How to determine the cutting length of chair bar in slab & footings
The chairs in reinforcement are provided for the following reasons.
1. It retains the gap among the two bars as well as upper and lower cage reinforcement.
2. It provides strong supports to the bars.
3. It improves the strength of the structure and retains the tension in RCC.
4. It raises the tension property of concrete.
5. It reduces the scope for collapsing of the building because of the failure of compression and tension zone.
6. While vibrating, it holds the upper cage bar from collapsing.
7. The diameter of the bar should not be lower than 12 mm.
The chair bars should be made of the scraps in the jobsite.
In this civil engineering article, detail information is given for finding out the cutting length of chair bar in slab and footings.
The height is treated as the most crucial part of any chair as when the height is known, it becomes easier to determine the leg and the length of head.
The height of the chair bar will be determined with the following formula :-
Height = Height of footing ? (2 x clear cover) ? (dia of bottom main bar) ? (dia of top main bar + dia of top distribution bar)
The head of the chair bar will be determined with the following formula :-
Head = (2 x spacing of top distribution bar) + 100
The leg of the chair bar will be determined with the following formula :-
Leg = (2 x spacing of bottom main bar) + 50
To learn the detail calculation process, go through the following video tutorial.
Video Source: L & T - Learning Technology