COMPARATIVE STUDY ON SEISMIC ANALYSIS OF CONVENTIONAL SLAB AND FLAT SLAB STRUCTURE WITH AND WITHOUT

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

COMPARATIVE STUDY ON SEISMIC ANALYSIS OF CONVENTIONAL SLAB AND FLAT SLAB STRUCTURE WITH AND WITHOUT SHEAR WALL USING ETABS

Pooja B K1 , Naveen Kumar S2

2

Abstract Inrecentconstructionactivity,Flatslabbuilding hasmanyprivilegeoverconventionalslabbuildingintermsof Architectural flexibility, Easier formwork, use of space, less construction time and Better quality control. But, flat slab structures are significantly more flexible than the conventional slab structures, thus becoming more vulnerable to seismic loading. Therefore in order to upgrade the performance, flat slab are usually provided with drops. The flat slab has less stiffness and less shear strength with more flexibility feature than the conventional slab. In the present work a G+12 commercial multistoried building having conventional slab and flat slab having drop with and without shear wall. The buildings are modeled and Analyzed by using ETABS software. The seismic analysis is done as per IS 1893(Par 1) The behavior of Conventional slab and Flat slab structure with and without shear wall in seismic zone II, III, IV and V with type II (medium) soil are taken for all instances. Analysis of buildings is done by Equivalent static method and Response spectrum method. The seismic evaluation result can be done based on the parameters like Storeydisplacement,Storeydrift,StoreystiffnessandNatural time period.

Key Words: Conventionalslab,Flatslab,Shearwall,Storey displacement, Storey drift, Storey stiffness, Natural time period

1. INTRODUCTION

Thesedays,thestructuresarebeingbuiltquicklybecauseof theexpansioninpopulation.AtpresentIndiaisthequickest developing country in economy this leads to demand in infrastructurefacilitiesalongwiththegrowthofpopulation. The demand for high rise building in urban areas is increasing day by day than the past decades. Due to urbanization,thedesiresofthepeoplehavebeenupgraded withrespecttolessconstructiontime,flexibilityintheroom layout, aesthetic appearance, better quality control, fire resistant, better diffusion of light and so on. To meet the demandofpeopledifferenttypeofconstructiontechnique has been adopted these days. Among these flat slab (i.e., beamlessslab)isone.

Generally,themultistorystructuresareconstructedwiththe conventional reinforced concrete slab which proves it to

1

have high storey stiffness and strength. But, due to the several advantages of beamless slab the old style constructioni.e.,conventionalslabarebeingslowlyreplaced byflatslabs.

The flat slab directly rest on the column and transfer the loadstothecolumnswithoutbeams.Flatslabbuildingsare prominent floor construction systems in commercial buildings, residential buildings and other multi storey buildings. Flat slab structures are favored by both architectureandclient.Intheconventionalslabstructures theslabisrestingonthebeams,theslabloadistransferred to beams and then beams to columns. But in flat slab structureloadistransferredfromslabtocolumnsdirectly.

1.1 Conventional slab system

Conventionalslabsystemisroutinemethodofconstruction consistsofcolumns,beamsandslab.Thissystemutilisedin the development of private structures and compact construction. Here all the four edges of the slab are supportedonbeamswheretheloadsaretransferredfrom slab to beams and then to columns. Hence weight of the structureincreasesandformworkisalsocostlycomparedto flatslab.Inthistype,thethicknessofslabissmallwhereas the depth of beam is large. It requires more formwork comparedwiththeflatslab.

1.2 Flat slab system

Flatslabusuallydoesnothavebeamsissupporteddirectly bythereinforcedcolumns.Itisalsocalledasbeamlessslab. Theprojectionbelowtheslabi.e.,thethickenedportionis calledasDrop.Flatslabispreferredbybotharchitectand client because of its aesthetic view and economic advantages.Thedrawbackofbeamlessslabistheirlackof resistancetolateralloads.

