International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 13 Issue: 04 | Apr 2026 www.irjet.net p-ISSN: 2395-0072
Review Paper on seismic Analysis of High-Rise Building with Plan and Vertical Irregularity
Er. Sunita Gosavi1, Prof. Dr. Mrs. R. A. Dubal2, Prof. M. D. Sawant3
1 MTech Structural Student, JSPM’s, Rajashri Shahu College of Engineering, Pune, 411033.
2 Professor, Dept of Civil Engineering JSPM’s, Rajashri Shahu College of Engineering, Pune, 411033.
3 Assistant Professor, JSPM’s, Rajashri Shahu College of Engineering, Pune, 411033
Abstract – This investigation assesses the seismic performanceofhigh-riseRCandsteelbuildings(G+10toG+49) featuring complex plan and vertical irregularities. Using advanced finite element software and nonlinear time-history analysis, the study demonstrates that features like torsional asymmetry,re-entrantcorners,and "softstories"significantly amplify inter-story drift and shear stresses compared to regular models. The results indicate that mass irregularities and geometric setbacks lead to abrupt changes in lateral stiffness, causing earlier entry into the non- linear range. Consequently, the research highlights that traditional prescriptive codes often un- Der estimate seismic demands, necessitating the adoption of performance-based seismic design (PBSD) to ensure the resilience of modern urban infrastructure.
This study demonstrates that architectural irregularities significantly increase seismic vulnerability by creating localized structural weaknesses. Plan irregularities, such as torsional coupling and re-entrant corners, cause excessive inter-story drift due to the eccentricity between the center of mass and rigidity. Vertical discontinuities, including "soft stories" and geometric setbacks, trig- ger abrupt stiffness changesthatleadtoprematurenonlinearfailure.Additionally, mass irregularities from heavy equipment or pools on upper floors substantially increase base shear demands. Ultimately, the research finds that traditional building codes often underestimatetheseeffects,advocatingforperformance-based seismic design (PBSD) and nonlinear time-history analysis to ensure high-rise resilience.
Key Words: Seismic Analysis, Stiffness Irregularity, Torsional Irregularity, Story Drift, Base Shear.
1. INTRODUCTION
1.1 General
Thestructuralintegrityandseismicresilienceofhigh-rise buildingsremainparamountinmodernurbanplanning,as theism are increasingly subjected to unpredictable and devastatingseismicexcitations.Moderntallbuildingsutilize high-strength materials and efficient structural systems, resultinginmoreslender,flexibleconfigurationswithlower damping ratios that are highly sensitive to lateral forces inducedbywindandearthquakes.Whileconventionaldesign philosophies prioritize adequate lateral strength, stiffness,
and ductility, the rapid growth of urbanization has necessitated the construction of buildings with complex, unsymmetrical configurations for both functional and aestheticrequirements.Thesearchitecturaldemandsoften introduce structural discontinuities that compromise the predictable seismic response seen in regular structures. Consequently, advancing seismic analysis through methodologiessuchasnonlineartime-historyanalysisand performance-based seismic design is essential to quantify structural vulnerabilities and ensure occupant safety in severeseismiczones.
1.2
Concept of irregularity
Structural irregularity in high-rise buildings arises from abrupt discontinuities in mass, stiffness, or geometry that disrupttheuniformflowoflateralforces.Planirregularity-es, suchastorsionalasymmetryandre-entrantcorners,create significant eccentricity be- tween the centers of mass and rigidity,amplifyingshearstressesandstorydrift.Vertically, "softstories,"geometricsetbacks,orconcentratedmassloads (exceeding150-200%ofadjacentlevelsperIS1893)alter dynamicpropertiesandcauselocalizedweaknesses.These factors collectively increase seismic vulnerability, often leadingtoprematurenonlinearbehaviorandahigherriskof collapsecomparedtosymmetricstructures.
