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How to Estimate Beam Reinforcement

An ordinary person can estimate reinforcement as lumsum. I see many people estimate reinforcement as a percentage of concrete volume. Such as 2% or 1.5% of concrete volume.

But as a construction professional you shouldn't estimate rebar quantity as percent of concrete volume. You should estimate that as shown in the structural drawing.

Estimating rebar quantity is easy. All you have to get the cutting length for each type of bar in the beam.

Let's start estimating. We'll use the following image as a structural drawing of beam.

estimating, beam reinforcement

Process of Estimating Beam Reinforcement

From the image above we have found -
  • Top longitudinal bar, T - 3D20
  • Bottom longitudinal bar, B - 3D20
  • Extra top bar on support1, Et1 - 2D20
  • Extra top bar on support2, Et2 - 2D20
  • Extra bottom Bar, Eb - 2D20
  • Stirrup, S1 - D10 @ 4" c/c

If you don't know the name of bar on different location in a beam then read the following post.

14 Terms About Beam Reinforcement a Supervisor Should Be Familiar With

You will also need the following data to estimate the beam reinforcement -
  • Clear cover for reinforcement
  • Lap length
  • Bend length
You'll get this data from the general notes sheet of structural drawing.

Read More:
Concrete Cover for Reinforcement Bar
17 Technical Terms about Reinforcement a Construction Supervisor Should Know
4 Terms to Understand to Truly Estimate Rebar Quantity

That's fine.

We have enough data to estimate the beam reinforcement. Let's estimate.

Top Longitudinal Bar (T)

Apply the following formula to get the cutting length of top longitudinal bar.

Cutting Length of top longitudinal bar is,
= Length of beam - 2 x clear cover + 2 x bend length - 2 x bend deduction length + lap length

Length of beam:  20" + (22'-8") + 20" + (8'-4") + 20" = 36' (from above image)
Clear cover: 1½"
Bend length: 12D = 12 x 20 = 240 mm, say 9½"
Bend deduction length: Bend deduction length for 90° bend is equal to two times of bar dia = 2 x 20 mm = 40mm = 1½"

So, the cutting length of the top longitudinal bar is,
= 36' - 2 x 1½" + 2 x 9½ - 2 x 1½" + 0
= 37'-1".

There are 3 numbers of top longitudinal bar in the above image. So the total length of top longitudinal bar is,
= 3 x (37'-1")
= 111'-3".

We know the full length of a reinforcing bar is about 40'. The length of a top longitudinal bar, we are estimating, doesn't exceed the length of a full bar. So you don't have to add lap length.

Bottom Longitudinal Bar (B)

The formula for calculating the cutting length of bottom longitudinal bar is same as the formula for top longitudinal bar. So the length is also same as T1 . That is 37'-1".

So the total length of B1 bar is,

= number of B1 bar x cutting length of a B1 bar

= 3 x (37'-1")

=111'-3".

Extra Top Bar on Support1 (Et1)

Calculating cutting length of extra top bar follow the following formula -
Cutting length of Et1 = extended length from support + width of support - clear cover + bend length - bend deduction length

Extended length from support: 7'-5"
Width of support: 20"
Clear cover: 1½"
Bend length: 9½"
Bend deduction length: 1½"

So the cutting length of Et1 is,
= (7'-5") + 20" - 1½" + 9½" - 1½"
= 9'-7½"

There are 2 number of Et1 bar shown in drawing (image above). So the total length of Et1 is,
=2 x (9'-7½")
= 19'-3"

Extra Top Bar on Support2 (Et2)

Extended length fron support: 7'-5"
Width of support: width of support for Et2  should be the width of support2 + distance between support2 and support3 + width of support3 = 20" + (8'-4") + 20" = 11'-8"
Clear cover: 1½"
Bend length: 9½"
Bend deduction length: 1½"

So, cutting length of Et2 = (7'-5") + (11'-8") - 1½" + 9½" - 1½"
= 19'-7½"

Total length of Et2 = 2 x (19'-7½")
= 39'-3"

Extra bottom bar (Eb)

Cutting length of extra bottom bar is,
=Distance between support - 2 x distance between extra bottom bar and nearest support
= (22'-8") - 2 x (2'-10")
= 17'

Total length of extra bottom bar is,
= 2 x 17' (there are 2 bar for Eb shown in the image above)
= 34'

Stirrup (S1)

For estimating  stirrup you have to calculate the required number of stirrup for the beam and cutting length of bar for a stirrup.

