BAR-BENDING SCHEDULE FOR BEAM

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In this post, we are going to see How to prepare bar bending schedule for Beam alias BBS for Beam.

Note – There is no one single version which is an absolute right. so please use the below calculations as a guide.

We hope that you remember about steel weight calculation post. if you have missed that post, please go ahead and read it.

Now we are going to prepare BBS for a beam in two types.

·         First one is BBS for the simple beam which we used normally at the site.

·         The second one contains many details as shown in the respective diagram

Let’s get started

Bar Bending Schedule for Simple Beam

As you can see in the figure, the beam has clear span of 3metre consists of 2 numbers of 16 mm dia at bottom and 2 numbers of 12mm dia bars at top with 8mm dia stirrups at 150mm Clear Cover

Assuming Clear Cover of 25 mm at both ends and sides of the beam

Observations

·         Clear Span of Beam = 3000 mm

·         Development Length Ld = 50d (assumption)

·         Clear Cover on any ends = 25 m

·         Bottom – 2 numbers of 16⌀

·         Top – 2 numbers of 12⌀

·         Stirrups – 8⌀ @ 150mm clear cover

Step 1 – Find cutting length of top bar

Cutting length of top bar = Clear Span of Beam + Development length (Anchorage) Ld on 2 sides – Clear Cover on 2 ends

= 3000+(2 x 50d) – 2 x 25 = 3000 + (2 x 50 x 12) – 50

= 4150 mm

Step 2 – Find cutting length of bottom bar

Cutting length of bottom bar = Clear Span of Beam + Development length (Anchorage) Ld on 2 sides – Clear Cover on 2 ends

= 3000+(2 x 50d) – 225 mm = 3000 + (2 x 50 x 16) – 50

= 4550 mm

Step 3 – Find out Number of Stirrups

Number of Stirrups required = (Clear Span of Beam/Spacing Stirrups)+ 1

      = (3000 / 150) +1 = 21 No.s

Step 4 – Find out cutting length of Each Stirrup

Let’s split the sides as (a, b) for easy calculation.

Length of One Hook = 9d 

Cutting length of Stirrup = Perimeter of stirrup + Number of Bends + Number of Hooks

= 2(a+b) + 3 numbers of 90 degree bends + 2 numbers of hooks

= 2(300+500) + (3 x 2d)+(2 x 9d) = 1600 + (3 x 2 x 8) + (2 x 9 x 8) = 1792 mm

	Diameter of Bar	Numbers	Cutting Length	Total Length
Top Bar	12	2	4150 mm	8300 mm
Bottom Bar	16	2	4550 mm	9100 mm
Stirrups	8	21	1792 mm	37632 mm

Bar Bending Schedule for Detailed Beam

As you can see that this diagram has more detailed and technical implementation of design aspects. Let’s get started

The above beam has the clear span of 6metre consists of two layers of the bottom (2 numbers of 20mm dia)  and one layer of the top (2 numbers of 12mm dia).

It consists of 3 Zones where Zone 1, 3 has stirrups of 150 mm spacing & Zone 2 has stirrups of 200 mm spacing.

Observations

·         Clear Span of Beam = 6000 mm

·         Development Length Ld = 50d (assumption)

·         Clear Cover on any ends = 25 mm

·         Bottom – 4 numbers of 25⌀

·         Top – 2 numbers of 12⌀

·         Stirrups

o    zone 1,3 = 8⌀ @ 150mm clear cover

o    zone 2 = 8⌀ @ 200mm clear cover

Step 1 – Find cutting length of top bar

Cutting length of top bar = Clear Span of Beam + Development length (Anchorage) Ld on 2 sides – Clear Cover on 2 ends

= 6000+(2 x 50d) – 2 x 25 = 6000 + (2 x 50 x 12) – 50

= 7150 mm

Step 2 – Find cutting length of bottom bar

Cutting length of bottom bar = Clear Span of Beam + Development length (Anchorage) Ld on 2 sides – Clear Cover on 2 ends

= 6000+92 x 50d) – 2 x 25 = 6000 + (2 x 50 x 25) – 50

= 8450 mm

Step 3 – Find out Number of Stirrups

As we said this beam has three types of zones where Zone 1 & 3 has stirrups has 150 mm spacing and Zone 3 has 200 mm spacing.

First calculate the length of zones = L/3 = 6/3 = 2 metre.

Number of stirrups required for Zone 1 = (Clear Span of beam/ spacing Stirrups)+ 1

           = (2000/150)+1 = 14.3   14 no.s

Number of stirrups required for Zone 3 = same as Zone 1 = 14 no.s

Number of stirrups required for Zone 2 = (Clear Span of beam/ spacing Stirrups) – 1 = (2000/200)-1 = 10 no.s

The reason for the “minus 1 “ is already zone 1 has end stirrup so we don’t need to again start from new one. we just continue the stirrups already existing with extra spacing.

Step 4 – Find out cutting length of Each Stirrup

Length of One Hook = 9d 

Cutting length of Stirrup = Perimeter of stirrup + Number of Bends + Number of Hooks

= 2(a+b) + 3 numbers of 90 degree bends + 2 numbers of hooks

= 2(300+500) + (3 x 2d)+(2 x 9d) = 1600 + (3 x 2 x 8) + (2 x 9 x 8) = 1792 mm

	Diameter of Bar	Numbers	Cutting Length	Total Length
Top Bar	20	2	7150 mm	14300 mm
Bottom Bar	25	4	8450 mm	33800 mm
Stirrups	8	21	1792 mm	37632 mm

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BAR BENDING SCHEDULE FOR COLUMN DETAILED PRACTICAL GUIDE

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In this post, we are going to explain “How to make bar bending schedule for Column?”

