RASHMI J1 , Prof SHIVASHANKAR K M2 1
Roy and Chandrasekaran (2006): The authors analysed10storeyRCframedstructurefromdynamicand staticanalysis.Theyhavereportedthatbaseshear,storey shear and storey drifts was increased as the height of structureincreased.Theyhavereportedthatpredominant ofhingeformationinpushoveranalysis.
Key Words: Stiffness,lateral,setbacks,irregularityetc...
2. Massirregularity
3. Verticalgeometricirregularity
1.1 Literature review
Chandler and Mendis (2000), studiedtheforcebased seismic design system and also the displacement based seismic assessment methodology. They also presented a casestudyforreinforcedconcretemomentresistingframes according to European and Australian code provisions havinglow,mediumandhighductilitycapacity.Theyused Elcentro NS earthquake ground motion as the seismic participationtogettheperformancefeatures.
Abuildinghavingdifferenceamongthecenterofmass and center of resistance is named as irregular building. Irregularityamongthebuildingsareclassifiedas
recognised as ‘setback building’. This structure form is attractiveandmorepopularincurrenthighrisestructure building mostly since of its functional and artistic architecture. Stepped structure is the one with vertical geometricirregularity,wherethehorizontaldimensionof thelateralforceresistingsysteminanystoreyisextrathan 150% of that in adjacent storey. These structural irregularityisn’tacceptablefromstabilitypointofview,as seismicactivityhasproventoaffectthestructureincaseof seismicactivity.Allthebuildingsduringseismicactivityis proventobesusceptiblebutthestructureswithsoftstorey configuration are being found to be mostly susceptible during seismic activity. Shortage of plain ground in mountainousregionsandurgeofmining,leadustobuild asymmetrical constructionsinthehills.Thus,thedanger factoroftheseasymmetricalbuildingsrisessharplyaseven the base of the buildings becomes inclined at slope. This deadly combination of geometric irregularity, mass irregularity,stiffnessirregularitymakesthebuildingstoo much weak to last during seismic activity. Hence, it is importanttostudytheresponsesofsuchbuildingstomake suchbuildingsseismic resistantandavoidtheirdownfallto savethedamageoflifeandproperty.
Abstract In high rise framed structures, harm from seismic activity ground motion generally initiates at specificdecreaseisverticalalongsideassociatedstoreys.duestructures.strengthfactorsstructuresresistinglocationsofstructuralweaknessespresentinthelateralloadframes.Theperformanceofhighriseframedduringstrongseismicactivitydependsontheincludingdistributionofmass,stiffness,andamongthehorizontalandverticalplanesofIncertaincases,theseweaknessesmayarisetodiscontinuityinstiffness,massamongadjacentSuchdiscontinuityamongstoriesarefrequentlywithabruptvariationsintheframegeometrytheheightofstructure.Acommonvarietyofgeometricalirregularityinbuildingstructuresarisesthepresenceofsetbacks,i.e.thepresenceofabruptofthelateralmeasurementofthestructureatlevelsoftheelevation.Thisstructuregroupis
Stiffness Irregularity It is one in which the lateral stiffnessislessthan70percentofthatinthestoreyabove Mass Irregularity It is considered when the seismic weightofthestoryisextrathan200percent of that of its contiguousstoreys.
In plane discontinuity The in plane discontinuity is consideredtoexistintheprimaryelementoflateralforce resisting system whenever a lateral force resistance elementisexistinginonestorybutdoesnotcontinue Discontinuity in capacity Discontinuity in capacity is consideredwhenthestoryshearstrengthisfewerthanthe storyabove.
