Response of High Rise Building With Lead Rubber Bearing, High Damping Rubber Bearing and Friction Pe

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Response of High Rise Building With Lead Rubber Bearing, High Damping Rubber Bearing and Friction Pendulum System

1PG Student, Dept. of Civil Engineering, Walchand College of Engineering, Sangli, Maharashtra, India, 416415 2Professor, Walchand College of Engineering, Sangli, Maharashtra, India, 416415 ***

Abstract- It has always been difficult for structural engineers to protect structures against earthquakes because safety is the primary concern for civil constructions in a seismically active zone. Base isolation technology, which may be used to retrofit both new and existingstructures, has grown in popularity over the past few decades in the field of seismic protection. This study's goal is to assess how Delhi, which is in zone IV, will respond to various seismic isolation techniques when constructing a building Firstly, the design of base isolation systems, i.e. lead rubber bearing (LRB) High Damping Rubber Bearing and friction pendulum bearing (FPB) by using UBC 97 and IBC 2000 Codes The building was modelled and the analysis was carried out by using SAP2000 software is used for response spectrum analysis. This finite element analysis software is utilizedto create model and to perform analyses. Five models of G+18 building i.e one model of fixed base building ,three models of base isolated building are used for this comparative study of base isolation system and one model of optimumbase isolationandbehavior of building studied by time history analysis on SAP2000 software Time period, maximum displacement, base shear, and story drift are utilized to express the results. In contrast, the Friction Pendulum System offered the decrease in elastic base shear based on this comparative analysis carried out . Isolation systems increase the basic time period of structures and reduce base shear, which in turn reduces the lateral force imposed due to earthquakes in the structures. Low isolator displacement from LRB was supplied for the adopted bearing properties. By using time history analysis, the study of the best base isolation with FPS based on the linear dynamic analysis (response spectrum analysis).

Key Words: safety, Lead Rubber Bearing (LRB), High Damping Rubber Bearing (HDRB), Friction Pendulum Bearing (FPB), SAP2000, response spectrum analysis , Time History Analysis.

1. INTRODUCTION

Earthquake is a natural disaster which is experienced throughout the world According to an Indian earthquake zone mapof 2002,59percentof thecountry'sterritory is vulnerable to seismically destruction. therefore civil engineer has come with solution for reducing the damage and made high rise structure earthquake resistant. Every year, earthquakes cause a huge number of fatalities and

extensive property damage. As an outcome, the seismic preservation of the structure has always placed a high priorityontheearthquakeresistantdesignstoensurethe safety of e4 the flexibility of the Structureand having adequate damping, constitutes base isolation, a well establishedseismicprotectiontechniqueforbuildings.The aspectof passivevibrationcontroltechnology,itisoneof the most effective earthquake engineering tools. The fundamentalgoalofbaseisolationbecametosafeguardthe buildings by minimizing the effect of earthquakes rather thanfightingthem.

1.1 Types of base isolation system

1)LeadRubberBearing(LRB)

2)HighDampingRubberBearing(HDRB)

3)FrictionPendulumSystem(FPS)

1.1.1

Lead Rubber Bearing:

The lead rubber bearings combine the roles of vertical support, stiffness at operating load levels, and horizontal flexibilityatseismicloadingtoofferoneofmostcost-effective alternative for the base - isolated problems. LRB offers dampening in the ranges from 2% – 3%. Lead Rubber Bearingsisrubberbearingswithacentralleadcorethatare composedofthinlayerofsteellaminates&hot vulcanized rubber.Byyielding,theleadcore'senergydissipationallows fortheachievementofanequalviscousdampingcoefficient ofuptoabout30%.

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1.1.2 High Damping Rubber Bearing:

Anexampleofanelastomericbearingisa rubberbearing, which offers horizontal flexibility through rubber and vertical rigidity with steel shim plates that are vulcanised inside the rubber. Layers of rubber and steel plates for reinforcementisprovidedintheHDRBisolators.Duetothe interiorsteelplate,thebearinghasaverticalstiffnessthatis 100 timesmorethanthehorizontalstiffness,althoughitis flexibleinthenormaldirection.A10to20%dampingrange isgivenbyHDRB.

