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# Difference between one way and two way slab in terms of their structural behaviour?

Question asked by madugula in #Civil & Structural on Feb 8, 2010
Rank D1 - MASTER
what is the difference between one way and two way slab in terms of their structural behaviour? Posted in: #Civil & Structural
CIVILPRINCESS · Feb 8, 2010
Rank A3 - PRO
Re: slabs

One way slabs are designed to transfer their loads to only two opposite support walls. Generally for spans up to 3.60 meters and with length/breadth ratio is greater than 0.60 one way slabs can be provided.the reinforcement will be along the longer direction.

Two way slabs are designed to transfer their loads to all the four support walls. Generally for spans greater than 3.60 meters and with length/breadth ratio is less than 0.60 two way slabs can be provided.the reinforcements will be placed along the length and the breadth i.e. the reinforcements will be perpendicular to one another.

A one way slab, have it structural strength in shortest direction.
A two way slab, have it structural strength in in two direction.
Guttu · Feb 10, 2010
Rank C3 - EXPERT
Re: slabs

One way slabs bend in one direction and load is distributed in one direction only. They behave like a beam. slabs with length/breadth ratio above 2 are considered as one way slabs.

Two way slabs are those where length/breadth ratio is below 2. The load is distributed in all four sides. Deflection and bending is reduced to a great extent compared to one way slab.

In both case main reinforcement is provided along long span.
Rank E2 - BEGINNER
Re: slabs

Guttu
One way slabs bend in one direction and load is distributed in one direction only. They behave like a beam. slabs with length/breadth ratio above 2 are considered as one way slabs.

Two way slabs are those where length/breadth ratio is below 2. The load is distributed in all four sides. Deflection and bending is reduced to a great extent compared to one way slab.

In both case main reinforcement is provided along long span.
Hi Mr.Guttu

Your explanation about one way & two way slabs was good, but you have mentioned "In both case main reinforcement is provided along long span" thats wrong. for one way slab the main reinforcement should be along the shorter span.
undo · Mar 26, 2010
Rank E2 - BEGINNER
Re: Difference between one way and two way slab in terms of their structural behaviou

for one way slab. the bending of slab is along the short span. technically.. we avoid doing bottom rebar splice at mid span.

but figuratively with a ruler, the bending is along the longest span. im quite confuse as my lecturer love to make bending examples with a ruler.
De Divine · Jul 11, 2014
Rank E2 - BEGINNER
For one way slab, the bending of slab is along the shorter span. Then where does two way bending takes place
Jitendra Tiwari · Jan 2, 2020
Rank E2 - BEGINNER

One way slab is supported on two opposite sides by rigid supports and carry the load in the direction perpendicular to the supports. the plane surface of the uniformly loaded slab deforms into a cylindrical surface and bending moment develops only in one direction.

Whereas two-way slab supported on four edges with the ratio longer span to shorter span less than 2. Two-way slab carries the load in two perpendicular directions.

SANDHYAKUMARI Rajput · Feb 22, 2020
Rank E2 - BEGINNER

What Is  Slab?

A slab is constructed to provide flat surfaces, typically horizontal, in building roofs, floors, bridges, and other types of structures. The slab could be supported by walls, by reinforced concrete beams normally cast monolithically with the slab, by structural steel beams, either by columns or from the ground.

A slab is a plate element having depth (D), very small as compared to its length and width. A slab is used as floor or roof in buildings, carry distribution load uniformly.

What Is a Two-Way Slab?

The design considerations of wall-supported two-way slabs are similar to those pertaining to one-way slabs.

The thickness of the slab is generally based on deflection control criteria, and the reinforcements in the two orthogonal directions are designed to resist the calculated maximum bending moments in the respective directions at the critical sections. [Additional reinforcement may be required at the corners of two-way slabs in some cases, as explained later].

The slab thickness should be sufficient against shear, although shear is usually not a problem in two-way slabs subjected to uniformly distributed loads.

If the slab is supported at all four edges and if  Ly/Lx < 2,

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