Design Example Of Six Storey Building - IIT Kanpur

Document No. :: IITK-GSDMA-EQ26-V3.0Final Report :: A - Earthquake CodesIITK-GSDMA Project on Building CodesDesign Example of a Six StoreyBuildingbyDr. H. J. ShahDepartment of Applied MechanicsM. S. University of BarodaVadodaraDr. Sudhir K JainDepartment of Civil EngineeringIndian Institute of Technology KanpurKanpur

This document has been developed under the project on Building Codessponsored by Gujarat State Disaster Management Authority, Gandhinagarat Indian Institute of Technology Kanpur. The views and opinions expressed are those of the authors and notnecessarily of the GSDMA, the World Bank, IIT Kanpur, or the Bureau ofIndian Standards. Comments and feedbacks may please be forwarded to:Prof. Sudhir K Jain, Dept. of Civil Engineering, IIT Kanpur, Kanpur208016, email: nicee@iitk.ac.in

Design Example of a BuildingExample — Seismic Analysis and Design of a Six Storey BuildingProblem Statement:A six storey building for a commercial complex has plan dimensions as shown in Figure 1. The building islocated in seismic zone III on a site with medium soil. Design the building for seismic loads as per IS 1893(Part 1): 2002.General1. The example building consists of the mainblock and a service block connected byexpansion joint and is therefore structurallyseparated (Figure 1). Analysis and design formain block is to be performed.2 The building will be used for exhibitions, as anart gallery or show room, etc., so that there areno walls inside the building. Only externalwalls 230 mm thick with 12 mm plaster onboth sides are considered. For simplicity inanalysis, no balconies are used in the building.3. At ground floor, slabs are not provided and thefloor will directly rest on ground. Therefore,only ground beams passing through columnsare provided as tie beams. The floor beams arethus absent in the ground floor.4. Secondary floor beams are so arranged thatthey act as simply supported beams and thatmaximum number of main beams get flangedbeam effect.5. The main beams rest centrally on columns toavoid local eccentricity.6. For all structural elements, M25 grade concretewill be used. However, higher M30 gradeconcrete is used for central columns up toplinth, in ground floor and in the first floor.IITK-GSDMA-EQ26-V3.07. Sizes of all columns in upper floors are kept thesame; however, for columns up to plinth, sizesare increased.8. The floor diaphragms are assumed to be rigid.9. Centre-line dimensions are followed foranalysis and design. In practice, it is advisableto consider finite size joint width.10. Preliminary sizes of structural components areassumed by experience.11. For analysis purpose, the beams are assumedto be rectangular so as to distribute slightlylarger moment in columns. In practice a beamthat fulfils requirement of flanged section indesign, behaves in between a rectangular and aflanged section for moment distribution.12. In Figure 1(b), tie is shown connecting thefootings. This is optional in zones II and III;however, it is mandatory in zones IV and V.13. Seismic loads will be considered acting in thehorizontal direction (along either of the twoprincipal directions) and not along the verticaldirection, since it is not considered to besignificant.14. All dimensions are in mm, unless specifiedotherwise.Page 3

C1(0,0)3(7.5,0)(15,0)B1C2B2421Design Example of a BuildingC3C4 (22.5,0)B3AXAC10(22.5,7.5)C8BC11B 23F.B.B 20AB8B 19CC12(22.5,15)F.B.B11Service blockExpansionjointB9(15, 15)F.B.F.B.F.B.B10B6(15, 7.5)(7.5,15)B 16F.B.B 24B 21F.B.F.B.F.B.B 137.5 mB 17B7C9(0,15)CF.B.F.B.AC7(7.5, 7.5)F.B.B 147.5 mBB5F.B.xB 22C6C5(0,7.5)Main blockF.B.B4F.B.F.B.F.B.B 18B 157.5 (22.5,22.5)7.5 m1m300 6005 m 500 5004321Z7.5 m(a) Typical floor plan7.5 m 31.5 m 30.5 m Terrace 30.2 m75mM25 25.2 m65mM25 20.2 m5mM25 15.2 m5mM25 10.2 m35mM25 5.2 m24.1 mM25 1.1 m 25.5 m Fifth Floor5m 20.5 m Fourth Floor5m5y 15.5 m Third Floor5m4 10.5 m Second Floor5mx 5.5 m First Floor4m0.100.600.800.900.10300 6002.5 2.1 m Ground FloorPlinth 0.0600 600Tie(b) Part section A-A11.1 m 0.0 mStoreynumbersM25(c) Part frame sectionFigure 1 General lay-out of the Building.IITK-GSDMA-EQ26-V3.0Page 4

