What is Chair Bar in Reinforcement:
The chair bar is used to provide space between bottom reinforcement and top reinforcement. It is a reinforced bar used to maintain the distance between reinforcement mesh.
If a chair bar is not provided then slab thickness can be reduced due to concrete pouring. Sometimes reinforced bars can be exposed.
The diameter of the chair reinforcement bar should not be less than 12 millimeters. It is normally used in slabs and footings. The main aim of the chair bar is to maintain the required spacing throughout the steel mesh.
The center to center distance between two chair bars is normally kept at 1000 millimeters.
There are three major components of the chair bar as shown in the above figure.
Head: Top horizontal portion of the chair bar is called the head.
Height: Vertical portion of the chair bar is called the height of chair reinforcement.
Leg: The horizontal portion of the chair bar is known as the leg.
Uses of chair reinforcement:
- It is provide to maintain space between reinforcement mesh.
- To avoid lateral movement of reinforcement.
- It is used to provide required concrete cover.
- It is used to ensure required concrete strength after concrete pouring.
- To avoid any movement due to application of vibrator machine.
- Chair bar provides support to the reinforcement mesh.
Frequently Asked Question
What should be the diameter of chair bars used in reinforcement fixing?
Answer: Normally diameter of the chair bar is kept at more than 12 mm. It can vary from 12 mm to 20 mm.
In some rare cases, a 10 mm dia bar can be used. 10 mm dia bar can be used only if there is no additional external load other than the reinforcement cage load.