1.3 Shear wall

Shearwallisaverticalstructuralelementdesignedtoresist the lateral loads in high rise buildings. It provides the stabilityagainstlateralforceduetoitslateralstrengthand stiffness which can be used to resist the wind loads and

M tech student, Dept of Civil Engineering, P.E.S College of Engineering, Mandya, Karnataka, India Assistant Professor, Dept. of Civil Engineering, P.E.S College of Engineering, Mandya, Karnataka, India

***

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

Volume: 09 Issue: 05 | May 2022 www.irjet.net p ISSN: 2395 0072

seismic loads. The position of the Shear walls is usually providedatcornersormiddleofthestructures.Theshear wallformsanefficientlateralforceresistingsystemwhenit issituatedatadvantageouspositionsofthestructure

2. OBJECTIVES OF STUDY

1. Toobtainthehighlyeffectivestructuretoresistthe horizontallateralloads.

2. Tostudytheeffectofconventionalslabandflatslab structurewithandwithoutshearwall.

3. Comparativestudyonvariousseismicparameters like storey displacement, storey drift, storey stiffnessandTimeperiod.

4. Thevariousmodelsthusgeneratedparametrically arecomparedandsuitableconclusionsaredrawn.

3. METHODOLOGY

The structure considered for an analysis is RC building. A G+12 story building geometry are considered such as ConventionalslabstructureandFlatslabwithandwithout shearwall.Thebuildingsaremodeledandanalyzedbyusing software ETABS for different seismic zones. Models are consideredforzonefactorII,III,IVandVandsoiltypeisII (medium)asperIS:1893(Part1)codeofpractice.

4. MODELLING

The models of G+12 storey building are analyzed in both EquivalentstaticmethodandResponsespectrummethod. TheanalysisresultsareobtainedforseismiczoneII,III,IV andV.

4.1 Types of models

1. Conventionalslabstructure(ZoneII,III,IV,V)

2. Flatslabstructurewithoutshearwall(ZoneII, III,IVandV)

3. Flatslabstructurewithshearwallatcorner (ZoneII,III,IVandV)

4.2 Model details

Table 1 StructuralandSeismicdetailsof13storey conventionalandflatslabstructure

PARAMETERS

Plandimension 36x25m

No.ofstories G+12

Heightofthestructure 39m

Bottomstoreyheight 3m

Gradeofconcrete M30

Gradeofsteel HYSD500

Floortofloorheight 3m

Slabthickness 150mm

Dropsize 2x2m

Dropthickness 200mm

Shearwallsize 200mm

Sizeofcolumn (600x600)mm

SizeofBeam (300x600)mm

Liveloadonfloors 4kN/m2

Terraceload 1.5kN/m2

Floorfinishload 1.5kN/m2

Zoneconsidered II,III,IVandV

Zonefactor 0.10,0.16,0.24and0.36

Importancefactor 1.2

Typeofsoil II(medium) Reductionfactor(SMRF) 5

Plan and 3D view

Fig 1: Conventionalslabstructure

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

Volume: 09 Issue: 05 | May 2022 www.irjet.net p ISSN: 2395 0072

Fig 2: Flatslabstructurewithoutshearwall

Chart 2: StoreydriftofbuildingforZoneII

Chart 3: StoreystiffnessofbuildingforZoneII

Fig 3:Flatslabstructurewithshearwallatcorner

5. RESULTS AND DISCUSSIONS

The results of each building model are presented in this chapter. The analysis is carried out by Equivalent static method and Response spectrum method. The results are obtainedfor13storeybuildingforthezonefactorII,III,IV and V for the parameters Story Displacement, Story Drift, StoryStiffnessandNaturaltimeperiod.

