This document is a mini project report submitted by Sandeep Kumar to fulfill the requirements for a Bachelor of Technology degree in Civil Engineering. The report describes designing and drawing a flat slab structure using the Indian Standard Code. It provides an introduction to flat slab construction, advantages of flat slabs like flexibility in design and reduced building height. It also discusses code regulations, design steps, and concludes with designing a flat slab according to the IS code.

1. A
Mini Project Report
On
DESIGNING AND DRAWING OF FLAT SLAB WITH THE HELP OF
I.S CODE
In partial fulfillments for the degree of
Bachelor of Technology
In
Civil Engineering
SUBMITTED BY
SANDEEP KUMAR
ROLL NO :-XXXXXXX
Under the Guidance of
Mr. RAJESH MEENA
DEPARTMENT OF CIVIL ENGINEERING
NOIDA INSTITUTE OF ENGINEERING AND TECHNOLOGY
Greater Noida, Uttar Pradesh APJ Abdul kalam Technical University
2019

2. ii
CERTIFICATE
Certified that minor project work entitled “ DESIGNING AND DRAWING OF FLAT SLAB
WITH THE HELP OF I.S CODE ” is a bonafide work carried out in the 7th
semester by
SANDEEP KUMAR in partial fulfilment for the award of Bachelor of technology in Civil
Engineering from “ NOIDA INSTITUTE OF ENGINEERING AND TECHNOLOGY ”
Greater Noida , during the academic year 2019-2020.
Project Guide : Project coordinator :
Mr. RAJESH MEENA Mr. RAJESH MEENA

3. iii
ACKNOWLEDGEMENT
I feel very proud to say that due to keen knowledge of the faculty of the Civil Department of
the Noida Institute Of Engineering and technology .It was very easy for me to learn a lot of
knowledge regarding the “DESIGNING AND DRAWING OF FLAT SLAB WITH THE
HELP OF I.S CODE”.
I am greatly thankful to our guide Mr. RAJESH MEENA for his kind support and guidance
to successfully complete my Project . I have highly benefited by this Project and have gained
a lot of knowledge about the various problems of designing & drawing of the flat slab using
I.S CODE used in a construction site.
Finally I would like to thanks all the faculty members and senior teachers who have helped me
and co-operated with me during my project work.
NAME : SANDEEP KUMAR
ROLL.NO: xxxxxxxx

4. iv
TABLE OF CONTENT
1. Introduction ........................................................................................... 1
1.1 Types of flat slab .......................................................................... 2
1.2 Use of column head ...................................................................... 2
1.3 Use of drop panels ........................................................................ 2
2. Advantages of flat slab ........................................................................... 4
2.1 Thickness of flat slab ................................................................... 4
2.2 Types of flat slab design ............................................................... 4
3. Benefits of flat slab ................................................................................ 5
4. Need of flat slab ...................................................................................... 6
5. Code regulations .................................................................................... 8
5.1 Methods of analysis ..................................................................... 8
5.1.1 Direct design method ................................................. 8
5.1.2 Equivalent frame method ........................................... 9
6. Design steps ............................................................................................. 10
6.1 Advantages .................................................................................. 10
6.2 Disadvantages .............................................................................. 10
7. Design of flat slab by IS code ………………………………………........ 11
8. Conclusion ............................................................................................... 15
7. References ................................................................................................ 16

5. v
LISTS OF FIGURES
Sr.no Figure Page no:
1.1 Flat slab 1
1.2 Types of flat slab 2
1.3 Flat slab with columns 3
4.1 Deflection diagrams 6
5.1 Design moment 9

6. vi
ABSTRACT
Designing of flat slab and drawing using the I.S CODE is very important for any construction
site and any project its help us to prepare a masonry structures likes :-
• Parking desk
• Commercial buildings
• Hotels
• Warehouses
• Places where beam are not required
Flat Slabs are considered suitable for most of the construction and for asymmetrical column
layouts like floors with curved shapes and ramps etc. The advantages of applying flat slabs are
many like depth solution, flat soffit and flexibility in design layout.
Even though building flat slabs can be an expensive affair but gives immense freedom to
architects and engineers the luxury of designing.
Structures having floors with irregular supports, large openings or bears heavy loads,
application of finite- element analysis is supposed to be very advantageous. Great thought is
put into choosing material properties or installing loads on the structures. Deflections and
cracked width can also be calculated using Finite- element analysis.
KEY WOEDS : ( Slab , Concrete , Support , Columns , Beams)