Number of stirrup:
Required number of stirrup for 1st span,
= (22'-8")/4" +1 = 69 + 1 = 70 nos.

Required number of stirrup for 2nd span,
= (8'-4")/4" + 1 = 25 + 1 = 26 nos.

Total number of stirrups = 70 + 26 = 96 nos.

Formula for calculating cutting length of a stirrup's bar is,
= 2 x (a+b) + 24D (for 135° hook)

Where,
a = length of stirrup's long side
b = length of stirrup's short side
D = dia of stirrup bar

So cutting length of the bar is,
= 2 x (21"+9") + 24 x 10mm
= 69½" (240 mm = 9½")
= 5'-9½"

Total length of bars for all stirrups,
= 96 x (5'-9½")
= 556'

Summary:
Total reinforcing bar we have estimated for the beam so far -

20 mm ø bar -
T = 111'-3"
B = 111'-3"
Et1 = 19'-3"
Et2 = 19'-7½"
Eb = 34'

So total 20 mm ø bar is,
 = 111'-3" + 111'-3" + 19'-3" + 19'-7½" + 34' = 296'.

10 mm ø bar,
S1 = 556'

But steel reinforcing bars are measured in kg in the market. So you have to convert the bar length to kilogram.

Unit weight of 10 mm ø bar is 0.188 kg/ft and 20 mm ø bar is 0.75 kg/ft. Read the following post to know how to calculate unit weight of reinforcing bar.

How to Calculate the Unit Weight of Steel Bars

So reinforcement required for our example beam,
  • 20 mm ø bar = 296' x 0.75 = 222 kg
  • 10 mm ø bar = 556 x 0.188 = 105 kg
That's it.

When you want to purchase reinforcing bar for the beam you should add 5% more with your estimated quantity as wastage.

You Turn:
Please share your experience about estimating in the comment below.

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4 Terms to Understand to Truly Estimate Rebar Quantity

Estimating Reinforcement is easy. All you have to get the cutting length of bar and convert them to weight.

When estimating rebar for a rcc member you have to understand few terms clearly regarding reinforcement.

estimating, reinforcement

4 Terms to understand to truly estimate rebar quantity

Below are 4 terms you should understand clearly to truly estimate the rebar quantity -

  1. True length of bar
  2. Cutting length of bar
  3. Bending length of bar
  4. Bend deduction length

1. True Length of Bar

For estimating rebar quantity we just calculate the length of some leaner shapes of bar.

For example, take a top longitudinal bar of a beam. The shape of the bar will look like the image below.

For estimating purpose we just get the length of the bar and convert it to the weight of bar.

Read More:
How to Calculate the Unit Weight of Steel Bars
Estimate the Neck Column's Reinforcement With these 8 Easy Steps

Let's calculate the bar in the image above. The length of that bar is,

=A+B+C

Suppose, A is = 20', B is = 1' and C is = 1'

So the length of the bar is,

= 20' + 1' + 1'

=22'

This is the true length of bar.

2. Cutting Length of Bar

As we know steel is ductile and subjected to elongation. When it bends it is increased in length.

So if you we cut the bar as its true length and bend it we won't get the desired shape after bend. To get the desired shape, the bar should be cut lesser than the true length.

The required length to get the desired shape of the bar is calledcutting length of bar.

3. Bending Length of Bar

Now the question is how much a reinforcing bar is increased in length when it is bent?

