A Thesis on

DYNAMIC ANALYSIS OF FLAT SLAB AND GRID SLAB

SYSTEM IN A MULTISTOREY BUILDING
Submitted in Partial Fulfilment of the Requirements for the Degree
of
MASTER OF TECHNOLOGY
In
STRUCTURAL ENGINEERING
by
SURAJ KUMAR RAVI
(1801431016)
Under the Supervision of
Mr. Mohd Bilal Khan
(Assistant Professor)

Department of Civil Engineering

INTEGRAL UNIVERSITY, Lucknow (UP)
2020

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 DECLARATION

I declare that the research thesis entitled “Dynamic Analysis Of Flat Slab And Grid
Slab System In A Multistorey Building” is bonafide research work carried out by me,
under the guidance of Mr. Mohd Bilal Khan, Assistant Professor, Department of
Civil Engineering, Integral University, Lucknow. Further, I declare that this work has
not previously formed the basis of award of any degree, diploma, associate-ship or other
similar degrees or diplomas, and has not be submitted anywhere else.

Date:

Place: Lucknow

SURAJ KUMAR RAVI

Roll No. 1801431016
Department of Civil Engineering
Integral University, Lucknow

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 CERTIFICATE

Certified that the thesis entitled “Dynamic Analysis Of Flat Slab And Grid Slab
System In A Multistorey Building” is being submitted by Mr. Suraj Kumar Ravi (Roll
no. 1801431016) in partial fulfilment of the requirement for the award of degree of
Master of Technology (Structures) of Integral University, Lucknow is a record of
candidate’s own work carried out by him/her under my supervision and guidance.

The result presented in this thesis has not been submitted to any other university or
institute for the award of any other degree or diploma.

Mr. Mohd Bilal Khan

Assistant professor
Department of Civil Engineering
Integral University, Lucknow

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 ACKNOWLEDGEMENT

All praises to Almighty GOD with whose grace I was able to complete this project
successfully.

I am extremely thankful to my Project guide Mr. Mohd Bilal Khan Assistant Professor,
Department of Civil Engineering, under whose guidance I was able to complete the
project. He provided me full support and material to remove the constraints and hurdles
which I faced while undergoing the project. I am also highly grateful to our dignified
HOD who has provided me all kind of support and encouragement which I required from
time to time.

Being the student of M. Tech Civil Engineering, I have chosen this project “Dynamic
Analysis of Flat Slab And Grid Slab System In A Multistorey Building” which I
believe will prove beneficial to me in my career and educational purpose.

I would also like to acknowledge my dear parents, who have given me the moral and
monitory support every time and specially in formulating the project job.

SURAJ KUMAR RAVI

Place: Lucknow Date:

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 TABLE OF CONTENTS

Contents page no.

Title Page………………………………………………………………... 1
Declaration…………………………………………………………..…... 2
Certificate…………………………………..……………………..............3
Acknowledgement…………………………………………...………..….4
Abstract……………………………………………………….………….9

Chapter 1: Introduction 10-17

1.1 General Introduction………………………………………............10

1.2 Objective Of The Research…………………………………….…11

1.2.1 Learning Outcome………………………………………...12

1.2.2 Establish Research Priorities …………………………..…12

1.3 Overview Of The Methodology …………………………………..13

1.3.1 Unit System ………………………………………….….14

1.3.2 Overview Of Etabs…………………………………..…….14

1.3.2.1 Fundamental Concepts…………………………………….15

1.3.2.2 Features Of Etabs………………………………………….16

Chapter 2: Literature 18-23

2.1 Literature Review…………………………………………………18

Chapter 3: Approach and Methodology 24-29

3.1 Structural Designing ……………………………………………24

3.2 Working Time And Location Of A Structural

Engineer ……………………25

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 3.3 Roles And Responsibilities Of Structural Design Engineers

In Construction ………………………….. 25

3.4 Description Of Model Type…………………………………......25

3.5 Loading…………………………………………………………..28

Chapter 4: Analysis And Design Result From Etabs 30-49

4.1 Structure Data 30

4.1.1 Story Data………………………………………………… 30

4.1.2 Loads……………………………………………………… 30

4.1.2.1 Load Patterns……………………………………….. 30

4.1.3 Functions…………………………………………………. 31

4.1.3.1 Response Spectrum Functions……………………… 31

4.1.3.2 Load Cases………………………………………….. 33

4.2. Analysis Results 33

4.2.1 Bending Moment…………………………………………….. 33

4.2.2 Shear Force Diagram………………………………………… 34

4.2.3 Displacement…………………………………………………. 35

4.2.4 Stress In Slab………………………………………………… 36

4.2.5 Story Displacement………………………………………….. 37

4.2.6 Story Response……………………………………………… 38

4.2.7 Story Drift……………………………………………………. 40

4.2.8 Story Shear ……………………………………………………40

4.2.9 Story Stiffness……………………………………………….....41

4.2.10 Story Overturning Moment…………………………………...44
4.3 Design Results……………………………………………………..…46

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Chapter 5: Conclusion………………………………………………………..…50

Chapter 6: Future Work Process…………………………………………… ...52

References………………………………………………………………………..53
List of Publication with certificate…….…………………………………….…56

LIST OF TABLES
Page No
Table 4.1 Story Data 30
Table 4.2 Load Patterns 30
Table 4.3 Response Spectrum Function 31
Table 4.4 Load Cases 33
Table 4.5 Story Response Values 39
Table 4.6 Story Stiffness 41
Table 4.7 Base Reactions 44
Table 4.8 Area of Reinforcement at mid span of Building 49

LIST OF FIGURES

Fig 3.1: Isometric view of Structure 26

Fig 3.2: 3D Rendered view of Building 27

Fig 3.3: AutoCAD file showing plan of structure 28

Fig 3.4: Plan of Structure . 29

Fig 4.1 (a): Earthquake Loading along-x 31

Fig 4.1 (b). Earthquake Loading along-y 31

Fig 4.2: Bending Moment Diagram 34

Fig 4.3: Shear Force on 3-3 axis 34

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Fig 4.4: Shear Force on 2-2 axis 34

Fig 4.5: Deformation in Building 35

Fig 4.6: Comparison in stress between the area of flat and waffle slab. 36

Fig 4.7: Stress Diagram 36

Fig 4.8: Stress in Flat Slab and Grid Slab. 37

Fig 4.9: Story Displacement. 38

Fig 4.10: Story Displacement (Response Spectrum). 39

Fig 4.11: Maximum Story Drift. 40

Fig 4.12: Story Drift due to Response Spectrum. 40

Fig 4.13(A): Story Shear due to EQ-X. 41

Fig 4.13(B): Story Shear due to EQ-Y 41

Fig 4.14: Story Stiffness by Response Spectrum 44

Fig 4.15: Story Overturning Moment 45

Fig 4.16: First Iteration 46

Fig 4.17: Second Iteration 46

Fig 4.18: Third Iteration 47

Fig 4.19: Fourth Iteration 47

Fig 4.20: Final Iteration 47

Fig 4.21: Reinforcement data in Beams and Columns 48

Fig 4.22: Diagrammatic representation of Reinforcement in Top Slab 49

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 ABSTRACT

Civil Engineers are facing a great challenge in structural designing. The design must fulfil various
parameters which include economical structure, durability and serviceability. But taking these
points in mind it becomes very difficult for an Engineer to fulfil all these requirements at a time
when a design is performed manually. This dissertation presents a research on digital tools used in
civil engineering and comparing their results by taking in mind the requirements of the above
points. In this research process a building is taken for analysis and design on well-known Software
ETABS. Based on the results taken from the Software some comparison is done with manual
analysis.

Nowadays every designing organisation is using these Software but there is a

question mark to which software we must go for designing. The parent organisations which have
developed these designing tools promote their Software by showing all the positive points. In
addition to this they are trying to fill all the loop holes which they found in their products but it
will never happen that another developing company will put the points in light what the negative
points are there in existing products. They keep on improving to deliver their best. In this project
work I will present the difference for future users to which tool you must go through to acquire
your needs. I am not saying that some products are not ok at all. I have designed a residential
building with proper loading which is being designed on both ETABS. Manual calculations make
it crystal clear the difference between the Software.

The main purpose of this study is to show detailed difference between well-known
simulation Software STAAD Pro and ETABS used by structural design engineers nowadays. This
study is focussed on the advantages of digital tools in our life to make it easy and reliable for us to
perform a difficult task. It is found that ETABS is good for building design and STAAD PRO on
the whole deals with RCC Structures as well as Steel Structures but by survey I found STAAD Pro
is mostly used to check analysis result. So, in this study I am going to check it out what is the
reason, why Engineers are taking analysis result in case of RCC Design why not design result while
using STTAD Pro.

