Page Assistant Professor, Pydah College of Engineering, Kakinada, AP, India.

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1 Aalysis Ad Desig Of Flat Slab By Usig Etabs Software B.Ajaeyulu 1, K Jaya Prakash 2 1 PG Scholar, Pydah College of Egieerig, Kakiada, AP, Idia. 2 Assistat Professor, Pydah College of Egieerig, Kakiada, AP, Idia. ABSTRACT Flat Slab is better uderstood as the slab without beams restig directly o supports (like colums & or walls).by virtue of that large Bedig Momet & Shear Forces are developed close to the colums. Flat slabs system of costructio is oe i which the beams used i t he covetioal methods of costructios are doe away with. The slab directly rests o the colum ad load from the slab is directly trasferred to the colums ad the to the foudatio. To support heavy loads the thickess of slab ear the support with the colum is icreased ad these are called drops, or colums are geerally provided with elarged heads called colum heads or capitals.absece of beam gives a plai ceilig, thus givig better architectural appearace ad also less vulerability i case of fire tha i usual cases where beams are used. Plai ceilig diffuses light better, easier to costruct ad requires cheaper form work.as per local coditios ad availability of materials differet coutries have adopted differet me thods for desig of flat slabs ad give their guidelies i their respective codes.the Fiite elemet aalysis & Equivalet frame aalysis is carried out by usig software ETABS, The aalysis & desig is performed by Equivalet Frame Method with staggered colum & without staggered colum as prescribed i the differet codes like IS , ACI are compared. I this process momets are distributed as colum strip momets & middle strip momets.for carryig out this project a iterior pael of a flat slab with dimesios 6.6 x 5.6 m ad super imposed load 7.75 KN /m2 was desiged usig the codes give above. INTRODUCTION 1.1 Geeral A flat slab is a two-way reiforced cocrete slab that usually does ot have beams ad girders, ad the loads are trasferred directly to the supportig cocrete colums. They are subjected to both vertical ad lateral loads. Lateral loads due to wid ad earthquake govers the desig rather tha the vertical loads. The buildigs desiged for vertical load may ot have the capacity to resist the lateral loads. The lateral loads are the premier oes because i cotrast to vertical load that may be assumed to icrease liearly with height; lateral loads are quite variable ad icrease rapidly with height. Uder a uiform wid ad earthquake loads the overturig momet at the base is very large ad varies i proportio to the square of the height of the buildig. The lateral loads are cosiderably higher i the top storey rather tha the bottom storey due to which buildig teds to act as catilever. These lateral forces ted to sway the frame. I may of the seismic proe areas there are several istaces of failure of buildigs which have ot bee desiged for earthquake loads. All these reactio makes the study of the effect of lateral loads very importat. I geeral ormal frame costructio utilizes colums, slabs & beams. However it may be possible to udertake costructio with out providig beams, i such a case the frame system would cosist of slab ad colum without beams. These types of slabs are called flat slab, sice their behavior resembles the bedig of flat plates. Pure rigid frame system or frame actio obtaied by the iteractio of slabs, beam ad colum is ot adequate. The frame aloe fails to provide the required lateral stiffess for buildigs taller tha 15 to 20 (50m to 60m) stories. It is Page 105