It depend on the size of bar and angle of the bend.

The increased length for specific diameter of bar for specific angle is called bending length of the bar.

4. Bend Deduction Length

It is confusing. Because bend deduction length conflicts with the bending length.

Actually both the terms are same. Then why the engineering world using both terms to confuse the fresher? This question is mine.

The purpose for writing this post is to eliminate the confusion between these two terms.

Don't be confused. Both terms are same. When we deduct the bending length from the true length of a bar then it is calledbend deduction length.

Mostly used bend angle in civil construction world are 45° and 90° bend.

For 45° bend, Bend deduction length is equal to dia of bar.

and

For 90° bend, bend deduction length is equal to two times of bar dia.

Bend deduction length is actually used for calculating the cutting length of bar in construction.

Let's calculate the cutting length of the bar shown in the image above.

Cutting length = true length of bar - (2 x dia of bar) x number of bend.

= 22' - 2 x ¾" x 2 (20 mm = ¾")

= 21'-9"

For estimating purpose only, you don't have to deduct the bend deduction length form the true length of bar. It is required when you are cutting bar or making bar bending schedule for placing reinforcement in the rcc member.

Your Turn:
How do you calculate bend deduction length for bar? Please share in comment below.
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How to Place Beam Reinforcement in 5 Easy Steps

Placing beam reinforcement is easy if you have some basic idea about the steps of placing beam reinforcement.

In this post I'll give you an idea for placing beam reinforcement in 5 easy steps.

5 Easy Steps for Placing Beam Reinforcement

Placing beam reinforcement involves following 5 easy steps -
  1. Studying drawing
  2. Calculating cutting bar length
  3. Cutting the bars
  4. Bending the bars, and
  5. Placing bars

1. Studying Drawing

Study the general notes sheet of structural drawing carefully. Collect the following data from general notes about beam reinforcement.
  • Lap length
  • Bend length
  • Clear cover
Lap length: Beam has mainly two types of longitudinal reinforcing bar. One is top longitudinal bar and another is bottom longitudinal bar.

When the length of a longitudinal bar is more than the full length of reinforcing bar then another reinforcing bar is provided by overlapping with existing one. The length of overlapping is called lap length. The lap length for different diameter bar is shown in the general notes sheet of structural drawing.

The lap length can be differed for top and bottom longitudinal bar of beam.

Collect lap length details for different diameter of top and bottom longitudinal bar of the beam.

Bend Length: As we know, all longitudinal bars of beam should be bend at the end of the bar. The length of bend is suggested by structural engineer in the general note sheet of structural drawing.

Check if there is any instruction found in the general note sheet about the bend length.

If not found follow a general formula for 90° bend suggested by ACI code. That is 12db. Where "db" is the diameter of bar.

Clear Cover for Reinforcement: Find out if there is any instruction for the clear cover for beam reinforcement in the general note sheet or beam layout sheet or in the beam reinforcement detailing sheet of structural drawing.

If not found you can follow the instruction shown in the following post.

Concrete Cover for Reinforcement Bar

Okay. We've collected required data for placing beam reinforcement. Now move on to next step that is calculating the cutting bar length.

2. Calculating Cutting Bar Length

For Calculating cutting length of bar you'll need a beam reinforcement detailing sheet of structural drawing.

From the drawing you'll find the size and number of bar to be placed in a beam.

Suppose you'll place the reinforcement for a beam (B1). Now look for B1 in the beam reinforcement detailing sheet. B1 will look like the image below in the beam reinforcement detailing sheet.

Placing beam reinforcement


From the image above you'll get following reinforcement details -
  • Top longitudinal bar = 3-D20
  • Bottom longitudinal bar = 3-D20
  • Extra top bar = 2-D20
  • Extra bottom bar = 2-D20
  • Stirrup s1 = D10 @ 4" c/c
  • Stirrup s2 = D10 @ 6" c/c

If you don't understand terms of beam reinforcement such as top bar, bottom bar, etc. then read the following post.

