Two Way Slabs

PREPARED BY:
Asst. Prof. GAURANG PRAJAPATI
CIVIL DEPARTMENT
TWO WAY SLABS
Mahatma Gandhi Institute Of
Technical Education
& Research Centre, Navsari (396450)
ELEMENTARY STRUCTURAL DESIGN
6TH SEMESTER
CIVIL ENGINEERING

INTRODUCTION
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TWO WAY SLABS
 TWO WAY SLAB
 If the slab is supported on all four edges and if
𝒍 𝒚
𝒍 𝒙
< 2, → Two way slab.
 The tendency of slab is to bend in both directions. Such slabs are called Two way
slabs.

INTRODUCTION
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TWO WAY SLABS
 In two way slabs, Main reinforcement is provided along 𝑙 𝑥 (Short span) as well as 𝑙 𝑦
(long span).
 In case of two way slabs, Deflection and bending is less as compared to one way
slabs. Therefore, B.M. is also reduced

TYPES OF SLABS BASED ON SUPPORT CONDITIONS:
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TWO WAY SLABS
 According to support conditions, there are two types of two way slabs:
1. Simply supported slab
2. Restrained slab

TWO WAY SIMPLY SUPPORTED SLAB: (CORNERS ARE NOT HELD DOWN)
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TWO WAY SLABS
 In simply supported two way slab, when slab is loaded, corners are lifted up.
 At corners, as torsion is not produced. Therefore, torsion reinforcement is not
provided.
 For the design, 1 m wide strip of slab is considered in both the directions. This strip
is designed as a beam.
Mx = 𝜶 𝒙 𝒘 𝒍 𝒙
𝟐
My = 𝜶 𝒚 𝒘 𝒍 𝒙
𝟐
IS 456
Clause No.: D - 2
Page No.: 90

RESTRAINED TWO WAY SLAB: (CORNERS ARE HELD DOWN)
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TWO WAY SLABS
 In case of Restrained Two way slabs, the edges of slab are restrained to the beams.
 When such slabs are loaded, corners are not lifted up, producing torsion at each
corner.
 Thus torsion reinforcement is provided at each corner.

TYPES OF SLABS BASED ON SUPPORT CONDITIONS:
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TWO WAY SLABS
No. Simply supported slab Restrained slab
1 Corners are not held down. Corners are held down.
2
When slab is loaded, corners are
lifted up.
When slab is loaded, corners are not
lifting up.
3
At corners, torsion is not produced.
Therefore, torsion reinforcement is
not required.
At corners, torsion Is produced.
Therefore, torsion reinforcement is
provided at each corners.
4 Edge strips are not provided. Edge strips are provided.
5
Design the slab as per
IS; 456, Clause No. D-2, Page No. 90.
Design the slab as per
IS; 456, Clause No. D-1, Page No. 90.

CONTINUOUS SLAB (OVER ALL FOUR EDGES):
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TWO WAY SLABS
 When slab is continuous over all four sides, Reinforcement is provided along
middle strip and over continuous edges.
 Torsion reinforcement is not provided in this kind of slab at corners.

REINFORCEMENT OF TWO WAY SLABS:
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TWO WAY SLABS

Two Way Slabs

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