Rubber Bearing (LRB), High Damping Rubber Bearing (HDRB), and Friction Pendulum System(FPS). B are comparedinthispaperdesigncomparison.Theperformance ofLRB,HDRB,andFPBisdemonstratedbyacomparisonof the findings in terms of duration, maximum isolator displacement, base shear, and story drift of the fixed base and isolated building. The best base isolation was chosen basedonanalysisoftheresponsespectraldata.Timehistory analysisisdoneforthisbestbaseisolationsystem.

1.2 Methods Of Analysis

1.2.1 Response Spectrum Analysis

Fig-2:HighDampingRubberBearing

1.1.3 Friction Pendulum System:

The bearing surface's curvature and diameter can be changed,andtheFPScanbeconfiguredtofulfilarangeof displacement magnitudes. The same theory underlies bearings as a simple pendulum. In the event of an earthquake, the A slider that is articulated Slides make modest,straightforwardharmonicmotionsoveraconcave surfaceofthebuilding.Usingthebearings,thependulum's speed, like a basic pendulum. buildings' natural deterioration by causing the building to slide down the concave inner surface of the bearing Deterioration by causingthebuildingtoslidedowntheconcaveinnersurface ofthebearing.

The idealized single degree freedom systems' maximum response to earthquake ground motions when their basic time periods are different but their damping rationis the same.Thisanalysis'smethodpermitsnumerousmodesofa building's reaction to be taken into consideration for the frequencyresponse.Manybuildingrulesmandatethis,with the exception of relatively straightforward or incredibly complicatedstructures.The"harmonics"inavibratingstring correlatetoavarietyofdifferentkinds(modes)thatmake up a structure's reaction. These modes can be found for a structure through computer analysis Based on the modal mass and modal frequency, which are subsequently combined,thedesignspectrumresponsestoeachmode.

1.2.2. Time History analysis

Fig-3:FrictionPendulumsystem

The three isolation systems for a 19-story reinforced concretestructureinDelhithatisperchedonaclass-Bsite are Lead Rubber Bearing (LRB), High Damping Rubber Bearing(HDRB),andFrictionPendulumSystem(FPS).The three isolation systems for a 19-story reinforced concrete structureinDelhithatisperchedonaclass-BsiteareLead

Nonlineardynamicanalysiscangenerateconclusionswith relativelylowuncertaintysinceitcombinesgroundmotion datawithathoroughstructuralmodel.Whenthemodelis subjected to a ground motion, estimates of constituent deformationsaremadeforeachdegreeoffreedomrecording for nonlinear dynamic research. The modal responses are then integrated using methods like the sum of all square roots &dynamic nonlinear analysis includes a time historyanalysis that takes the structure's non-linear properties into consideration. Estimates of component deformationsarecreatedforeachdegreeoffreedominthe modelwhenitissubjectedtoagroundmotionrecordingfor nonlineardynamicresearch.Themodalresponsesarethen integrated using methods like the sum of squares at the square root. Dynamic nonlinear analysis includes a time historyanalysis that takes the structure's non-linear propertiesintoconsideration.Forstructureswithunusual geometries or of particular significance, the toughest approach is required by some building regulations. The predictedresponse,however,maybehighlydependenton theparametersofeachgroundmotionemployedasseismic input.

a)Modaltimehistoryanalysis(Non-linear)

b)Directintegrationtimehistoryanalysis(non-linear)

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Inthispapertimehistoryanalysisofbaseisolatedbuildingis carriedoutbymodaltimehistoryanalysis.

2. OBJECTIVES

Thefollowingaretheobjectivesoftheplanneddissertation work:

1) Formulation of problem statement, developing of methodology and possible validation with high quality researcharticle.

2)Toexaminetheeffectofvariousbaseisolationsystemson seismicperformanceofhighrisestructures.

3)Tocompareseismicperformanceoffixedbaseandbase isolatedhighrisestructures.