2. LITERATURE REVIEW
Manoj KumarSharma & HemantKumarSain(2024) providesanextensiveinvestigationintotheseismicanalysis of high-rise and interconnected structural systems, while concurrentlydocumentingthehistoricalevolutionofvertical construction. The authors highlight that the proximity of interconnected buildings creates complex dynamic interactions that can significantly alter seismic impact compared to isolated structures. Defining skyscrapers as edificesexceeding40floorsor150meters,thestudynotes howhigh-strengthmaterialsandmodernelevatortechnology have enabled these mega-structures. By synthesizing historicalmilestonesfromancientzigguratstosteel-framed towers, the paper emphasizes that contemporary designs
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 13 Issue: 04 | Apr 2026 www.irjet.net p-ISSN: 2395-0072
mustincorporatestructuralbarrierstomitigatewindloads and ensure occupant comfort. Ultimately, the re- view concludesthatasurbanizationintensifies,advancingseismic analysisand under- standing structural interdependencies are vital for maintaining the resilience of modern urban environments. [1]
Apoorva & Sushma C K (2021) presentsacomparative seismic performance evaluation of 30-story vertically irregularRChigh-risebuildingslocatedinseismiczoneIV. Using ETABS software to model regular, setback, massirregular,andsteppedconfig-unrations,thisstudyassessed seismic performance based on IS 1893:2016 standards. Through response spectrum and static pushover analyses, the research evaluated story drift, ductility ratios, and performance points. The results revealed that while all modelsstayedwithinsafetylimits,thesteppedconfiguration exhibitedthehigheststorydriftinupperlevels,whereasthe setback model achieved the greatest global ductility. Ultimatily, the study concludes that geometric irregularities impact seismic drift more significantly than mass irregularities, requiring more rigorous design focus for structuresinhigh-seismiczones. [2]
Anjeet Singh Chauhan & Rajiv Banerjee (2021) performedresearchoveraG+10RCCstepbackbuildingwas modeledandanalyzedusingETABSsoftwaretoinvestigate seismicperformanceonslopingground.Thisstudyanalyzed four configure- rations bare step back, mass-irregular, diaphragm-irregular, and combined-irregular frames on various slope inclinations in seismic zone V. Using the ResponseSpectrumMethod,theresearchfoundthatsteeper slopes increase structural stiffness, which in turn attracts higher lateral forces, base shear, and story displacement. Resultsidentifiedthemass-irregularstepbackframe(Model2) on a 45° slope as the most vulnerable due to excessive seismicweight.Incontrast,thediaphragm-irregularframe (Model-3) ona 20°slopeproved the moststableandleast susceptibletoseismichazards. [3]
Behzad Mohammadzadeh & Junsuk Kang (2019) made study of 12-story high-rise steel moment-resisting frame building,withatotalheightof41.6m,wasmodeled andanalyzedusingacombinationofSAP2000andABAQUS software This study compared three structural cases regular,torsionallyirregular(plan),andstiff-ness-irregular (verticalsoftstory) usingSAP2000fordesignandABAQUS for non- linear time-historyanalysis based onthe Vrancea Earthquake data.Bymodelingstructural membersaswire
elementsforcomputationalefficiency,theresearchevaluated deformed shapes, reactions, and story drifts. The results confirm that regular buildings exhibit superior seismic performancewithminimaldeformation.Notably,thestudy concludesthatplanirregularity(torsion)triggersthemost severeseismicresponse,producinghigherstorydriftsthan bothregularandverticallyirregularconfigurations.[4]
Ravindra N.Shelke & U. S.Ansari(2017)investigateda 15-story(G+14)verticallyirregularRCbuildingframewas modeled and analyzed using ETABS software. This study evaluated vertical irregularities specifically mass (swimmingpools),stiffness(ground-levelsoftstories),and geometricsetbacks usingequivalentstaticandRe-sponse SpectrumAnalysis(RSA)forseismiczoneIII.Resultsshow thatmass-irregularbuildingsexperiencesignificantlyhigher base shear, while stiffness-irregular structures exhibit reduced base shear but much larger inter-story drifts. Ultimately, the study con- cludes that dynamic analysis is essential for irregular high-rises, as the equivalent static methodisoverlyconservativeandfailstocapturethenonlineardistributionofseismicforces. [5]
