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How Does A Suspended Slab Work, In A New Home Construction
Suspended reinforced concrete slabs are used in many applications in the construction industry.
The advantage of a suspended reinforced concrete slab is that it is possible to get high strength, but at
the same time keep the weight low.
Concrete slabs can be pre-fabricated in a factory and then sent to the site, or they can be cast in-situ.
This depends on site conditions and the type of project.
A typical concrete slab can be between 100 to 500 mm in thickness and will be steel reinforced.
SUSPENDED REINFORCED CONCRETE
DESIGNS:
There are different designs used for suspended reinforced concrete slabs. All the designs ensure a high strength
to weight ratio.
The designs used for the suspended slabs
are:
* Corrugated Slab
* Ribbed Slab
* Waffle Slab
Corrugated Slab:
A corrugated suspended reinforced concrete slab is made using a combination of steel and concrete.
Concrete is poured onto a strong steel tray, which gives it added strength for use in building or other
construction purposes.
The tray will have a corrugated design. The corrugations will run across the short dimension from end to
end.
Corrugations add to the strength of the concrete slab.
In addition to having high compressive strength, it does not bend or deflect. The corrugations will always be
on the underside of the concrete slab.
When a corrugated slab is used in a building or construction, it enhances the ability to withstand
fluctuations of temperature and/or adverse environmental conditions.
The advantages of a corrugated suspended reinforced concrete slab are that it has a high strength to
weight ratio.
It is ideal to use for large suspended concrete slabs.
Ribbed Slab:
It is lighter and stiffer than a comparative flat slab. Since they are light weight but strong, the extent of
the foundations can be reduced.
This helps in saving costs.
Ribbed slabs have wide band beams which run between columns.
It has equal depth narrow ribs which span the orthogonal direction. To complete the system a thick top
slab is used.
The advantages of a ribbed slab are that it is relatively light and flexible.
It gives considerable added strength in one direction. Since it has good vibration control, it can be used
in conditions where vibrations are an issue.
The use of a ribbed slab speeds up construction work. It is robust, has good thermal mass and is fire
resistant.
Waffle Slab:
A waffle slab is usually deeper than a comparable ribbed slab.
They have a thin top with narrow ribs spanning both directions. The column heads or band beams have
the same depth of the ribs.
A waffle slab gives additional strength in both directions. The advantage of a waffle slab is that it has
excellent strength to weight ratio.
It is light and relatively flexible. Due to its comparative light weight, it saves on the cost of the
foundation.
It is robust, fire resistant and has good thermal mass.
The use of waffle slabs speeds up construction.
REINFORCEMENT DESIGN FOR A CONCRETE
SLAB:
Reinforcement designs of concrete slabs come in two types.
* Oneway slab - in this slab it needs moment resisting reinforcement only in the direction of its shorter
side.
This is because the moment on the longer axis is minimal and can be ignored.
When the ratio of the length of long to short side is > 2, it is considered as a one way slab.
* Two way slab - It needs moment resisting reinforcement in both directions.
If the ratio of the length of the long to short side is < 1, then it requires reinforcement of the moment in
both directions.
CONSTRUCTION METHODS FOR
SUSPENDED REINFORCED CONCRETE SLAB:
A concrete slab may be prefabricated or cast in-situ.
A pre-fabricated slab is cast in a factory and transported to site.
It can be pre-stressed in the factory or post-stressed at the site. At times it may be unstressed.
A concrete slab can also be cast in-situ. It uses formwork into which the wet concrete is poured. If the
slab
is reinforced, then rebars are placed in the correct position within the formwork.
Concrete is then poured into the formwork.
For suspended slabs, the formwork will be in the shape of a tray, with supporting slabs underneath. After
the concrete sets the formwork and supports are removed.
Suspended Slabs
Are Widely Used In The Construction Industry.
Due to it's many advantages it speeds up construction as well as saves on costs.
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"Important NOTE" Information Provided On This
Website Is Intended For "GENERAL INFORMATION ONLY"
And Must Be Only Be Used Only As A "GUIDE" It Must Not Be Used For Decision
Making, Or
Be Used For Any Building Purposes Or Legal Proceedings. Refer To Our Policies On This Website.
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