5.1 EQUIVALENT STATIC METHOD

Chart 1: StoreydisplacementofbuildingforZoneII

Chart-4: StoreydisplacementofbuildingforZoneIII

Chart-5: StoreydriftofbuildingforZoneIII

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

Volume: 09 Issue: 05 | May 2022 www.irjet.net p ISSN: 2395 0072

5.2 RESPONSE SPECTRUM METHOD

Chart 6: StoreydisplacementofbuildingforZoneIV

Chart 10: StoreydisplacementofbuildingforZoneII

Chart 7: StoreydriftofbuildingforZoneIV

Chart 11: StoreydriftofbuildingforZoneII

Chart 8: StoreydisplacementofbuildingforZoneV

Chart 12: StoreystiffnessofbuildingforZoneII

Chart-9: StoreydriftofbuildingforZoneV

Chart 13: StoreydisplacementofbuildingforZoneIII

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

Volume: 09 Issue: 05 | May 2022 www.irjet.net p ISSN: 2395 0072

Chart 14: StoreydriftofbuildingforZoneIII

Chart 18: StoreydriftofbuildingforZoneV

Chart 15: StoreydisplacementofbuildingforZoneIV

Chart 19: NaturalTimeperiodofbuilding

5.3 COMPARISION OF STRUCTURES FOR DIFFERENT SEISMIC ZONES BY EQUIVALENT STATIC ANALYSIS

Chart 16: StoreydriftofbuildingforZoneIV

Chart 20: DisplacementvsZoneforstructures

Chart 17: StoreydisplacementofbuildingforZoneV

Chart-21: DriftvsZoneforstructures

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

Volume: 09 Issue: 05 | May 2022 www.irjet.net p ISSN: 2395 0072

Chart 22: stiffnessvsZoneforstructures

Chart 26: stiffnessvsZoneforstructures

6. CONCLUSIONS

1. The storey displacement is high at the top storey andlessatthebase.Withtheincreaseintheheight ofthestructurethedisplacementgoesonincreases. Storeydisplacementofflatslabstructurewithout shearwallshowsmaximumvalue.

Chart 23: TimevsZoneforstructures 5.4

OF STRUCTURES FOR DIFFERENT SEISMIC ZONES BY RESPONSE SPECTRUM ANALYSIS Chart 24: DisplacementvsZoneforstructures

COMPARISION

Chart 25: DriftvsZoneforstructures

2. Thestoreydriftfollowsaparabolicpathalongthe storey height. Storey drift of flat slab structure withoutshearwallismaximum

3. Thestoreystiffnessismoreatbaseanditdecreases as the height of the structure increases. Storey stiffness of flat slab structure with shear wall at cornerismaximum

4. Thetimeperiodofflatslabstructurewithoutshear wallismaximum.

5. It is observed that as the seismic zone increases from zone II to V, the storey displacement and storeydriftincreasesandstoreystiffnessandtime periodremainssame.

6. Flatslabstructurewithshearwallatcornergives the best results, because the Time period, Storey displacement,storydriftislessandStorystiffnessis morethanothertwostructures

REFERENCES

[1] SandeshD.Bothara,Dr.ValssonVarghese.(July August 2012) “Dynamicanalysisofspecialmoment resistingframebuildingwithflatslabandgridslab” ,Vol.2,Issue4,pp.275 280,ISSN:2248 9622.

[2] M A Rahman (2012) “Effects of openings in shearwall onseismicresponseofstructures”, Vol 2,issue10july2012.

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

[3] R.S.More,V.S.Sawant,Y.R.Suryawanshi.(2013) “Analytical study of different types of flat slab subjectedtodynamicloading”,IJSR,ISSN(Online): 2319 7064.

[4] SharadP.Desai,SwapnilB.Cholekar(2013) “Seismic performance of reinforced Concrete building with flat slab”; Volume 2, Number 10; April June,2013.

[5] Lakshmi K O (2014), “Effect of shear wall locationinbuildingssubjectedtoseismicloads”,ISOI JournalEngineeringandComputerScience,Volume 01,December2014.

[6] Salman I Khan and Ashok R Mundhada. (February 2015) “Comparative study of seismic performanceofmultistoriedrccbuildingswithflat slabandgridslab”,Vol.4,No.1,,ISSN2319 6009.

[7] NKRISHNARAJUBookofadvancedreinforced concretedesign”.

[8] Government of Bureau of Indian Standards: IS 875, part 2 (1987), Live Loads on Buildings and Structures,NewDelhi,India.

[9] Plain&ReinforcedConcreteCodeof Practice” FourthRevisionIS:456:2000.

[10] IS 1893 (Part I) : Criteria for Earthquake Resistant Design of Structures, Part I General ProvisionsandBuildings,FifthRevision,Bureauof IndianStandards,NewDelhi.

Turn static files into dynamic content formats.

Create a flipbook