14 Terms About Beam Reinforcement a Supervisor Should Be Familiar With

Now let's start calculating the cutting length of different bar.

For getting cutting bar length follow the following rules.

For top longitudinal bar,
= Length of beam - 2 x clear cover + 2 x bend length + lap length.

Let's calculate from the example image above.

Length of beam:
 = 20" + (22'-8") + 20" + (8'-4") + 20"
= 36'

Clear cover:
Clear cover for reinforcement is 1½" (from step1)

Bend Length:
Bend length is 12db for one bend which we found in step-1.

As the top bar dia is 20 mm the bend length will be,

= 12x20

= 240 mm

Say, " (25mm = 1")

Lap Length:
As we know the full length of a reinforcement bar is about 40' and the length of top longitudinal bar of our example beam doesn't exceed that length so you don't have to provide lap for top longitudinal bar.

So the top longitudinal bar length for B1 is,

= 36' - 2 x 1½" + 2 x 9½"

=37'-4".

For Bottom longitudinal bar,
The length of bottom longitudinal bar is same as the top longitudinal bar. That is 37'-4".

For Extra top bar,
In the example drawing (above image), extra top bar is shown in two places. One is on support1 and another is on support2. See support2 and support3 hold the same extra top bar.

Let's calculate.

Length of extra top bar on support1 is,
= extended bar length from support1 + width of support1 + bend length - clear cover.

= (7'-5") + 20" + 9½" - 1½"

= 9'-9"

Length of extra top bar on support2 is,
= extended length from support2 + distance between support2 and support3 + width of suppot2 + width of support3 + bend length - clear cover

= (7'-5") + (8'-4") + 20" + 20" + 9½" - 1½"

=19'-9"

Length of extra bottom bar,
= distance between support1 and support2 - 2 x distance between support and extra bottom bar.

From the example drawing (image above),

Length of extra bottom bar is,

= (22'-8") - 2 x (2'-10")

= 17'.

Stirrup: Calculate the cutting length of bar for the stirrup of the beam and make required number of stirrups before star placing reinforcement of beam.

Read the following post to know more about how to make stirrup.

4 Easy Steps for Making Column Stirrup

3. Cutting the Bars

Number, size and length of bars we have found so far -

Number of top longitudinal bar = 3
Length of top longitudinal bar = 37'-4"

Number of bottom longitudinal bar = 3
Length of bottom longitudinal bar = 37'-4"

Number of extra top bar on support1 = 2
Length of extra top bar on support1 = 9'-9"

Number of extra top bar on support2 = 2
Length of top extra bar on support2= 19'-9"

No. of extra bottom bar = 2
Length of extra bottom bar = 17'

All of these bars are 20 mmø. So slice 20 mmø bars as required length and number.

4. Bending Bars

  • Make 90° bend at both end of top longitudinal and bottom longitudinal bar.
  • Make bend at one end of extra top bars.
  • Make required number of stirrups.

If all the bars are ready then you can start placing them.

5. Placing Bars

You can't directly place the bars into the form of beam. For placing bars you have to make stand on the supports (column) to hold beam's reinforcement.
  • Hang the top longitudinal bars on the stand.
  • Hang stirrups on top longitudinal bars and bind them with top longitudinal bars by binding wire.
  • Now insert the bottom longitudinal bars into stirrups and bind them also with stirrups.
  • Then place extra bottom bars on the bottom longitudinal bar. Don't forget to put spacer between bottom longitudinal bar and extra bottom bar.
  • Following same rule bind the extra top bar.

If everything is perfect then place them into the form of beam.

Here one thing I want to explain that you can't place reinforcement of single beam into the form. You have to finish binding reinforcement for all beams of a floor and place them simultaneously into the form. We call this dropping beam.

Before dropping beam don't forget to put cover block below reinforcement.

Conclusion
I think you noticed one thing that I didn't deduct the extended length for bend from the cutting length of bar. Because it doesn't have any major effect in our example beam.

