As usual, before diving into the topic make sure to read the below topics for better understanding.
There may be other methods to find out bar bending schedule for column. The below method is just a guide. Some people will calculate for each floor, here we discussed the bar bending schedule for a column to a whole building at once.
BBS For Column – Important Notes
Ensure to follow the below rules while bar bending for column
- Always tie the column at the centre of each floor Since the axial loads & internal forces are maxim at top & bottom of the column.
- Always lap alternate bars
- Always lap top bar over the bottom bar
- Try to minimize the lap length and cutting of the bar as much as you can.
- Slab Thickness – 175 mm & 125 mm
- Floor height – 2750 mm
- Basement height – 650 mm
- Footing height – 1200 mm
- Footing Development Length – 250 mm
- Column Size – 600 x 300 mm
- Column Cover – 40 mm on each side
- Column Reinforcement – 6 nos of 16mm dia
- Stirrups – 8 mm of 200 c/c
- Ld = 50d (assumption)
Step 1 – Find the total length of vertical bar height
Vertical Bar Length = Footing Development Length + Footing height + basement height + Height of all floors + Slab thickness of all floors + Development length at the end of the column top
Vertical Bar Length = 250+(1200-30-25-20)+650+(4*2750)+(175+150+150+125+125)+50d
= 13750+(50*16)= 14550 mm or 14.55 m
Step 2 – Find Lap Length of Column Reinforcement
As you know the steel comes at a predetermined length of 12.25 m or 40 feet. From the above calculations, we know that we have to lap the column at least once in order to attain the height.
Assuming, Lap Length of column reinforcement as 40d
Lap Length = 40d = 40*16 = 640 mm or 0.64m
Total Vertical Reinforcement = 14550+640 = 15190 mm or 15.19m
Step 3 – Find Number of Stirrups
Number of Stirrups = (Total Vertical Bar Height / Spacing) + 1
Total Vertical Bar Height = Footing height + basement height + Height of all floors + Slab thickness of all floors
= (1200-30-25-20)+650+(4*2750)+(175+150+150+125+125) = 13500
Number of Stirrups = (13500/200)+1 = 68.5 or 69 Nos
Step 4 – Find Cutting Length of Stirrups
Cutting Length of Stirrups = Perimeter of Stirrup + 2 hook length – 3 * 90° bends – 2 * 135° bends
= 2(520+220)+(2*9d)-(3*2d) – (2*3d) = (2*740)+(2*9*16)-(3*2*16)-(2*3*16)=1576 mm
Step 5 – Bar Bending Schedule – Column Format
|Description||Dia of Bar (mm)||Number of Bars||Length(m)||Weight Per metre||Quantity (Kg)|
Happy Learning 🙂