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Steps to determine the BBS of trapezoidal footing

Construction Software

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

Steps to determine the BBS of trapezoidal footing