However, I'll discuss about that in some other day here in this blog. So please subscribe to email newsletter to get that to your inbox when it happens.

Your Turn
Do you have any better idea for placing beam reinforcement? And also how do you calculate the extended length for bend of bar? Please share in comment below.

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14 Terms About Beam Reinforcement a Supervisor Should Be Familiar With

Beam is a horizontal member of a structure. It carries its own load and imposed load and transfers them to its support (such as column or wall).

Beam can be various types and can be made with various types of material. One of the most used material for beam is reinforced cement concrete.

Reinforcement is a major item of a reinforced cement concrete beam. Deformed mild steel bar is the most used material as beam reinforcement.

In this post I'll share 13 terms about beam reinforcement which you should be familiar with as a construction supervisor.

Terms of beam reinforcement

14 Terms About Beam Reinforcement a Supervisor Should Be Familiar With

Following are the 14 terms about beam reinforcement -

1. Top Bar: This reinforcing bar is placed in the top of beam. It is also called compression reinforcement.

2. Bottom Bar: Bottom reinforcing bar is placed in the bottom of beam. It is also called tension reinforcement.

3. 2nd Layer Reinforcement: When one more layer of reinforcing bar is used on top of bottom bar or below the top bar that is called 2nd layer reinforcement. When using 2nd layer reinforcing bar in beam you should also use spacer between two layers of bar.

4. Extra Top Bar: Extra top bar is provided on supports and it doesn't go through the beam. It is cut at one-third length of clear span of beam.

5. Extra Bottom Bar: This bar is provided at the bottom of beam. But this bar is not extended up to support. Beam section sheet of structural drawing shows where to cut the bar.

6. Stirrup: It is the shear reinforcement of the  beam. It is provided around the longitudinal bars of the beam. It is also called ring.

Read More:
4 Easy Steps for Making Column Stirrup

7. Clear Cover: Clear cover or clear concrete cover or reinforcement cover, whatever you call this, it is the distance between the rebar surface and the nearest surface of the beam. For the beam above ground clear cover should not be less than 1½" and for the beam below ground clear cover should not be less than 2½" or whatever is suggested in the drawing by structural engineer.

Read More:
Concrete Cover for Reinforcement Bar

8. Rebar: Rebar is the short form of reinforcing bar. In another word whatever steel reinforcement we use in the beam is called rebar.

9. Spacer: We provide a separator between two layers of bar that is called spacer. It should not be less than 1". You can use 25mmø bar as a spacer.

Read More:
Types of Rebar Support in RCC Member

10. Cover Block: Cover Block is used to keep up the clear cover of reinforcement. It can be pre-cast cement mortar block.

11. Chair: Chair is made with 10mmø or 12mmø MS rod. It is used to support the top layer of reinforcing bar specially in slab and footing.

12. Lap: when a reinforcing bar need to be extended in length then another reinforcing bar is joined by overlapping one another. That is the lap of reinforcement. The length maintained in overlap is called the lap length.

Lap length should be suggested by code or by structural designer in drawing.

13. Development Length: The reinforcing bar of a rcc member should be embedded in concrete at both end of the member to prevent slipping possibility of the bar. It is done by providing hook to the bar and embed it in the concrete of the support. The total length of hook and embedded length is called development length. It is also called the anchoring of reinforcement. Development length is expressed by Ld.

14. Fastening Bar: If the beam depth is increased, some additional bars are used at the mid position of the beam-depth those are called Fastening bar. It is also called additional bar or face bar.

These are the terms about beam reinforcement you should be familiar with to work smoothly.

Your Turn:
Do you want to add any term in this list? Please share in comment below.
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Inspection Checklist for Footing: 12 Points to Check Before Casting

If you have a handy inspection checklist then your job will be more easier.

It always happens to me. When I check something without an inspection checklist I always forget some points to check.

After checking when I come back to my desk then I remember oh! I forgot to check that point!

