A Study On Dynamic Analysis Of Tall Structure With Belt .

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International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue 08, August-2015A Study on Dynamic Analysis of Tall Structurewith Belt Truss Systems for Different SeismicZonesVijaya Kumari Gowda M RManohar B CPG StudentDepartment of Civil EngineeringAlpha College of EngineeringAssistant ProfessorDepartment of Civil EngineeringAlpha College of EngineeringBengaluru, India.Bengaluru, IndiaAbstract— Tall building development has been rapidlyincreasing worldwide introducing new challenges that need tomeet through engineering decision. As the height of the buildingincreases the stiffness of the building reduces. Therefore toimprove the performance of the building under seismic loading,belt truss system is proposed in the present study of work. In thepresent work, contains a comparative study on type of belt trusshas been used which provide more economical for human beingsunder different seismic zone criteria with and without shearcore for building. The modelling of the structure is done using‘ETABS” software. The analysis of the model is carried out byequivalent static method and response spectrum method. Toknow most economical and stiffness building here we find %reduction of displacement and storey drift for different seismiczones with and without shear core.Keywords— Tall building; Different belt truss; Seismic zones;ETABS; Response spectrum; Displacement; Storey drift.I.INTRODUCTIONElevated towers and buildings have enthralled mankindfrom the establishment of civilization. Contemporary tallbuildings begins to development in the 1880 has mostly forcommercial and residential building purposes. Due to quickaugmentation of population and pressure on the limited spaceavailable tends to increase tall buildings. Tall buildings areconstructed based on purpose they use whether it may be forcommercial or residential purposes. Loads act on a buildingwill be of vertical, horizontal or torsion type of load whichgive different effects on building. The primary function of thestructural elements is to resist the gravity loading from theweight of the building and its contents. Secondary function ofthe vertical structural elements is to resist the wind andearthquakes whose magnitude will be varied from theepicenter to epicentral distance whose magnitude obtained inthe IS 1893 2002 code book. As height of structure increasesits displacement, story drift, story shear of the buildingdecreases abruptly. So, in order to restrain those parameter inthe building especially under seismic and wind load suitablemethod to be taken to reduce those effect in the building.Convection currents develop in the viscous mantelbecause of high temperature and gradient crust and core dueto convective flours of mantle material cause the crust and afew section of the mantel to slide on the blistering moltenIJERTV4IS080254outer core. This sliding of earth’s mass takes place in piecescalled tectonic plates. The surface of the earth consist ofseven of foremost tectonic plates and there plates more indifferent direction [plate in the front slower then, the plate atthe rear and vice versa and other types of plates moves sideby side i.e., it may be of convergent, divergent and transformboundaries] and at different speeds since those of theneighboring ones the plates will be in motion. Bulky seismicactivity at huge spaces can generate strong waves that maynot harm buildings or humans. Then, sensitive mechanismslike seismograph and accelerograms can measure these. Thismakes it happen to find far-away earthquakes. Still, fromengineering point of view, strong movements that canprobably harm structures are of interest. This can happen withearthquakes in surrounding area or even with largeearthquakes at reasonable medium to large distances. Thus, aseismic zone map is necessary so that buildings and otherstructures situated in different regions can be designed tohold out different level of ground quaking. The present zonemap subdivides India into II, III, IV, and V.In present tall buildings, lateral loads induced by wind orearthquake forces are often resisted by a system of belt Truss.Belt truss can be defined as the truss provided to theperipheral column of the structure around the core atparticular height of the building, in order to provide sufficientfirmness and strength against lateral loads. The building canhave one or a number of belt truss; the more trusses used.They should be located at locations within the building wherethe diagonal bracing will not interfere with the building'sfunction. The structural principle of employing belt trusses atthe top and mid-height of a building seems to be costeffective in applications up to roughly 60 stories. Shear corepresent at the center also had the capacity to reduce deflectionand acts as a uniformly distribution of load throughoutstructures along with increasing the stiffness of building. Belttruss can be used different types it may be of x, v, inverted v,diagonal etc. Each type of trusses gives different results fordifferent seismic zones so, based on economical condition wehave choose belt truss. Belt truss drew to the model in theETAB software will be shown in below.www.ijert.org(This work is licensed under a Creative Commons Attribution 4.0 International License.)158