9
 CHAPTER 1

INTRODUCTION

1.1 GENERAL INTRODUCTION

An RCC framed structure is basically an assembly of slabs, beams, columns and foundation inter
-connected to each other as a unit. The load transfer, in such a structure takes place from the slabs
to the beams, from the beams to the columns and then to the lower columns and finally to the
foundation which in turn transfers it to the soil. The floor area of a R.C.C framed structure building
is 10 to 12 percent more than that of a load bearing walled building. Monolithic construction is
possible with R.C.C framed structures and they can resist vibrations, earthquakes and shocks more
effectively than load bearing walled buildings. Reinforced concrete is a composite material in
which concrete's relatively low tensile strength and ductility are counteracted by the inclusion of
reinforcement having higher tensile strength and ductility. The reinforcement is usually embedded
passively in the concrete before the concrete sets.

The reinforcement needs to have the following properties at least for the strong and durable
construction:

• High toleration of tensile strain.

• Good bond to the concrete, irrespective of pH, moisture, and similar factor.

•Thermal compatibility, not causing unacceptable stresses in response to changing temperatures.

Design needs to have good hand on numerical problem, to counter different challenges while
getting twisted in a design. After complete knowledge of analysis and design one can design any
structure but it is not possible for a single person to go through all fields. It is necessary to get a
full knowledge in a particular field. Building analysis and design needs complete knowledge of IS
Codes and numerical analysis. One must be well versed about loading which are considered in a
building. Building can be of various types and can be residential, commercial, industrial and
institutional. So, while performing a design we need to go through different design codes. Some
of the codes are given below with their description of loading.

IS- 875 (Part 1) – Design Code for Dead Loads.

IS- 875 (Part 2) – Design Code for Live Loads.

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IS- 875 (Part 3) – Wind Load Design Code.

IS- 1893 – Earthquake Design Code.

In addition to above codes we have other codes too to take proper loading and to follow the steps
as per standard code recommendation. Engineers which are dealing with Analysis and Design of
Structures are known as Structural Design Engineers. They are professional in design both by
manual process and by software means. But there is a question that which method we must choose
while designing nowadays. It is not as easy as it looks to design a problem it needs mathematical
calculation and practice in that field. With this specialization one must have good hand on
numerical calculation and must have good experience as well.

1.2 OBJECTIVE OF THE RESEARCH:

The main approach of this research is to test the basic assumptions that others in the field have
used. It is quite possible for an assumption to become accepted fact simply because several authors
have stated or cited the same idea, even though it has never been systematically tested or proven.
I got the opportunity to find such an untested assumption and can think of a way to test it, then my
work can be of great value to the field (provided it is well executed)
Technology is growing nowadays with an alarming rate. It is necessary for every individual to get
know about latest technologies as they make life easier from time to time. Great scientist’s and
creative work force are involved in the process of making changes in technologies and to make
complex things easy as much as possible.
With this research I will get to know about latest technologies and will compare some
results how much difference is being acquired and how much accurate is the result given by
technologies used in our field. The points which will be taken into consideration while going
through the research are listed below:
• Modelling and analysis of G+14 R.C. framed structure by the use of ETABS and to detail
the process using various design code algorithms for concrete member selection.
• To assign a suitable cross section which will resist load as well as fulfill some design
requirements such as economy and serviceability.
• Comparison of results obtained in terms of storey drift, displacement, base shear, stresses
and deflection in the portion of building with flat slab and the portion of building with
grid slab and finally verifying the results.

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1.2.1 LEARNING OUTCOME
With this research I am now familiar with various Software, which can be now added to my
technical skills. Now onwards I can be able to perform various projects whether it may be
building or any other structure. Things were very tough for me till date as I have solved various
problems in my college level but while going through this, I found it don’t need much efforts to
design or analyse a structure. Models can be easily created using objects and can understand the
concepts when editing and creating complex models.
You will be able to recognize story levels and be able to input building data in a logical and easy
manner. You will be a productive, innovative, and communicative engineer, with an ability to work
with people spanning different disciplines. You will create only one model of the floor systems
and the vertical and lateral framing systems to be able to analyse and design the entire building due
to the integrated system of ETABS. You can keep your design data and design intellectual property
in graphics, tabular form or send it to a printer or export it to a database file or even save it as an
ASCII file and manage them in a safe, centralized place. You can let your team collaborate with
you at any stage of product development.

Many design companies use these Software for their project design purposes. So, this project
mainly deals with the comparative analysis of the results obtained from the design of a multi storey
building structure when designed using ETABS Software separately. For first case, structure is
modelled using ETABS Software. The height of each storey is taken as 3m. Analysis and design
of the structure is done and then the results generated by these Software are compared and a
conclusion is drawn from them.

1.2.2 ESTABLISH RESEARCH PRIORITIES

The structure needs to be designed based on some priorities which can be achieved based on some
facts and standard codes. The codes give us detailed knowledge about loading and some
recommendations. The design performed which will not consider SI recommendation’s will be
considered dead end and will be not be considered as serviceable and durability. Some values are
considered on the basis of different topography, site conditions and locations. Design codes are
assigned according to the location. Every country has its own design codes. These codes are drafted
based on knowledge collected from previous data.

This research considered all the values which must consider based on the functionality of
the structure. The values are taken from design codes and then analysis is done. After completion

12
of analysis design is prepared by making some assumptions. The assumptions which are made are
mentioned below:

- Material is homogenous all over the member.

- All the structural elements are considered monolithic.
- Concrete will resist compression force and steel will resist tension.
- Force applied is less than the load resisted by member.

1.3 OVERVIEW OF METHODOLOGY

The research consists of various values which are considered to know the fact which I was
searching for. The methodology must be well known and should be of practically applicable. So,
in this research I found it suitable to select ETABS for my fact-finding process as they are widely
used nowadays. Experts are available in case there is any need of assistance while having some
technical issue. The brief history of these two Software is given below:

In structural design and analysis various types of software uses like: -

▪ STAAD PRO

▪ ETABS

▪ SAP

▪ SAFE

▪ ANSYS

▪ STAAD PRO FOUNDATION

▪ STAAD PRO RCDC

Many design alternatives run in parallel with the cloud services of STAAD PRO and view the
results in clear side-by-side graphical comparisons. Design for high-seismic regions or everyday
conditions, using Finite Element analysis. Optimize BIM concrete and steel workflows with full
physical and surface integration.

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1.3.1 UNIT SYSTEM:

The user is permitted to input data and request output in almost all commonly used engineering
unit systems, including MKS, SI, and FPS. In the input file, the user can change units as many
times as needed. Mixing and matching of units of length and force from different unit systems is
also allowed. The unit of input angle (or rotation) is degrees. However, in the JOINT
DISPLACEMENT output, the rotations are provided in radians. The program defines the units for
all output clearly.

The Geometry of Structure and Coordinate Systems: "A structure is an assembly of individual
components such as beams, columns, slabs, plates, etc. In ETABS frame elements and platform
elements can be used to model structural components. Typically, structure geometry modeling
consists of two steps: a. identification and description of joints and nodes.

Generally, the term MEMBER refers to frame elements and the term ELEMENT refers used to
refer to plate / shell elements. MEMBER's connectivity may be provided by the MEMBER
INCIDENCE command, while ELEMENT's connectivity may be provided by the ELEMENT
INCIDENCE command. ETAB is one of the software discussed above in which we can find results
whatever we need. We can make changes in the structure easily so that the project will meet needs
according to objective of research.

1.3.2 OVERVIEW OF ETABS

The innovative and revolutionary new ETABS is the ultimate integrated software package for the
structural analysis and design of buildings. Incorporating 40 years of continuous research and
development, this latest ETABS offers unmatched 3D object-based modelling and visualization
tools, blazingly fast linear and nonlinear analytical power, sophisticated and comprehensive design
capabilities for a wide-range of materials, and insightful graphic displays, reports, and schematic
drawings that allow users to quickly and easily decipher and understand analysis and design results.
From the start of design conception through the production of schematic drawings, ETABS
integrates every aspect of the engineering design process. Creation of models has never been easier
- intuitive drawing commands allow for the rapid generation of floor and elevation framing. CAD
drawings can be converted directly into ETABS models or used as templates onto which ETABS
objects may be overlaid. The state-of-the-art SAP Fire 64-bit solver allows extremely large and

14
complex models to be rapidly analysed and supports nonlinear modelling techniques such as
construction sequencing and time effects (e.g., creep and shrinkage).

The structural analysis software plays an important role to carry out the seismic calculation for the
infrastructures. In this modern period of time, where computer has reached every phase of life,
using the traditional book system for analytical development of the students, which is no doubt
necessary, is no longer sufficient. Moreover, construction and design has become so much
competitive in this world that using computers became mandatory. In this chapter, an introduction
to the structural analysis software ETABS has been presented.