But it is not happened now. I made inspection checklist format for different items of building for myself.

In this post I'll share an inspection checklist for footing.

inspection Checklist for footing

Inspection Checklist for Footing: 12 Points to Check Before Casting

There are various types of footing. This inspection checklist focuses specifically on the shallow footing.

To truly inspect the footing you have to go through following three steps -

  • Form work
  • Reinforcement
  • Pre-Concreting

Inspection Checklist for Form work of a Footing (1-4)

We mostly use wooden form in footing.

For inspecting form-work of a footing you have to check the following 4 points -

1. Form work Material: Form work material should be strong enough to withstand against the load of concrete.

If you use wooden shutter material for form-work, make sure the thickness of wood is not less than 1". And it is free from defects.

2. Water-Tightness of Form: Make the form leakage-proof by using 32 gauge thin metal sheet in the wood joints. Fix the metal sheet with nail to make the form water-tight.

3. Footing Dimension: Make sure the form is made with specified footing dimension in drawing. Check the inside dimension of the form for inspecting length, width and height of the footing.

4. Placing Form: Check the form is properly placed related to grid-line.

Inspection Checklist for Footing's Reinforcement (5-8)

5. Quality of Reinforcing Bar: Make sure all reinforcing bars are straight and free from cracks. Check they are cleaned and no excessive mortar or other materials on the bar's surface.

6. Size and Spacing of Reinforcing Bars: Check the diameter of reinforcing bar and they are spaced correctly as specified in the drawing.

7. Clear Cover for Reinforcement: Clear cover for reinforcement should not be less than 3" for footing or specified in the drawing. Make sure it is maintained properly in all around the reinforcement.

Also check all rebars are properly placed and tied. Make sure rebars are supported properly with chairs, spacers and mortar blocks.

8. Column's Reinforcement: As we know footing is constructed to get the load from column and transfer it to the base-soil. So make sure column's reinforcement are placed correctly as specified in the structural drawing.

Also check the size, numbers and placement of column's reinforcement as shown in the column layout sheet of structural drawing.

Read More:
How to Place Steel Reinforcement of Neck Column

Pre-Concreting Checklist for Footing (9-12)

9. Accessibility to footing: Make sure the footing zone in easy accessible and safe for concreting.

10. Ingredients of concrete: If you plan to cast the footing with machine mix concrete, make sure you have enough materials, such as stone chips, sand and cement available in the project.

Make sure concrete ingredients are cleaned throughly by water.

If you plan to cast the footing with ready-mix concrete, contact with supplier when they can supply the concrete.

Make sure you have enough man-power available to pour concrete.

11. Tools and machineries: Required tools and machineries for concreting of footing are -
  • Vibrator
  • Generator
  • Mixture machine
  • Drainage pump
  • Shovel
  • Trowel, etc.

Make sure all the required tools and machineries are available in the project and in working order. Also make sure fuel and constant power supply are available when required.

12. Cleaning Form-work: Throughly wash the inside of the form with water. But no water should be allowed inside the footing. Unwanted materials also should not be allowed inside the form of footing.

If all the check points are satisfactory you can now move on to pouring concrete.

Your Turn:
Do you want to add any point in this checklist? Please do this in the comment below.
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How to Estimate Concrete Volume for Grade Beam

Grade beam is normally constructed on neck column and It connects two or more column together.

In another word, grade beam carries the load from ground floor slab and transfer to column.

Grade beam is normally constructed on ground.

Purpose of this post is not to define what the grade beam is. I just giving some idea about grade beam so that newbie can understand the grade beam well.

The purpose of this post is to show you how to estimate the concrete volume of grade beam.

So let's do this.

Estimating Concrete Volume for Grade Beam

For estimating the concrete volume for grade beam you'll need following structural drawing sheets.


  • Grade beam layout
  • Cross-sectional dimension of grade beam
  • Column layout
  • Cross-sectional dimension of column


Grade Beam Layout: This sheet of structural drawing shows how to place grade beam on column.

