How to calculate the numbers of bars in footing
In this exclusive civil engineering video tutorial, you will learn how to prepare bar bending schedule of footing as well as work out the numbers of bars in footing.
For RCC slab, beam and column, it is required to provide reinforcement rods with several lengths according to drawings. Working out the length of straight length by adding crank and hooks is known as cutting length.
Bar bending schedule stands for a method of cutting and bending reinforcement bars into shapes. It comprises of an extensive lists which denote the location, mark, type, size, length, number and bending details of every bar in a reinforcement drawing of a structure. The method of listing is known as scheduling.
A BBS offer the followings :-
1. Member identification
2. Bar Mark
3. Shape of bending
4. Diameter of bar
5. Length of each bar
6. Total numbers of bars
7. Total length
In BBS of footing, you will get the numbers of bars with different lengths and sizes in both x axis and y axis along with the cutting length to complete a footing.
The calculation is done based on the following dimensions :-
The size of footing = 1 m x 1.2 m
Spacing of bar = 100 cm C/c
Footing cover = 50 mm
The cutting length of x-axis is calculated with the following formula :-
Cutting Length = Length (X-Axis) – (2 x Cover) + (2 x Height) – 4 Cover – Bend
Cutting Length = 1000 – (2 x 50) + (2 x 300) – (4 x 50) – 2 x 2 x 12;
4 x 50 = Cover is provided on both sides in top and bottom
2 x 2 x 12 = For 90 degree bend, 2d is deducted and there are two bends in both corners; dia = 12 mm
So, cutting length = 900 + 600 – 200 – 48 = 1.25 m
Same formula will be used to work out the cutting length of y-axis, but the length will be changed here.
Cutting length of Y-axis = 1200 - (2 x 50) + (2 x 300) – (4 x 50) – 2 x 2 x 12 = 1.45 m
Now, the numbers of bars will be calculated with the following formula :-
No. of X-Axis = [Length – (2 x Cover)] / Spacing + 1
No. of X-Axis = [1200 – (2 x 50)] / 100 + 1 = (1100/100) + 1 = 12 Nos (as the bars will be placed towards Y axis, so length is taken as 1200).
Similarly, the numbers of bars toward Y-axis will be as follow :-
No. of Y-axis = [1000 – (2 x 50)] / 100 + 1 = (900/100) + 1 = 10 Nos.
Video Source: Tutorials Tips