This Research introduces you to ETABS Version 8. The step-by-step instructions guide to you
through development of your first model. The intent is to demonstrate the fundamentals and to
show how quickly and easily a model can be created using this program. ETABS is an extremely
versatile and powerful program with many features and functions. This manual does not attempt
to fully document all of those features and functions. Rather, we briefly show how to work with
the program, providing some commentary along the way. To grasp the full value of ETABS, you
should use this introductory manual in conjunction with the other ETABS documentation, such as
the graphical user interface reference manual and the steel, concrete, shear wall, and composite
floor design manuals. It is the first step in changing the way you work, for the better.

ETABS is a stand-alone finite-element-based structural analysis program with special purpose

features for structural design and analysis of building systems. Embedded beneath the simple,
intuitive user interface are very powerful numerical methods, design procedures and international
design codes that allow you to be versatile and productive, whether you are designing a simple 2-
dimensional frame or performing a dynamic base isolation analysis of a complex high-rise.

1.3.2.1 FUNDAMENTAL CONCEPTS

ETABS works off of an integrated database. The basic concept is that you create only one model
consisting of the floor systems and the vertical and lateral framing systems to analyse and design
the whole building. Everything you need is integrated into one versatile analysis and design system
with one user interface. There are no external modules to maintain and no worries about data
transfer between modules. The effects on one part of the structure from changes in another part are
instantaneous and automatic.

15
ETABS is a refined and convenient special purpose analysis and design program developed
especially for building systems. With its integrated system and the ability to handle the largest and
most complex building model’s configuration, it assures:

• Powerful CAD-like drawing tools in a graphical and object-based interface.

• Increased productivity of structural engineers in the building industry.
• Significant savings in time and efficiency over general purpose programs.

ETABS can help you convert your ideas into product designs quickly and effectively. It enhances
your ability to learn the geometry of building systems. In ETABS, model creation and reporting of
results are accomplished at the object level. It enables the designer to focus on macroscopic
performance targets. ETABS is well equipped to handle simplified lateral procedures, Push-over
analysis, Response Spectrum Analysis and Response History Analysis. The data output options are
much more conducive to lateral design in special purpose software like ETABS. ETABS can also
be utilized for handling large scale seismic projects including those that involve Non-Linear
Modelling. It comes with libraries of various pre-built or pre-designed code-dependent
formulations so that the user does not have to re-define basic parameters depending on the
conditions.

1.3.2.2 FEATURES OF ETABS

It is more updated with latest version of ETABS of 2015. Hence revisions in Codal provisions
and developments are incorporated every version. STAAD Pro on the other hand has its latest
version in 2008.With that said, minor improvements are made every version. CSI, the company
of ETABS is in close association & touch with NICEE, IIT Roorkee and other IITs. Hence field
and lab observations are incorporated in ETABS. Design processor of ETABS is improved in
every way possible, like in beams. (This was said by Prof Yogendra Singh, IIT Roorkee). So
especially when Indian IS codes are used, enhanced efficiency is obtained.

STAAD Pro always gives higher demand for steel reinforcement. (Which sometimes is illogical
and when checked manually proves to be excessive). This is why reputed structural consultants in
Delhi, Blore, Mumbai moved to ETABS long ago, in addition to reasons mentioned above. eg.
Vintech consultants, Delhi who designs many buildings of DLF, Jaypee used ETABS in its office.
Also, they do this after proving the credibility of ETABS by manual calculations.

ETABS is used in structural design of Burj Khalifa, Taipei 101 and many other prominent high
rises. Hence credibility. SOM, world’s leading consultant who also design Burj Khalifa, China TV

16
tower mostly uses ETABS. Also, most local Gulf/Middle east consultants use ETABS too. For
Burj Khalifa, read paper by the designer William Baker, SOM- ETABS have robust feature of
pushover/P-delta analysis and time history analysis. IIT Guwahati is providing PhD degrees
basically on Pushover designs using ETABS. Hence the vastness of the software. Newer versions
of ETABS has detailing provisions. E.g. as per SP 34. As we know detailing takes time and sucks.
But ETABS does it post analysis and design and generates detailing drawings too. Awesome right!
(Could be a bane to Draftsmen\U0001f62c) Once you correctly define materials in ETABS, things
are taken care in the modelling process. Like ETABS automatically takes care of dead load. You
have to assign dead loads manually in STAAD Pro. If you seriously want to be strong in your
analytical skills, read the book written by the man behind ETABS- Ed Wilson "Three Dimensional
Static and Dynamic Analysis of Structures" ETABS is basically product of University of
California, Berkeley. Credibility. ETABS is good over STAAD Pro if u designing a reinforced
concrete structure. The user interface is easy and the analysis values of RC structures are better
and we get economical steel data from ETABS compared to that of STAAD pro.

STAAD Pro is good over ETABS for the analysis of steel structures frames as the codes and user
ETABS and STAAD Pro both, I feel it's reliable for reinforced concrete design as it provides inbuilt
options for optimization, seismic analysis parameter calculations like p∆ analysis, It Even has
options for wind analysis with loaded codes and can consider gust loads. Few of the above options
are not available with STAAD Pro.

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 CHAPTER 2

2.1 LITERATURE REVIEW

Various literature has presented in the form of technical papers on grid slab. Various issues and
points are covered in the review paper like seismic analysis of grid slab building as per seismic
zones, storey displacement, storey drift and equivalent static and response spectrum method as per
different IS-codes. Some of those are discussed below:

Lalit Balhar et.al (2019): carried out the research on multi-storied RC slab buildings having flat
slabs & conventional RC slabs with and without shear walls. All modelling is done in STAAD
PRO software. For the analysis he was considering buildings of stories G+10. Building is subjected
to gravity and dynamic loads and seismic zone V is selected. Analysis is done by time history
analysis, response spectrum analysis, equivalent static analysis. From the analysis it has been
observed that the lateral displacement is increasing from bottom level to top level and storey drift
is minimum at bottom level and is increasing upto the middle stories and after that it will decreases
upto top level of building for all types of models [1]

Indrani V et. al (2018): It studies the Dynamic Analysis of Multistory RCC Building Frame with
Grid Slab and Flat Slab. It is revealed from the study that base shear of grid slab building is more
than the base shear of flat slab in building in both directions. Drift in grid slab building and flat
slab building is within limit in both X and Y-directions. Axial force in intermediate columns of
grid slab building is less as compared to flat slab building. Building drift in flat slab building is
more as compared to grid slab building in each story and in both X and Y-directions. Axial force
in end columns of flat slab building is less as compared to grid slab building [2]

Ashwini Waghule et.al (2018): Reviewed on bubble deck slab and concluded that the usage is
reduced by replacing the concrete by recycled plastic and reduces production of cement. Which
will help in reduction of global CO2 emissions. Hence this technology is environmentally green
and sustainable. Reducing material consumption made it possible to make the construction time
faster and reduces the overall cost of construction. By using this technology dead weight of slab is
reduced up to 18%. Foundation sizes become smaller due to the reduced dead weight. The Bubble
Deck configuration gives much improved shear capacity, flexural capacity and stiffness when the
same amount of reinforcement and the concrete is used as in the solid slab. Waste plastic material
18
is utilized in construction as it gives same strength or load carrying capacity as that of conventional
slab. This type of slab is advantageously utilized for longer spans halls such as auditorium and
theatre halls.[3]

Mohd Aasim Ahmed et.al (2018) Analysed that the Quantity of Concrete required for grid slab is
more than conventional slab followed by flat slab for shorter spans. The Quantity of Steel required
for grid slab is more than conventional slab followed by flat slab for shorter spans. As Span
increases the Quantity of steel required for a slab system increases. The Maximum Joint
Displacement (lateral sway) was found to be more for grid slab system followed by conventional
slab system and least for flat slab system. The Maximum Joint Displacement (downward
deflection) was found to be more for flat slab system followed by grid slab system and least for
conventional slab system. The Maximum Storey Drift was found to be least for flat slab followed
by conventional slab and more for grid slab system. The Maximum Column forces was found to
be more for grid slab followed by conventional slab and least for flat slab system. The Maximum
Column Moments was found to be more for grid slab followed by conventional slab and least for
flat slab system.[4]

S.V Mahamuni et.al (2018) has done the analysis of the various methods by which grid floor
system can be analysed. He has done the analysis of grid slab manually by using Plate theory,
Rankine-Grashoff method, Stiffness method. Used various approaches for analyzing the grid slab
system. For carrying out study, ratio of hall dimensions (L/B) from 1 to 1.5, halls having constant
width 10.00m are considered. After applying the theoretical formulas, he observed that by using
stiffness method, bending moment in x direction is increasing linearly by increasing L/B ratio. By
using Rankine-Grashoff method it will give the lowest values of bending moment in x direction,
which the lowest value among all the methods that is used in the analysis.[5]

