Estimating Sheet

# Steps to determine the BBS of trapezoidal footing

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In this civil engineering video tutorial, you will learn how to prepare the bar bending schedule alias BBS of any trapezoidal footing.

The reinforcement along x axis (taken as L) of the footing underneath = 1200 mm

The reinforcement along y axis (taken as Y) of the footing underneath = 1500 mm

The height of the footing (concreting work) = 500 mm

The reinforcement is provided in both x and y axis. It is perpendicular in y axis.

In both sides, 12 dia bars are used with spacing 150 c/c.

The clear cover is provided as 50 mm on both sides.

The calculation is done on the following ways :-

To calculate the number of bars along x-axis (bottom bar), the following formula is used :-

B – (2 x clear cover) / Spacing + 1

= 1500 – (2 x 50) / 150 + 1 = 10 numbers

To calculate the number of bars along y-axis (top bar), the following formula is used :-

L – (2 x clear cover) / Spacing + 1 = 1200 – (2 x 50) / 150 + 1 = 8 numbers

Now, it is required to determine the cutting length of bottom bar

### Also Read: How to calculate the volume of concrete in a trapezoidal footing

L – (2 x clear cover) + (2 x H) – (4 x clear cover) – Bend Deduction [top and bottom clear cover in 1 side and it will 4 in two sides]

= 1200 – (2 x 50) + (2 x 500) – (4 x 50) – (2 x 2 x 12) [ for two bends with 90 degree i.e. 2d; d = dia]

= 1852 mm or 1.852 m

Now, determine the cutting length of top bar

B – (2 x clear cover) + (2 x H) – (4 x clear cover) – Bend Deduction

= 1500 – (2 x 50) + (2 x 500) – (4 x 50) – (2 x 2 x 12)

= 2152 mm = 2.152 m

To get more details, go through the following video tutorial.

Video Source: L & T - Learning Technology