4)Toevaluatenon-linearseismicperformanceofhighrise structureswithoptimalbaseisolationsystem.

3. MODELLING OF BUILDING

For the study, In order to study the effect of the base isolationonhighrise building,abuildingsituatedinDelhi regionisconsidered.Threedimensional19storyreinforced concrete (SMRF) residential building is considered The buildingfallszoneIVasperIS1893:2002. Thebuildinghas symmetricalplaninbothtwodirectionsandnumberofbays consideredineachdirectionisfour.Thethicknessofwallis considered0.230mforexteriorand interiorpartitions.The plan for Square building is 12x12m The building is consideredwiththelift.Shearwallareusedintheinterior coreregionof lifts.ThedeadloadsconfirmingIS875Part-1, 1987andimposedloadsconfirmingIS875Part2oftheRC buildingsaretaken.SoiltypeB-mediumorstiffsoil.Time historyanalysisisdoneasaparametertostudythebehavior of buildings by nonlinear dynamic analysis. The buildings squareinplanarestudiedbyResponsespectrum analysis andTimehistoryanalysistocalculatethemaximumstorey drift, base shear and acceleration .Five building were modelledforthestudyofeffectofbaseisolationasperthe newversionof



IS1893:2016forzoneIV,soiltypeIIforfixedbase thebuilding.



IS 1893:2016 for zone IV, soil type II and use frictionPendulumSystem(TimeHistoryAnalysis)

3.1 Preliminary Data:

Sr.No Building Specifications Type/size/weight 1 Structure SMRF(Special Moment Resisting Frame) 2 No.ofStories 19 3 Floortofloorheight 3m 4 SizeOfBuilding 12mx12m

Member Properties



IS1893:2016forzoneIV,soiltypeIIAndUselead rubberisolation



IS1893:2016forzonelV,soiltypeIIandusehigh dampingrubberisolation



IS 1893:2016 for zone lV, soil type II and use frictionPendulumsystem

1

BeamSize 250mmX450mm 2 GradeofBeam M25 3 ColumnSize 350mmX750mm 4 ColumnGrade M30 5 SlabThickness 150mm 6 SlabGrade M25 7 Thicknessofwall 230mm

Seismic Properties(As per 1893:2002) 1 Zonefactor 0.24 2 Importancefactor 1 3 Response Reduction factor 5 4 SoilType II(MediumSoil) 5 SeismicZone IV

Material Properties 1 GradeofConcrete M25&M30 2 GradeofSteel Fe415 3 DensityOfSteel 78.5KN/m3 4 Density of Reinforced Concrete 25KN/m3 5 BrickSpecificweight 19KN/m3 6 Liveload 3KN/m2

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From fixed base model maximum of base reaction force 3434KNwhichisinverticaldirection.Foramaximumbase reaction , base isolation system is designed. According to NaeimandKelly'sdocumentedUniformBuildingCode(UBC 97) and International Building Code 2000 (IBC 2000), the designofnewseismicallyisolatedstructureswilllikelybe controlled by one ofthese two codes.. Based on this link PropertiesoftheLRB,HDRBandFPBSystemaredesigned for the maximum base reaction .Maximizing the seismic performance of the building required designing and analyzingthestiffnessparametersofthebearings Firstly,baseisolatorpropertiesusedforresponsespectrum method are linear properties only and for time history analysis non-linear link properties used. For time history analysis the earthquake of "Friuli_ Italy-01" in 1976 at station"Conegliano"chosenandThe groundmotionofthis earthquakearematchedbyusing‘SeismoMatch’softwarefor givensoilconditionandseismiczone.

4. RESULTS AND DISCUSSION

4.1 Maximum Time Period

Fig-8:Maximumtimeperiod

TheaboveFig-8 fora1st modetimeperiodforafixedbase building is minimum(3.155 sec) and for FPS is maximum(3.828sec).Asmodechangesfrom1to12 time period for structure goes on decreasing and frequency increasing.

