysisofhigh-risebuildingshasbeen explored extensively using both experimental approaches (primarily scaled shake-table tests) and numerical simulations (linear and nonlinear time-history models). Experimentalinvestigations,oftencarriedoutonreducedscale models in earthquake laboratories, have been invaluableforvalidatingnumericalmodelsandforobserving complex phenomena such as local yielding, connection behavior, and global mode coupling that are difficult to capture analytically. These tests typically subject instrumented models to sets of recorded or synthetically generatedgroundmotionsandmeasureresponsessuchas story drift, acceleration, base shear and residual deformation.Textsandreviewarticles(e.g.,Chopra,2012; Kunnath, 2004) summarize how shake-table results have guided choices of damping models, nonlinear material models, and connection details used in numerical studies. Although full-scale experimental work on complete outrigger–belttrussbuildingsisrare(becauseofcostand complexity), many laboratory studies have focused on critical components such as outrigger-to-core connections, truss joints, and column–beam interfaces and these component tests have been used to inform and calibratecomprehensivenumericalmodels.
5. COMPARATIVE DISCUSSION
5.1 Performance Comparison between OutriggerOnly, Belt Truss-Only, and Combined
Systems
Comparative studies consistently show that each system outrigger, belt truss, and their combination bringsclearbutdifferentbenefitstoatallbuilding’slateral performance. Outriggers are particularly effective at increasing the global bending stiffness of the building by mobilizing perimeter columns as flanges of a deep cantilever;thisreducesoverturningmomentsandpeakroof displacement substantially in many cases. Belt trusses, by tyingtheperimetercolumnstogether,acttoequalizeaxial
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forces around the façade and reduce local differential deformations,whichcanimprovefaçadeperformanceand reducecornerdeflections.Whenusedtogetherthesystems actsynergistically:theoutriggertransferscoremomentto theperimeterandthebelttrussdistributesthatloadamong manycolumnssotheinducedforcesaresharedratherthan concentrated. The net result reported across reviews and parametric studies is that combined outrigger–belt truss systems typically provide the largest reductions in peak lateral displacement and inter-story drift compared with either system used alone though the exact percentage improvementvarieswithbuildinggeometry,loadcase,and systemdetailing.
5.2 Influence of Outrigger Position (Top, MidHeight, Multiple Locations)
The vertical placement of outriggers is one of the mostimportantdesigndecisionsinfluencingperformance. Multiple investigations indicate that a single outrigger located near mid-height frequently produces a large proportion oftheattainable stiffness benefitfor manytall buildings,becausemid-heightplacementtargetstheportion of the structure with substantial modal contribution to lateraldisplacement.Forverytallbuildings,atwo-level(or multi-level)arrangement commonlywithoneoutrigger around one-third height and another around two-thirds height, or with one at mid-height and one near the top givesbettercontrolofhighermodeeffectsandreducesinterstory drifts more uniformly along the height than a single top-leveloutrigger.Importantly,optimizationstudiesusing nonlinear time-history inputs have shown that the “best” locationpredictedbyspectrum-basedorstaticmethodsmay differ from the optimum under realistic time histories, so placement decisions for seismic design should consider time-historyresultsratherthanrelyingsolelyonsimplified procedures.
5.3 Role of Belt Truss in Load-Transfer Efficiency
Belttrussesimprovetheefficiencyofloadtransfer by creating a rigid circumferential frame that forces perimetercolumnstoacttogetherwhenanoutriggerinjects momentintotheexteriorframe.Thisreducestherelianceon a few heavily stressed corner columns and helps smooth axialforcedistribution,whichcanbothimprovestructural redundancyandreducethelikelihoodoflocalizedoverstress orbuckling.Inmanyparametricstudies belt trusses were showntoreducecornerdeflectionsatoutriggerlevelsandto mitigate unequal column shortening effects, thereby improving serviceability (façade alignment, window performance) as well as strength demands. For practical design, this means belt trusses can allow designers to downsizeindividualperimetercolumnswhilemaintaining equivalent global performance, or alternatively to meet stricterdriftoraccelerationcriteriawithoutmajorincreases inmaterial.