Sumit Sharma et.al (2018) observed that thickness of the building having flat slab with shear
wall changes with the storey height. Flat slab provides more flexibility to the building as compare
to conventional slab. Flat slab also provides more stability and aesthetic view to the building. In
case of industrial structures constructed in a square and rectangular layout the displacement is
more in case of flat slab as compare to waffle system and displacement is increases with the
increases in the height of the building.[6]

R.S.More et.al (2015) has done analytical study of different types of flat slab subjected to
dynamic loading . Drift of flat plate is maximum than grid floor slab and flat slab. Grid slab has
19
less drift compared to others. He gives the result that all slabs deflect within the limit when strata
is of type one i.e. rock, or hard soil. There is definite correlation between increase in shear force
and storey drift with change in soil condition for particular type of slab. [7]

Ch. Rajkumar et.al (2017) analysed a multistoried building and observed that the results are
more conservative in Static analysis when compared with the dynamic analysis results in an
uneconomical structure. Overall stiffness of the building increases therefore the sway problem in
the structure reduces. As building is not regular the behaviour in x and y directions are not similar.
For earthquake load the story drift values in x and y direction is higher than the wind load. For
spectrum loads the storey shear is maximum in the top storey location. For top stories location the
twisting moment increases from top to bottom stories. The story shear and twist increases from
top to bottom storey for the bottom storey location and will be maximum for bottom storey. For
force in z direction the support reaction values are maximum. [8]

Anitha.K et.al (2017) has done the analysis of grid slab and Observed the influence of various
parameters on the economical spacing of the transverse beams in grid floor. The bending moment,
the shear force and the mid span deflection developed in grid floor beams have been predicted by
conventional and numerical methods and the results are compared. Area of steel required in the
slab at a critical section for column are determined and also for the middle strips. Span to depth
ratio 16 to 60 considered. The spacing of 0.5m to 2.0 m is used for transverse beams. the model is
made by ANSYS 12.0 software. For the optimum performance of grid floors range of the
magnitude of the various parameters to be considered in this paper.[9]

Avinash Patel et.al (2017) studied the behaviour of flat slab, grid slab and conventional slab
separately. A comparative study was done to know which slab system is best. For this he performed
the dynamic analysis of multi-storeyed building having flat slab, grid slab and conventional slab
separately. In all the systems, the storey drift is within the permissible limits according to the
IS:1893 (Part 1). Cost of grid slab system is more than the other slab systems. Storey drift in Flat
Slabs are least than the other slab systems. The quantity of concrete and steel in case of Grid Slab
system is huge when compared to Conventional Slabs or Flat Slabs. Flat Slabs resist the lateral
loading most effectively than grid slab or conventional slab. [10]

Sudhir Singh Bhaduria et.al (2017) have studied the Comparative Analysis and Design of
Conventional Slab System, Grid Slab System and Flat slab system. After the analysis, observed
that the flat slab structure is more economical than the other slab systems. The quantity of steel
and concrete required for grid slab system is maximum but for the flat slab system is minimum. In
20
case of grid slab system maximum bending moment, maximum displacement and maximum force
is found to be maximum. In flat slab system it is observed that the maximum bending moment,
maximum displacement and maximum force is minimum in all the direction. [11]

Harish M K. et .al (2017) Analysed G+4 having Grid Slab in Building by Using Response
Spectrum Method. The writer perform analysis for both seismic, gravity and wind force conditions
according to the IS codes. The grid slab system is analyzed by using ETABS software. Because of
the Box effect of modular type scheme, the overall stiffness of the building increasing due to this
the sway problem in the structure is reduced. For irregular building the behavior is not similar in
both directions x and y. For spectrum loads storey shear is maximum in the top stories location.
For bottom storey, storey shear will be maximum. The storey shear increases from top storey to
bottom storey for the bottom storey location. For earthquake load, storey drift values in x and y
direction is higher than the wind load.[12]

Mayuri S. Sethia et.al (2017): Compared to different types of Flat slab. Concrete and steel
required is less in Flat with Drop panel. Drops are important criteria in increasing the shear strength
of slab. For high rise structure, in order to increase rigidity of slab, column heads are incorporated.
Drop panel increase negative moment capacity of slab. It stiffens the slab and therefore reduces
deflection. Compared to different grids of grid Slab, Concrete and steel required is less in (1.5*2.0
m) grid panel. Rate of shuttering of grid slab is almost double the rate of Flat slab. Grid slab
requires special or proprietary formwork, due to which flat slab with drop is preferred.[13]

Avinash Patel et.al (2017): Analysed that in all the systems, the storey drift is within the
permissible limits as per IS:1893 (Part 1). However grid floor system show better results when
compared to other slab systems. When it is compared to Flat Slabs there is an increase of 163.57
% in the cost of Grid Slabs and increase of 45.97 % in the cost of Conventional slabs. This results
in a reduction of 66.12 % in the amount of storey drift in Flat Slabs. There is a huge increase in
the quantity of steel and concrete in Grid Slabs system when compared to Conventional Slabs or
Flat Slabs.It is because of the increase in the number of beams in the Grid Slabs system. In Flat
Slab system the lateral loading is most effectively resisted. Grid floor systems have longer service
life. Due to the earthquake hazards flat slabs with shear walls are provided. Variation of cost is
affected by the response reduction factor. Earthquake resisting techniques like base isolation,
shear walls can be used to increase the effectiveness of the structure.[14]

Uttam V Chothani et.al (2016) Analysed that the flat slab with drop is the most economical from
the economic point of view when it is compared to the rcc grid slab and flat slab without drop.
21
They considered the flat slab with drop and reinforced concrete flat slab, flat slab without drop.
The thickness of reinforced concrete flat slab are 22% and 32% greater respectively and its cost
are 25% and 27% greater respectively. The cost increases gradually if the panel sizes increases.
The pure reinforced concrete flat slab structural system is more flexible for horizontal loads than
the traditional RC frame structure which contributes to the increase of its exposure to seismic
effects. Flat slab with drop is more economical than flat slab without drop and grid slab. Concluded
that the Concrete required in grid slab is more as compared to flat slab without drop and flat slab
with drop.[15]

Chintha Santhosh et.al (2016): Analysed a Multistory Building with Grid Slab by Using ETABS
software. It is showed in the study that the maximum displacement is observed in flat slab with
drop compare to grid slab without and with infills in both zones. Maximum Time period of grid
slab is less in compare with flat slab without and with drop without and with infills structures in
zone IV. Deflection is observed more in zone IV than zone III. Storey drift values of different types
of buildings are within the permissible limit as per IS-1893-2002 code provision that is the 0.4%
of height the floor. Structures having infills have less time period compare to structure without
infills. Grid slab systems have maximum base shear in comparison with flat slab without and with
drop in zone III and IV.[16]

Salman I Khan et.al (2015) analyse the seismic performance of multi-storied buildings having
different floor heights and having different floor systems like Flat slabs, conventional solid slab-
beam systems and Grid slabs. The storey drift in building with flat slab construction was
significantly more as compared to conventional RCC building. The axial force in the intermediate
columns are more in case of flat slabs than grid slabs. Buildings having the flat slab system are
weaker in shear as compared to those with conventional or even grid slab systems. As a result,
additional moments were developed. Therefore, the columns of such buildings should be designed
by considering additional moments caused by the drift. The base shear of a multi-storey structure
with grid slab is more as compared to flat slab.[17]

Mohana H.S et.al (2015) studied the Comparative Study of Conventional Slab and Flat Slab
Structure Using ETABS for the Different Earthquake Zones of India . In this paper he observed
that the storey shear of flat slab is 5% more than that of conventional grid-slab structure. The axial
forces on flats slab building is nearly 6% more than conventional building. The difference in storey
displacement of conventional building and flat building are about 4mm in each floor. Storey shear
22
intensities, displacement, axial force are the parameters that increases with the increase of seismic
level.[18]

Amit A. Sathawane et.al (2012) Analysed that the drops are important criteria in increasing the
shear strength of the slab and increase resistance to punching failure at the junction of concrete
slab and column. By introduction of heads in slab, rigidity of slab increases. Steel required in Flat
slab without Drop is more as compared to Flat slab with Drop and Grid slab. Concrete required in
Grid slab system is more when it is compared to the Flat slab with Drop and Flat slab without
Drop. Flat slab with drop is more economical than flat slab without drop and grid slab. Rate of
flat slab system with drop was found to be more economical than the flat slab without drop and
grid slab [19]