This article will be quite long. Brace Yourself.

First of all, there are some criteria & assumptions that need to be met while making bar bending schedule for a column. Let’s get started.

Loads Acting on Column

We hope that you know the typical load action on a column.

Just take a look at the below diagram.

If you see the internal forces and moment diagram, the column has maximum moments at top and bottom and less at centre.

Never tie a column at top & bottom where the critical moment is high. Always tie the column at centre.

For practical always tie the bars at 5 feet height. Since every roof should not be more than 10 feet.

·         Minimise the cutting of bar and lapping as often as possible.

·         Always lap alternate bars at a time.

·         Always overlap top bars with bottom bars.

·         Maintain sufficient end to end spacing between the laps.

Bar Bending Schedule for Column

From the diagram,

·         Slab Thickness – 125 mm & 100 mm

·         Floor height – 3000 mm or 3 m

·         Ground Floor Level – 3300 mm

·         Footing Height – 300 mm

·         Development Length – 50d

·         Column has 6 numbers of 20 mm dia bars

·         8mm stirrups @ 150 mm C/C

·         Footing Clear Cover – 40 mm

·         Slab Clear Cover – 25 mm

Step 1 – Find the length of Vertical Bar

Length of Vertical bar = Development length (Ld) + Height of Ground Level + Floor Heights (1,2,3)+ Slab Thicknesses + Overlap Length (Det.B)

= (50×20)+3300+ (3×3000)+(3×125)+100 +(50×20)

= 14775 mm or 14.78 m

Now we know the length of one vertical bar. Normally column reinforcement drawings won’t come with lapping details.

Step 2 – Find out lapping

As we know that lapping length required is 50d = 50 * Diameter of the bar = 50×20 = 1000 mm.

We know that each bar is 12.25 m or 40 feet length (approx).

Total Length of Vertical Bar = 14.2 m which is more than 12.25 m so each rod will be lapped at least once to attain the required length.

So we have added the lapping length with the total length = 14775+1000 = 15775 mm or 15.78 m

As we mentioned earlier in this post, consider the points while lapping the bar. There is no one correct method we can use. Just remember the lines.

·         Never tie a column at top & bottom

·         Always lap at alternate bars

·         Always overlap top bars with bottom bars

Step 3 – Cutting Length of Stirrups

Length of One Hook = 9d (As per Estimating and Costing in Civil Engineering P.No.214)

Cutting length of Stirrup = Perimeter of stirrup + Number of Bends + Number of Hooks

= 2(a+b) + 3 numbers of 90 degree bends + 2 numbers of hooks

= 2(500+200)+(3 x2d)+(2x9d)= 2×700+3x2x20+2x9x20

Cutting length of Stirrup = 1880 mm

Step 4 – Number of Stirrups

Number of stirrups required = (Total length of Column/spacing of stirrups)+1

      = (3300+125+3000+125+3000+125+3000+100)/150 + 1

Number of stirrups                = 85 no.s

Step 5 – Bar Bending Schedule

	Diameter of Bar	Numbers	Cutting Length	Total Length
Vertical bar	20 mm	6	14.2 m	85.2 m
Stirrups Bar	8 mm	85	1.88 m	159.8 m

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POINTS TO REMEMBER BEFORE CONCRETING

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Plaster for the sheet gaps: Once centering is completed this activity need to be performed. This will be done to avoid concrete mix leaks.

before keeping steel mat for molding this activity need to be performed. You can observe that in below mentioned picture

Oil for sheets:

Used engine oil will be applied to iron sheets so that at the time of sheet removal it will be easier

In below picture for left side portion sheets oil is not applied but for the right side portion sheets oil is applied

Sheets with oil

Mats for Molding:

Now a days people are using mats on top of metal sheets.

With this we have two advantages.

§  While pouring cement mixture, cement mix will not go waste because of gaps in between sheets

§  No need of hocking at the time of centering removal.

Points to consider:

§  Spray water before pouring concrete on these mats so that gaps will get reduced.

§  These mats are made up with “Jammu” it will get expanded little bit if you pour water on it

§  Remove these mats immediately after centering sheets are removed. it will be easier to remove when it is wet.

§  other wise you need to spray water and remove them which will be an extra work

Observe below pictures to get clear idea

Inverted beams:

§      Usually Inverter beams will come if you are going to construct a wall where there is no beam.

§      So for example during ground floor molding time you should have first floor plan ready.      

Hooks in the roof:

§  Hooks in the roof will be helpful to hang caddles in hall and bedroom.

§  This will be useful for the families who has infants/children.

§  <attach photo here>

Binding extension pillars with rings:

§      After molding no one should hold pillar rods. If some holds pillar rod and leaves, it will create few small vibations and these vibrations will leave small gaps in pillars.

 vibrator

§      Check Vibrator is in working condition or not

§      Usually Meastri’s won’t bring Petrol while bringing Vibrator. So bring petrol beforehand

Concrete ready roof:

Sufficient Meterial:

§      Owner has to make sure he has sufficient sand, jelly and cement for Molding

§      For 30*40 Site (Molding area will be around 1000 sft excluding beams)

        bring 100 bags of cement, ~ 700 cft of sand, ~700 cft of 20 mm gravel (20 MM jelly).

covering stones:

§      Covering stones are the most important thing which you need to remember with out fail

§      Covering stone is a flat thin piece of a stone. These stones will be kept below steel rods to avoid contact between sheet centering and steel rod

§      These stone will keep some gap between molding sheet and steel rod. So that concrete will go in between