Kusuma B (2017) conducted research over a 50-story (G+49)high-riseRCframedstructurewithanunsymmetrical planwasmodeledandanalyzedusingETABSsoftware.The studyevaluatedtheimpactoffivespecificirregularities:reentrant corners, mass irregularity, vertical geometric irregularity, diaphragm discontinuity, and stiffness irregularity. Seismic analysis was conducted using the responsespectrummethodforseismiczoneIVandsoiltype IIIconditions.Keystructuralresponseparameters,including modeperiod,lateraldisplacementandstorydrift,baseshear, andstorystiffness,wereobtained.Theresultsindicatethat storystiffnessissignificantlyreducedinallirregularmodels comparedtotheregularcontrolstructure.Notably,thereentrant corner con- figuration demonstrated the worst seismic performance, exhibiting the highest lateral displacement and story drift. Furthermore, the study observedthatmassirregularityresultedinthehighestbase shearduetoincreasedseismicmass,whilestiffness-irregular modelsexhibitedthelongestmodeperiods. [6]
Ali Ruzi Özuygur (2015) a50-story(198m)reinforced concrete residential building with an extremely irregular floor plan was designed using performance-based seismic design (PBSD) principles.Located in Istanbul, Turkey, this structureconsistsoftwohigh-riseblockslinkedbyslabsof varyingstiffnessacrossdifferentfloorlevels.Per-formance wasevaluatedusinglinearresponsespectrumanalysisfor
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 13 Issue: 04 | Apr 2026 www.irjet.net p-ISSN: 2395-0072
the Design Basis Earthquake (DBE) and nonlinear timehistoryanalysis(NLTHA)viaPERFORM-3DfortheMaximum Considered Earthquake (MCE). The findings revealed that traditionalelasticanalysissignificantlyunderestimatedshear demands in walls compared to NLTHA, necessitating additionalreinforcement.Furthermore,axialforcesinshear walls at the irregular plan’s boundaries exceeded safety limits during MCE events, requiring capacity redesigns. Ultimately, the study concludes that Performance-Based SeismicDesign(PBSD)providesamoreaccurateassessment of displacements and higher-mode effects for complex, irregularhigh-risebuildings. [7]
Dileshwar Rana & Prof. Juned Raheem (2015) a comparative seismic analysis of regular and vertical geometric irregular RCC building frames was performed using STAAD.Pro V8i. This study analyzed 40 building models,rangingfrom4to16stories,toevaluatetheseismic impactofsetbacksinzoneIV.Resultsshowthatregularconfigurations consistently outperform irregular setback structures,whichsufferfromsignificantlyhighershearforces and bending moments due to reduced structural stiffness. The findings indicate that four-bay frames are suitable for shorter buildings, while eight-bayconfigurationsare more effective for taller structures (12–16 stories) as they minimizecriticalseismicparameters.Ultimately,amongthe irregularmodelstested,theTypeV1setbackconfiguration demonstratedthebestperformance. [8]
Arvindreddy & R.J.Fernandes (2015) researchedover 15-story (G+14) regular and irregular reinforced concrete framestructuresweremodeledandanalyzedusingETABS 2013 software. Focusing on seismic zone V, this study evaluatedfiveirregularities mass,stiffness,diaphragm,reentrantcorner,andtorsion usingstatic,responsespectrum, and nonlinear pushover analyses, alongside a time-history simulationoftheBhujearthquake.Theresultsindicatethat staticanalysistypicallyunderestimatesstorydisplacement compared to the response spectrum method due to its inability to capture nonlinear force distributions. While diaphragm-irregular buildings showed lower drift than regular models, stiffness-irregular structures entered the non-linearrangeearlierandrecordedthelowestbaseforce during dynamic testing. Ultimately, the authors concluded that stiffness irregularities are particularly high-risk and noted that the performance of stiffness and diaphragm configurations can shift significantly as building height increases. [9]
Anupam Rajmani & Prof Priyabrata Guha (2015) Inthis research paper, the seismic and windload performance of
four different building plan geometries circular, rectangular,square,andtriangular wasinvestigatedforhighrisestructuresThisstudyanalyzedbuildingsof15,30,and45 storieswithaconstantbaseareatoevaluate the impactof buildingshapeonstructuralstability.Resultsindicatedthat performance varies significantly with height: for 15-story structures,circularshapesaremostearth-quake-resistant, whiletriangularshapesexcelunderwindloads.At30stories, rectangular configurations are most stable for both load types, but at 45 stories, circular and rectangular shapes performbestforseismicandwindexcitations,respectively. Ultimately, the study concludes that triangular and rectangularshapesexperiencethe highestdisplacementat extreme heights, highlighting aerodynamic shaping as a critical, cost-effective strategy for minimizing lateral movementintallbuildings. [10]
