SEISMIC ANALYTICAL STUDY OF RC AND STEEL STRUCTURES WITH LEAD RUBBER BEARING IN DAMPERS USING ETABS

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

Volume: 09 Issue: 07 | July 2022 www.irjet.net p ISSN: 2395 0072

SEISMIC ANALYTICAL STUDY OF RC AND STEEL STRUCTURES WITH LEAD RUBBER BEARING IN DAMPERS USING ETABS

Prabakar N1, Revathi V2

1PG Student, Student, Department of Civil Engineering, K.S.R. College of Engineering, Tamil Nadu, India 2Professor, K.S.R. College of Engineering, Tamil Nadu, India ***

Abstract The efficiency of lead rubber bearings in dampers in lowering the seismic response of both reinforced concrete (RC) and steel structures is compared in this study. The main goal is to use ETABS to compare how constructions with LRBs and fixed base buildings behave. Based on the ground vibrations of the El Centro earthquake, non linear analysis was used to analyse the dynamic reaction of the structures. Storey displacements and storey drifts were among the seismic reaction metrics for the constructions. Time history analysis was used to analyse the buildings, and the results were taken as storey displacements and storey drifts values for unmanaged constructions ranging from 35 to 65 percent. It is also acknowledged that the aspect has a significant impact on the best location for the dampers.

Key Words: Base Isolators, Lead Rubber Bearing, Fixed Base, Time History Analysis, Storey Drifts, Storey Displacements

1. INTRODUCTION

Earthquakes are one of the natural occurrences that most buildingengineersmustcopewith.Buildingsneedtobebuilt towithstandseismicforces.Thetopicofresearchformany years has been seismic protection for large, tall constructions.Becauseoftheirintrinsicdampeningcapacity, buildings are generally more susceptible to earthquake forces.Earthquakesarecausedbydynamicforcesbrought aboutbyfaultmovementinthecrustoftheplanet.Seismic wavesarecreatedwhenfaultsmove,releasingenergy.The foundation of the structure is where seismic waves first cause movement. Building’s experience horizontal and vertical vibrations known as reactions because of these complex movements. Examples of these reactions include displacements,velocities,andaccelerations.

Excessivevibrationmayoccurwhenstructuresare strengthened to withstand earthquake forces. Extreme vibrationsmayresultinthelossofthebuilding'sfunctional requirements, as well as human life. As a result, energy dissipation based devices minimise vibrations more effectively.Thedampeningdeviceswillfunctionsimilarlyto automotive shock absorbers. As a result, the building's lifespan will be extended, and vibration frequency will be reduced.

Thestructureisisolatedfromthefoundationandshockis absorbedusingthebaseisolationmethod.Thebaseisolator absorbs more energy when seismic energy approaches a structure,forcingthestructuretovibrateslowly.

The seismic performance of reinforced concrete and steel structures with lead rubber bearings was studied by Mathkar and Patil in 2021. Lead Rubber Bearing (LRB) systemwasusedtocreatetheframe,anditscharacteristics wereusedtomodelLRBfortheRCframe.Resultsfromstatic and push over studies reveal a consistent pattern in the frame's behaviour. A.B.M. Saiful Islam, et al. (12) investigatedtheanalyticalnonlinearseismicresponseofa ten story building isolated by the Lead Rubber Bearing (LRB) and Friction Pendulum System under the Natore Earthquakerecord(FPS).ThebestdecisionbetweenHDRB andLRBshouldbebasedonfloordisplacement reduction and rigid body displacement amplification. The superstructure's dynamic behaviour was examined using SAP2000. Donato Cancerllara andcolleagues(3)studied theseismicbehaviourofamulti storyreinforcedconcrete building with two base isolation systems. The results showed that LRB isolators had a 15% to 30% higher dissipative capacity than HDRB isolators. The influence of soilstructureinteractionontheresponseofabaseisolated buildingwasexploredby Bahkear et al (2019). Numerical results reveal that when the flexibility of the soil is addressed,theseismicresponseofastructuresittingonan inelastic base isolation system may be higher than the correspondingresponseobtainedbydisregardingtheeffects of soil structure interaction. According to Ahmet Hilmi Deringol and Esra Mete Guneyisi (2020),baseisolations arerecognisedasaneffectiveseismicprotectivetechnique for building structural systems. It was discovered that by using LRB, the seismic response of regular and irregular framesinelevationmaybeenhancedtosomeextent.

The significance, necessity, and application methodologies for analysing multi story buildings were examinedinthecurrentstudy.Thebase'sprimarybenefits thereductionofthestructuralandnon structuraleffectsof isolation damage to the structure's components, which increases the lowering the seismic risk will increase the building'scomponentsafety forcesindesign.RCandsteel structureswithtenstoriesbothfixedbaseandbaseisolation models and analyses utilising ETABS to create structures.