See the image below.

estimating, concrete volume, grade beam

In the above image, the grade beam layout just shows the grade beam number (GB1, GB2, etc.). It also shows the cross-sectional dimension that is 12" x 20". So you don't need to look out for cross-sectional dimension of grade beam. You'll get it from here.

Column Layout: The grade beam layout we have in the above image doesn't show the length of beam. If you want to calculate concrete volume of grade beam you'll need it. So you'll need to go to column layout for the length of beam.

See the image below.

estimating, concrete volumn, grade beam

The above image is a column layout sheet of structural drawing.

To get the grade beam length you have to calculate the distance between columns.

I told before that you'll also need the cross-sectional dimension of column for calculating concrete volume of grade beam. See the above image you'll get this from there. Such as C1 (15" x 45"), C2 (20" x 45"), C3 (20" x 35"), etc. So you don't need any further cross-sectional dimension sheet for column.

Are you still here? Then let's estimate the concrete volume for grade beam.

We'll estimate concrete volume for GB1 shown in the 1st image.

For estimating concrete volume of GB1 you'll need following data -


  • Cross sectional dimension of grade beam (GB1)
  • Length of grade beam (GB1)
  • Cross sectional dimension of column (C1, C2 and C3)
  • Height of column


Cross Sectional Dimension of Grade Beam (GB1)

From the grade beam layout sheet (1st image) you'll find the cross sectional dimension of GB1. That is,

12" x 20".

Length of Grade Beam

Length of grade beam shows nowhere in grade beam layout sheet (1st image). sometimes it's shown on the reinforcement detailing layout sheet of grade beam in structural drawing.

You can also calculate the length of grade beam from column layout drawing sheet (2nd image).

For finding the length of grade beam (GB1) you have to find the distance between C1 and C2 as well as the distance between C2and C3.

Distance Between Column C1 and C2:
For finding distance between column C1 and C2 you have to find the gap between grid-1 and grid-2. Then you have to deduct column portion inside the grid-lines. Let's do this.

Gap between grid line 1 and 2 is 24'-1".

Column portion inside grid-line1 and grid-line2:

C1 = 7½"
C2 = 10"

So the distance between c1 and c2 is,

= (24'-1") - 7½" - 10"

= 22'-7½"

Applying same process you can find the distance between c2 and c3. That is,

= (18'-3") + (5'-10") - 10" - 12½"

=22'-2½"

So the length of the grade beam (GB1) is,

= 22'-7½" + 22'-2½"

= 44'-10"

Therefore, the volume of grade beam is,

= 44'-10" x 12" x 20"

= 74.87 cubic feet.

Wait, we are not finished yet.

To get the concrete volume of grade beam you also have to estimate the concrete volume for column head.

Column head is the portion of column which intersect with beam.

Estimating Concrete for column head:

In the 2nd image you'll find three column heads connecting by the grade beam (GB1).

So you have to estimate the concrete volume for these column heads also.

Let's do this.

Cross Sectional Dimension of Column


C1 - 15" x 45"
C2 - 20" x 45"
C3 - 20" x 35"

So the area of the those three column heads are,

(15" x 45") + (20" x 45") + (20" x 35")

= 15.80 sft.

Height of Column

The height of all three column heads are same as height of the grade beam. That is  20".

So the volume of column heads are,

= 15.80 x 1.67 (20"= 1.67')

= 26.39 cft (cubic feet).

So total concrete volume for the grade beam (GB1) is,

= 74.87 + 26.39

= 101.26 cft.

Following this process you can estimate the concrete for all grade beams of your project.

If you want to cast the grade beams manually by mixture machine then you have to calculate required concrete ingredients for the volume of concrete. Read the following post to know how to calculate concrete ingredients.

