What are the Differences between One Way Slab and Two Way Slab?

Most civil engineering students’ gets confused when asked about the questions related to the differences between one way slab & two way slab. If you want to know about their differences, this article explains it in detail with definitions and comparison chart.

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Before going into the list of differences between one way & two-way slab, we are going to discuss what Slab is & what the types of slab are & what differentiates them from each other.

SLAB:

Slab is the horizontal member of structure the top and bottom surfaces of slab is parallel to each other. The depth of slab is very small compared to its span. slab is constructed on the top of walls, beams or columns of the structure. In multi-story building the top slab is called roof slab & in the lower slab are called floor slab. Slab may be constructed from different materials such as steel, concrete, bricks etc. it creates flat horizontal surfaces like floors, roof decks and ceilings. Usually the depth of slab is slightly thick and supported by beams, columns, walls, or the ground.

Slabs are classified into two types:

One Way SlabTwo Way SlabOne Way Slab

According to IS 456:2000 the slab in which the ratio between longer span (L) and shorter span (B) is equal or greater than 2 is called one way slab. In case of one way slab the load is carried in one direction & on that direction main bars are designed & on the other direction thin bars are used compered to main bars which are called distribution bars.

One way slab = Longer span / shorter span > 2

Verandah is the best example of one way slab.

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Figure of One way slab

Two Way Slab

The slab in which the ratio between the longer span (L) & the shorter span (B) is less than 2 is called two way slabs. In case of two way slab loads are distributed in both direction and it is supported from all sides which is why the load can be distributed on both direction in square shape area the main bars can be used on the either side but the main bars will always beneath the distribution bars but if the shape of area is in rectangular shape then the main bars should be used in the shorter direction & distribution bars should be used in the longer direction.

Two way slab = Longer span / shorter span 2

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Figure of Two way Slab

Differences between One Way Slab & Two Way Slab:

The difference between One Way Slab & Two Way Slab are shown in the table which is given below:

S. NoOne Way SlabTwo Way Slab
1The length of the longer span is two times equal or greater than the length of the shorter spanThe length of the longer span is equal or less than two times length of shorter span.
2In IS code 456:2000, The ratio of longer span (L) to shorter span(b) which is (L/B) greater than 2 is known as One way slabIn two way slab, the ratio of longer span to shorter span is less than 2.
3Based on the deflection and considering the span the thickness of slab may vary from 4 inch to 6 inch(100mm to 150mm)Based on the deflection and considering the span the thickness of the slab may vary from 4 inch to 8 inch (100mm to 200mm)
4One way slab is reinforced by beams on the 2 shortest sides to transmit the load along one direction.Two way slab is reinforced by beams on all the 4 sides and the loads are transmitted by the supports along both directions,
5One way slab curves, deflect or bend in a direction vertical to the supporting endsTwo way slab curves, deflect or bend in both directions.
6Bent shape of one way slab is cylindrical.Bent shape of two way slab is dish-shaped.
7One way slab has strength in shortest direction. These types of slab are used for verandah and terrace. Two way slab has strength in both direction. These types of slabs are mostly used in the floor of multistory buildings.
8Main reinforcement is provided on shorter direction due to the bending.Main reinforcement is provided in both directions due to bending happens on both sides.
9One way slab is economical as compared to two way slabIt’s more expensive compared to one way slab because steel bars are used more in it.
10In one way slab the load is carried on one directionIn two way slab the load is carried on both direction
11Beams supported the One way slabs on two sidesBeams supported the two way slabs on four sides
12Mostly the shape of one way slab is rectangularMostly the shape of two way slab is square.
13The design of one way slab is totally different from two way slab.Design of two way slab there equations, steps of methods everything is different from one way slab.
14In one way slab the extra bar or crank bar are provided on one direction or on two sidesIn two way slab the extra bar or crank bar are provided on both direction or on four sides
15The Deflection of one way slab looks like cylindrical.

See more: How Many Cm Is 70 Inches To Cm, How Many Cm In 70 Inches

The deflection of two way slab looks like bowl
Conclusion:

The main objective of this article “Differences between One Way Slab & Two Way Slab” is that the ratio between longer span to shorter span will be greater than two (2) in one way slab and carried the load on only one direction while in two way slab the ratio between longer span to shorter span will be less than two (2) and carried the load on both direction.

So friends I have written all the difference between one way slab and two way slab as much as I know. If this article is helpful do share it with your friends and leave a comment