4.2 Maximum Base Shear:

Fig-9:maximumBaseShear

The above Fig-9 shows that the maximum base shear for fixedbasestructureismaximumi.e1095.4KN andforFPS baseisolatedstructuredrecesesto856.533KN.

4.3 Maximum Displacement:

Fig-10:maximumDisplacement

The maximum displacement for fixed base is minimum(0.0649m) as compared to LRB,HDRB and FPS base isolated structure as shown in above Fig-10. The displacement for base isolated with FPS structure is maximum(i.e.0.147m)

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4.4 Story Drift

Fig-11:StoryDrift

Above Fig-11 shows that the story drift for fixed base building is minimum as comapred to the base isolated building.InbaseisolatedSystem,frictionpendulumsystem hashigherstorydriftascomparedtobuildingwithLRBand HDRBisolator

4.5 Response spectrum Curve :

Fig-12:ResponsespectrumcurveforFPS

TheabovegraphgivesthepseudospectralaccelerationinX directionforadampingupto5%Forsafrictionpendulum Isolator.

Fig-13:Deformedshapeofbuildingat0.5secinX Drection.

Theabove Fig-13 shows thatthe buildingdeformedin Xdirectionintimehistoryanalysisatthetimeof0.5second.

Fig-14:Deformedshapeofbuildingat0.5secinY Drection.

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The above Fig-14 shows that the building deformed in ydirection in time history analysis at the time of 0.5 second.Forthetimehistoryanalysis,topstory displacement is 204.6 mm in x direction at 5 sec and Bottom story displacement is 6.76mm in X direction at 4.85 sec. Base Shear in X direction is 698.90 KN and in Y direction is reduced to 589.64 KN. Acceleration at the top of story is 472.5mm/s2andfortheYdirectionandAccelerationatthe bottomstoryis93.12mm/s2.

5. CONCLUSIONS

i) For fixed base building time period is minimum as comparedtobaseisolatedstructurei.e.duetobaseisolation timeperiodofstructureisincreased FPSisolationsystem provides more time period than HDRB and LRB isolation systems.

ii)Allotherbuildingshavingabaseisolationsystemexhibit an increase in lateraldisplacement atthe base of building anddisplacement of fixed base buildings displays zero displacementatbaseSimilarly,lateraldisplacementinbase isolated buildings as compared to fixed base buildings buildingsdrasticallyriseswithheight.IncomparisontoLRB andHDRBisolators,theFPSbaseisolatorprovideshigher displacement.

iii) For a fixed base building base shear is maximum as compared to base isolated buildings. A building with FPS isolator shows minimum base share as compared to LRB andHDRBisolator.

iv) The story Drift of Fixed base Building is minimum as comparedtobuildingwithbaseisolator. Forbuildingwith FPS isolator is maximum as compared to LRB and HDRB isolator. The maximum story drift of building with FPS isolatorshouldbewithinalimitasperIBC2000.

v) Based on the results, it was found that among three isolators, FPS base isolator give better performance comparedtoHDRBandLRBisolators.

vi)Thenon-lineartimehistoryanalysisofbuildingwithFPS isolatorshowsthatthehigherdisplacementandbaseshare also reduces as compared to response spectrum analysis andthismethodgivestheactualbehaviourofthebuilding.

6. REFERENCES

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[2]TomohiroS.,EijiS.,KeriL.,TaichiroO.,StephenA.,Koichi K.,(2012), “NEES/E-Defense Base-Isolation Tests:

Effectiveness of Friction Pendulum and Lead-Rubber BearingsSystems”,15WCEELISBOA2012.

[3] Rama rao G. , Sunil J.,Vijaya R.(2021), “Soil-structure interaction effects on seismic response of open ground storey buildings”, Indian Academy of Sciences, Sadhana (2021) 46:105https://doi.org/10.1007/s12046-021-01633-0.

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[11]FredericoamaralandLuísguerreiro(2014),“Effectof vertical component of earthquake on the response of a friction pendulum bearing base isolation system”, Second Europian Conference On Earthquake Engineering And SeismologyIstmbul,Aug.25-29.2014