ANALYTICALIDENTIFICATIONOFTHEMOSTAPPROPRIATELOCATIONOFASOFTSTOREYINRCBUILDING

1JITENDRAKUMAR,2Dr.VIVEKGARG,3Dr.ABHAYSHARMA

1M.Tech.Student(StructuralEngineering),DepartmentofCivilEngineering,MANIT,Bhopal,INDIA

2AssistantProfessor,DepartmentofCivilEngineering,MANIT,Bhopal,INDIA

3AssociateProfessor,DepartmentofCivilEngineering,MANIT,Bhopal,INDIA

E‐Mail:jitu.lnct@gmail.com

ABSTRACT

Thetermsoft‐storeydescribesonelevelofastructurethatisconsiderablygreaterflexiblethanthestoriesaboveandbelowit.Soft‐storeybuildingsareparticularlysusceptibletoearthquakedamage. Generally,thesoftorweakstoreyusuallyexistsatthegroundfloorlevel,buttherehasbeenaneedtodesignsoftstoreyatthefloorotherthengroundlevel.Inpresentstudy,themostappropriatelocationofasoftstoreyinRCbuildingframeisstudied.A5storeyRCbuilding,subjectedtoseismicforceisconsidered for analysis. The various analyses are performed for different location and height of soft storey. STAAD Pro.Softwarehasbeenusedforanalysis.Thestructuralforces,displacementandmaterialquantityobtainedfromvariousanalysesarecomparedtoidentifythemostappropriatelocationofsoftstoreyinRCbuildingframe.Theresultsindicatethatsoftstoreylocatedat first/secondstoreycauseshigher forces in thestructure.Also,thestructure is foundmoreeconomicalwhensoftstorey isavoided from first/secondstorey.Thestructural forcesanddisplacement increaseswiththe increase insoftstoreyheight.

Keywords‐Softstorystructure,STAADPROsoftware,SeismicLoading,Driftetc.

1. INTRODUCTION

Structures are classified as having a soft story if, thatlevel is less than 70% as stiff as the floor immediatelyaboveit,orlessthan80%asstiffasaveragestiffnessofthe three floor above it. Often, open‐ground‐storeystructures are also called soft storey building, eventhough their ground storey may be soft or weak.Generally, the soft orweak storey usually exists at thegroundfloorlevel,butitcouldbeatanyotherfloorlevelaswell.Softstorybuildingsarecharacterizebyhavingastory which is situated over ground level with hugeopening, such as parking, garage or series of retailsbusiness with large windows etc. The behavior of softstorey building in seismic force is very significantbecause soft storey structure is more flexible thannormal floor. In seismic condition vibration happensmore in soft storey building as compared to normalbuildingandthereforeitbecomesimportanttostudyitsbehavior during such a mishap. In order to make itearthquakeresistantweprovideshearwallandbracinginsoftstoreybuilding.Thestoryhavinglessstiffnessduetoreducedbrickworkinfillwallsiscalledassoftstorey.This soft story is thecauseofamajorweaknessdue tolarge retail spaces without brickwork infill walls. Thesoftstoryisofteninthegroundlevelofabuildingbutinpast there has been a need to design soft story at thefloorotherthengroundlevel.

Figure1:Softstoreystructure

ChenandConstantinou(1990)studiedthatthepracticalsystemonpurposeintroduceflexibilityatthefirst floorof abuildingswasdescribe. In the structureuseTeflonsliders to carry a part of the superstructure. EnergydissipationisprovidedbythefirststoryductilecolumnsandbytheTeflonsliders.

Sashi K. Kunnath (1991) emphasized the in‐planeflexibility of floor‐slab systems has been observed toinfluence the earthquake response of many types ofreinforced concrete structures. The assumptionof rigidfloor diaphragms is often used to simplify engineeringanalyses without significant loss in the accuracy ofearthquakeresponsepredictionformoststructures.Thestudy shows that the in‐plane deflections of floor slabsimpose a larger demand on strength and ductility offlexible frames than predicted values using the

JITENDRA KUMAR et al. DATE OF PUBLICATION: SEPTEMBER 01, 2014

ISSN: 2348-4098 VOLUME 2 ISSUE 6 AUGUST 2014 (VER II)

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assumptionofrigidorelasticslabs.Thesedemandsmayin turn lead to a failure of the gravity‐load supportingsystem.

Mo and Chang (1995) studied a practical systemcombining a flexible first story with sliding frictionalinterfaces.ThesystemutilizesTeflonslidersatthetopofthefirststoryreinforcedconcreteframedshearwallstocarryaportionofthesuperstructure.