2 because of the shear takig compoet of deflectio. Produced by the bedig of colums ad slab causes the buildig to deflect excessively. There are two ways to satisfy these requiremets. First is to icrease the size of members beyod ad above the stregth requiremets ad secod is to chage the form of structure ito more rigid ad stable to cofie deformatio. First approach has its ow limits, whereas secod oe is more elegat which icreases rigidity ad stability of the structure ad also cofie the deformatio requiremet. I earthquake egieerig, the structure is desiged for critical force coditio amog the load combiatio. I the preset study the respose of multi-storey commercial reiforced cocrete. Frame ad r c flat slab to the lateral ad vertical loads have bee doe. 1.2 Scope of the study This work icludes the desig ad estimate for flat slabs of various spas, ragig from 6.0 m to 12.0 m, by reiforced cocrete.c. Ad prestressed cocrete techiques. For smaller spas, associated with ormal buildig works, prestressed cocrete costructio becomes too cumbersome, irrespective of the ecoomics ivolved. Itesity of assumed loadig is kept sufficiet eough, so that the factored bedig momet will be comparable to that developig i cases of commercial buildigs. Post-tesioig is preferred as it is i vogue, i costructio of large spa slabs. All structural costs, floor framig is usually the largest compoet. Likewise, the majority of a structure s formwork cost is usually associated with the horizotal elemets. Cosequetly, the first priority i desigig for ecoomy is selectig the structural system that offers lowest overall cost while meetig load requiremets. Posttesioig is the key to cost-effective multifamily costructio. I additio, post-tesioed structures ca be desiged to have miimal deflectio ad crackig, eve uder full load. Thier floors provide lower buildig weight, which creates a correspodig reductio i other structural elemets. There are also some associated labour ad time savigs 1.3. Objectives To study the performace of flat slab ad covetioal slab structure subjected to various loads ad coditios. To the study the behavior of both structure for the parameters like storey shear, storey displacemet drift ratio, axial forces. Comparisos of flat ad covetioal buildig for the above parameters. The mai objective of the aalysis is to study thedifferet forces actig o a buildig. The aalysis is carried out i etabs software. Results of covetioal reiforced cocrete.c structure i.e. Slab, beam ad colum ad flat slab reiforced cocrete.c structure for differet heights are discussed. Covetioal reiforced cocrete.c structure ad flat slab reiforced cocrete.c for differet height are modeled ad aalyzed for the differet combiatios of dyamic loadig. The compariso is made betwee the covetioal reiforced cocrete.c structure ad flat slab reiforced cocrete.c. Buildigs are situated i seismic zoe iv. To study the vulerability of purely frame ad purely flat-slab models uder differet factors which are storey drift, lateral displacemet, time period ad base shear have bee obtaied for RESULTS AND ANALSIS Geeral ETABS is a special-purpose computer program developed specifically for buildig structures. It provides the Structural Egieer with all the tools ecessary to create, modify, aalyze, desig, ad optimize buildig models. These features are fully itegrated i a sigle, Widows-based, graphical user iterface that is umatched i terms of easeof-use, productivity, ad capability. The iovative ad revolutioary ew ETABS is the ultimate itegrated software package for the structural aalysis ad desig of buildigs. Icorporatig 40 years of cotiuous research ad developmet, this latest ETABS offers umatched 3D object based modelig ad visualizatio tools, Page 106