International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue 08, August-2015Objectives Belt trusspro A 3-Dimensional plan building is modeled.For the model, additional belt truss is implementedand analyzed.Analysis is carried out using Equivalent static andresponse spectrum method as per IS 1893 – 2002.Response of the buildings are studied and comparedand conclusions are drawn regarding theeffectiveness of structural systems for differentseismic zone of the building.Finding the % reduction of displacement and storydrift of the different seismic zone of the building.III.Fig1: shows belt truss provided to the exterior columnsEffect of earthquake on Reinforced concrete buildingsIn recent past year’s reinforced concrete buildingshave become common in urban places. The main challenge intall building is to resist the wind and earthquake forces. Thereinforcing steel bars and concrete are the two key materialsused in reinforced concrete building. A typical RC tallbuilding is made of horizontal and vertical member andsupported by foundation on rest of the ground. To resist theearthquake forces the RC frames plays a vital role. Theinertia forces generated by earthquake shaking areproportional to mass of the building. The mass of the buildingis present at the floor level, the inertia forces due toearthquake is always induced at floor levels. As the forcesfrom top of the building are transferred to the base of thebuilding, the base of the building is more affected by theearthquake induced forces.II.SCOPE AND OBJECTIVE OF WORKModelling: - Modeling will be done using ETAB [extendedthree dimension analysis of building system] software ofversion 9.7.4. M1-Base model of 30 story building. M2- 30 story building with x type of belt truss. M3- 30 story building with shear core and x type ofbelt truss. M4- 30 story building with inverted v type of belttruss. M5- 30 story building with shear core and inverted vtypes of belt trussLoading: - loading will be taken from As per IS-875 (Part 1) 1987 for dead load is2KN/M2 As per IS 875 (Part 2) 1987 for live load is 4 KN/M2 The earthquake parameter considered from code asper IS 1893(part-1)-2002 for analysis are givenbelow tables.Table 1: Earth quake different parameter used for analysisValuesPage noTableClausesImportanceFactorResponsereduction factor11876.4.232386.4.2Soil typeII1626.4.2Scope of workThe Present work aims towards analyzing the behavior of aplan with 30 storey high rise building, with theimplementation of different belt truss system. To know theimportance belt truss systems, a conventional base model iscreated with only beams, slabs and columns, and it iscompared with implementation of different belt truss systems.As per code IS 1893 2002 dynamic analysis is carried out byresponse spectrum method before that equivalent staticprocess of analysis is carried using ETABS. The shear corewall has been exhibited as shell element with meshing, beamsand columns are exhibited as beam elements with concretestructure. Further study is extended to find out the %reduction of displacement and storey drift at the differentseismic zones.IJERTV4IS080254METHODOLOGYTable 2: Zone factor for different seismic zone as per clause(6.4.2) in IS- 1893 2002Seismic zoneIIIIIIVVSeismic intensityLowModerateSevereVery severewww.ijert.org(This work is licensed under a Creative Commons Attribution 4.0 International License.)Zone factor (Z)0.100.160.240.36159

