Slabs by Rhythm Murgai

L -3 T -0 P-0COURSE TITLE: STRUCTURE SYSTEMS AND DESIGN
COURSE CODE: ARC054
WEEK NO.: 4 LECTURE NO.: 13
LECTURE DETAIL : BULK ACTIVE STRUCTURES –SLABS
COURSE INSTRUCTOR: AR. SHIVALIKA KANWAR UID: 19514
CA CATEGORY: ______________
EXAM CATEGORY: 55: Mid Term Exam: All Subjective
LSAD : AD01 : ARCHITECTURE

2
LECTURE NO.10
CONTENT TOPIC: BULK ACTIVE STRUCTURES
ELEMENTS OF BULK ACTIVE
STRUCTURES
 COLUMNS
 BEAMS
 SLABS

3
LECTURE NO.10
CONTENT TOPIC: BULK ACTIVE STRUCTURES- SLABS
R.C.C. SLABS
Reinforced Cement Concrete Slab
•A Reinforced Concrete Slab is the one of the most important component in a
building. It is a structural element of modern buildings. Slabs are supported on
Columns and Beams.
•RCC Slabs whose thickness ranges from 10 to 50 centimetres are most often
used for the construction of floors and ceilings.
•Thin concrete slabs are also used for exterior paving purpose.

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LECTURE NO.10
R.C.C. SLABS

5
LECTURE NO.10
R.C.C. SLABS
Reinforcement design-
•One way slab has
structural strength in
shortest direction.
•Two way slab has
two directions.
•Flat plate slab
•Flat slab
•Grid slab
Onthebasisofreinforcement
Various types of slabs

6
LECTURE NO.10
R.C.C. SLABS
Onthebasisofreinforcement
Reinforcement design-
•One way slab has
shortest direction.
•Two way slab has
two directions.
•Flat plate slab
•Flat slab
•Grid slab

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LECTURE NO.10
R.C.C. SLABS- two way slab

8
LECTURE NO.10
R.C.C. SLABS- flat plate slab

9
LECTURE NO.10
R.C.C. SLABS – flat slab

10
LECTURE NO.10
R.C.C. SLABS
Onthebasisoftypeofconstruction
•Prefabricated concrete slabs are cast in a factory and then transported to the site
ready to be lowered into place between steel or concrete beams.
•They may be pre-stressed (in the factory), post-stressed (on site), or unstressed.
Care should be taken to see that the supporting structure is built to the correct
dimensions to avoid trouble with the fitting of slabs over the supporting structure.
•In situ concrete slabs are built on the building site using formwork. Formwork is a
box-like setup in which concrete is poured for the construction of slabs.
•For reinforced concrete slabs, reinforcing steel bars are placed within the
formwork and then the concrete is poured.
•Plastic tipped metal, or plastic bar chairs are used to hold the reinforcing steel
bars away from the bottom and sides of the form-work, so that when the concrete
sets it completely envelops the reinforcement.
•Formwork differs with the kind of slab. For a ground slab, the form-work may
consist only of sidewalls pushed into the ground whereas for a suspended slab, the
form-work is shaped like a tray, often supported by a temporary scaffold until the
concrete sets.
A concrete slab can be cast in two ways: It could either be prefabricated or cast in
situ.

LECTURE NO.10
R.C.C. SLABS
Onthebasisofsupport
These slabs could be cantilevered or Simply Supported Slabs.
cantilevered

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LECTURE NO.10
R.C.C. SLABS
For a suspended slab, there are a number of designs
to improve the strength-to-weight ratio. In all cases
the top surface remains flat, and the underside is
modulated:
•Corrugated, usually where the concrete is poured
into a corrugated steel tray. This improves strength
and prevents the slab bending under its own weight.
The corrugations run across the short dimension,
from side to side.
•A filler slab, is normal RCC slabs where bottom half
(tension) concrete portions is replaced by filler
materials.
•A ribbed slab, giving considerable extra strength on
one direction.
•A waffle slab, giving added strength in both
directions.
OnthebasisofPROFILE