Manabu Yoshimura, (1997) studied the strengthdeterioration was considering member nonlinearity,They virtual how the building behave and finallycollapsedduringtheearthquakeeffect.Theanalysiswasfound to same structure and observed damages well,such as left displacement, mechanism and damages tomembers.

Kim Sang‐Cheol and White Donald W (2004) studiedrecent seismic codes and standard generally use thesame single degree‐of‐freedom (SDOF) model for low‐rise building with inflexible diaphragms. On the otherhand,flexiblediaphragmstructuresbehaveingeneralasmany degree‐of‐freedom (MDOF) systems. A simplifiedlinear staticmethodology, applicable to structureswithflexible storey, was proposed in this paper. Theprocedure was based on the assumption that thediaphragmstiff‐nessesaresmallrelativetothestiffnessofthewalls,andthattheflexiblediaphragmswithinthestructuretendtorespondindependentlyofoneanother.

A.Plumier,et.al(2005)theobjectiveofthestudywastopromote safety not including too much changing theconstructionalpracticeofreinforcedconcretestructures.A test plan was realize on cruciform beam‐to‐columnnodes with a column inserted between infill. Thecomplex solution increases the ductility significantly.Themostcommonfailuremannerofreinforcedconcretemoment–frame building is the so called “soft storey”mechanism. It consists in the positions of structures’becausetheearthquakedeformationsandruptureinthebottomstoriesofthestructures.

Ari Wibowo, et. al (2010) observed that precast softstoreystructurehadadequatedisplacementcapacityforlower earthquake regions, but the performance wasconsideredinsufficientforhigherearthquakeregions.

Varadharajan et. al. (2013) conducted an extensiveparametric studyonplaneRCmoment resisting frameswithsetbacks.Firstly,aparametercalledas irregularityindex was proposed based on the dynamiccharacteristics of the frame to quantify the setbackirregularity. Secondly, thispaperaims todetermine theaffect of setback presence on inelastic deformationdemands.Toachievethispurpose,buildingframeswithdifferent arrangements of setbacks are modeled anddesigned in accordance with the European standardcodeofpractice.

From the literature survey it is observed thatresearchers have worked in following areas of softstoreybuilding‐

Analysis of soft storey building using Teflonsliders.

Seismicanalysisofsoftstoreythreedimensionalasymmetricmultistorybuilding.

Seismic performance of soft storey buildingconsideringasmoment‐resistingsteelframe.

Seismic analysis of earthquake response ofmultistorymono‐symmetricbuilding

Seismic analysis of earthquake response ofmultistorymono‐symmetricbuilding

2. PROBLEMFORMULATION

Inthepresentworktheeffectofsoftstoreyonstructuralperformancehavingdifferentgeometricalconfigurationsunder earthquake force is studied. This problemassociated with the soft story structure consideringdifferent geometrical and earthquake parameters. Hereanalysisofdifferentstructureof12mx16minplanareaand5storey(G+4)heightischosenforstudy.Theresultsofmemberforces,drift,displacementandsteelquantityfordifferentgeometrical configurationarecompared tostudy the effect of soft storey position on structuralbehavior.

TableNo.1Detailsofsoftstoreystructures

Five soft story cases are generates for each type ofstructuresasgiveninTable2

TableNo.2:Differentcasesofsoftstoreylocation

JITENDRA KUMAR et al. DATE OF PUBLICATION: SEPTEMBER 01, 2014

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Figure2:Isometricviewofsoftstoreybuilding(Type‐A,BandC)

Figure3:Planofsoftstoreybuilding(Type‐A,BandC)

Figure4:ElevationofType‐Astructure

Liveload:

Liveloadontopflooristakenas=2KN/m²

Liveloadonintermediateflooristakenas=4KN/m²

Table3:Deadloads

Figure5:ElevationofType‐Bstructure

Figure6:ElevationofType‐Cstructure

Structuralcomponent Deadload(kN)

(I)Outsidewall

(ii)Insidewall

12.88kN/m

7.28kN/m

(iii) Exterior member load atsoftstory(4m)floorheight 17.48kN/m

(iv) Exterior member load atsoftstoryof(4.5m)floorheight

19.78kN/m

(v) Exterior member load atsoftstoryof(5m)floorheight

22kN/m

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3. DISSCUSSION

Discussthestructuralforce(bendingmomentincolumnand beam, shear force in beam, axial force in column),displacement in storey, storey drift, quantity of steelwhensoftstoreyatdifferentlocationforTypeA,BandCstructure.Thedetailstudiesareshowninbelow‐

3.1Bendingmomentincolumn

Table 5: Depict the maximum bending moment incolumn for different soft storey location in Type‐Astructureandalsoobtainedmaximumbendingmomentatfirstandgroundstorey.

