CHAPTER - 1

1

1.1 INTRODUCTION

In general normal frame construction utilizes columns, slabs &Beams.

However it may be possible to undertake construction without providing beams,

In such a case the frame system would consist of slab and column without

beams. These types of slabs are called flat slab, since their behavior resembles

the bending of flat plates.

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. A flat slab may be solid slab or may have recesses formed on the soffit

so that the soffit comprises a series of ribs in two directions.

The recesses may be formed by removable or permanent filler blocks.

1.2TYPES OF FLAT SLABS:

There are three different kind of flat slabs

Flat slab without drop and column head.

Flat slab with column head and no drop.

Flat slab with column head and drop.

COMPONENTS OF FLAT SLABS:

DROPS:

To resist the punching shear which is predominant at the contact of slab

and column Support, the drop dimension should not be less than one -third of

panel length in that Direction.

2

COLUMN HEADS:

Certain amount of negative moment is transferred from the slab to the

column at the support. To resist this negative moment the area at the support

needs to be increased. This is facilitated by providing column capital/heads

COLUMN STRIP :

Column strip means a design strip having a width of 0.25 I,, but not

greater than 0.25 I, 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 I, is the -span transverse to I

MIDDLE STRIP :

Middle strip means a design strip bounded on each of its opposite sides

by the column strip.

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.

3

Fig 1 Flat slab with drop panel & column head

4

1.3 ABOUT STAAD Pro

STAAD Pro 2007 is the most popular structural engineering software

product for 3D model generation, analysis and multi-material design. It has an

intuitive, user-friendly GUI, visualization tools, powerful analysis and design

facilities and seamless integration to several other modeling and design

software products. The software is fully compatible with all Windows

operating systems but isoptimizedforWindows8.

For static or dynamic analysis of bridges, containment structures,

embedded structures (tunnels and culverts), pipe racks, steel, concrete,

aluminum or timber buildings, transmission towers, stadiums or any other

simple or complex structure, STAAD Pro has been the choice of design

professionals around the world for their specific analysis needs

1.4 OVERALL PROCEDURE IN WORKING WITH STAAD.PRO

1.4.1 MODELGENERATION:

There are two methods for building a model and assigning the structure

data using STAAD Pro.

a. Using the command file

b. Using the graphical model generation mode or graphical

user interface (GUI).

1.4.2 PERFORMING ANALYSIS AND DESIGN

STAAD offers two analysis engines – the STAAD engine for

general purpose Structural Analysis and Design and the STARDYNE engine

for advanced analysis options.

The Modeling Mode of the STAAD Environment is used to prepare

the structural input data. After the input is prepared, we may choose the

analysis engine depending up on the nature of the analysis required. If we are

5

performing the STARDYNE. Advanced analysis, several additional

parameters need to be defined specific to the nature of the analysis.

1.4.3 POST-PROCESSINGThe Post Processing mode of STAAD offers facilities for on- screen

visualization and verification of the analysis and design results. It allows

displacements, forces, stresses, etc- both graphically and numerically.

1.5 OBJECTIVES To analyze the properties of flat slab in residential buildings.

Analyze and design using STADD pro.

6

CHAPTER -2

7

LITERATURE REVIEW

2.1 LITERATURE REVIEW

Analysis And Design of Flat Slab And Grid Slab And Their Cost Comparison

Amit A. Sathawane & R.S. Deotale (2004) -Yeshwantrao Chavhan College of Engineering, Nagpur, India carried out a work with he aim of the project to determine the most economical slab between flat slab with drop, Flat slab without drop and grid slab.

Irregular flat slabs designed according to structural membrane approach

K. Baskaran (2003) carried out a work on Department of Civil Engineering, University of Moratuwa, Sri Lanka.

Review and Design of Flat Plate/Slabs Construction in India

Gowda N Bharath; Gowda S. B. Ravishankar; A.V Chandrashekar (2001) carried out a work on the use of flat plate/slab construction in India and their applications in buildings.

Analysis and design of Flat slabs using various codes

B.Q.Rahman, J.J.Vijay, M.Anitha, (2007) International Institute of Information Technology” ,Hyderabad . In their design of Flat slab they have implemented the use of Drops and Column heads.

Evaluation and enhancing the punching shear resistance of flat slabs using IS Codes

N.Subramanian (2005) carried out a work on the use of flat slabs improves the punching shear resistance allowing higher forces to be transferred through the slab column connection. In this paper, the evaluation of punching shear resistance of flat slabs with respect to some of the major codes of practices.

With reference to these literatures we have studied that flat slabs are constructed in square or rectangular type we are going to implement it as a circular flat slab in a circular shaped residential building.