International Research Journal of Engineering and Technology (IRJET) e ISSN: 2395 0056 Volume: 09 Issue: 03 | Mar 2022 www.irjet.net p ISSN: 2395 0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page1633
Dept. of Civil Engineering, ACS College of Engineering, Bangalore 2Professor, Dept. of Civil Engineering, ACS College of Engineering, Bangalore ***
SEISMIC PERFORMANCE OF SETBACK RC BUILDINGS WITH SOIL STRUCTURE INTERACTION PG Student,
1.INTRODUCTION
4. Inplanediscontinuityinverticalelements resistinglateralforce
VerticalIrregularity Astructureissaidtobevertically irregular when the horizontal dimension of lateral force resistingsysteminthestoryisotherthan150percentof thatinitsadjacentstorey.
1. Stiffnessirregularity
5. Discontinuityincapacity
2. To study the seismic performance of set back building on varying soil conditions by linear static method.
International Research Journal of Engineering and Technology (IRJET) e ISSN: 2395 0056 Volume: 09 Issue: 03 | Mar 2022 www.irjet.net p ISSN: 2395 0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page1634
1.2 Objectives of the study
Inthepresentstudy,Pushoveranalysishasbeencarried outonthe23modelsconsistingofsetbackbuildingwiththe differentfoundationproperties.
2. Modelling and Analysis
From the above literature review, we can see many researcheshaveanalysedfordifferentconfigurationssuch asset back buildings, fromthe studydone it is observed thatsetbackbuildingperformsbetterunderseismicloads. Also it is observed that pushover results were accurate enough for design applications. And the outcome of soil conditionsalsoaffectsthestructuremajorly.
Inthepresentthesis,92modelsofsetbackandstepback weremodelledandanalysedforthedifferentfoundation conditionsusingETABS
Table3.1:TheSETBACKmodelsconsideredforthe analysis
1 R 6 FixedFoundation 6storeybuilding nobays floorremovedwereinanyHard MediumsoilsoilSoftsoil
3 R 10 FixedFoundation 10storeybuilding
SlNo Model FoundationProperties Descriptionofthe Model
5 R 15 FixedFoundation 15storeybuilding nobayswere removedinany floor Hard MediumsoilsoilSoftsoil
1. To analyze the nonlinear static behavior of the verticalirregularstructures.
2 R 8 FixedFoundation 8storeybuilding nobays floorremovedwereinanyHard MediumsoilsoilSoftsoil
3. Tolearntheoutcomeofnumberofbaysandheight of the building which is resting on different soil conditions.
7 S1 6 FixedFoundation 6 storey building onebayon4th,two bays on 5th floor and three bays on the 6th floor has beenremoved Hard MediumsoilsoilSoftsoil
Poursharifi and Yasrebinia (2012): The authors analysed unsymmetrical concrete structures using pushoveranalysisandtimehistoryanalysisfordissimilar stories(4,6and8)withfixedbase.Theyhavereportedthat both pushover analysis and time history analysis had extreme lateral storey displacement and maximum base shear and pushover analysis was very sensitive for the givenloading.Theresearchersalsostatedthatthedirection of loading plays an significant role for determining the criticalconditionofthebuildings.