R.Arvind et.al : This paper deals with voided slabs using U-boot beton technology made by
recycled polypropylene, the technology is designs for lightweight slabs in RCC. It is solution to
build slabs of large spans with more bearing capacity. U-Boot its lightweight, stability, modularity,
can be used to make structures without mechanical helps of equipment and it’s also foundation
rafters can be created with a low amount of concrete with big thickness. By using U-boot beton, it
is easy to build raft foundations with a low quantity of concrete. It is used in high rise buildings to
reduce the weight of the structure. It reduces the construction time and also requires less labours.
It has high fire resistance and it’s economical. Higher number of floors can be built. The u- boot
beton is so economical, efficient, Fire resistance, and Eco friendly. Thus, the result gives a clear
view of u-boot beton that is very useful for construction purpose.[20]

23
 CHAPTER 3
APPROACH AND METHODOLOGY

3.1 STRUCTURAL DESIGNING

Structural engineers have proper technical knowledge for structural detailing and their analysis.
So, they are more experienced to design structures. The structural designing procedures carried out
by the structural engineers include calculating the loads and the stresses acting on the building,
analysis results for the applied loading, design of sections of structures to sustain the loads,
so that the structure designed will withstand the loads predicted safely.
The structural engineers are also involved in the selection of materials best suited for the structure.
This will hence ask for good knowledge about the different materials that are used in the
construction at the current condition like their economic factors, strength factors and durability
factors.
The quality factors of different building materials can be analysed by a structural engineer to
finalize their suitability in the design of the beams, columns or the foundations.
Another skill of a structural designer is the analysis of structures. This is presently carried out by
the software like ETABS, STAAD PRO, SAP etc. As years pass new software are being developed
for the analysis of structures at different conditions of loads like wind, earthquake etc.
Most of the structural engineers have to study and work with this software with a knowledge of
both the technical details and the programming details. In some organizations, the analysis is
carried out by a programmer who may not have the civil engineering graduation but is assisted by
a structural engineer.

Whatever be the mode of analysis done, the structural engineer must have the ability to understand
and interpret the results from the software to know the validity of the values provided as output.
Some organization won’t completely rely on the computer results, they conduct a separate man-
made calculation for assurance.
Even though structural engineers are the ones that bring and develop the design ideas and detail,
he can only see it happen on the site only if the structure is constructed as desired. For this
interpretation and ideas have to conveyed with the other members of the projects.

The structural engineer has to make coordination and consult other members like the site engineers,
other design engineers, geotechnical engineers, landscape architects, architects, project managers
24
etc. Proper knowledge helps in spreading correct information among the group avoiding confusion
and errors.

3.2 WORKING TIME AND LOCATION OF A STRUCTURAL ENGINEER

When looking into the working time and the place spent by the structural engineers, most of the
highly involved structural engineers will be working in office as well as on the construction sites.

They can work by splitting the time between both the contexts. The locations of work vary based
on the working environments. Rural or metropolitan areas have different working schedules and
environment.

The structural engineers may have to work for long hours sometimes similar to site engineers,
which mainly depend on the size of the project and the size of the organization. If the structure of
the organization is well defined and large, it will have sufficient members for the design team,
planning team, execution team with a group of professionals, skilled as well as semi-skilled
employees and workers. This will reduce some burden on the structural engineer.

3.3 ROLES AND RESPONSIBILITIES OF STRUCTURAL DESIGN

ENGINEERS IN CONSTRUCTION

A strong knowledge of physics, creative problem solving and three-dimensional conceptual skill
must be gained by a structural engineer. Other than these, the roles and the responsibilities of the
structural engineer includes:
• Structural Designing
• Site and Work Investigations
• Communication

Adequate Training is required for a Structural Engineer to make him technically sound so that he
can solve complex problems, find solutions of various problems and can make efforts to rectify
errors as much as possible. The structural model is composed of framed structure, with beams and
columns being monolithically considered.

3.4 DESCRIPTION OF MODEL TYPE

The model consists of RCC frame with concrete as a base material. This project mainly consists of
Grid Slab and Flat slab in building at each level. Flat slab is being used at front portion of building
to make beamless area for aesthetic purpose whereas inner side of building is having grid slab to
25
resist loads easily and to increase rigidity of the structure. This consideration of both flat slab and
grid slab helps us to minimize use of closely spaced columns. The various parameters taken for
analysis and design process are mentioned below:

Fig3.1: Isometric view of structure.

No of Floors = G+14

Height of each Floor = 3m

Beam Size = 300 mm X 250 mm

Column Size’s taken = 500mm X 400mm, 350mmX300mm, 450mmX350mm

and 550mmX500mm.

Flat Slab Thickness = 150 mm

Grid Slab Thickness (Waffle Slab) = 450 (Overall)

Live load on each floor = 3 KN/M2

26
Load due to Floor Finish = 0.75 KN/M2

Type of Soil = Medium

Zone = III

Grade of Concrete used = M25

Grade of Steel = Fe-415

Fig 3.2: 3D Rendered view of building.

The structure composes of both flat and grid slabs. Above diagram makes it clear by showing
rendered view of structure. When slabs are used without beams, they are called flat slabs. That
means load coming on slab is resisted by slabs itself but not transferred to beams. In case of flat
slab load is directly transferred from slab to columns. In this configuration of slabs, load is not
distributed in one way or two way phenomenon. Drop panels were used to prevent the structure
from punching failure.

The Plan decided to complete this research was of greater importance. So, accordingly I chose a
Plan which can fulfil all the requirement’s in the whole analysis process. The Plan taken for
modelling of a building is shown below:

27
 Fig 3.3: AutoCAD file showing PLAN of Structure.

3.5 LOADING

Consideration of loading is the main aspect which must be taken very carefully as the Analysis and
Design Process is based on loading conditions. The various codes to finalize the magnitude of
loading are mentioned below:

IS-875 (Part 1) ________ Design Code for Dead Loads.

IS-875 (Part 2) ________ Design Code for Live Loads.

IS-875 (Part 3) ________ Wind Load Design Code.

IS-456 :2000 _________ Concrete Design Code.

IS -800: 2007 __________ Steel Design Code.

IS-10262: 2009 ________ Mix Design Code.

IS-1893: 2002 _________ Earthquake Design Code.

28
 Fig 3.4: Plan of Structure
Above figure shows the plan view of structure labelled with waffle slab and flat slab.

Loads are the main parameters which we must consider while designing to make the final project
such that it can resist all loading. The loads variety according to the function of the structure. The
residential buildings are considered in general structures whereas institutional or commercial
buildings are considered in important structures. The load distribution is same in case of residential
and commercial structures as the building blocks are of same properties and mechanism but there
is variation in amount of material used only. The loads are distributed from slab to beams. The
slabs may distribute load in two ways that is either by one-way distribution or two-way distribution.

In case of one-way distribution, the load is transferred to longer span beams and shorter
span beams experience minimum loading which is neglected in calculation process. A slab is said
to be One-way slab when the ratio of longer span to shorter span is greater than 2 whereas a slab
is said to be Two-Way when the ratio of longer span to shorter span is less or equal to 2.

After the transfer of loads from slab to adjacent beams, the load is transferred to columns and then
finally to foundation.

29
 CHAPTER 4

ANALYSIS AND DESIGN RESULT FROM ETABS.

4.1 STRUCTURE DATA

This chapter provides model geometry information, including items such as story levels, point
coordinates, and element connectivity.

4.1.1 Story Data

Table 4.1 - Story Data

Height Elevation Master Similar Splice
Name
Mm mm Story To Story
Story15 3000 45000 Yes None No
Story14 3000 42000 No Story15 No
Story13 3000 39000 No Story15 No
Story12 3000 36000 No Story15 No
Story11 3000 33000 No Story15 No
Story10 3000 30000 No Story15 No
Story9 3000 27000 No Story15 No
Story8 3000 24000 No Story15 No
Story7 3000 21000 No Story15 No
Story6 3000 18000 No Story15 No
Story5 3000 15000 No Story15 No
Story4 3000 12000 No Story15 No
Story3 3000 9000 No Story15 No
Story2 3000 6000 No Story15 No
Story1 3000 3000 No Story15 No
Base 0 0 No None No

4.1.2 Loads

This chapter provides loading information as applied to the model.

4.1.2.1 Load Patterns

Table 4.2 - Load Patterns

Self Weight
Name Type Auto Load
Multiplier
Dead Dead 1
Live Live 0
30
 Self Weight
Name Type Auto Load
Multiplier
Superimposed
Masonry 0
Dead
Ex Seismic 0 IS1893 2002
Ey Seismic 0 IS1893 2002

Fig 4.1(a): Earthquake loading along-X Fig 4.1(b): Earthquake loading along-Y

The lateral loads considered for this structure in shown by two graphs above. Intensity of
earthquake depends on the zone in which building is located. The consideration of earthquake zone
for this building is zone III and location for the construction site is Lucknow UP, India. Earthquake
loading is the main cause of building failure in earthquake prone areas. So, to make building
earthquake resistant we consider earthquake loading while analysing a structure. Dynamic analysis
is the main consideration if building is of 5 or more than 5 stories.