8

CHAPTER 3

9

METHODOLOGY

10

PLAN

LOAD CALCULATION

MODELING USING STADD PRO

DESIGN

RESULT

ANALYSIS USING STADD PRO

DETAILING OF REINFORCEMENT

Fig 2 Plan of ground floor

11

Fig 3 Plan of first floor

12

Fig 4 Beam and Column layout of building

13

3.2 LOAD CALCULATION

Self weight of slab = 3.75 kN/m²

Dead load due to extra thickness of slab at drops = 1.25 kN/m²

Live load = 4.00 kN/m²

Finishes = 1.00 kN/m²

Total load = 10 kN/m²

Factored load = 15 kN/m²

Load combination =1.5 (ll+dl)

14

Fig 5 Model of the building done using STADD pro

15

Fig 6 Figure showing 3D view of load acting on the building

16

3.4 ANALYSED RESULT USING STADD PRO

============================================================================

C O L U M N N O.43 D E S I G N R E S U L T S

M30 Fe415 (Main) Fe415 (Sec.)

LENGTH: 3000.0 mm CROSS SECTION: 450.0 mm X 600.0 mm COVER: 40.0 mm

** GUIDING LOAD CASE: 2 END JOINT: 1 TENSION COLUMN

REQD. STEEL AREA : 2160.00 Sq.mm.

REQD. CONCRETE AREA: 267840.00 Sq.mm.

MAIN REINFORCEMENT : Provide 20 - 12 dia. (0.84%, 2261.95 Sq.mm.)

(Equally distributed)

TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 190 mm c/c

SECTION CAPACITY BASED ON REINFORCEMENT REQUIRED (KNS-MET)

----------------------------------------------------------

Puz : 4288.14 Muz1 : 194.91 Muy1 : 141.60

INTERACTION RATIO: 0.01 (as per Cl. 39.6, IS456:2000)

SECTION CAPACITY BASED ON REINFORCEMENT PROVIDED (KNS-MET)

----------------------------------------------------------

WORST LOAD CASE: 2

END JOINT: 43 Puz : 4318.49 Muz : 203.96 Muy : 148.02 IR: 0.01

============================================================================

C O L U M N N O. 54 D E S I G N R E S U L T S

17

M30 Fe415 (Main) Fe415 (Sec.)

LENGTH: 3000.0 mm CROSS SECTION: 450.0 mm X 600.0 mm COVER: 40.0 mm

** GUIDING LOAD CASE: 2 END JOINT: 12 TENSION COLUMN

REQD. STEEL AREA : 2160.00 Sq.mm.

REQD. CONCRETE AREA: 267840.00 Sq.mm.

MAIN REINFORCEMENT : Provide 20 - 12 dia. (0.84%, 2261.95 Sq.mm.)

(Equally distributed)

TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 190 mm c/c

SECTION CAPACITY BASED ON REINFORCEMENT REQUIRED (KNS-MET)

----------------------------------------------------------

Puz : 4288.14 Muz1 : 194.75 Muy1 : 141.49

INTERACTION RATIO: 0.01 (as per Cl. 39.6, IS456:2000)

SECTION CAPACITY BASED ON REINFORCEMENT PROVIDED (KNS-MET)

----------------------------------------------------------

WORST LOAD CASE: 2

END JOINT: 54 Puz : 4318.49 Muz : 203.79 Muy : 147.90 IR: 0.01

STAAD SPACE -- PAGE NO. 19

============================================================================

18

C O L U M N N O.62 D E S I G N R E S U L T S

M30 Fe415 (Main) Fe415 (Sec.)

LENGTH: 3000.0 mm CROSS SECTION: 600.0 mm dia. COVER: 40.0 mm

** GUIDING LOAD CASE: 2 END JOINT: 20 TENSION COLUMN

STAAD SPACE -- PAGE NO. 24

REQD. STEEL AREA : 2261.95 Sq.mm.

REQD. CONCRETE AREA: 280481.41 Sq.mm.

MAIN REINFORCEMENT : Provide 21 - 12 dia. (0.84%, 2375.04 Sq.mm.)

(Equally distributed)

TIE REINFORCEMENT : Provide 8 mm dia. circular ties @ 190 mm c/c

SECTION CAPACITY BASED ON REINFORCEMENT REQUIRED (KNS-MET)

----------------------------------------------------------

Puz : 4490.53 Muz1 : 183.79 Muy1 : 183.79

INTERACTION RATIO: 0.01 (as per Cl. 39.6, IS456:2000)

SECTION CAPACITY BASED ON REINFORCEMENT PROVIDED (KNS-MET)

----------------------------------------------------------

WORST LOAD CASE: 2

END JOINT: 20 Puz : 4524.20 Muz : 192.24 Muy : 192.22 IR: 0.01

============================================================================

19

74. DESIGN BEAM 61 67 TO 90 109 115 TO 138

STAAD SPACE -- PAGE NO. 44

============================================================================

B E A M N O. 61 D E S I G N R E S U L T S

M30 Fe415 (Main) Fe415 (Sec.)