6 R 18 FixedFoundation 18storeybuilding nobayswere removedinany floor Hard MediumsoilsoilSoftsoil
Literature outcome
nobayswere removedinany floor Hard MediumsoilsoilSoftsoil
4 R 12 FixedFoundation 12storeybuilding nobayswere removedinany floor Hard MediumsoilsoilSoftsoil
© 2022, IRJET | Impact
11 S1 15 FoundationFixed 15 storey building one bay on 13th, two bays on 14thfloorandthreebayson the 15th floor has been removed Hard MediumsoilsoilSoftsoil
FoundatioFixedn
18storeybuilding one bayon13th and14th,two bays on 15th and 16th floor and three bays on the 17th and 18th floor hasbeenremoved
12 S1 18 FoundationFixed 18 storey building one bay on 16th, two bays on 17thfloorandthreebayson the 18th floor has been removed Hard MediumsoilsoilSoftsoil
14 S2 8
10 S1 12 FoundationFixed 12 storey building one bay on 10th, two bays on 11thfloorandthreebayson the 12th floor has been removed Hard MediumsoilsoilSoftsoil
15storeybuilding one bayon10rh and11th,two bays on 12th and 13th floor and three bays on the 14th and 15th floor hasbeenremoved
8 storey building one bay on 1st and 2nd, two bays on 3rd and 4th and 5th floor and three bays onthe6th and7th and8th floorhasbeen removed Hard MediumsoilsoilSoftsoil
International Journal Engineering Technology e ISSN: 2395 0056
9 S1 10 Fixed Foundation 10 storey building one bayon8th,twobayson9th floorandthreebaysonthe 10th floor has been removed Hard MediumsoilsoilSoftsoil
13 S2 6 FoundationFixed 6storeybuilding onebay on1st and2nd,twobayson 3rd and4th floorandthree baysonthe5thand6thfloor hasbeenremoved
FoundationFixed 8storeybuilding onebay on3rd and4th ,twobayson 5thand6th floor and three baysonthe7thand8thfloor hasbeenremoved
15 S2 10
17 15S2
FoundatioFixedn
FoundationFixed 10 storey building one bayon5thand6th,twobays on 7th and 8th floor and three bays on the 9th and 10th floor has been removed Hard MediumsoilsoilSoftsoil
12storeybuilding one bay on 7th and 8th, two bayson9th and10th floor and three bays on the 11th and 12th floor has beenremoved Hard MediumsoilsoilSoftsoil
16 12S2
20 10S3
(IRJET)
and
21 12S3
FoundatioFixedn
18 18S2
| ISO 9001:2008 Certified Journal | Page1635
FoundatioFixedn
Hard MediumsoilsoilSoftsoil
FoundatioFixedn
Research
12storeybuilding one bayon4th and5th and6th ,twobays on7th and8th and 9th floor and three baysonthe10th and11th and12th floorhas beenremoved
Hard MediumsoilsoilSoftsoil
8 S1 8 FoundationFixed 8storeybuilding onebay on6th,twobayson7thfloor and threebays on the 8th floorhasbeenremoved Hard MediumsoilsoilSoftsoil
10storeybuilding one bayon2ndand3rdand4th , two bays on 5thand 6th and 7th floor and three bays on the 8th and 9th and10th floorhas beenremoved Hard MediumsoilsoilSoftsoil
Hard MediumsoilsoilSoftsoil
FoundatioFixedn
22 15S3
19 8S3
Hard MediumsoilsoilSoftsoil
Hard MediumsoilsoilSoftsoil
value:
Volume: 09 Issue: 03 | Mar 2022 www.irjet.net p ISSN: 2395 0072 Factor 7.529 Fig3.1:ModelofR 6
of
Hard MediumsoilsoilSoftsoil
15storeybuilding one bayon7thand8thand9th , twobayson10thand11th and 12th floor and three baysonthe13th and14th and 15th floor has been removed
FoundatioFixedn
International Research Journal of Engineering and Technology (IRJET) e ISSN: 2395 0056 Volume: 09 Issue: 03 | Mar 2022 www.irjet.net p-ISSN: 2395-0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page1636 Fig2.3:ModelofS Fig2.1:ModelofR 6 Fig2.4:ModelofS2-8 Fig2.2:ModelofR-8
International Research Journal of Engineering and Technology (IRJET) e ISSN: 2395 0056 Volume: 09 Issue: 03 | Mar 2022 www.irjet.net p-ISSN: 2395-0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page1637 Fig3.23:ModelofS3 18
7. RuntheAnalysis
5. DefinetheLoadpatterns
Define the Load patterns
main
1. DevelopingaGeometricalmodel
Creating a geometrical model
The dead load, live load, wall load and earthquake loads are defined. The earthquake loads are defined by the code provisionofIS1893.Thelateralloadisauto generatedinthesoftwareitself.
6. DefineLoadcases
A building of 6, 8,10,12,15 and 8 stories have been modelledwiththeplandimensionof24mx24mwithabay widthof6moneithersideofthemodel.Theheightofeach flooris3m.