4.1.3 Functions

4.1.3.1 Response Spectrum Functions

Table 4.3 - Response Spectrum Function - IS 1893:2002

Period Accelerat
Name Damping Z Soil Type
sec ion
Responce
0 0.36 5 0.36 III
Spectrum
Responce
0.1 0.9
Spectrum
31
 Period Accelerat
Name Damping Z Soil Type
sec ion
Responce
0.67 0.9
Spectrum
Responce
0.8 0.7515
Spectrum
Responce
1 0.6012
Spectrum
Responce
1.2 0.501
Spectrum
Responce
1.4 0.429429
Spectrum
Responce
1.6 0.37575
Spectrum
Responce
1.8 0.334
Spectrum
Responce
2 0.3006
Spectrum
Responce
2.5 0.24048
Spectrum
Responce
3 0.2004
Spectrum
Responce
3.5 0.171771
Spectrum
Responce
4 0.1503
Spectrum
Responce
4.5 0.1503
Spectrum
Responce
5 0.1503
Spectrum
Responce
5.5 0.1503
Spectrum
Responce
6 0.1503
Spectrum
Responce
6.5 0.1503
Spectrum
Responce
7 0.1503
Spectrum
Responce
7.5 0.1503
Spectrum
Responce
8 0.1503
Spectrum
Responce
8.5 0.1503
Spectrum
Responce
9 0.1503
Spectrum

32
 Period Accelerat
Name Damping Z Soil Type
sec ion
Responce
9.5 0.1503
Spectrum
Responce
10 0.1503
Spectrum

4.1.2.3 Load Cases

Table 4.4 - Load Cases - Summary
Name Type
Dead Linear Static
Live Linear Static
RS Response Spectrum
Masonry Linear Static
Ex Linear Static
Ey Linear Static

4.2 ANALYSIS RESULT

4.2.1 Bending Moment

Two figures shown below gives the bending moment of whole structure along two axes. Bending
moment gives the idea about how much reinforcement is required for a section to resist external
loading. Below shown diagrams are the calculation of bending moment on design combination 16.
Bending moment goes on increasing as we move from top to bottom. This makes it clear that area
of reinforcement requirement for below members will be more as compared to top members.

It is also found that bending moment will be greater at grid slabs and lesser at flat slabs
as there are no beams. So, in this case reinforcement provided will be greater in the region of grid
slabs as compared to flat slabs.

33
 (a) Along 2-2 axes (b) Along 3-3 axes.

Fig 4.2: Bending Moment Diagram.

4.2.2 Shear Force Diagram:

This force is the algebraic sum of vertical forces at a section. Shear force at a section gives idea
about the provision of shear reinforcement to prevent cracking.

Fig 4.3: Shear Force on 3-3 axis. Fig 4.4: Shear Force on 2-2 axis

34
4.2.3 Displacement

Displacement is due to external loads, in this project maximum displacement takes place in the
area where there are flat slabs. Some pictorial representation showing displacement due to dead
load in slabs are shown below:

Fig 4.5: Deformation in Building

It is found that max displacement in slabs reach up to 240X10-3 mm shown in red zone. It can be
clearly depicted that flat slabs experience maximum displacement as compared to grid slabs.

35
4.2.4: Stress in slab

Image showing Stress due

to Brick masonry on slab. Max. Stress due to
Brick Masonry.

Flat slab with no

Brick Masonry.

Fig 4.6: Comparison in stress between in the area of flat and waffle slab.

Some green spots can be seen near columns showing less stress in slabs near columns.
Stress analysis in slabs was broadly checked to know the different nature of flat and grid
slabs. Above pictures show stress at top storey.

Fig 4.7 Stress Diagram

Picture showing Stress levels in each zone of slab. Slabs are shown apart to make it
clear. This is the stress diagram of visible face.

36
 Fig 4.8 : Stress in Flat Slab and Grid Slab.

Above picture shows that magnitude of stress is less in grid slabs as compared to flat
slabs. Above panels are waffle slabs and below panels are showing flat slabs. It can be
seen that purple color is spread more in the area of flat slabs. As per scale shown below
picture purple color shows region with greater stress whereas blue color shows less
stress. Here it is clear that stress will be maximum at mid span of slab. Slab portion near
columns experience less stress shown by yellow color. Above portion in slab shows
color between red and orange while as bottom portion shows maximum area with purple
color. But stress at column looks same in both the cases.

4.2.5: Storey Displacement

Displacement is calculated for each member of building including beams, columns and
slabs. The results are taken to know effect at each load combination. It is necessary to
check storey displacement to know if it found under limit. Below graph shows the storey
displacement. Here maximum displacement occurs on top storey with magnitude of less
than 13.5X10-3mm and displacement on base is zero. Red line shows displacement along

37
Y-axes whereas blue line shows displacement along x-axes. As there is large span along
X-axis that is why stiffness of building is greater in this direction. And it clear that
displacement along Y direction will be maximum because of small span.

Fig 4.9 : Storey Displacement.

4.2.6 Story Response - Maximum Story Displacement

This is story response output for a specified range of stories and a selected load case or
load combination.

Input Data

Name StoryResp1
Display Type Max story displ Story Range All Stories
Modal Case Modal Top Story Story15
Mode Number 1 Bottom Story Base

38
 Fig 4.10: Storey Displacement (Response Spectrum)

Tabulated Plot Coordinates

Table 4.5 : Story Response Values

Story Elevation Location X-Dir Y-Dir
m mm mm
Story15 45 Top 2.65E-07 0.01
Story14 42 Top 4.657E-07 0.01
Story13 39 Top 3.924E-07 0.01
Story12 36 Top 3.824E-07 0.009
Story11 33 Top 3.716E-07 0.009
Story10 30 Top 3.588E-07 0.008
Story9 27 Top 3.444E-07 0.008
Story8 24 Top 3.285E-07 0.007
Story7 21 Top 3.112E-07 0.006
Story6 18 Top 2.926E-07 0.005
Story5 15 Top 2.728E-07 0.005
Story4 12 Top 2.532E-07 0.004
Story3 9 Top 2.25E-07 0.003
Story2 6 Top 2.893E-07 0.002
Story1 3 Top 2.083E-06 0.001
Base 0 Top 0 0

39
4.2.7 Storey drift:

The resultant drift in two adjacent storey define storey drift. Below graph makes it clear
to know the condition of the building for storey drift due to external loading.

Fig 4.11: Maximum Storey Drift Fig 4.12: Storey drift due to Response
. Spectrum

It is found that Storey drift along X-axis is minimum as compared to Y -axis because
displacement along y axis is greater than the displacement along x-axis. It mainly depends
on orientation of building. If building is symmetrical along both the axes then there will
be same drift along both the axes.

4.2.8: Storey Shear

Shear is the resultant force at a point. Below graph shows along X axes and Y axes. Graph
“A” shows Shear due to earthquake along X axes. This graph makes it clear that shear
due to earthquake along x-axes will be maximum as loading will be in that direction and
shear will be zero along y direction in this case as shown clearly in graph. In addition to
this it can be found that shear will be maximum always at base as magnitude of earthquake
increases from top to bottom. It will be minimum at top of structure.

40
Fig 4.13(A): Storey Shear due to EQ-X Fig 4.13(B): Storey Shear due to EQ-Y

Similarly red line in figure “B “ shows shear on consecutive storey’s due to earthquake
loading along Y-axis.

4.2.9 Storey Stiffness

This is the reaction of storeys towards force being exerted on it. Storey stiffness defines
the amount of force that will lead to failure along and the resistance of storey to counter
act that critical load.The values of story stiffness are tabulated below.