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LECTURE NO.10
CORRUGATED SLAB
• Corrugated sheet steel profile (support sheet), the
indentations of which allow it to provide support to the
concrete.
• Anti-fracture mesh, which is positioned in a similar
manner to when employed for solid slabs and the
objective of which is the prevention of fractures
provoked by retraction and temperature.
• Negative Framework, which is installed in the upper
section of the slab and centred in the indentations. Its
purpose it to absorb the tensile stresses generated in
the adjacent slabs’ supports.
• Fire-resistance framework, which installed in the same
way as the negative framework but in the lower side
of the indentations. This is a positive framework that is
installed to ensure that the slab’s fire-resistance
complies with the project’s specifications.
• Concrete, which is poured directly onto the composite
slab.
OnthebasisofPROFILE

14
LECTURE NO.10
FILLER SLABOnthebasisofPROFILE
• Filler slabs are normal RCC slabs where bottom
half (tension) concrete portions are replaced by
filler materials such as bricks, tiles, cellular
concrete blocks, etc. these filler materials are so
placed as not to compromise structural strength,
result in replacing unwanted and non functional
tension concrete, thus resulting in economy. These
are safe, sound and provide aesthetically pleasing
patterns ceiling and also need no plaster.
Light weight, inert and inexpensive materials such as
low gradeMangalore tiles, Burnt Clay Bricks, Hollow
Concrete blocks, Stabilized Mud blocks/ Hollow Mud
blocks, Clay pots, Coconut shells etc. can be used as
filler materials. These materials are laid in the grids of
steel reinforcement rods and concreting/concrete
topping is done over them.
http://sepindia.org/ihd-sep/ceeef-technologies/filler-slab-technology/

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LECTURE NO.10
R.C.C. SLABS- waffle slab
A waffle slab gets its name for its appearance as it
visually resembles its namesake, the food. Waffle slab is
a reinforced concrete roof or floor containing square
grids with deep sides. This type of slab is used in
construction projects needing intense strength to
weight ratios. Waffle slab is a popular option for
commercial construction work such as industrial
building projects, bridges and others needing extra
stability.
http://civilengineersforum.com/waffle-slab/

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LECTURE NO.10
RIBBED SLAB
•A ribbed slab, giving considerable extra strength on
one direction.
OnthebasisofPROFILE

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LECTURE NO.10
ADVANTAGES- RIBBED AND
WAFFLED SLAB
• Flexible
• Relatively light, therefore less
foundation costs and longer
spans are economic
• Speed of construction
• Fairly slim floor depths
OnthebasisofPROFILE
Ribbed and waffle slabs provide a lighter and stiffer slab than an equivalent flat
slab, reducing the extend of foundations. They provide a very good form where
slab vibration is an issue, such as laboratories and hospitals.
Ribbed slabs are made up of wide band beams running between columns with
equal depth narrow ribs spanning the orthogonal direction. A thick top slab
completes the system.
Waffle slabs tend to be deeper than the equivalent ribbed slab. Waffle slabs have a
thin topping slab and narrow ribs spanning in both directions between column
heads or band beams. The column heads or band beams are the same depth as
the ribs.
• Robustness
• Excellent vibration control
• Thermal mass
• Good for services integration
• Durable finishes
• Fire resistance

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LECTURE NO.10
R.C.C. SLABS- failure

19
LECTURE NO.10
R.C.C. SLABS- cracking of slab

20
LECTURE NO.10
R.C.C. SLABS- damp or wet floor
slab

LECTURE NO.9
STRUCTURES

Salk Institute, La Jolla
Architect: Louis Kahn
Engineer: Komendant and Dubin
Perspective section and photo
Chord depth varies with global
shear
25

28
S.No Structural Element L/D Ratio Span
1 RCC GRID 1/13- 1/14
2 SKEW GRID 1/40- 1/60
3 2 WAY SLAB 33 - 40
4 2 WAY BEAM & SLAB 45-55
5 1 WAY SLAB 24-36
6 1 WAY RIBBED SLAB 24-36
7 RCC BEAMS 16-26
8 WAFFLE SLAB 28-30
LECTURE NO.9
SLABS

HOMEWORK/ REVISION/ QUESTIONS:
LSAD : AD01 : ARCHITECTURE LECTURE NO. Slide No.27

Slabs by Rhythm Murgai

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