International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue 08, August-2015Modelling data of Building1Type of Structure Multi Story: Ordinary MomentResisting Frame: RCC2 Zone: II, III, IV, V3 Layout Plan Dimension (X, Y): 40 m x 20 m,Each Bay 5 m4 No. Of Stories: 30 Stories5 Total Height of the Building above Ground Level:91 m6 Floor HeightsAll Typical Floors 3.00 m,Bottom Story Ht. 4m7 External walls: 6 kN/m28 Live load:4.0 kN/m29 Super Dead Load: 2 kN/m210 Materials:M25, Fe 50011 Section PropertiesBeam450x750 mmColumns450x750 mmSlab Thickness 175mm12 Seismic analysis: Equivalent static and responsespectrum method as per IS 1893 – 2002.The model will be regular building of dimension 40mx20m inwhich each bay having 5m as shown in below fig. Forstructure fixed support had given at ground level. Thebuilding will be of 30 stories at bottom is 4m height andremaining will be of 3m height. The three dimensionalanalysis for the model is carried out. The columns and beamsare represented by frame type element. Building plan viewwill be shown belowFig 2 : plan viewAnalysis: - For an 30 story building with and without shearcore using ETAB software results will be extracted by usingequivalent static and response spectrum method (dynamicanalysis) for different seismic zones done by providingdifferent type of belt trusses to the model.Extraction of Results: The results obtained under differentseismic zones will be compared and a graph will be drawn tocheck which model is more suitable for the seismicprotection. Than we have to find the percentage reduction ofdisplacement and story drift for 30 story building.IJERTV4IS080254As per IS 1893 (part 1) 2002, for different seismic zone andimportance factor is I 1. The medium type of soil is usedwith response reduction factor (R) is 3. The fundamental timeperiod is calculated as per clause 7.6.2 isTa 0.075h0.075Method of AnalysisIn this present study method of analysis is made forEquivalent Static method and Dynamic analysis method (onlyresponse spectrum method) for seismic loads acting on thestructure.1. Seismic analysis is the calculation of the building responseof structure to earthquake and is a relevant part of structuraldesign where earthquakes are prevalent.2. The seismic analysis of a structure involves evaluation ofthe earthquake forces acting at various levels of the structureduring an earthquake and the effectiveness of such forces onthe behavior of the overall structure. The analysis may bestatic or dynamic in approach as per the code provisions.3. In the process of structural analysis system the analysis iscarried out to predict its behaviors by using mathematicalequation and physical laws.4. Under various load effects, the main objective of structuralanalysis is to determine internal forces, stresses anddeformation of structures.The analysis of the building is carried out by followingmethods of analysis1.Equivalent Static Analysis Method2.Dynamic Analysis MethodEquivalent Static Analysis: The dynamic nature of theload must be considered when designing against seismicloads. The equivalent linear static method is sufficient foranalysis for simple regular structure by using formula givenin the IS code the distribution and estimate of base shear iscalculated. Tall buildings with second and higher modes canbe important with torsion effects are less suitable for thismethod and require more complex method to be used in thesecircumstances. Equivalent static Analysis method is used forestimation of structural displacement demands. The totalapplied force shall be equal to the product of the accelerationresponse spectrum (ARS) and the tributary weight. Thehorizontal force shall be applied at the vertical centre of thesuperstructure mass and is distributed horizontally inproportion for mass distribution.Dynamic analysis: It should be performed to get the designseismic force, and its allotment to different levels along theheight of the building and to different lateral load resistingelements, for the following buildings: Regular buildings- Those are bigger than 40 m inheight in zone IV, V and those are bigger than 90 mheight in zones II,III, and Irregular buildings-All framed buildings elevated than12 m in zone IV and V, and those are bigger than 40 min height in zone II and III.www.ijert.org(This work is licensed under a Creative Commons Attribution 4.0 International License.)160