5.4 Impact of Time History Analysis Outcomes on Design Recommendations
Time-historyanalysesfrequentlychangethepicture thatsimplermethodspaint.Becausetimehistoriescapture sequence,duration,frequencycontentandmulti-directional effects of real earthquakes, they reveal higher-mode contributions, torsional responses, and inelastic redistributionthatresponse-spectrumorequivalentstatic methodscanmiss.Severalstudiesthereforerecommendthat when outriggers and belt trusses are part of the lateral system especially for seismically active sites designers shouldvalidatekeydesignchoices(outriggerlevel,number oflevels,bracingtype,connectiondetailing)withnonlinear time-history simulations. Such studies often show that optimal outrigger/belt placements derived from linear or spectrummethodsshiftwhennonlineardynamiceffectsand realisticrecordsareused;theyalsoidentifypotentiallocal failures (for example, at outrigger–core connections) that would not appear from linear analysis. Consequently, modern performance-based design practice tends to treat time-history analysis not as optional but as a necessary checkfortallbuildingswithcomplexlateralsystems.
5.5 Identified Limitations and Challenges
Despite their performance advantages, outrigger and belt truss systems have practical and analytical limitations that designers must confront. Construction sequencinganddifferentialaxialshorteningbetweencore andperimetercolumnscancomplicatetheerectionofrigid outriggers;heavytrussesandcomplexconnectionsmayslow constructionandincreasecost.Asymmetriclayoutsorplan irregularities may induce unfavorable torsional coupling withoutriggeraction,sosymmetryandcarefuldistribution of outriggers/belts are often required to avoid amplifying torsion.Fromananalysisperspective,accuratelycapturing connection behavior, joint flexibility, and soil-structure interaction in time-history models is challenging but essential oversimplified models can give misleadingly optimistic results. Finally, there are trade-offs between stiffness (which reduces drift) and ductility/energy dissipation(whichreducesdamageinstrongshaking);very stiffoutriggersorbelttrussesthatpreventdriftmaytransfer larger forces into other elements unless detailed inelastic capacityandconnectionsareprovided.Thesepracticaland modeling challenges are well documented in reviews and designguidanceandformthebasisforongoingresearchinto damped or “virtual” outrigger concepts, hybrid materials, andimprovedconnectiondetailing.
6. CONCLUSION
The review of time history analysis of high-rise buildings equipped with outrigger and belt truss systems highlights the critical role these structural arrangements playinimprovinglateralstiffness,reducinginter-storydrift, andcontrollingoverturningmoments.Outriggersystemsact
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aseffectivelinkagesbetweenthecentralcoreandperimeter columns, while belt trusses distribute forces uniformly across the facade, resulting in enhanced load-sharing efficiency. When integrated, the two systems provide a synergistic response, delivering superior performance compared to their individual application. Time history analyses, in particular, have revealed that these systems substantiallyimproveseismicresiliencebycapturinghighermodeeffects,nonlinearbehavior,anddynamicinteractions that simplified static or spectrum-based methods often overlook. Thus, the evidence strongly suggests that integratedoutrigger–belttrusssystemsrepresentoneofthe most efficient solutions for modern high-rise buildings in bothwindandearthquake-proneregions.
7. LIMITATIONS
Despitetheirdemonstratedeffectiveness,outrigger and belt truss systems are not without limitations. A significant challenge arises from the complexity of construction,particularlyintallbuildingswheredifferential columnshortening,heavytrussmembersandcomplicated connectionscandelayprojecttimelinesandincreasecosts. Analyticallimitationsalsoexist;manystudiessimplifyjoint flexibility,soil–structureinteraction,andnonlinearmaterial behavior, which may lead to overestimation of structural capacity.Additionally,mostexperimentalresearchhasbeen confined to scaled models or component-level testing, leaving a gap in full-scale experimental validation of integratedsystems.Anotherlimitationisthecontext-specific nature of results: optimal outrigger location, number of levels,and trussconfigurationsvarydependingonheight, geometry, seismic zone, and soil conditions, meaning that generalizeddesignrulesareoftendifficulttoestablish.
8. FUTURE SCOPE
Future research on high-rise buildings with outriggerandbelttrusssystemsshouldfocusonseveralkey areas. First, there is a need for more performance-based seismic design frameworks that integrate nonlinear time historyanalysiswithpractical designcodes,ensuringthat dynamic demands are fully considered in routine engineeringpractice.Second,thedevelopmentofhybridand innovative materials, such as composite steel–concrete outriggersoradvanceddampedtrusssystems,couldoffer improvementsinbothstrengthandconstruct-ability.Third, the use of virtual outriggers and supplemental damping devices may provide an alternative to heavy structural elements while maintaining drift control and energy dissipation.Furthermore,morecomprehensivestudies on soil–structure interaction and torsional effects under real ground motion records are required to better capture the behavior of irregular and asymmetrical buildings. Finally, futureresearchshouldalsoincludelife-cyclecostanalysis andsustainabilityassessments,ensuringthattheefficiency of outrigger–belt truss systems is balanced with
environmental and economic considerations in the long term.
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