7. 1
CHAPTER 1
INTRODUCTION
Flat slab is a reinforced concrete slab supported directly by concrete columns without the use
of beams. Flat slab is defined as one sided or two-sided support system with sheer load of the
slab being concentrated on the supporting columns and a square slab called ‘drop panels’.
Drop panels play a significant role here as they augment the overall capacity and sturdiness of
the flooring system beneath the vertical loads thereby boosting cost effectiveness of the
construction. Usually the height of drop panels is about two times the height of slab.
FIG 1.1 FLAT SLAB
Flat Slabs are considered suitable for most of the construction and for asymmetrical column
layouts like floors with curved shapes and ramps etc. The advantages of applying flat slabs are
many like depth solution, flat soffit and flexibility in design layout.Even though building flat
slabs can be an expensive affair but gives immense freedom to architects and engineers the
luxury of designing.
Benefit of using flat slabs are manifold not only in terms of prospective design and layout
efficacy but is also helpful for total construction process especially for easing off installation
procedures and saving on construction time. If possible, try to do away with drop panels as
much as possible and try to make the best use of thickness of flat slabs. The reason is to permit
the benefits of flat soffits for the floor surface to be maintained, ensure drop panels are cast as
part of the column.

8. 2
1.1TYPES OF FLAT SLAB CONSTRUCTION
Following are the types of flab slab construction:-
• Simple flat slab.
• Flat slab with drop panels.
• Flat slab with column head.
• Flat slab with both drop panels and column head.
Fig 1.2 TYPES OF FLAT SLABS
1.2Uses of Column Heads
• It increase shear strength of slab.
• It reduce the moment in the slab by reducing the clear or effective span.

9. 3
1.3 Uses of Drop Panels
• It increase shear strength of slab
• It increase negative moment capacity of slab.
• It stiffen the slab and hence reduce deflection.
FIG 1.3 FLAT SLAB WITH COLUMN

10. 4
CHAPTER 2
Advantages of Flat Slabs
It is recognized that Flat Slabs without drop panels can be built at a very fast pace as the
framework of structure is simplified and diminished. Also, speedy turn-around can be achieved
using an arrangement using early striking and flying systems.
Flat slab construction can deeply reduce floor-to –floor height especially in the absence of false
ceiling as flat slab construction does act as limiting factor on the placement of horizontal
services and partitions. This can prove gainful in case of lower building height, decreased
cladding expense and pre-fabricated services.
In case the client plans changes in the interior and wants to use the accommodation to suit the
need, flat slab construction is the perfect choice as it offers that flexibility to the owner. This
flexibility is possible due to the use of square lattice and absence of beam that makes
channelling of services and allocation of partitions difficult.
2.1 Thickness of flat slab
Thickness of flat slab is another very attractive benefit because thin slab provides the advantage
of increased floor to ceiling height and lower cladding cost for the owner. However, there is
profound lower limit to thickness of slab because extra reinforcements are needed to tackle
design issues. Besides this, added margin must be provided to facilitate architectural alterations
at later stages.
2.2 Types of Flat Slab Design
Multitudes of process and methods are involved in designing flat slabs and evaluating these
slabs in flexures. Some of these methods are as following:
• The empirical method.
• The sub-frame method.
• The yield line method.
• Finite –element analysis.

11. 5
CHAPTER 3
1. Benefits of flat slab
❖ Flexibility in room layout
• Introduce partition walls anywhere required • Change the size of room layout • Omit
false ceiling
❖ Saving in building height.
• Lower storey height will reduce building weight • approx. saves 10% in vertical
members • reduce foundation load.
❖ Shorter construction time
• flat plate design will facilitate the use of big table formwork to increase productivity.
❖ Ease of installation of M&E services
• All M & E services can be mounted directly on the underside of the slab instead of
bending them to avoid the beams.
• Avoids hacking through beams.

12. 6
CHAPTER 4
2. NEED OF FLAT SLABS
• When plain ceiling is required.
• When floor to ceiling height is very less.
• Where deep beam provides obstruction and reduces headroom.
• Where beams may obstruct movement of goods. eg. Godowns & Store rooms.
FIG 4.1 DEFLECTION DIAGRAMS

13. 7
Engineers very often use flat slabs in the building because of its advantages over reinforced
concrete floor system (7 Reasons Why the Flat Slab with Drop Panels is Widely Used). Some
of the advantages are:
1. Flexibility in room layout – where the installation of the partition walls can be done
anywhere.
2. Easier reinforcement placement – detailing of reinforcement on flat slab is simple, and
easier to place.
3. Ease framework installation- in flat slab can be used a big table framework.
4. Building height can be reduced- As no beam is used, floor height can be reduced and
consequently the building height will be reduced.
5. Less construction time needed because of the big table frameworks used.
6. Prefabricated welded mesh are standard sizes, need less installation time and better
quality control.
7. The Auto sprinkler is easier.