2. DefineandAssigningtheMaterialpropertyand Sectionalproperty
Table 3.2: Materials properties and dimension consideredformodellingDefinetheLoadpatterns
4. DefineResponseproperties
3. DefineandAssigningtheFoundationproperties
Live loads:
The stages involved in the geometric modelling and analysingofthestructure
Table3.5Liveloadsonthestructure
Imposed loads are those loads whose positioncanbechangefromonepositionto another position. Imposed loads can generallybetakenfromthecodeIS875(part 2).
Gradeofconcrete ofsteelfor reinforcement Fe415 ofsteelfortransverse Fe250 dimension
Grade
reinforcement
Defining and Assigning the material property and sectional property
Modelling and Analysis of the Structure
Columndimension 0mm450mmx50 Beam
0mm450mmx50 Slabthickness 125mm CoversColumnBeam 40mm25mm Level (KN/mloadsLive2) levelRoof 1.5 Floorlevel 3
52M Grade
Fig3.3storydisplacementofR 10alongx direction
=11.26kN m
Analysis
Deadloadsarethestationaryorpermanentloadswhich areduetoitsownweightofmembers,whicharegoingto stay throughout the lifespan of the structure. This load intensity depends on the type of the material, as earlier mentioned it varies based on its density. As the density increases, its self weight also increases. Dead loads generallybedeterminedaccordingtoIS875(Part 1)
Wallloadonthefloors=19.2*(3 0.45)*0.23 =(density)*(height)*(wallthickness)
ead loads:
Consider25%oftheliveloadand100%contribution fortheotherloads.
Themodelhasbeenanalysedforthegivencombination andtheresultsareobtainedforstoreydisplacement,storey drift, storey shear, overturning moments. The graph has beendrawnwithrespecttoavailableresults.
Fig3.1:StoreydisplacementofR 6alongXdirection
Fig3.2:Storeydisplacementof R 8alongXdirection
3.Results and discussions
In the current thesis work, the outcomes were evaluated for different models and the Displacement, Drift,Shear,overturningmomentsarecomputedforthe setback buildings. These models were analysed for differentflexiblefoundationconditionofzoneⅣasperIS 1839 2016(part Ⅰ).
Wall Load
Parapetwallloadontheroof=19.2*1.5*0.23 =(density)*(height)*(wallthickness) =6.624kN m
Comparison of storey displacement for all the setback models along X direction
International Research Journal of Engineering and Technology (IRJET) e ISSN: 2395 0056 Volume: 09 Issue: 03 | Mar 2022 www.irjet.net p ISSN: 2395 0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page1638
Comparison of storey drift for all the setback models along X direction
Fig3.8:StoryDriftofR 8alongXdirection
©
e
|
www.irjet.net p
Volume: 09 Issue: 03 | Mar 2022 ISSN: 2395 0072 2022, IRJET Impact Factor value: 7.529 ISO 9001:2008 1639
|
International Research Journal of Engineering and Technology (IRJET) ISSN: 2395 0056
Fig3.6:StoreydisplacementofR 10alongYdirection
Fig3.7:StoryDriftofR 6alongXdirection
Comparison of storey displacement for all the setback models along Y direction
Certified Journal | Page
Fig3.5:StoreydisplacementofR 8alongYdirection
Fig3.4:StoreydisplacementofR 6alongYdirection
Fig3.9:StoryDriftofR 10alongXdirection
2. Thestoreydriftismaximumwhenthesoilissoft (i.e.Softsoil).Thestoreydriftismaximumatthe1st storeyofallthesetbackmodelsexceptforthefixed foundationcondition.Thevariationofdisplacement onboththedirectionsofthestructureistoosmall (3%to4%)foralltypesoffoundation,thisisdueto theeffectofflexibilityofsoil.
International Research Journal of Engineering and Technology (IRJET) e ISSN: 2395 0056 Volume: 09 Issue: 03 | Mar 2022 www.irjet.net p ISSN: 2395 0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page1640 4. CONCLUSIONS
1. Thedisplacementis maximum whenthesoilis soft(i.e.Softsoil).Thedisplacementismaximumin the top storey of the structure. The variation of displacementonboththedirectionsofthestructure istoosmall(3%to4%)foralltypesoffoundation, this is due to the effect of variation of mass and stiffness.