S Monish & S Karuna (2015) 20-storyRCordinarymomentresisting frame building was modeled and analyzed using ETABS2013toevaluatetheimpactofplanirregularities.This studyexaminedsevenbuildingconfigurationstoassessthe impactofdiaphragmdiscontinuities(H,C,and+-shapes)and re-entrant corners (L-shapes with 40%, 60%, and 80% projections)inseismiczoneV.Usingbothstaticandresponse spectrum methods, the research found that story displacementincreaseswithheightandisconsistentlyhigher in static models due to linear assumptions. The H-shaped modelprovedthemostvulnerablediaphragmconfiguration, whileseismicsusceptibilityinL-shapedmodelsintensifiedas the re-entrant projection size increased, peaking at 80%. Ultimately,thestudyconcludesthatanalyticalfundamental periodsprovideamoreaccurateassessmentthanempirical formulas, noting that IS 1893:2002 standards do not fully capturethehigh-seismicrisksassociatedwiththesecomplex irregularities. [11]
Khaled M. Heiza & Magdy A. Tayel (2012) Inthisresearch paper,a 15-story(G+14) reinforcedconcrete building was modeledandanalyzedusingETABS2013software.Focusing onseismiczoneV,thisstudycomparedaregularstructure againstfiveirregularmodels:mass,stiffness,diaphragm,reentrantcorner,andtorsion.Performancewasassessedusing linear static, response spectrum, and nonlinear pushover analyses, alongside a time-history simulation of the Bhuj earthquake.Thefindingsshowthatstaticanalysistypically underestimates story displacement compared to the responsespectrummethod.Amongthemodels,thestiffnessirregularstructureenteredthenon-linearrangeearliestand recorded the lowest base force during dynamic testing. Ultimately,theresearchconcludesthatstiffnessirregularities
International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 13 Issue: 04 | Apr 2026 www.irjet.net p-ISSN: 2395-0072
pose a high risk ("non-con- servative") and that the performanceofstiffnessversusdiaphragmirregularitiescan shiftsignificantlyasbuildingheightincreases. [12]
3. CONCLUSIONS
Reviewingnumerousstudiesonhigh-risestructuresconfirms thatseismicresilienceisheavilycompromisedbystructural and architectural asymmetries, which create localized weaknesses in lateral load-resisting systems. Regular configurations consistently outperform irregular models, showing lower deformation and more efficient energy dissipation. Plan irregularities specifically torsional asymmetryandre-entrantcornersposethegreatestthreat bycreatingeccentricitybetweenthecentersofgravityand rigidity, leading to amplified shear stresses and excessive story drifts. Additionally, vertical setbacks and stiffness irregularitiescauseabruptrigiditychanges;whilestiffnessirregular structures may show reduced base shear, they sufferfromsharplyincreasedinter-storydriftandpremature entryintothenonlinearbehaviorrange.
Conventionallinearstaticproceduresoftenfailtoaccurately predictthedynamicresponseofirregularhigh-risesbecause they neglect complex mass-stiffness distributions, necessitating advanced methodologies like PerformanceBased Seismic Design (PBSD) and Nonlinear Time-History Analysis(NLTHA)toevaluatehigher-modeeffectsandplastic hingedevelopment.Whilemassirregularities,suchasupperfloorswimmingpools,primarilyincreaseinertialforcesand base shear, geometric and plan asymmetries specifically torsionalcoupling exertamoreprofoundimpactonstory drift and shear stress. From a structural dynamics’ perspective,thesediscontinuitiesaltermodalcharacteristics andconcentratestressincriticalzones;whileneglectingsoilstructure interaction can lead to underestimating spectral acceleration demands on slender structures. To mitigate theserisks,incorporatingoptimizedaerodynamicshapeslike circular or rectangular configurations and utilizing highductility link slabs are essential strategies to ensure structural resilience and energy dissipation during major seismicevents.
REFERENCES
[1] ManojKumarSharma&HemantKumarSain“AReview on Seismic Analysis of Connected and High-Rise Buildings”
[2] Apoorva&SushmaCK“Comparativestudyofdifferent verticallyirregularhigh-rise buildings inhighseismic zones”
[3] Anjeet Singh Chauhan & Rajiv Banerjee “Seismic responseofirregularbuildingonsloppingground”
[4] Behzad Mohammadzadeh & Junsuk Kang “Seismic analysis of High-rise steel frame building considering irregularitiesinplanandelevation”
[5] Ravindra N. Shelke & U. S. Ansari “Seismic analysis of verticallyirregularRCbuildingframes”
[6] KusumaB“SeismicAnalysisofaHigh-riseRCFramed StructurewithIrregularities”
[7] AliRuziÖzuygur“Performance-basedseismicdesignof anirregulartallbuilding–acasestudy”
[8] DileshwarRana&Prof.JunedRaheem“SeismicAnalysis ofRegular&VerticalGeometricIrregularRCCFramed Building”
[9] Arvindreddy & R.J.Fernandes “Seismic analysis of RC regularandirregularframestructures”
[10] Anupam Rajmani & Prof Priyabrata Guha “Analysis of wind&earthquakeloadfordifferentshapesofhighrise building”
[11] SMonish&SKaruna“Astudyonseismicperformanceof high-riseirregularRCframesbuildings”
[12] KhaledM.Heiza&MagdyA.Tayel“ComparativeStudy ofTheEffectsofWindandEarthquakeLoadsonHighriseBuildings”