Table4:Data/Parametersforanalysis

Table5:Max.Bendingmoment(KN‐m)incolumnsofType‐Astructure

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Figure7:MaximumbendingmomentincolumnofTypeAStructure

3.2 Comparisons of critical bending moment incolumnforTypeA,BandCstructures

Comparisonofcriticalbendingmomentincolumnwhensoft storey at different location for Type A, B and Cstructures. It found critical bending moment at firststoreyamonginallstoreyineachtypeofstructures

Table6:Comparisonofcriticalbendingmoment(kN‐m)atdifferentstoriesofstructures

Figure8:Comparisonofcriticalbendingmoment(kN‐m)atdifferentstoriesofstructures

3.3Bendingmomentinbeam:

Table7:DepicttheMaximumbendingmomentinbeamwhen soft storey at different location for Type‐A

structureand foundmaximumbendingmomentat firstandsecondflooramongallfloor.

Table7:Max.BendingmomentinbeamsofdifferentstoreyforType‐Astructure

Figure9:Max.BendingmomentinbeamsofdifferentstoreyforType‐Astructure

3.4 Comparison of critical Bending moment beamforType‐A,BandCstructures

Table8:Thecomparisoncriticalbendingmomentwhensoft storey at different location for Type‐A, B and Cstructure and it found critical bendingmoment at firstand second floor in each type of structures when softstoreylocatedatfirstfloor.Thisisrepresentsgraphicallyinfig.10

Table8:ComparisonofcriticalbendingmomentinbeamsforType‐A,BandCstructures

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Figure10:ComparisonofcriticalbendingmomentinbeamsforType‐A,BandCstructures

3.5ShearforceinbeamforType‐Astructure

Table9:DepicttheMaximumShearforceinbeamwhensoftstoreyatdifferentlocationforType‐Astructureandfoundmaximumshearforcefirst/secondflooramonginallfloor.

Table9:Max.Shearforce(kN)inbeamsofvariousstoreyforType‐Astructure

Figure11:Max.Shearforce(kN)inbeamsofvariousstoreyforType‐Astructure

3.5 Comparison of critical Shear force inBeam forType‐A,BandCstructures

Table 10: Comparison of max. Shear force when softstoreyatdifferentlocationforType‐A,BandCstructureand it observed maximum shear force at first floor

among in all floor. This is also represent graphically infig.12

Table10:Comparisonofcriticalshearforce(kN)inbeamforType‐A,BandCstructure

Figure12:Comparisonofcriticalshearforce(kN)inbeamforType‐A,BandCstructure

3.6Comparisonofmax.Displacement

Table 11: shows the comparison of maximumdisplacement between Type‐A, B and C structure. ThemaximumdisplacementisfoundinfifthfloorforcaseII

Table11:Comparisonofcriticaldisplacement(mm)infloorsofType‐A,BandCstructures

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Figure13:RepresentationofCriticalcaseduetomaximumdisplacementinfloorsofdifferentstructures

3.7.ComparisonofsteelquantityinType‐A,BandCstructures

Table 12: Comparison of maximum quantity of steelwhenlocationofsoftstoreyatdifferentstoreyforType‐A, B and C structure, and found maximum quantity ofsteel are required in case II andminimum in case‐V ineach type of structures. This also represent graphicallyinfig.14

Table12:Comparisonofquantityofsteel(kN)requiredindifferentcasesforTypeA,BandC

structure

Note:ValueinthebracketindicatespercentageincreaseinsteelwithrespecttocaseV

Figure14:ComparisonofquantityofsteelsindifferentcasesforTypeA,BandCstructure.

4. CONCLUSIONS

Theimportantconclusionsdrawnfromthestudyareasfollows‐

1. For different locations of soft storey the bendingmomentincolumnisfoundtobehigheratgroundstoreyand first storey columns however lower bendingmoment is found in top storey columns. In a particularstorey bending moment value is found to be criticalwhen soft storey is located at that storey. The columnforcesincreasewiththeincreaseinsoftstoreyheight.

2. For different locations of soft storey the bendingmoment inbeamis foundtobehigherat first floorandsecond floor beam however lower bending moment isfound at top floor beam. In a particular storeybendingmomentisfoundtobecriticalwhensoftstoreyislocatedatthatstorey.