3. The storey shear is maximum for the fixed foundationcondition.Thestoryshearismaximum at 1st story for all conditions. Variation of displacementonboththedirectionsofthestructure istoosmall(3%to4%)foralltypesoffoundation, thisisduetotheeffectofexcessiveforcegenerated insomeofthemembers.
In the present analysis of setback buildings (92) models wereanalysedandhasbeendiscussedinchapter3.Basedon the outcomes discussed from chapter 4, the subsequent inferencesaredrawn.
4. KraavasilisT.L,BazeoesNandBeskosD.E(2007), Estimation“SeismicResponseofPlaneSteelMRFWithSetbacks:ofInelasticDeformationDemands”,
6. Thetimeperiodismaximumwhenthereissoft soilcomparedtofixedsupportthisisbecauseofthe property of soil which changes resulting in maximumtimeperiod.
1. The study may be continued for time history analysis.
5. ThePushoverCurveismaximuminBaseShear forallthefixedfoundationcondition.Variationof BaseShearonboththedirectionsofthestructureis too small (3% to 4%) for all types of foundation, thisisduetotheeffectofirregularity.
3. Pushoveranalysisonretrofittedstructuresfor differentirregularitiesandsoilconditionscan bestudied
References
1. Bahram M. Shahrooz and Jack P. Moehle (1990), “SeismicResponseandDesignofSetbackBuildings”, JournalofStructuralEngineering,ASCE,Vol 116,pp 1423 1439.
6. PradipSarkar,A.MeherPrasadandDevdasMenon (2010). “Vertical Geometric Irregularity in Stepped Building Frames”, Engineering structures, Elsevier, pp2175 2182.
7. Themassismaximumforregularbuildingthisis becausethemassisdistributedalongthemembers offrame.
7. Pandey A.D, Prabhat Kumar and Sharad Kumar (2011), “Seismic Soil Structure Interaction of BuildingsonHillSlopes”,Internationaljournalofcivil andstructuralengineering,Vol 2,pp544 555.
8. PradipSarkar,DevdasMenon,andA.MeherPrasad (2012),“SeismicEvaluationofRCSteppedBuilding Frames”, DOI 10.1007/978 81 322 0757 3_82, # SpringerIndia2013
4. Theoverturningmomentsismaximumforallthe fixed foundation condition. These moments are maximum at the base of the structure for all the foundationconditions.variationofdisplacementon boththedirectionsofthestructureistoosmall(3% to4%)foralltypesoffoundation,thisisduetothe effectofirregularity.
9. Sehgal.V.K and Ankush Mehta (2014) “Pushover Analysis of Symmetric and Asymmetric Reinforced Concrete Buildings” Advances in Structural Engineering,DOI10.1007/978 81 322 2187 6167
10. Yang Liu and Kuang.J.S (2017) “Spectrum based pushoveranalysisforestimatingseismicdemandof tall buildings” Bull Earthquake Eng DOI 10.1007/s10518 017 0132 8
2. ofThestudymaybecarriedoutfordifferentzonesearthquakeanddifferentsoilconditions.
2. Chandler,A.M.andMendis,P.A.(2000).“Performance of Reinforced Concrete Frames Using Force and displacement Based Seismic Assessment Methods”. EngineeringStructures.Elsevier22,352 363.176
3. Martino.R, Spacone.E, Kingsley.G(2000) “Nonlinear Pushover Analysis of RC Structures” Earthquake Engineering34,DOI10.1007/978 3 319 07118
Journal of constructional steel research, ScienceDirect,pp644 654.
5. Athanassiadou, C.J. (2008) Seismic performance of R/Cplaneframesirregularinelevation.Engineering structures.Elsevier30,1250 1261.
Scope of future work