How to calculate a one way or two way slab?

How do we calculate a one way or two-way slab? If L/b ratio is greater than or equal 2 or then it is considered a one-way slab. (Longer span / Shorter span) L / b ≥ 2. If L/b ratio is less than 2 then it is considered a two-way slab. (Longer span / Shorter span) L / b < 2

What's the difference between two way slab and flat plate slab?

Such a slab is called the flat plate. A flat slab with a recess formed (by removable and filler blocks) on soffit so that it comprises a series of ribs in two directions called waffle slabs . The slabs supported on a series of intersecting long grid beams is called slab grid.

Which is the best definition of a slab?

1 : a thick plate or slice (as of stone, wood, or bread): such as. a : the outside piece cut from a log in squaring it. b : concrete pavement (as of a road) specifically : a strip of concrete pavement laid as a single unjointed piece.

Why is a slab an important structural element?

Slab is an important structural element which is constructed to create flat and useful surfaces such as floors, roofs, and ceilings. It is a horizontal structural component, with top and bottom surfaces parallel or near so.

Which is one way slab or two way slab?

Slab carries the loads imposed on it and duly transfers the forces either in a one way or in a two-way mechanism. Thus, slab serves both as a load-bearing surface as well as a walking surface. Depending upon the requirement and the design of the structure, different types of slab such as concrete slab, flat slab, waffle slab etc can be used.

How is a slab used in a building?

Slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs, bridges, and other types of structures. The slab may be supported by walls, by reinforced concrete beams usually cast monolithically with the slab, by structural steel beams, by columns, or by the ground.

What is the function of main reinforcement in slab?

As the name suggests the main reinforcement is the one that takes the tensile stresses resulting from critical bending. This is provided along the short span of slabs since the critical bending happens along the shorter span. Without main reinforcement the slab will not have sufficient design strength.

Difference Between One Way Slab and Two Way Slab | What Is Slab? | What Is One-Way Slab? | What Is Two Way Slab? | What Is Flat Slab?

Q: What's the difference between two way slab and flat plate slab?

Such a slab is called the flat plate. A flat slab with a recess formed (by removable and filler blocks) on soffit so that it comprises a series of ribs in two directions called waffle slabs . The slabs supported on a series of intersecting long grid beams is called slab grid.

Q: Which is the best definition of a slab?

1 : a thick plate or slice (as of stone, wood, or bread): such as. a : the outside piece cut from a log in squaring it. b : concrete pavement (as of a road) specifically : a strip of concrete pavement laid as a single unjointed piece.

Q: Why is a slab an important structural element?

Slab is an important structural element which is constructed to create flat and useful surfaces such as floors, roofs, and ceilings. It is a horizontal structural component, with top and bottom surfaces parallel or near so.

Q: Which is one way slab or two way slab?

Slab carries the loads imposed on it and duly transfers the forces either in a one way or in a two-way mechanism. Thus, slab serves both as a load-bearing surface as well as a walking surface. Depending upon the requirement and the design of the structure, different types of slab such as concrete slab, flat slab, waffle slab etc can be used.

Q: How is a slab used in a building?

Slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs, bridges, and other types of structures. The slab may be supported by walls, by reinforced concrete beams usually cast monolithically with the slab, by structural steel beams, by columns, or by the ground.

Q: What is the function of main reinforcement in slab?

As the name suggests the main reinforcement is the one that takes the tensile stresses resulting from critical bending. This is provided along the short span of slabs since the critical bending happens along the shorter span. Without main reinforcement the slab will not have sufficient design strength.

Difference Between One Way Slab and Two Way Slab (3)

Table of Contents

What Is Slab?

In the structural system of buildings, slabs are an important element of the floor system. Slabs usually transfer loads such as gravity loads, dead loads, and live loads to a vertical framing system such as columns. Slabs are used as floor and ceiling in various buildings.

Slabs cover a large area of concrete in a building. So during an earthquake, various external forces are attracted to the surface of the slab.

Slabs are represented by different designs in different types of compositions. Such as to obtain flat surfaces in a particular building and as a deck slab of a bridge. The slab is usually formed by the structure of a reinforced concrete beam.

The two main types of slabs used in the construction of a building are widely used as one-way slabs and two-way slabs. In this article provides information about the difference between a one-way slab and a two-way slab.

Also Read : What Is a Concrete Wall Finish? | Types of Concrete Finishes

Function of Slab

Depending on the design as per the requirement of the structure, some of the main functions of the slab are shown below.