International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue 08, August-2015Dynamic analysis can be performed by time history methodor by the response spectrum method. Though in bothmethods, the design base shear (Vb) should be compared witha base shear (vb) calculated using a basic period Ta. When(Vb) is less than (vb) all the response quantities shall bemultiplied by Vb /vb .The values of damping for a buildingmay be taken as 2 and 5 percent of the critical, for thepurpose of dynamic analysis of steel and reinforced concretebuildings, respectively.IV.Results obtained for 30 storey building in Zone 2Table 3:- % Reduction of zone 2 along x and y axis ofequivalent and response spectrum method.MethodsEquivalent staticmethodRESULTS AND DISCUSSIONS M1-Base model 30 story building.M2- 30 story building with x type of belt truss.M3- 30 story building with shear core and x type ofbelt truss.M4- 30 story building with inverted v type of belttruss.M5- 30 story building with shear core and inverted vtypes of belt truss.30 story building has been used for extraction of results.Results are extracted using ETAB software. The building willbe of concrete so, concrete type of belt truss are provided areeffective at coupling exterior columns to the core of a tallbuilding. The belt truss would result in a stiffer buildingwhich is not the more flexible so we have provide core to thebuilding tends to give effective results. Belt trusses engage allthe exterior column during application of seismic load so theload from core has converted to horizontal forces from coreto the outrigger through belt truss.The results we extracted from two methods one is equivalentstatic and other is response spectrum method. Here, live loadand dead load implemented from code book IS 875 (part 1and part 2). And earthquake values are taken from code bookIS 1893 2002 (part 1) and dynamic analysis are done basedon code book than the results had been checked after runningthe analysis. The results extracted will be for displacementand storey drift.After extracting results we can see from the graph that forzone 2, zone 3, zone 4 and zone 5 displacement value along xand y increases both in equivalent and response spectrumincreases in the base model. After implementation of belttruss at top and middle there will be % reduction ofdisplacement and storey drift along both axis in both method.Reduction of displacement will be around 35% in responsespectrum and in equivalent method below 10% under allseismic zones.% Reduction ofDisplacementThe lateral displacement and storey drift play an importantrole, especially for tall building due to sudden variation ofload because of its more deflection and less stiffness. Toincrease stiffness and strength of the building we are going toprovide belt truss and also shear core. Models which we usedfor results extraction are AxisResponsespectrum methodX- axisM2 & M47M3 & M531Y-axisM2 & M43.46X-axisM3 & M5M2 & M4325Y-axisM3 & M531M2 & M4M3 & M52.636Under zone 2 the intensity of earthquake will be of 0.10 so,that less effects to the building will happen under earthquakeload. Here, for 30 storey building lateral displacement andstorey drift for X and Y axis in equivalent and responsespectrum method will be found.In Equivalent method along X and Y displacement value willbe of 32.86 and 61.14, after application of belt truss X andinverted V type to the building without shear core 7% and3.46% along X-axis and Y-axis reduction take place. And Ifthe building with belt truss and shear core than, % reductionvalue will be of 31% and 32% along X and Y axis.In response spectrum method along X and Y displacementvalue will be of 25.24 and 45.24, after application of belttruss X and inverted V type to the building without shearcore 5% and 2.6% along X-axis and Y-axis reduction takeplace. And if the building with belt truss and shear core than,% reduction value will be of 31% and 36% along X and Yaxis.In case of storey drift, both in equivalent and responsespectrum method from the graph shown in fig (3, 4, 5 and 6),in base model a drift will be more at top up to middle thansudden falling of drift take place due to that stiffness reducesand building damage take place. So, after providing belt trussof X and inverted V only at the middle drifting will reducesand at top and bottom will be of same as base model. But, ifwe provide the building with shear core drift at bottom, topand middle reduces because of coupling phenomena andtends to increasing of stiffness in the building.Fig 3:- Storey drift values of equivalent along x-axisIJERTV4IS080254www.ijert.org(This work is licensed under a Creative Commons Attribution 4.0 International License.)161

International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue 08, August-2015Fig 4:- Storey drift values of equivalent along y-axisFig 7: % reduction of displacement.Fig 5:- Storey drift values of response spectrum method along x-axisFig 8: % reduction of storey drift.From the graphs shown in fig (7 and 8) we can say that inzone 2 if we provide the model with X or inverted V type ofbelt truss, at bottom no changes in displacement only afterbelt truss provision at the middle, from there to top it willreduces. In case of drift only at the middle drift reduces but,in case of shear core reduction will take place in top, middleand bottom both in drift and displacement.So, we can say that in zone 2 due to less intensity from aneconomical purposes we can provide a building with invertedbelt truss without shear core and also we built building withshear core along with inverted V or X type of belt truss canbe used.Results obtained for 30 storey building in Zone 3Fig 6:- Storey drift values of response spectrum method along y-axisGraphs are drawn to know the % reduction and which modelTable 4:- % Reduction of zone 3 along x and y axis ofequivalent and response spectrum methodis best suitable in zone 2MethodsAxisEquivalentStatic methodX- axisY-axisResponsespectrummethod% Reduction ofDisplacementM2 & M46.68M3 & M5M2 & M4M3 & M5X-axisM2 & M4M3 & M5Y-axisM2 & M4M3 & M5IJERTV4IS080254www.ijert.org(This work is licensed under a Creative Commons Attribution 4.0 International License.)313.5323.131136162

International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 4 Issue 08, August-2015Under zone 3 the intensity of earthquake will be of 0.16 so,more effects to the building compare to zone 2 underearthquake load. Here, for 30 storey building lateraldisplacement and storey drift along X and Y axis inequivalent and response spectrum method have to be find.In Equivalent method along X and Y displacement value willbe of 52.57 and 97.82, after application of belt truss X andinverted V t

response spectrum method) for seismic loads acting on the structure. 1. Seismic analysis is the calculation of the building response of structure to earthquake and is a relevant part of structural s are prevalent. 2. The seismic analysis of a structure involves evaluation of the earthquake forces acting at various levels of the structure

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