3 blazigly fast liear ad oliear aalytical power, sophisticated ad comprehesive desig capabilities for a wide-rage of materials, ad isightful graphic displays, reports, ad schematic drawigs that allow users to quickly ad easily decipher ad uderstad aalysis ad desig results. From the start of desig coceptio through the productio of schematic drawigs, ETABS itegrates every aspect of the egieerig desig process. Creatio of models has ever bee easier - ituitive drawig commads allow for the rapid geeratio of floor ad elevatio framig. CAD drawigs ca be coverted directly ito ETABS models or used as templates oto which ETABS objects may be overlaid. Desig of steel ad cocrete frames (with automated optimizatio), composite beams, composite colums, steel joists, ad cocrete ad masory shear walls is icluded, as is the capacity check for steel coectios ad base plates. Models may be realistically redered, ad all results ca be show directly o the structure. Comprehesive ad customizable reports are available for all aalysis ad desig output, ad schematic costructio drawigs of framig plas, schedules, details, ad cross-sectios may be geerated for cocrete ad steel structures. ETABS provides a uequaled suite of tools for structural egieers desigig buildigs, whether they are workig o oe-story idustrial structures or the tallest commercial high-rises. Immesely capable, yet easy-to-use has bee the hallmark of ETABS sice its itroductio decades ago, ad this latest release cotiues that traditio by providig egieers with the techologically-advaced, yet ituitive, software they require to be their most productive..fiite elemet method The fiite elemet method is a umerical techique to fid approximate solutios of partialdifferetial equatios. It was origiated from the eed of solvig complex elasticity ad structuralaalysis problems i civil, mechaical ad aerospace egieerig. I a structural simulatio, fiite elemet method helps i producig stiffess ad stregth visualizatios. It also helps to miimize materialweight ad its cost of the structures. Fiite elemet method allows for detailed visualizatio ad idicates the distributio of stresses ad strais iside the body of a structure. May of fe software are powerful yet complex tool meat for professioal egieers with the traiig ad educatio ecessary to properly iterpret the results. This powerful desig tool has sigificatly improved both the stadard of egieerig desigs ad the methodology of the desig process i may idustrial applicatios. The use of fiite elemet method has sigificatly decreased the time to take products from cocept to the productio lie. Oe must take the advatage of the advet of faster geeratio of persoal computers for the aalysis ad desig of egieerig product with precisio level of accuracy Etabsaalysis ad desig procedure Defie Pla Grids ad Story Data Defie Material Properties Defie Frame Sectios Defie Slab Sectios Defie Load Cases Draw Beam Objects (Frame Members) Draw Colum Objects (Frame Members) Assig Slab Sectios Assig Restrais Assig Slab Loads View Iput Data i Tabular Form Ru the Aalysis View Aalysis Results Graphically Desig Cocrete Frame Elemet Fig.1 view of whole stucture data Page 107

4 G1 3.Structure data This chapter provides model geometry iformatio, icludig items such as story levels, poit coordiates, ad elemet coectivity. 3.2 Story data Table.1 - story data Height Elevatio Master story Similar to Splice story Story es Noe No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Story No Story15 No Base 0 0 No Noe No 3.3 Grid data Table 2 - grid systems Type Cartesia Grid system Story rage origi M origi M Rotatio Deg Bubble size Default Grid directio Table 3 - grid lies Grid id Visible Bubble locatio Ordiat e M G1 A es Ed 0 G1 B es Ed G1 C es Ed 7.2 G1 D es Ed 12 G1 E es Ed 17 G1 1 es Start 0 G1 2 es Start G1 3 es Start 5.9 G1 4 es Start 9.8 Grid system Color Ffa0a0a 0 Grid directio Grid id Visible Bubble Ordiat e locatio M G1 5 es Start G1 6 es Start 16.3 G1 7 es Start 18.2 G1 8 es Start Poit coordiates Table 4. - joit coordiates data Page 108

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6 Properties This chapter provides property iformatio for materials, frame sectios, shell sectios, ad liks Materials Table 5. - material properties - summary Type 4000psi Cocret e E Mpa Ν 0.2 Uit weight K/m³ Desig stregth s Fc= mpa Page 110

7 A615gr 60 Type Rebar E Mpa Ν Uit weight K/m³ Frame sectios Table 6. - frame sectios - summary Materia l Coccol 4000psi Shape Cocrete rectagula r Shell sectios Table 7- shell sectios - summary Drop1 Slab1 Desig type Slab Slab Eleme t type Shellthi Shellthi Materia l Desig stregth s Fy= mpa, fu= mpa Total thicke ss 4000psi psi Reiforcemet sizes Table 8. - reiforcig bar sizes Diamet Area er ² Assigmets This chapter provides a listig of the assigmets applied to the model. RECOMUNDATIONS AND CONCLUSION 4.1.Recomedatios After completig this mai project, based o our experiece the followig recommedatios are made. 1. Oe caot igore the importace of the geotechical egieerig report which idicates the estimatio of soil bearig capacity. 2. The egieerig who is ivolved i aalysis ad desig of multistoried buildig should have the proper back groud i the followig techical areas. a. Egieerig mechaics b. Egieerig drawig c. Stregth of materials d. Structural aalysis e. Structural desig of RCC ad steel 3. I additio to the techical skill oe should have the followig basic skills. a. Commuicatio skills b. Report writig skills c. Microsoft office d. AUTOCAD e. Structural egieerig soft wares f. Architectural soft wares 4. The desig egieer should have the basic backgroud i electrical ad plumbig egieerig also. 5. A ovice desig egieer may use our mai project report as a guide lie. 4.2.Scope of future work Absece of beams allows lower story heights ad as a result cost savig i vertical claddig, partitio walls, mechaical systems, plumbig ad a large umber of other items of costructio especially for medium ad high rise buildig. Total height of buildig is restricted usig flat slab results i more stories accommodated withi the set height. Fig 2. : Aalysis ad desig deformatio shape of whole structure Page 111