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

Volume: 09 Issue: 07 | July 2022 www.irjet.net p ISSN: 2395 0072

Thecomparisonfindingstherewereseparateconstructions betweenthebaseandthepermanentbasestudiedforaten story structure. In El Centro the non linear earthquake groundmotionrecordistakenanalysis.

2. LEAD RUBBER BEARING

Leadrubberbearings,whichareemployedinbuildingand bridgestructures,areapracticalandaffordablechoicefor seismicisolation.Alaminatedelastomericbearingpad,top andbottomsealingandconnectingplates,aleadplugputin thecentre,andthesecomponentsmakeupthebearing.

Fig 2:FixedBaseBuildingandIsolatedBaseBuilding

Theleadplugwillslidewiththelaminatedrubberduringan earthquake,butitwillconverttheenergyofthemovement into heat, lowering the inertial force on the structure and minimisingvibration. The rubbercomponentwill keep its originalshapeinthemeantimeduetoitsgreatelasticity.

3. Methodology

Fig -1:LeadRubberBearing

Among the many base isolation approaches, lead rubber bearings (LRB) were frequently used. One or more lead plugs are inserted into the holes, and it is composed of alternatinglayersofrubberandsteelplates. Theleadcore deforms in shear, providing initial stiffness against weak earthquakesandstrongwindsaswellasabilinearresponse (i.e.,hystereticdampingintheisolatedstructure).Thesteel platesintheelastomericbearingcreatesubstantialplastic deformations.Asaresult,aleadplugwasusedinplaceofan elastomericbearing,anditwastested.Theyieldforceofthe leadinsertcanbecalculatedusingtheyieldstressofthelead inthebearing.

2.1 FEATURES:

Therigidandstrongintheverticaldirection,butflexiblein the horizontal. Modify the bearing's form to better withstand the force produced by earthquakes. Rubber's strong elastic force enables structures to maintain their original placements and shapes. To alter the dampening, alterthenumberofleadplugs.

Itissimpletoinstallwithoutaseparatedamper.Stable,low maintenancebilinearbehaviour.

2.2 WORKING MECHANISM:

The un isolated building will move back and forth and in different directions during the earthquake as a result of inertialforces,whichwilldistortandharmthestructure.

3.1 Modelling of Isolators

The base isolator is modelled using ETABS using the connection/supportpropertydatathatneedstobedefined in order to add the necessary features. Buildings were initiallygivenfixedsupports,andeachsupportofthecolumn at the base of the structure was given a link. Calculations basedonthebaseisolationdesignwereusedtoestablishthe link'sspecifications.

3.2 Method of Analysis

In this work, nonlinear time history analysis was the methodologyused.Itisanonlineardynamicanalysis,which isamethodicalwaytoascertainhowthestructurewillreact asitadaptstoseismicloadsfortheparticularearthquake. The analysis will use the seismic record that shows the design earthquake. The data is subsequently converted to digitalformintimeintervalsof1/40to1/25seconds.The structureisthenassessedtoidentifytheresponsesofeach lumpedmasstoacceleration,velocity,anddisplacementat each interval. The experiment utilised an average acceleration approach with values of 0.5 and 0.25, respectively.

Modelling and analysis of RC and steel structures: The structurewasexaminedbothwithandwithoutLRB.

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

Volume: 09 Issue: 07 | July 2022 www.irjet.net p ISSN: 2395 0072

Fig 3:RCandSteelBuildingPlan

Fig. 5: ElevationofRCBuilding

Fig 4: 3DViewoftheRCandSteelBuilding

Theslab'sthicknessisassumedtobe0.15m.Thebuilding's boundaryconditionisusedasfixedsupport.Aliveloadof3 kN/m2isappliedtoallfloors.Theearthquakeloadsandload combinationsaredefinedbyIS1893 2016.Thedampers arepositionedinfourdifferentconfigurationstodetermine theoptimumpositioningofthedampers(Figure5&6)

Fig. 6:

ElevationofSteelBuilding

For this study, El Centro time history records were employed.ETABSwasusedtoanalysethestructuresusing Non LinearTimeHistoryAnalysis.

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

Volume: 09 Issue: 07 | July 2022 www.irjet.net p ISSN: 2395 0072

4. RESULTS AND DISCUSSION:

In this study, a ten story RC and steel structure was modelled and examined using ETABS. Non linear time history analysis was utilised for both fixed base and base isolation,andtheresultswerecomparedandexaminedfor bidirectional seismic ground motion recordings. The performance and efficacy of the base isolation were examinedusingnon lineardynamicanalysis,andtheresults were contrasted with fixed base structures. the RC Structure's displacement and interstorey drifts with and withoutbaseisolators.

