Slab in construction | Slab types | Application, advantages and disadvantages

 Slab

Slabs are used to create flat, usually horizontal surfaces in building floors, roofs, bridges, and other constructions. The slab can be supported by walls, reinforced concrete beams (which are normally cast monolithically with the slab), structural steel beams, columns, or the ground. There are 16 different types of slabs.

Different Types of concrete slabs in construction

In the construction industry, there are 16 main varieties of slabs. Some of them are obsolete, but many of them are still widely used. In this article, I'll go through each slab in detail and show you how to use each one. The various varieties of concrete slabs are listed below:

Flat slab

The flat slab is a concrete slab that is directly supported by concrete columns or caps. The Flat slab must be at least 8 inches thick (0.2 metres). Because a flat slab lacks beams, it is also known as a beam-less slab. They're supported by the columns themselves. Loads are transferred straight to columns. A plain ceiling is achieved in this form of building, which gives it a beautiful architectural appearance. The simple ceiling diffuses light better and is considered more fire resistant than the standard beam slab structure. The flat slab is more straightforward to build and requires less formwork. This is an example of a concrete slab.

Application

1.       Flat Slabs are utilised to provide a plain ceiling surface that allows for improved light diffusion.

2.       Constructability is simple, and the formwork is cost-effective.

3.       Larger headroom or a lower storey height, as well as a more appealing appearance.

4.       This type of slab is available in the parking lot.

5.       Flat slabs are commonly utilised in parking garages, commercial buildings, hotels, and other locations where beam projections are undesirable.

Flat Slab has the following advantages:

1.       It reduces floor-to-floor heights when a deep false ceiling is not required.

2.       The height of a building can be decreased.

3.       It is simpler to use an automatic sprinkler.

4.       Construction time is reduced.

5.       It improves the slab's shear strength.

6.       Reduce the clear or effective span to reduce the moment in the slab.

Flat slab disadvantages:

1.       A large span is impossible to achieve using a flat plate method.

2.       Not recommended for fragile (masonry) partitions.

3.       Increased slab thickness.

There are four different types of concrete Flat Slabs:

1.       Slab without drop and column without column head(capital).

2.       Slab with drop and column without column head.

3.       Slab without drop and column with column head.

4.       Slab with drop and column with column head.

Conventional Slab

A conventional slab is defined as one that is supported by beams and columns. The slab thickness is minimal, but the beam depth is great, and the load is passed to the beams and subsequently to the columns in this kind. When opposed to a flat slab, it necessitates additional formwork. There is no requirement for column caps in a traditional slab. The thickness of a standard slab is 4′′ (10cm). If the concrete will be subjected to large loads on a regular basis, such as mobile homes or garbage trucks, 5′′ to 6′′ inches is advised.

Concrete slabs are typically square in shape and 4 metres long. In a traditional slab, reinforcement is provided in the form of horizontal bars, which are referred to as Main Reinforcement. The term "Distribution bars" refers to vertical bars and bars.

Conventional Slab is divided into two varieties based on its length and breadth:

·         One-way slab

·         Two-way slab

A.    One-way slab

To carry the load in one direction, a one-way slab is supported by beams on both sides. One-way slabs have a ratio of longer spans (l) to shorter spans (b) that is equal to or greater than 2. The slab will bend in one way in this case, namely in the direction of its shorter span. However, distribution steel is used as a minimum reinforcement along the longer span above the primary reinforcement to evenly distribute the load and resist temperature and shrinkage stresses.

equations for a one-way slab and a two-way slab:

The slab is typically 4 metres long. However, on one way slab, one side is 4m long and the other is longer than 4m. As a result, the aforementioned equation is satisfied. The shorter span receives main reinforcement, whereas the longer span receives distribution reinforcement. The main bars are cranked to prevent stresses from forming.

B.     Two-way slab

It is known as a two-way slab because it is supported by beams on all four sides and the weights are carried by the supports in both directions. The ratio of longer span (l) to shorter span (b) in a two-way slab is less than 2. Due to the likelihood of the slabs bending in both directions to the four supporting edges, distribution reinforcement is supplied in both directions.

This type of slab has a length and width of more than 4 metres. In a two-way slab, distribution bars are installed at both ends to prevent the buildup of strains. These slabs are utilised in the construction of multi-story building levels.

Hollow core ribbed Slab or Hollow core slab

The voids or cores that run through the units give hollowcore ribbed slabs their name. The cores can be used as service ducts, reducing the slabs' self-weight and increasing structural efficiency. The cores also help to reduce the amount of concrete needed, which is good for the environment. Units are typically available in conventional widths of 1200 mm and depths ranging from 110 mm to 400 mm. The length of units can be whatever you choose. These slabs are precast and are utilised in situations when building must be completed quickly.

Between four and six longitudinal cores run through the hollow core ribbed slabs, with the major objective of the cores being to reduce the weight and material within the floor while maintaining maximum strength. The slabs are reinforced longitudinally with 12mm diameter steel strand to add even more strength. This is an example of a concrete slab.

Using tower cranes to construct hollow core slabs Between the beams, hollow slabs are put. Screed is used to fill up the gaps between the slabs.

Hollow core ribbed slabs have a high span capacity, with a capacity of 2.5 kN/m2 over a 16-meter span. The capacity to span a considerable distance is beneficial for office, retail, and parking developments. Depending on the needs, units are erected with or without a structural screed. Slabs come with a smooth pre-finished soffit when they arrive on site. Pre-finished soffits are a low-maintenance option for car parks and other open constructions.

Hollow core ribbed Slab has the following advantages:

1.       The hollow core ribbed slab not only saves money on construction, but it also reduces the structure's overall weight.

2.       Because of its thickness, hollow core slabs have excellent fire resistance and sound insulation.

3.       It removes the requirement for electrical and plumbing components to be drilled into slabs.

4.       Installing it is simple and time consuming.

5.       Construction is completed quickly.

6.       Reinforcing the hollow block masonry does not require any additional formwork or specific construction tools.

Hollow core ribbed slab disadvantages:

1.       The hollow core ribbed slab units may be damaged during shipment if not handled appropriately.

2.       Producing suitable connections between the precast parts becomes tough.

3.       Lifting and moving the precast units will necessitate the use of specialised machinery.

4.       For short periods, it is not cost effective.

5.       Repairing and strengthening it is difficult.

 

 

Hardy slab

In Dubai and China, hardy slabs are common. Sturdy Bricks are used to build the hardy slab. Hardy bricks are built of concrete hollow blocks and are hollow bricks. This type of block is used to fill in gaps in the slab. Hardy slabs save concrete, which reduces the slab's own weight. When compared to the traditional slab, this one has a thickness of 0.27m.

 

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