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A flat plate floor system is a reinforced concrete frame system with a uniform thickness that is supported directly over the columns or the load-bearing walls. The flat plate floor system is a common floor construction type employed in the construction of the building.

Fig.1.Flat Plate Floor System

The important features, construction and the advantages of employing a flat plate floor system are briefly explained in this article.

Features of Flat Plate Floor System

The important features of the flat plate floor system are enlisted below:

  1. One of the important features of a flat plate floor system is the thickness of the floor. It is constructed with uniform thickness with a flat soffit.
  2. The soffit constructed for a flat plate system requires simple formwork which hence makes the construction easier.
  3. The flat plate floor system is the best choice for serving the purpose of a horizontal floor over a suspended ceiling.
  4. The flat plate floor is constructed with an economical span that takes up medium loads and avoids the chances of long-term deflection.
  5. A flat plate floor system depending upon the load and deflection criteria can be either pre-cambered or prestressed.

Construction Details of Flat Plate Floor System

A flat plate floor can be constructed with an economical span of 6 to 8m for ordinary reinforced flat plate floor. For prestressed construction, the economical span can be increased to 8 to 12m.

In general, if D is the depth of the slab, then

Span ‘L’ for a Simply Supported Reinforced Concrete Flat Plate System = D x 28

Span ‘L’ for an End Span Continuous Reinforced Concrete Flat Plate System = D x 30

Span ‘L’ for an Internal Continuous spanned Reinforced Concrete Flat Plate System = D x 32

If the flat plate system is prestressed, the span L can change to D x 30, Dx 37 and D x 40 respectively.

Advantages of a Flat Plate Floor System

The basic advantages of a flat plate floor system are:

  1. A flat plate floor system does not demand any beam.
  2. The use of zero beams helps to have underfloor spaces and more service areas.
  3. The flat plate floor system requires simple formwork. This system is suitable for a direct fix or sprayed ceiling.
  4. The structural depth of a flat plate floor is minimum.
  5. Reduced depth of slab helps to increase the floor to floor height of the building.

Disadvantages of Flat Plate Floor System

The basic disadvantages of a flat plate floor system are:

  1. The lateral load capacity of a flat plate floor system is limited compared to a moment frame.
  2. The spans employed are medium length
  3. Special reinforcement for shear must be provided at the columns or larger columns must be constructed.
  4. Long-term deflection is an expected factor that requires full life control.
  5. A flat plate floor system is not a good choice for supporting partitions that are too brittle. For example Masonry Walls.
  6. A flat plate floor system is not a good choice to take up heavy loads.

About Neenu ArjunVerified

Neenu is a Civil and Structural Engineer and has experience in Design of Concrete and Steel Structures. She is an Author, Editor and Partner at theconstructor.org.