7 Top Ribbed Slab Advantages and Disadvantages | Types of Ribbed and Waffle slabs

7 Top Ribbed Slab Advantages and Disadvantages | Types of Ribbed and Waffle slabs

What Is a Ribbed Slab? |Ribbed Slab Advantages and Disadvantages | Characteristics of Ribbed Slab | Uses and Benefits of a Ribbed Slap

What Is a Ribbed Slab?

The ribbed slab is a slab with ribs at regular intervals along the length, and is often used for mounting on concrete. Such a slab is usually made of reinforced concrete and is cast in sections of a fixed length.

The ribs perform the function of corner reinforcement, particularly on a lower-height slab.

Ribbed or waffle slabs are slab designs made up of a set of parallel reinforced concrete T segment consists reinforced concrete girders. The slab is the beam’s flange, and the extended part is the web.

Ribs are the expanded section of the body. In average, the rib spacing should be between 20 and 30 inches.

In the construction industry, a ribbed slab is a concrete slab that is formed with a series of convex ribs.

The ribs are designed to provide additional reinforcement for the slab and help to limit cracking on the surface of the slab.

Concrete slabs can also be designed to create ribbed floors, roof slabs, tank-walls, and more

Types of Ribbed and Waffle slabs

There are two types of ribbed slab system

1. One-way ribbed slab system

One-way ribbed slab is a floor slab system in which ribs run vertically from the foundation slab to the wall plate. The ribs run in one direction only.

2. Two-way ribbed slab system

In two-way ribbed slabs, both edges of the slab become supported by walls or columns at different levels with one of the edges having a waffle design pattern.  The ribs are vertical to one edge, and inclined to the other edge.

Characteristics of Ribbed Slab

  1. In comparison to others, the volume of concrete used is quite little.
  2. The ribbed slab’s reinforcement comes in the shape of mesh or individual bars.
  3. In the case of a ribbed slab, no separate excavation for beams is required.
  4. The bottom surface of the slab resembles a waffle, which is achieved by using cardboard panels or pods, for example.
  5. Ribbed Slab are best suited for flat areas.
  6. Ripped slab resists shrinking and is less expensive than strengthened rafts and footing slabs.
  7. The ideal thickness of waffle slab is 85 to 100 mm, with a maximum overall depth of 300 to 600 mm.
  8. The breadth of the beams or ribs in a ribbed slab is typically 110 to 200 mm.
  9. Rib spacing should be between 600 and 1500 mm.

Benefits of a Ribbed Slap

A ribbed slab is a concrete slab made of many expanded metal tubes that are tightly woven together to create the walls of a building. The ribs provide extra support for the slab and will prevent it from cracking as it is being poured

A ribbed slab will not crack, as long as there are enough fibers in each direction. The problem with ribbed slabs is that they are costly to build, and they give a very thin wall around the foundation.

The rib-slab is unique in that it creates a lighter and stronger slab than an equal flat slab, allowing foundations to be built with less depth because the ultimate load is lowered. When slab vibration is an issue, they provide an excellent form.

Ribbed Slab FAQs

1. What is a ribbed slab?

The waffle slab, also known as the ribbed slab, is a structural component with a plain top and a grid-like arrangement on its lower surface.

The ribbed slab’s top is typically thin, and the bottom grid lines are frequently ribs that can be set perpendicular to one another.

It is typically employed in situations when vast spans are required to avoid many columns obstructing space.

2. What are the advantages of the ribbed slab?

The two greatest advantages of a ribbed slab are its relative light weight and flexibility in design. The thin layers of concrete minimize the overall weight of the slab, making it easier to lift and to install when compared with a flat-slab.

The flexible design capabilities for which ribbed slabs are renowned can be used in many ways to not only to hide structural flaws but also to increase thermal comfort in buildings by creating greater thermal mass in walls.

3. What are the disadvantages of a ribbed slab?

The cost of the ribs and additional cast-in-place layers, making it more expensive, make concrete slabs prone to cracking, can be used in certain situations. They are not suitable for sloping locations; if a sloping space exists, it must be filled by leveling or digging.

4. What are the benefits and uses of the waffle slab?

The various benefits of a waffle slab are that they can be lightweight, cost-effective, and easier to install. This is because the build-up with ribbed slabs is usually much quicker as it requires less concrete and eliminates the need for formwork.

Due to their lightweight, these slabs can be utilized in situations where higher spans are required such as warehouses, supermarkets, commercial buildings, and hospitals.

5. Why should I choose ribbed slabs?

In many more cases than not, ribbed slabs are simply better suited to the structure and load demand than other construction methods, such as flat slabs. In some cases, waffle slabs of equal thickness may be lighter than flat slabs. In most cases, they are less likely to crack and will be much more resistant to deflection.

6. How do I install a ribbed slab?

The ribbed and waffle slabs require the formwork to be installed first. The formwork is constructed in the same way as for other types of concrete construction.

Most formwork for sites where the ribs are going to be visible are ribbed-slab specific and allow for a ribbed-slab installation.

However, there is a lot of extra work on the slab itself. In addition to this, the job is likely to take longer as there is more surface area to work with.

Advantages and Disadvantages of Ribbed Slab

Ribbed Slab Advantages and Disadvantages

There are many advantages to use ribbed slabs, however, they may not be suitable for all buildings.

Advantages of Ribbed Slab

Some of the advantages include:

  1. Lightweight: – Ribbed and waffle slabs provide a lighter and stiffer slab than an equivalent flat slab, reducing the extent of foundations. They provide a very good form of construction where slab vibration is an issue, such as laboratories and hospitals.
  2. Design to long spans: – Waffle slabs are used for big span slabs or flooring used when there is a limited need for multiple columns.
  3. Offer design benefits: – All electrical appliances can be readily put in the gap between the ribs, which can be physically attractive.
  4. Flexible installation and formwork: The use of simple formwork can facilitate the installation of ribbed slabs saving time and money.
  5. The slabs are lighter: – Ribbed slabs can be formed with a lesser amount of concrete equaling less cost. These slabs are lighter and require much less amount of concrete, so it is economical.
  6. Thinner Design: -Slab thickness of ribbed or waffle slabs is less than other slab systems. Therefore, the weight of the slab is reduced. This saving of weight can change in structural characteristics.

Disadvantages of Ribbed Slab

  1. Cost: – Ribs add to the cost of the slab, since they are labor-intensive and demand an extra layer for each rib in addition to normal concrete reinforcement. It has higher formwork costs than other slab systems
  2. They are not suitable for sloping locations; if a sloping space exists, it must be filled by leveling or digging.

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