8 Comparisos of flat plate (without drop) ad flat slab (with drop) ca be studied for all seismic zoes. Comparisos of pretesio ad post tesioed flat slab with or without drops. Cost comparisos of various types of slabs available. i this project compariso of covetioal beam slab ad grid slab is made o the basis of major material requiremets of the slab. 4.3.Coclusio Flat plate/slab costructio is a developig techology i idia flat slabs has may advatages over covetioal slabs ad hece it ca be a very good optio for moder costructios demadig structural stability ad state of art aesthetic aspects ad prospects. Flat plate/slab ca be desiged ad built either by covetioal reiforced cocrete. or posttesioig. However, due to issues metioed above with post- tesioig costructio i idia ad its higher cost, covetioal reiforced cocrete desig should be the preferred choice for spas up to 10 meters. Desig of covetioal reiforced cocrete. flat plate/slab i idia, utilizig idia codes, has may shortcomigs, which have to be addressed ad revised soo. Refereces 1.Park et al. (2008) foud that equivalet frame method is ot appropriate i accurately predictig the respose of two-way slab systems uder lateral loads. Curretly desig.code, aci [2.1] permit the efm for the aalysis of two-way slab system uder gravity loads ad lateral loads such as seismic loads. 2.Subramaia et al (2005) foud that to icrease the puchig shear stregth of flat slab, the shear reiforcemet is foud to provide ecoomical solutio. They ot oly ehace the shear capacity but also result i flexural failure of the slab ad thus icreasig the ductility of flat slab, which is very importat i earthquake proe zoe. 3.Faella, David A. Cocrete Floor Systems: Guide To Estimatig Ad Ecoomizig. 2d Editio. Portlad Cemet Associatio, 2000 Guide To Log-Spa Cocrete Floors, Cemet Ad Cocrete Associatio Of Australia. 4.Gowda N Bharath; Gowda S. B. Ravishakar; A.V Chadrashekar Review Ad Desig Of Flat Plate/Slabs Costructio I Idia, Structural Desig Guide To The Aci Buildig Code, Third Editio, Va Nostrad Reihold Compay. New ork Idia Stadard Is 456:2000, Plai Ad Reiforced Cocrete Code Of Practice. 7.Purushothama P., Reiforced Cocrete Structural Elemets, Tata Mcgraw-Hill Publicatio Compay Ltd. New Delhi Verghesep.C.,Advaced Reiforced Cocrete Desig, Pretice-Hall Of (Idia Private Ltd. New Delhi Notes O Aci , Buildig Code Requiremet For Reiforced Cocrete, Portlad Cemet Associatio. Usa Structural Desig Guide To The Aci Buildig Code, Third Editio, Va Nostrad Reihold Compay. New ork Keeth Leet Ad Dioisio Beral, Reiforced Cocrete Desig Third Editio, Mcgraw-Hill, Usa Alaa G. S. Ad Walter H.D., Aalysis Ad Deflectio Of Reiforced Cocrete Flat Slabs, Caadia Joural Of Civil Egieerig, Vol Nilsso A.H. Ad Walter D.B., Deflectio Of Two-Way Floor Systems By The Equivalet Frame Method, Aci Joural, Vol. 72, No Idia Stadard Is 1893 (Part 1): 2002, Criteria For Earthquake Resistat Desig Of Structures. Page 112