14. 8
CHAPTER 5
3. CODE REGULATIONS
• Column strip
Width of column strip 0.25L2 on each side but not greater than 0.25L1.
• Middle strip
Middle strip means a design strip bounded by column strip on all the four sides.
• Drop
The drop when provided shall be rectangular in plan, and have a length in each direction
not less than one third of the panel length in that direction.Thickness of Drop shall not
be less than ¼ of thickness of slab.
• Thickness of slab
The slabs with drop conforming to above clause, l/d ratio given in IS 456 2000 ,
Cl.23.2 shall be applied directly ; otherwise ratio multiplied by 0.9.The minimum
thickness of slab shall be 125 mm.
• Shear in flat slab
The critical section for shear shall be at a distance d/2 from the periphery of the
column /capital or drop pane. And permissible shear stress = k uc.
• Slab reinforcement
Spacing shall not be more than 2 times slab thickness.
3.1METHODS OF ANALYSIS
1.DIRECT DESIGN METHOD.
2.EQUIVALENT FRAME METHOD.
5.1.1 DIRECT DESIGN METHOD
1. LIMITATIONS
• Minimum three continuous span.
• Aspect ratio (Ly/Lx) shall not be greater than 2.
• The successive span lengths in each direction shall not differ by more than
one third of the longer span.
• The end span may be shorter but not longer than interior span.
• Design live load shall not exceed three times the design dead load.

15. 9
2. DESIGN MOMENTS
• The total bending moment in each direction is equal to Mo=(W.Ln)/8.
• Total negative design moment (Mn)= 0.65Mo.
I. Negative moment taken by column strip= 0.75Mn.
II. Negative moment taken by middle strip= 0.25Mn.
• Total positive design moment(Mp)= 0.35Mo
.
I. Positive moment taken by column strip= 0.6Mp.
II. Positive moment taken by middle strip= 0.4Mp.
5.1.2 EQUIVALENT FRAME METHOD
ASSUMPTIONS
• The structure shall be considered to be made up of equivalent frames consist of
two successive columns and slab between them.
• Each frame may be analysed floor wise.
• Relative stiffness of members may be determined by moment of inertia of members
considering gross c/s of the concrete alone.
• Variation of moment of inertia due to thickness of drop may be ignored.
DESIGN MOMENTS
FIG 5.1 DESIGN MOMENT

16. 10
CHAPTER 6
6. DESIGN STEPS
I. Trial depth.
II. Loading calculations.
III. Provision of drop and column capital.
IV. Stiffness and Distribution factors.
V. Fixed end moments and moment distribution table.
VI. Distribution of moments across the panel.
VII. Check for Depth against flexure.
VIII. Determination of area of steel.
IX. Check for deflection.
X. Check for shear.
6.1. ADVANTAGES
• It provides larger clear ceiling height.
• It is ideally suitable for Godowns and Store rooms.
• The construction is simple and economical.
• The plain ceiling gives an attractive andpleasing appearance.
• Acoustical treatment is easy.
6.2. DISADVANTAGES
I. The stiffness of the structure comprising offlat slab and column is slight less.
II. These are suitable for only low to mediumrise buildings.
III. In broad sense, these are economical for spansup to 10 meters.
IV. Serviceability problems may arise withexcessive long term deflection.

17. 11
CHAPTER 7
7.0 Design of flat slabs by IS: 456
The term flat slab means a reinforced concrete slab with or without drops, supported generally
without beams, by columns with or without flared column heads (see Fig. 12). A flat slab may
be solid slab or may have recesses formed on the so fit so that the soffit comprises a series of
ribs in two directions. The recesses may be formed by removable or permanent filler blocks.
Components of flat slab design:
a) Column strip :Column strip means a design strip having a width of 0.25 I,, but not greater
than 0.25 1, on each side of the column centre-line, where I, is the span in the direction moments
are being determined, measured centre to centre of supports and 1, is the -span transverse to 1,,
measured centre to centre of supports.
b) Middle strip :Middle strip means a design strip bounded on each of its opposite sides by
the column strip.
c) Panel: Panel means that part of a slab bounded on-each of its four sides by the centre -line
of a Column or centre-lines of adjacent-spans
Division into column and middle strip along:
Longer span Shorter span
L1 =6.6 m , L2 =5.6 m L1 =5.6 m , L2 =6.6 m
( i ) column strip ( i ) column strip
= 0.25 L2 = 1.4 m = 0.25 L2 = 1.65 m
But not greater than 0.25 L1 = 1.65 m But not greater than 0.25 L1 = 1.4 m
(ii) Middle strip (ii) Middle strip
= 5.6 – (1.4+1.4) = 2.8 m = 6.6 – (1.4+1.4) = 3.8 m