Table 4.6 - Story Stiffness

Stiffness Stiffness
Load Shear X Drift X Shear Y Drift Y
Story X Y
Case kN mm kN mm
kN/m kN/m
721882.36 544208.82
Story15 RS 1004.0369 1.391 947.9339 1.742
9 4
775453.72
Story14 RS 1844.3391 2.378 1719.6557 2.866 599929.85
5
815749.59 631996.22
Story13 RS 2460.4419 3.016 2263.0174 3.581
5 3
1095415.3
Story12 RS 2930.011 2.675 2672.1854 3.242 824277.67
17
1083902.2 804669.89
Story11 RS 3350.2201 3.091 3044.0616 3.783
59 5
1114596.9 840762.29
Story10 RS 3707.4804 3.326 3360.5014 3.997
72 3
1212488.7 914132.32
Story9 RS 4024.0344 3.319 3641.5952 3.984
14 4

41
 Stiffness Stiffness
Load Shear X Drift X Shear Y Drift Y
Story X Y
Case kN mm kN mm
kN/m kN/m
1308982.4 1044004.3
Story8 RS 4332.7138 3.31 3917.5974 3.752
17 85
1455746.3 1244486.7
Story7 RS 4641.682 3.189 4195.4063 3.371
98 82
1390720.6 1103201.9
Story6 RS 4945.3359 3.556 4470.6671 4.052
06 2
1418400.2 1131839.1
Story5 RS 5239.1512 3.694 4732.1099 4.181
21 93
1514311.9
Story4 RS 5548.8036 3.664 5016.8718 4.133 1214000.8
4
1706963.1 1490248.4
Story3 RS 5861.3737 3.434 5314.2148 3.566
41 06
1868583.8 1613519.9
Story2 RS 6115.5485 3.273 5562.435 3.447
76 61
1683823.0 1456903.3
Story1 RS 6229.1227 3.699 5674.747 3.895
41 14
665411.10
Story15 Ex 750.1542 1.127 0.0338 0.071 0
7
733841.14
Story14 Ex 1422.3534 1.938 0.0705 0.147 0
2
782225.60
Story13 Ex 2005.1942 2.563 0.1083 0.179 0
7
1056634.2
Story12 Ex 2508.1534 2.374 0.1471 0.235 0
69
1049236.2
Story11 Ex 2936.3259 2.799 0.1862 0.225 0
76
1081559.3
Story10 Ex 3293.4478 3.045 0.2259 0.272 0
15
1186607.8
Story9 Ex 3587.4915 3.023 0.2652 0.158 0
86
1334464.2
Story8 Ex 3825.2535 2.867 0.3045 0.043 0
3
1455740.1
Story7 Ex 4013.537 2.757 0.345 0.116 0
49
1350816.4
Story6 Ex 4156.7912 3.077 0.3862 0.185 0
23
1378005.0
Story5 Ex 4260.565 3.092 0.4267 0.21 0
21
1475835.2
Story4 Ex 4332.6516 2.936 0.4644 0.128 0
52
1759977.3
Story3 Ex 4379.648 2.488 0.4982 0.01 0
68
1868481.0
Story2 Ex 4407.8467 2.359 0.5288 0.066 0
27

42
 Stiffness Stiffness
Load Shear X Drift X Shear Y Drift Y
Story X Y
Case kN mm kN mm
kN/m kN/m
1678947.9
Story1 Ex 4421.4889 2.633 0.5474 0.046 0
61
494706.03
Story15 Ey 0.031 0.005 0 671.0183 1.356
6
573323.32
Story14 Ey 0.064 0.007 0 1272.9651 2.22
6
616266.24
Story13 Ey 0.0973 0.017 0 1795.5261 2.914
9
820475.44
Story12 Ey 0.1309 0.016 0 2247.074 2.739
7
Story11 Ey 0.1644 0.026 0 2632.1143 3.268 805510.02
844029.56
Story10 Ey 0.199 0.024 0 2953.8462 3.5
4
917100.67
Story9 Ey 0.2337 0.024 0 3219.3066 3.51
7
1047654.6
Story8 Ey 0.2683 0.071 0 3434.4789 3.278
19
1246482.4
Story7 Ey 0.3052 0.048 0 3605.5769 2.893
37
1100712.2
Story6 Ey 0.3425 0.022 0 3736.7427 3.395
46
1131821.8
Story5 Ey 0.3788 0.023 0 3832.4851 3.386
05
1201513.4
Story4 Ey 0.4129 0.042 0 3899.6672 3.246
1
1488117.2
Story3 Ey 0.4441 0.026 0 3943.9524 2.65
25
1610494.4
Story2 Ey 0.4718 0.024 0 3971.2203 2.466
36
1446160.3
Story1 Ey 0.4887 0.02 0 3984.9021 2.756
33

43
 Fig 4.14:Storey Stiffness by Response Spectrum.

It can be interpreted from above graph that story stiffness values are minimum along Y
direction whereas it is found maximum in X direction. This is the configuration of
building, longer span shows greater value for stiffness whereas shorter span shows
minimum magnitude for stiffness. The above graph depicts values on Response spectrum.

4.2.10 Story Overturning Moment:

When the building is subjected to earthquake forces then there leads to shear at base and
overturning moment which is due to inertia of building. These are considered for design
of building with eathquake loading. It is found from graph below that overturning moment
is maximum at base and goes on decreasing when we move upwards. Similarly shear is
also found maximum at base and minimum at top.

Table 4.7 - Base Reactions

Load
FX FY FZ MX MY MZ X Y Z
Case/C
kN kN kN kN-m kN-m kN-m m m m
ombo
-
119123. 3028737 -
Dead 0 0 2.046E- 0 0 0
6812 .4458 2721819
06
48652.4 1216512 -
Live 0 0 0 0 0 0
391 .5711 1111755
5933.64 5354.60 143804. 161641. 194604.
RS Max 0 0 0 0
5 95 3093 6492 3748
44
 Load
FX FY FZ MX MY MZ X Y Z
Case/C
kN kN kN kN-m kN-m kN-m m m m
ombo
- -
Masonr 41902.3 1149466
0 0 957888. 3.819E- 0 0 0
y 8 .0882
4068 06
-
- 3.843E- 107766.
Ex 0 0 144314. 0 0 0
4160.32 06 5797
118
- -
128273.
Ey 0 3697.89 0 0 84514.0 0 0 0
5301
83 094
DSlbU1 8900.46 8031.91 107211. 2941570 - 291906.
0 0 0
6 Max 75 42 3131 .1652 2207174 5621
- - -
DSlbU1 107211. 2510157 -
8900.46 8031.91 291906. 0 0 0
6 Min 313 .2372 2692099
75 42 5621
DCon16 8900.46 8031.91 241539. 6483011 - 291906.
0 0 0
Max 75 42 0918 .7649 5277098 5621
- - -
DCon16 241539. 6051598 -
8900.46 8031.91 291906. 0 0 0
Min 0917 .8369 5762023
75 42 5622

Fig 4.15: Story Overturning Moment.

45
4.3 DESIGN RESULTS

Design results are taken after completion of analysis process. Analysis gives idea of
reaction of building members towards applied load and gives the values at different
sections. Design inturn is the selection of member sections to resist load coming on it and
the amount of reinforcement needed to counteract bending moment and shear force
generated at a section. The main aim of all the process of loading and analysis is done to
get an idea about selection of cross section and amount of reinforcement provided.

To get sections and reinforcement data is the final stage of design of a structure
so that drawings can be created which is then implemented for construction.In this project
there were some iterations to get best cross section for beams and columns so that they
can resist loading without failure. It can be seen from pictures that there are some red
lines which shows failed members. We know that as we go from top to bottom the section
of columns goes on increasing because axial forces on columns increase as we go
downwards. Similarly section of beams are found larger in interior beams as compared to
outer beams.

RED LINES
SHOWING
FAILED
MEMBERS.

Fig 4.16: First Iteration. Fig 4.17: Second Iteration

46
 RED LINES
ALMOST
FINISHED.

Fig 4.18: Third Iteration. Fig 4.19: Fourth Iteration.

ALL MEMBERS
PASSED.

Fig 4.20: Final Iteration

In first iteration it can be seen that there are number of red lines showing failed members
and we have red lines at bottom sides as top members are passing for assigned cross
section. After changing cross section for failed members in second iteration some
members get passed but all members do not take this section as final cross section. It is
observed from these iterations that we keep on passing members whether it may be beams

47
or columns. In case of beams outer beams are passing first and then interior beams
because practically load is found maximum on interior beams that is why they need bigger
cross section as compared to outer beams.

Fig 4.21: Reinforcement data in beams and columns.

In case of columns top columns pass for design and then bottom columns. This
process of changing cross section after back to back analysis help us to know the
minimum cross section which we can provide and this helps to make economical cross
section. In final stage a message prompt that “All concrete frames passed the design
check”. Area of reinforcement in case of slabs for top floor only was taken from four
strips of grid slab and four strips of flat slab to make comparison of change in area of
reinforcement for both the cases. Following is the diagrammatic representation showing
area of reinforcement.

48
 GRID SLABS

FLAT SLABS

Fig 4.22: Diagrammatic representation of Reinforcement in Top Slab.

Table 4.8 : Area of Reinforcement at mid span of slab.