Design Example of a Building1.1.Data of the ExampleThe design data shall be as follows:: 4.0 kN/m2 at typical floorLive load: 1.5 kN/m2 on terraceFloor finish: 1.0 kN/m2Water proofing: 2.0 kN/m2Terrace finish: 1.0 kN/m2Location: Vadodara cityWind load: As per IS: 875-Not designed for windload, since earthquake loads exceed thewind loads.Earthquake load: As per IS-1893 (Part 1) - 2002Depth of foundation below ground: 2.5 mType of soil: Type II, Medium as per IS:1893Allowable bearing pressure: 200 kN/m2Average thickness of footing: 0.9 m, assume isolated footingsStorey height: Typical floor: 5 m, GF: 3.4 mFloors: G.F. 5 upper floors.Ground beams: To be provided at 100 mm below G.L.Plinth level: 0.6 mWalls: 230 mm thick brick masonry wallsonly at periphery.Material PropertiesConcreteAll components unless specified in design: M25 grade allEc 5 000f ck N/mm2 5 000f ck MN/m2 25 000 N/mm 2 25 000 MN/m 2 .For central columns up to plinth, ground floor and first floor: M30gradeEc 5 000f ck N/mm2 5 000f ck MN/m2 27 386 N/mm 2 27 386 MN/m 2 .SteelHYSD reinforcement of grade Fe 415 confirming to IS: 1786 is used throughout.1.2.Geometry of the BuildingThe general layout of the building is shown inFigure 1. At ground level, the floor beams FB areIITK-GSDMA-EQ26-V3.0not provided, since the floor directly rests onground (earth filling and 1:4:8 c.c. at plinth level)and no slab is provided. The ground beams arePage 5

Design Example of a Buildingprovided at 100 mm below ground level. Thenumbering of the members is explained as below.Foundation top – Ground floor1from upper to the lower part of the plan. Giving90o clockwise rotation to the plan similarly marksthe beams in the perpendicular direction. Tofloor-wise differentiate beams similar in plan (saybeam B5 connecting columns C6 and C7) invarious floors, beams are numbered as 1005,2005, 3005, and so on. The first digit indicates thestorey top of the beam grid and the last threedigits indicate the beam number as shown ingeneral layout of Figure 1. Thus, beam 4007 is thebeam located at the top of 4th storey whosenumber is B7 as per the general layout.Ground beams – First floor21.3.First Floor – Second floor3Second floor – Third floor41.3.1. Unit load calculationsAssumed sizes of beam and column sections are:Third floor – Fourth floor5Fourth floor – Fifth floor6Fifth floor - Terrace71.2.1.Storey numberStorey numbers are given to the portion of thebuilding between two successive grids of beams.For the example building, the storey numbers aredefined as follows:Portion of the building1.2.2.Storey no.Column numberIn the general plan of Figure 1, the columns fromC1 to C16 are numbered in a convenient way fromleft to right and from upper to the lower part ofthe plan. Column C5 is known as column C5 fromtop of the footing to the terrace level. However,to differentiate the column lengths in differentstories, the column lengths are known as 105,205, 305, 405, 505, 605 and 705 [Refer to Figure2(b)]. The first digit indicates the storey numberwhile the last two digits indicate column number.Thus, column length 605 means column length insixth storey for column numbered C5. Thecolumns may also be specified by using grid lines.1.2.3.Floor beams (Secondary beams)All floor beams that are capable of free rotation atsupports are designated as FB in Figure 1. Thereactions of the floor beams are calculatedmanually, which act as point loads on the mainbeams. Thus, the floor beams are not consideredas the part of the space frame modelling.1.2.4.Main beams numberBeams, which are passing through columns, aretermed as main beams and these together with thecolumns form the space frame. The general layoutof Figure 1 numbers the main beams as beam B1to B12 in a convenient way from left to right andIITK-GSDMA-EQ26-V3.0Gravity Load calculationsColumns: 500 x 500 at all typical floorsArea, A 0.25 m2, I 0.005208 m4Columns: 600 x 600 below ground levelArea, A 0.36 m2, I 0.0108 m4Main beams: 300 x 600 at all floorsArea, A 0.18 m2, I 0.0054 m4Ground beams: 300 x 600Area, A 0.18 m2, I 0.0054 m4Secondary beams: 200 x 600Member self- weights:Columns (500 x 500)0.50 x 0.50 x 25 6.3 kN/mColumns (600 x 600)0.60 x 0.60 x 25 9.0 kN/mGround beam (300 x 600)0.30 x 0.60 x 25 4.5 kN/mSecondary beams rib (200 x 500)0.20 x 0.50 x 25 2.5 kN/mMain beams (300 x 600)0.30 x 0.60 x 25 4.5 kN/mSlab (100 mm thick)0.1 x 25 2.5 kN/m2Brick wall (230 mm thick)0.23 x 19 (wall) 2 x 0.012 x 20 (plaster) 4.9 kN/m2Page 6