LENGTH: 3000.0 mm SIZE: 450.0 mm X 600.0 mm COVER: 25.0 mm

SUMMARY OF REINF. AREA (Sq.mm)

----------------------------------------------------------------------------

SECTION 0.0 mm 750.0 mm 1500.0 mm 2250.0 mm 3000.0 mm

----------------------------------------------------------------------------

TOP 525.36 525.36 525.36 525.36 525.36

REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm)

BOTTOM 525.36 525.36 525.36 525.36 525.36

REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm)

----------------------------------------------------------------------------

SUMMARY OF PROVIDED REINF. AREA

----------------------------------------------------------------------------

SECTION 0.0 mm 750.0 mm 1500.0 mm 2250.0 mm 3000.0 mm

----------------------------------------------------------------------------

TOP 7-10í 7-10í7-10í7-10í7-10í

REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)

20

BOTTOM 7-10í 7-10í 7-10í 7-10í 7-10í

REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s)

SHEAR 2 legged 8í 2 legged 8í 2 legged 8í 2 legged 8í 2 legged 8í

REINF. @ 200 mm c/c @ 200 mm c/c @ 200 mm c/c @ 200 mm c/c @ 200 mm c/c

----------------------------------------------------------------------------

============================================================================

********************END OF BEAM DESIGN RESULTS********************

21

3.5 DESIGN

3.5.1 DESIGN OF FLAT SLABS Ultimate load of flat slab =15 KN/m²

Panel size = 4.75×4.75 m

Diameter of flat slab column = 600mm

Dimension of drop of flat slab = 1000×1000 mm

Thickness of slab = 150 mm

Thickness at drops = 200 mm

(i) Column strip moments

Positive bending moment = 26 KN.m

Negative bending moment = 60 KN.m

(ii) Middle strip moments

Positive bending moment =18.3 KN.m

Negative bending moment =18.3 KN.m

Check for shear

Shear force = 314.69 KN

Shear force /metre width of

perimeter ,Vu =70.82 KN/m

tv =Vu÷(b×d)

= 0.41 N/mm2

Ks×tc =1.12 N/mm2

Tv <Ks×tc

Hence shear is safe

Column strip provide 12 mm @ 270 mm c/c

Middle strip provide 12 mm @ 300 mm c/c

22

3.5.3 DESIGN OF RING BEAM: Size of ring beam = 300×450 mm

Self weight = 57.73 KN

Uniformly distributed load = 5.30 KN/m

Negative bending = 12.89 KN.m

moment at support

Positive B.M at centre of = 6.49 KN.m

span

Torsion moment =1.29 KN.m

Shear force at support = total load / 2×no of column

= 9.43 KN.m

Shear resisted by concrete = tc ×b×d ÷1000

= 43.2 KN

Vus = V-(tc ×b×d)

= 33.77 KN

Sv =σst× Asv ×d ÷ Vus

=185 mm

Ms =T((1+(D/b)÷1.7)

= 1.89 KN.m

Ve =V+1.6(T/6)

= 3.76 KN

tve =Ve÷(b×d)

=0.30 N/mm2

Top reinforcement 3 -12mm dia.

Torsion reinforcement 3 - 12 mm dia.

Bottom reinforcement 2-16 mm dia.

Provide 2-10 mm dia Hanger bar.

Providing 2-leg 8mm @ 175mm c/c @ shear reinforcement.

23

3.5.4 DESIGN OF COLUMN

FOR C1 Dimension of column = 450×600 mm

Total load = 169.879 KN

Load on each column = 18.89 KN

Self weight of column = 13.5 KN

Total load on column = 202.269 KN

Factored load = 303.756 KN

Moment ,M = load × distance

= 36.3 KN.m

Mxx =Myy = 36.3KN/m

Equivalent moment =1.15 (Mxx2+Myy

2)1/2

=59.03 KN.m

By using chart 44 of SP 16

MuX1 = MuY1 = 36.045 KN.m

Puz = 0.45 ×fck×Ac+0.75×fy×Asc

= 3520.04×103 N

Pu = 0.057 N

Pu< 2

So αn =1

(MuX/MuX1)+(MuY/MuY1)=0.9

Since the value is less than 1, It is safe against byaxial bending

Provide 8 no’s 16 mm as longitudinal reinforcement and 8 mm lateral

ties as 300 mm c/c

24

FOR C2 Dimension of column = 600 mm

Total load = 169.879 KN

Load on each column = 18.89 KN

Self weight of column = 13.5 KN

Total load on column = 202.269 KN

Factored load =303.756 KN

Moment ,M = load × distance

= 36.3 KN.m

Mxx =Myy = 36.3KN/m

Equivalent moment =1.15 (Mxx2+Myy

2)1/2

=59.03 KN.m

By using chart 44 of SP 16

MuX1 = MuY1 = 36.045 KN.m

Puz = 0.45 ×fck×Ac+0.75×fy×Asc

= 3520.04×103 N

Pu = 0.057

Pu< 2

So αn =1

(MuX/MuX1)+(MuY/MuY1)=0.9

Since the value is less than 1, It is safe against byaxial bending

Provide 8 no’s 20 mm as longitudinal reinforcement

Provide 8mm lateral ties @300 mm c/c.