18. 12
The drops when provided shall be rectangular in plan, and have a length in each direction
not less than one- third of the panel length in that direction. For exterior panels, the width of
drops at right angles to the non- continuous edge and measured from the centre -line of the
columns shall be equal to one -half the width of drop for interior panels.
Since the span is large it is desirable to provide drop.
Drop dimensions along:
L1 =6.6 m , L2 =5.6 m L1 =5.6 m , L2 =6.6 m
Not less than L1 /3 = 2.2 m Not less than L1 /3 = 1.866 m
Hence provide a drop of size 2.2 x 2.2 m i.e. in column strip width.
e) column head :Where column heads are provided, that portion of a column head which
lies with in the largest right circular cone or pyramid that has a vertex angle of 90”and can
be included entirely within the outlines
of the column and the column head, shall be considered for design purposes
Column head dimension along:
Adopting the diameter of column head = 1.30 m =1300 mm
f) Depth of flat slab:
The thickness of the flat slab up to spans of 10 m shall be generally controlled by
considerations of span ( L ) to effective depth ( d ) ratios given as below:
Cantilever 7
Simply supported 20
Continuous 26
For slabs with drops, span to effective depth ratios gi ven above shall be applied directly;
otherwise the span to effective depth ratios in accordance with above shall be multiplied by
Longer span Shorter span
Longer Span Shorter Span
L1 =6.6 m , L2 =5.6 m L1 =5.6 m , L2 =6.6 m
Not greater than L1 /4 = 1.65 m Not greater than L1 /4 = 1.4 m

19. 13
0.9. For this purpose, the longer span of the panel shall be considered. The minimum thickness
of slab shall be 125 mm.
Depth of flat slab:
Considering the flat slab as a continuous slab over a span not exceeding 10 m
Taking effective depth of 25mm
Overall depth D = 260 +25 = 285 mm > 125 mm (minimum slab thickness as per IS: 456)
It is safe to provide depth of 285 mm.
g) Estimation of load acting on the slab:
Dead load acting on the slab = 0.285 x 25 = 6.25 2 KN/m^2 =Wd1
Floor finishes etc. load on slab = 1.45 2 KN/m^2 = Wd2
Live load on slab = 7.75 2 KN/m^2 = Wl
Total dead load = Wd1 + Wd 2 =7.7 2 KN/m^2 =Wd
The design live load shall not exceed three times the design dead load.
Check:
Wl/Wd =7.75/7.7 = 1.006<3
OK
Total design load = Wd +Wl = 15.45 KN/m^2
h) Total Design Moment for a Span

20. 14
The absolute sum of the positive and average and is given by negative bending moments in
each
direction shall be taken as:
Mo = (W*Ln /8)
Mo = total moment.
W = design load on an area L1 and L2
Ln = clear span extending from face to face of columns, capitals, brackets or walls, but not less
than 0.65 L1
L1 = length of span in the direction of M0 .
L2= length of span transverse toL1
Circular supports shall be treated as square supports havi ng the same area.
Equivalent side of the column head having the same area:
a = (3.14*d^2 / 4) = 1.152m
Clear span along long span = Ln = 5.448m> 4.29
(Should not be less than 0.65 L1 )
OK
Clear span along long span =Ln = 4.44m> 3.64
(Should not be less than 0.65 L1)
OK

21. 15
CONCLUSION
By studying results obtained after analysis, design and cost comparison with normal beam
slab construction, we can conclude that, by constructing flat slab economy can be achieved
up to great extent for medium span and low to medium class superimposed loads.
But flat slab construction may prove to be uneconomical for span larger than 10 mts. and high
intensity superimposed loads. So it is wise to construct flat slab instead of normal slab-beam
construction, considering various aspects mentioned in the design to achieve economy as well
as functional requirements with aesthetic view.

22. 16
REFERENCES
1. Dr. V.L. Shah, Late Dr. S.R. Karve, Limit State Theory And Design Of
Reinforced Concrete, Structures Publications, Edition-Oct-2002.
2. Shushil Kumar, Design Of Reinforced Concrete Structure.
3. Indian standard 456-2000.
4. Indian standard 875-part(1).
5. Indian standard 875-part(2).