0 0 0 0

535.4mm2 524.48mm2 523.22mm2 529.95mm2

0 6.73mm2 6.54mm2 0

499.56mm2 498.22mm2 506.25mm2 539.9mm2

0 0 0 0

403.23mm2 348.12mm2 352.8mm2 412.95mm2

0 0 0 0

257.35mm2 163.18mm2 162.94mm2 258.37mm2

GRID SLAB

FLAT SLAB

Above table shows reinforcement consisting of data from four panels of flat slab and four
panels of grid slab. Reinforcement data is taken at mid span of edges of each panel to
make comparison with flat and Grid slab on the basis of reinforcement. It can be clearly
figured out that area of reinforcement needed for Grid slabs is more than Flat slabs.

49
 CHAPTER 5

CONCLUSION

Although the approaches to check various results of different slabs in a single building is
different but main focus is same, which is to check the effectiveness on their structural
point of view. Static and dynamic analysis is being carried out to know the collective
reaction of slab and beams to external loading. Economical section is being checked by
many researches at different load conditions. Storey drift is minimized by provision of
grid slabs. By going through all these papers, I came to know if we consider economical
point of view then grid slab is not necessary. But if we are designing an important
structure where there is need of large spaces Grid slabs plays a vital role at that place.
Some structural Engineers recommend to provide floating columns in parking lots, open
spaces etc but in return that needs extra reinforcement for nearby beams and columns
which bypass the loading which is transferred by that column.
To know the inter-relation between grid slab and flat slab and their dependency
on adjacent beams and to check the effect on reinforcement, section detailing. By going
through some of the researches done previously I came to conclusion by this research
that:
1. Flat slab makes it best for design purpose instead of grid slab if we take economic
point of view.
2. Reinforcement provided for flat slabs is minimum as compared to grid slabs.
3. Grid slabs help to minimize provision of number of columns as they are rigid and
can be used for longer spans. But flat slabs cannot resist that much amount of load
as they are not supported by beams.
4. Stress is found to be maximum on flat slab as compared to grid slab. So, chances
of cracks will be more in flat slabs.
5. As found in analysis result stress is minimum at column joints in both the cases
but in case of flat slab drop panels are used to minimize stress on columns. Drop
panels transfer loading uniformly from all sides.
6. Deflection is always found more in case of flat slabs as they are not supported by
beams whereas grid slabs show good resistance for deflection.
7. By this research work I came to conclusion that if it is any important building like
public building then it is necessary to use grid slabs to make frame as rigid as
possible. On the other hand, it will cost more but will be durable and safe as
50
 compared to flat slabs. Flat slabs are mostly used in the cases where we prioritize
aesthetic look of building and where we want to provide any different
architectural look in building.
Designing the building with Flat Slab and Grid slab for long span building on ETABS, it
is clear that ETAB gives best result for reinforcement data. This is the main reason which
I found while going through this research. Secondly ETABS gives the reinforcement
detailing with drawing in the form of distinct tables,

In case of ETABS failed members can be checked simply after design step. “Check failed
members” in design section directly select those members and Design Engineer can
change the section of those members by taking them in “view selected objects only”. And
then section is changed to those members to make them pass for the given loading.
ETABS consists of multiple steps to complete a design by assigning each parameter of
design that is why results were taken by use of this software.

51
 CHAPTER 6

FUTURE WORK PROCESS

Using ETABS, the research of review document and journal discovered the different
outcome and conclusion on the grounds of these results and the further work is evaluation
of multi-storey construction (G+14) such as strengthening, shear force, bending moment
etc. This research will help to select technology accordingly if project type is known to
get better results. In next research processes this research can be used to know the best
point of application of each technology to make some adjustments in case of slabs to get
best results. This process does not end here it is a vast field there is lot of research to know
about strengthening process of structures by these results. Future projects can be analysed
by using other materials on both slabs to get economical design and can be made various
changes. This was for the purpose of education but this definitely gives us the practical
idea of use of different slabs at various conditions.

Some researchers are still going there on types of slabs to be provided at different
instances. This research will help other researchers to get idea and to put fore front its
results and then elaborate it with other techniques. There might be some flaws in this
research which can be fulfilled onwards by engineers going for higher studies.

52
 REFERENCES

[1] Lalit Balhar, Dr. J.N. Vyas, “Review Paper On Comparative Analysis Of Flat
Slab & Convetional RC Slabs With and Without Shear Wall”, International
Research Journal of Engineering and Technology (IRJET). Volume: 06 Issue:
02 | Feb 2019.
[2] Indrani V ,“Dynamic Analysis of Multistory RCC Building Frame with Flat
Slab and Grid Slab”, International Journal of Trend in Scientific Research and
Development (IJTSRD)
[3] Ashwini Waghule1 Patil Harshal, Waghmare Ratnakumar , Kadam Shubham,
Biradar Ballav , Udatewar Diksha , “Review Paper on Bubble Deck Slab”,
Journal of Advances and Scholarly Researches in Allied Education. Vol. XV,
Issue No. 2, (Special Issue) April-2018, ISSN 2230-7540.
[4] Mohd Aasim Ahmed, “Comparative Analysis & Design of FLAT & GRID
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Buildings”, IJSRD - International Journal for Scientific Research &
Development| Vol. 6, Issue 05, 2018 | ISSN (online): 2321-0613
[5] S.V Mahamuni, Prof. Dr. S.A Halkude,“Comparison of Various Methods of
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[6] Sumit Sharma,Ashish Yadav and Mukesh Dubey, “Review Paper On RCC
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Research Development Volume 5, Issue 02, February -2018.
[7] R.S.More, “ Analytical Study of Different Types of Flat Slab Subjected to
Dynamic Loading”, International Journal of Science and Research (IJSR)
Volume 4 Issue 7, July 2015 ISSN (Online): 2319-7064
[8] C.H.Rajkumar, Dr.D.Venkateswarlu , “Analysis and Design of Multi-storey
Building with Grid Slab Using ETABS” , International Journal of
Professional Engineering Studies Volume VIII /Issue 5 / JUN 2017.
[9] Anitha.K, R.J Rinu Isah ,“Design And Analysis of Grid Floor Slab”,
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2017, 109-115 ISSN: 1311-8080 (printed version); ISSN: 1314-3395.
[10] Avinash Patel, And Seema Padamwar ,”The Response Of Flat Slab and Grid
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521, 2017 ISSN: 2250-0138.

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08 | Aug -2017.
[12] Harish M K, “ Analysis and Design of Grid Slab in Building Using Response
Spectrum Method”, 2017 IJRTI | Volume 2, Issue 6 | ISSN: 2456-3315
[13] Mayuri S. Sethia, Prof. R.S Deotale, P.S. Patankar , “Analysis and Design of
Flat Slab, Grid Slab and Bubble Slab”, IJSRD - International Journal for
Scientific Research & Development| Vol. 5, Issue 02, 2017 | ISSN (online):
2321-0613.
[14] Avinash Patel, And Seema Padamwar, “Studying The Response Of Flat Slab
and Grid Slab Systems in Conventional RCC Buildings”, Indian J.Sci.Res. 14
(2): 516-521, 2017 ISSN: 2250-0138.
[15] Uttam V Chothani ,Jashmin Gadhiya, Hitesh K Dhameliya , “Comparative
Study of Seismic Behaviour and Cost Comparison of Multi-Storey Flat Slab
and Conventional Reinforced Concrete Framed Structure”, IJSRSET |
Volume 2 | Issue 3 | Print ISSN : 2395-1990 | Online ISSN : 2394-4099
[16] Chintha Santhosh,“Analysis and Design of Multistory Building with Grid Slab
Using ETABS”,International Journal of Innovative Research in Science,
Engineering and Technology Vol. 5, Issue 9, September 2016| ISSN(Online) :
2319-8753
[17] Salman I Khan and Ashok R Mundhada, “Comparative Study of Seismic
Performance of Multistoried RCC Building with Flat Slab and Grid Slab”,
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[20] R.Arvind , P.C.Balamurugan, R.Aravind, C.S. Aslam Basha, “A Review
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55
 LIST OF PUBLICATIONS

1. Suraj Kumar Ravi , Mr. Mohd Bilal Khan., "Comparative Dynamic Analysis Of
Flat Slab And Grid Slab System” SCIENCE AND ENGINEERING
JOURNAL(SAEJ), ISSN No: 0103-944X, UGC Approved, GOOGLE
SCHOLAR and SCOPUS INDEXED Journal. Published in - Volume 15 | Issue
7 | August 2020
Link: http:// saejournal.com/volume-24-issue-8

2. Suraj Kumar Ravi , Mr. Mohd Bilal Khan., "Comparative Dynamic Analysis Of
Flat Slab And Grid Slab System” INTERNATIONAL JOURNAL OF RESARCH
AND ANALYTICAL REVIEWS (IJRAR), E-ISSN – 2348-1269, P-ISSN 2349-
5138 , UGC and ISSN Approved Journal. Published in – Volume 7 | Issue 2| June
2020
Link: http://www.ijrar.org/IJRAR19S1282.pdf

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