Design Example of a BuildingFloor wall (height 4.4 m)4.4 x 4.9 21.6 kN/mMain beams B1–B2–B3 and B10–B11–B12ComponentGround floor wall (height 3.5 m)3.5 x 4.9 17.2 kN/m0.5 x 2.5 (5.5 1.5)Terrace parapet (height 1.0 m)1.0 x 4.9 4.9 kN/mParapet6.9 1.90 04.9 04.9 0Total11.8 1.94.9 0kN/mkN/mSlab load calculationsComponentTerraceTypical(DL LL)(DL LL)Self (100 mmthick)2.5 0.02.5 0.0Waterproofing2.0 0.00.0 0.0Floor finish1.0 0.01.0 0.0Live load0.0 1.50.0 4.0Total5.5 1.5kN/m23.5 4.0kN/m21.3.3.B2From SlabGround floor wall (height 0.7 m)0.7 x 4.9 3.5 kN/m1.3.2.B1-B3Beam and frame load calculations:Two point loads on one-third span points forbeams B2 and B11 of (61.1 14.3) kN from thesecondary beams.Main beams B4–B5–B6, B7–B8–B9, B16–B17– B18 and B19–B20–B21From slab0.5 x 2.5 x (5.5 1.5) 6.9 1.9 kN/mTotal 6.9 1.9 kN/mTwo point loads on one-third span points for allthe main beams (61.1 14.3) kN from thesecondary beams.Main beams B13–B14–B15 and B22–B23–B24ComponentB13 – B15B14B22 – B24B23----6.9 1.9Parapet4.9 04.9 0Total4.9 011.8 1.9kN/mFrom Slab0.5 x 2.5 (5.5 1.5)(1) Terrace level:Floor beams:From slabkN/m2.5 x (5.5 1.5) 13.8 3.8 kN/mSelf weight 2.5 0 kN/mTotal 16.3 3.8 kN/mTwo point loads on one-third span points forbeams B13, B15, B22 and B24 of (61.1 14.3)kN from the secondary beams. 61.1 14.3 kN.(2) Floor Level:Reaction on main beam0.5 x 7.5 x (16.3 3.8)Floor Beams:Note: Self-weights of main beams and columnswill not be considered, as the analysis softwarewill directly add them. However, in calculationof design earthquake loads (section 1.5), thesewill be considered in the seismic weight.IITK-GSDMA-EQ26-V3.0From slab2.5 x (3.5 4.0)Self weightTotalReaction on main beam0.5 x 7.5 x (11.25 10.0) 8.75 10 kN/m2.5 0 kN/m11.25 10 kN/m 42.2 37.5 kN.Page 7

Design Example of a BuildingMain beams B1–B2–B3 and B10–B11–B12ComponentB1 – B3B2Two point loads on one-third span points forbeams B13, B15, B22 and B24 ofFrom Slab0.5 x 2.5 (3.5 4.0)4.4 5.00 0Wall21.6 021.6 0Total26.0 5.0 21.6 0kN/mkN/m(42.2 7.5) kN from the secondary beams.(3) Ground level:Two point loads on one-third span points forbeams B2 and B11 (42.2 37.5) kN from thesecondary beams.Outer beams: B1-B2-B3; B10-B11-B12; B13B14-B15 and B22-B23-B24Walls: 3.5 m high17.2 0 kN/mInner beams: B4-B5-B6; B7-B8-B9; B16B17-B18 and B19-B20-B21Main beams B4–B5–B6, B7–B8–B9, B16–B17–B18 and B19–B20–B21Walls: 0.7 m highFrom slab 0.5 x 2.5 (3.5 4.0) 4.4 5.0 kN/mThe loading frames using the above-calculated

as the part of the space frame modelling. 1.2.4. Main beams number Beams, which are passing through columns, are termed as main beams and these together with the columns form the space frame. The general layout of Figure 1 numbers the main beams as beam B1 to B12 in a convenient way from