3.Forshear force inbeamis foundtobehigherat firstfloorandsecond floorandminimum in top floorbeam.Inaparticular storey shear force is found tobe criticalwhen soft storey is located at that storey. The beamforcesincreaseswiththeincreaseinsoftstoreyheight

4. The results of present study indicate that thestructural forces and displacements are found to behigherwhensoftstoreyislocatedatfirst/secondstorey.The reinforcement quantity required in structure isfound to be approximately 10%higher if soft storey isprovided at first/second storey in comparison to softstoreyprovidedattopstorey.Hence,softstoreyshouldbeavoidedatfirst/secondstorey.However,ifneeded,itcanbeprovidedattopstorey.

5. Fordifferent locationof soft storey thedisplacementinfloorisfoundtobehigherattopfloor.Thelesserfloordisplacement is found for the floors located above thesoft storey. The floor displacement increases with theincreaseinsoftstoreyheight.

6. Whereas drift in floors are found to be higher atsecond floor and found nature of drift is parabolic andmaximum value of drift at second floor.

JITENDRA KUMAR et al. DATE OF PUBLICATION: SEPTEMBER 01, 2014

ISSN: 2348-4098 VOLUME 2 ISSUE 6 AUGUST 2014 (VER II)

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REF

[1] José“SeismomMex12,P

[2] MohFinisWoo14,P

[3] respanalVolu

[4] IwatpiezApp

[5] andEngi441

[6] of aflexiIssu

[7] “UsesoftIssu

FERENCES

ArturoTLuis Luna‐

smicbehavioment‐resistinxico city”, EnPages3681‐3

Asiz A.,hammad M.shestoStrucod Frame BuPages1572‐1

Asthanaponse spectrlysis of fleume12,Issue

Adachitsubo Takuoelectric daliedAcoustic

Awkar Jresponse

ineeringStru

Balendraa submergedible foundatie1,Pages39

Chen Y.QeofTeflonslifirst storeye4,Pages24

Tena‐ColungaArroyo, Gonorofcode‐deg frame RCgineering Str3707

, Chui Y.H.,(2011); “CocturalPerformuildings”, Pro1581

A.K., Dattarum methoxible base”,e3,Pages185

Kazuhiko,uzo (2004);mping systecs,Volume65

J.C., Lui E.M.of multis

uctures”,Volu

a T., Lee S.L.d sphericalon”, Enginee9‐44

Q., Constantiidersinamoy”, Engineeri43‐253

a,HéctorCornzalo Gatica‐signedmediubuildings inructures, Vol

, Doudak Gntribution omanceofMuocedia Engine

T.K.(1990);d for rand, Engineerin5‐194

Kitamura “Integrateem for flexib5,Issue3,Pag

(1999); “Sestory semi‐ume21,Issue

(1987); “Seistructure suering Structu

inou M.C. (Oodificationofing Structure

rrea‐Arizmen‐Avilés (2008umrisespecn soft soilslume 30, Iss

G., Ni C. aof Plasterboaulti‐storeyLigeering, Volum

“A simplifidom vibrating Structur

Yoshitsuged designble structurges293‐310

eismic analyrigid framee5,Pages42

ismic responupported onures, Volume

October 1990ftheconceptes,Volume 1

ndi,8);cialofue

ndardghtme

iedones,

gu,of

re”,

sises;25‐

nsea9,

0);of12,

[8TestIs

[9“TPr

B

8] Cheneflonsliderstorey”, Constssue2,Pages

9] ChoprTheory and Arentice‐Hall.

IOGRAPHY

Y.Q., Constainamodificatruction and97‐105

ra, A. K., DynApplicationsInc.,Englewo

Y

JitendStudenDepartMANITIndia

Dr. VProfessDepartMadhy

Dr. AProfessDepartMadhy

antinou M.C.ationofthecoBuildingMat

namics of Stto Earthqua

oodCliffs,New

draKumar,nt, Structuratment of CiviT,Bhopal,Ma

Vivek Garsor, Civiltment MANyaPradesh,In

AbhaySharsor, Civiltment MANyaPradesh,In

(1992); “Usonceptofsoftterials,Volum

tructures (19ake EngineerwJersey.

, M.Techl Engineerinil EngineerindhyaPradesh

g, AssistanEngineerin

NIT, Bhopandia

rmaAssociatEngineerin

NIT, Bhopandia

se oftfirstme 6,

995):ring”,

h.ngngh,

ntngal,

tengal,

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