Fig. 8: StoreyDriftofRCBuilding LRBandFixed

From the examination of RC multistoreyed buildings, the LeadRubberBearingIsolatorshowedhigherperformancein reducingdisplacementsandinterstoreydrifts.DuetoLRB, the percentage of storey drifts was reduced by 61.78 percent.

The displacement and interstorey drifts of the Steel StructurewithandwithoutBaseIsolator.

Fig. 7: StoreyDisplacementofRCBuilding LRBandFixed

Fig. 9: StoreyDisplacementofSteelBuilding LRBand Fixed

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

Volume: 09 Issue: 07 | July 2022 www.irjet.net p ISSN: 2395 0072

inthe baseisolatedconstructionsubstantiallydiminish in contrasttothefixedbasebuilding.Baseisolationisavery effectivewaytobringdownthepriceoftheconstructionand lightenitsload.Itisalsoknownthattheaspectratioofthe buildinghasasignificantimpactonthebestlocationforthe dampers.

Thebuildingswereanalysedusingtimehistoryanalysis,and theresultsweretakenintheformofstoreydisplacements andstoreydriftsvaluesrangingfrom35 to65percentfor unmanagedstructures.

REFERENCES

1. Mathkar,Ganapat,L.Patil.Savita,N.(2021)“Reviewon Comparative Study of RCC Building by Using Base Isolator of Various Thickness”, International Research JournalofEngineeringandTechnology,Vol.08,No.06, pp.4165 4169.

2. SaifulIslam.A.B.M,MohammedJameelandMohdZamin Jumaat, (2011)” Seismic isolation in buildings to be a practical reality: Behavior of structure and installation technique”, Journal of Engineering and Technology ResearchVol3(4),pp99 117.

Fig. 10: StoreyDriftofSteelBuilding LRBandFixed

Fromtheexaminationofsteelmultistorybuildings,theLead Rubber Bearing Isolator showed greater performance in reducing displacements and interstorey drifts. When comparedtothepermanentfoundationstructure,thesteel constructionhada44.98percentlowerinterstoreydrift.

5. CONCLUSIONS

Based on the conclusions, the performance of LRB was lookedat.Thestatisticsshowthatthebaseisolationgreatly minimises the seismic reaction when compared to a fixed construction. The following findings were drawn from a comparisonoftheresultsoffixedbasestructureswithbase isolatedstructures:

From the examination of RC multistoreyed buildings, the LeadRubberBearingIsolatorshowedhigherperformancein reducingdisplacementsandinterstoreydrifts.DuetoLRB, the percentage of storey drifts was reduced by 61.78 percent.

The examination of steel multistoreyed buildings showed thattheLeadRubberBearingIsolatorperformedbetterin reducing displacements and interstorey drifts. When comparedtothepermanentfoundationstructure,thesteel constructionhada44.98percentlowerinterstoreydrift.

Abaseseparatedbuildinghasasignificantamountoflateral displacementatthebase,whereasafixedbasebuildinghas zero displacement at the base in both RC and steel constructions.Asthefloorheightrises,theinterstoreydrifts

3. Bahekar, Rohini. L. Kuldeep Dabhekar, Atulkumar Manchalwar. (2019) “Seismic Response of Structure Equipped with Lead Rubber Bearing Considering SSI”, IOSRJournalofEngineering,pp.48 52.

4. AhmetHilmiDeringol,EsraMeteGuneyisi.(2020)“Effect ofLeadRubberBearingonSeismicResponseofRegular andIrregularFramesinElevation”PamukkaleUnivMuh BilimDerg,Vol.26,No.6,pp.1076 1085.

5. Hamid, N. HAzmi. I.F. Shin,S. (2018) “Trends of Using Based Isolation System in High Seismic Regions”, International Journal ofAppliedEngineeringResearch, Vol.13,No.18,pp.13439 13447.

6. Mohammad Ganji, Hossein Kazem. (2017) “Comparing SeismicPerformanceofSteelStructuresEquippedwith Viscous Dampers and Lead Rubber Bearing Base IsolationunderNear FieldEarthquake”,CivilEngineering Journal,Vol.3,No.2,pp.124 136

7. Minal Ashok Somwanshi, Pantawane, Rina N. (2015) “Seismic Analysis of Fixed Based and Base Isolated Building Structures” International Journal of Multidisciplinary and Current Research, Vol.3 pp.747 757.

8. International Code Council,” International Building Code”,IBC2018

9. Code and Commentary on IS: 1893 2016 (Part I), IITK_GSDMA EQ05 V2