Two way slabs are slabs that are supported on all four edges and have a ratio of less than 2 between their long and short spans. This causes them to bend in both directions. There are two types: simply supported and restrained. Simply supported slabs have corners that lift up under loading while restrained slabs have corners that are held down, producing torsion. Reinforcement is provided differently depending on the type of slab.

1. 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

2. 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.

3. 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

4. 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

5. 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

6. 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.

7. 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.

8. 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.

9. REINFORCEMENT OF TWO WAY SLABS:
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TWO WAY SLABS