The slab provides a platform to work on the structure.
The one-way slab or two-way slab method is properly used to transfer the load on the slab.
The slab provides a flat surface to work with easily.
The design of multi-story building has been made possible by slabs.
The slab can be used as a sound, heat as well as a fire insulator.
The slab helps to keep the room private.

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Type of slabs

Based on support conditions,

One Way Slab
Two Way Slab
Flat Slab Resting Direction on a Column Without Beam
Grid Slabs or Waffle Slab

What Is One-Way Slab?

A one-way slab is designed in such a way that the load on the beam carries in one direction. One way slab is usually used for a short span.

According to IS 456: 2000, the ratio of long span (L) to short span (B) in one way slab is greater than 2.

Mathematically;

Longer Span / Shorter Span ≥ 2.

One-way slabs can be constructed only on two parallel beams or walls in building construction. One-way slabs are commonly used for short spans in a building.

Reinforcement for one-way slabs is arranged by the main reinforcement in a short span and distribution reinforcement in a long span.

Some examples of one-way slabs include cantilever slabs, chajja, and verandas.

The supported slab on each of the two walls is always supported by one slab.

A slab supported by less than 4 sides in a slab of Structure in a building can be designed as a one-way slab.

All cantilever slabs are a simple example of a one-way slab.

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What Is Two Way Slab?

Two-way slabs are supported from all four sides. The load is transferred in both directions through this slab. The main reinforcement for the structure of a two-way slab is given in both directions.

A two way slab is designed when the ratio of long span to short span is less than two. This type of slab carries the load in two directions.

The thickness of the two away slab depends on the deflection control criteria. In this type of slab, the reinforcement in the directions is designed to resist the bending moments.

Two-way slabs are commonly used to suit the needs of multi-story and commercial buildings.

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What Is Flat Slab?

A flat slab is a type of reinforced concrete slab. There are no beams and girders as support for the formation of a flat slab. In this type of flat slab, the load is transferred directly to the concrete columns.

Flat slabs are used by engineers for the construction of the building as required in different situations.

Some of the advantages of the flat slab are as follows,

Due to the flat slab can be properly planned for partition walls.

Using a flat slab for a building can give the owner the opportunity to choose a room layout as needed.

Using a flat slab in a building eliminates the need for false ceilings.

The floor height can be increased as no beams are used in the flat slab.

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What Is Grid Slab?

For a large room slab, a slab is formed over a number of beams on the column at the corner end. This type of slab structure is called a grid slab.

Sometimes grid slabs are designed for large column-free areas in large halls, public places, auditoriums, marriage halls, etc. For the formation of this type of slab, deep depth may be allowed for the column to column main beam.

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Analysis of Slab

The structural design of the slab is the same as that of the beam. The slab is analyzed as follows,

Elastic Analysis

The 1 m wide strips of the slab is analyzed as a base. The load on this base is calculated. Thus, a 1 m strip of the slab is analyzed by assuming a dummy beam as 1 m.

Code Coefficients:

The slab is analyzed by yield line theory. The analysis of the slab can be directly relied on as a coefficient as shown in the code.

The calculation of redistribution of moments is not taken into account for slab analysis.

Yield Line Theory

Yield line theory is a method of analysis based on the final bending moment for the edge of a fall for a slab.

At collapse loads, the slab starts to crack because the slab is usually under-reinforced.

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Reinforcement Details In Slab

The design of reinforcement in the slab is used to safely distribute the forces coming on the slab to the column.

One Way Slab Reinforcement Details

In a one-way slab, the load is transferred from one side to the other. In this type of slab, the maximum load will be transmitted in a long span. Therefore it is necessary to give proper reinforcement on the long span side.
So in a one-way slab to provide adequate support to the long span side, the main reinforcement is placed parallel to the short span by proper spacing, and the distribution reinforcement is placed on the long side according to the correct spacing.
Therefore, one-way slabs are preferred over the short span of the slab. Where main reinforcement is given on long-span due to bending. Reinforcement of one Way Slab is given as shown in the figure.

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Two Way Slab Reinforcement Details

In a two-way slab, the applied external load is transferred to both sides in a long span and short span.
In two way slab, the main reinforcement is laid on both sides. In this type of slab, the load on both sides is evenly distributed.
In RCC two Way slab each of the four sides is held on the beam by main reinforcement. A load of a two-way slab is transferred through structural elements such as beams.

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Types of Loads Acting on Slab

There are different loads on the slab. This is shown as follows

Wind load
Live load
The dead load of the slab
Earthquake loads
Snow load

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