25

FOR C4 Dimension of column = 300×300 m

Total load = 96.2 KN

Load on each column = 24.05 KN

Self weight of column = 4.5 KN

Total load on column = 124.75KN

Factored load =187.23 KN

Moment ,M = load × distance

= 10.2 KN.m

Equivalent moment =1.15 (Mxx2+Myy

2)1/2

=16.58KN.m

By using chart 44 of SP 16

MuX1 = MuY1 = 10.035 KN.m

Puz = 0.45 ×fck×Ac+0.75×fy×Asc

= 1374.4×103 N

Pu = 0.023 N

Pu< 2

So αn =1

(MuX/MuX1)+(MuY/MuY1)=0.7

Since the value is less than 1, It is safe against byaxial bending

Provide 6 no’s 16 mm as longitudinal reinforcement Provide 8mm lateral ties @ 300 mm c/c

26

3.5.5 DESIGN OF FOOTING: Total load = 223 KN.

S.B.C of soil = 50 KN/m2

Ultimate bearing capacity = 75 KN/m2

Size of footing = 2m×1.5m.

Axial factored load =202.269 KN

Pu = axial factored load ÷ size of footing

=67KN/m².

Bending moment = Pu l2 /2

=10.5 KN.m (for shorter side)

= 16.45 KN.m (for longer side)

Depth of footing =Mu / 0.187 fck b

=650 mm

tv =0.27 N/mm2

Reinforcement in footing

Mu= 0.87×fy×Ast×d(1- (Ast×fy / b×d×fck)

Check for shear

tv < tc

Hence it is safe

Provide 4no. 16mm ϕ @300mm c/c both in shorter direction and longer

direction.

27

3.5.6 DESIGN OF STAIRCASE

Number of steps for one flight =10 no’s

Width of landing beam = 300 mm

Effective span = 3.3 m

Thickness of waist slab = Span /20

=165 mm

Dead load of slab on slope =Thickness ×fck

=4.125 KN/m

Dead load of slab on horizontal

Span =4.6 KN/m

Load of step / metre length = 1.89 KN/m

Finishes = 0.5 KN/m

Total dead load = 6.97 KN/m

Live load = 3 KN/m

Total load = 9.97 KN/m

Factored load = 1.5 ×total load

=15 KN/m

Mu =0.125 Wu×L2

=20.42 KN.m

Check for effective depth

drequired =86 mm

dprovided =140 mm

drequired < dprovided

Hence it is safe

Provide 10 mm @ 165 mm c/c as main reinforcement

Distribution steel = 198 mm2

Use 8mm @ 200 mm c/c

28

3.6 DETAILING OF REINFORCEMET

29

FIG 7 FLAT SLAB REINFORCEMENT

30

FIG 8 BEAM REINFORCEMENT

31

32

FIG 9 COLUMN REINFORCEMENT

33

34

35

FIG 10 STAIRCASE REINFORCEMENT

CHAPTER - 4

\

36

RESULTS

4.1 RESULTS AND DISCUSSIONS

Residential building is planned , loads are calculated.

Flat slab is implemented in the building.

Analysis and design is done by STADD Pro software .

Detailing of reinforcement is drawn in AUTO CADD software.

37

CHAPTER - 5

38

CONCLUSION

5.1 CONCLUSION

We conclude that the flat slab can be designed and it can be implemented

in the Residential buildings. Analysis and design as per IS code is done using

STADD Pro packages and also detailing of drawing is done using AUTO

CADD software.

39

5.2 REFERENCE

Reference books:

1. Indian Standard IS 456:2000, Plain and Reinforced Concrete Code of

Practice.

2. Alaa G. S. and Walter H.D.,(1998) Analysis and Deflection of Reinforced

Concrete Flat Slabs, Canadian Journal of Civil Engineering, Vol. 25.

3. P.C.Varghesh ., Limit State Design of reinforced concrete.

4. N. Krishna Raju .,Advanced Reinforced Concrete Design

5. Krishna Raju, N., Design of RC Structures , Oxford & IBH Publishers

and Distributers, New Delhi.

6. M.L.Gambhir, B.C.Punmia., Reinforced concrete design

40