Concrete Ingredients

Summary

  • Concrete volume for grade beam (GB1) only= Length x width x height


= (22'-7½" + 22'-2½") x 12" x 20"

= 74.87 cft


  • Concrete volume for column heads = Area of column heads x height of column head


= 15.80 sft x 20"

= 26.39 cft


  • Total volume of concrete for grade beam (GB1) is,


= 74.87 + 26.39

= 101.26 cft.


Symbol and notation used in this post

sft - square feet

cft - cubic feet

' - foot

" - inch

C1, C2, C3 - column symbol

GB1, GB2, GB3 -grade beam symbol


Your Turn:
Do you have any better idea for estimating concrete volume of grade beam? Please share in comment below.
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4 Easy Steps for Making Column Stirrup

A rcc column has two types of bar. One is longitudinal bar and another is horizontal bar.

As horizontal bar we use stirrups and ties in column. Stirrup also has some other name in construction sector. Such as ring, shear reinforcement, etc.

For making stirrup for column you have to calculate the cutting length of bar for stirrup, you have to calculate the number of stirrups and you have to determine the size of stirrup.

You can do this in 4 easy steps.

4 Easy Steps for Making Column Stirrup

Making column's stirrup involves following 4 steps of work.

  1. Determine the size of stirrup
  2. Calculating cutting bar length for stirrup
  3. Calculating the number of stirrups
  4. Bending the bar in stirrup's shape


1. Determine the Size of Stirrup



column stirrup making, column, stirrup, ring, shear reinforcement

See the above image. The column size is 20" x 40". We know the concrete clear cover for reinforcement of column is 1½".

So the length of stirrup will be 40"-2x1½"=37" and width will be 20"-2x1½"=17".

So the size of the stirrup is 37"x17".

2. Calculating Cutting-Bar-Length for Stirrup


Before cutting the bar you have to calculate the cutting bar length for the stirrup.

There are two terms - actual bar length and cutting bar length.

The actual bar length of stirrup is,

2 x length + 2 x width + 2 x hook's length

= 2 x 37" + 2 x 17" + 2 x 3"

= 114" or 9.5'.

Let's discuss a little about hook length.

Hook length is calculated by a formula that is 6db (diameter of bar).

So the hook length for 10mmø bar is,

 6 x 10 = 60 mm. 

But length of hook should not be less than 75mm (as per code).

So the hook length for the stirrup is 3" (75mm = 3").

The actual bar length of the stirrup is 9.5'. But the cutting bar length will be less than the actual bar length.

column stirrup making, column, stirrup, ring

See the above image. That is our stirrup. The stirrup has three 90° bend and two 135° hook.

For each bend, the length of bar will be reduced. There is a certain formula to calculate the reduced length for bend.

The formula needs various calculation process. I'll write about the formula some other day in this blog. So subscribe via Email to get it in your inbox when it happens.

Below I'm giving a chart for reduced length for a 90° bend for different diameter of bar.

10 mmø bar - 1"
12 mmø bar - 1¼"
16 mmø bar - 1½"

Since, we are using 10 mmø bar for our stirrup so the cutting bar length will be,

9.5' - 3 x 1" (bend deduction is ignored for 135° bend).

= 9'-2"

So, you have to cut 9'-2" length of 10mmø bar.

That means, cutting bar length for the stirrup is 9'-2".

3. Calculating the Number of Stirrups


Making column stirrup

See the image above. There are two types of spacing for stirrups. One is S1 and another is S2. S1 is spaced 4" c/c and S2 is spaced 8" c/c.

S1 is provided in the bottom ¼th portion and top ¼th portion of clear column's length. S2 is provided in the middle half portion of clear column's length.

Clear column's length means the height of column between the top of floor to bottom of beam.

You also should provide 2 numbers of stirrup for column into beam-column joint.

Now let's calculate the numbers of stirrups for column.

The floor height is 10'. 

Beam height is 2'

Clear height of column is,

= floor height - beam height

= 10' - 2'

=8'

Number of stirrups are,

= 4'/4" + 4'/8" + 2 + 1 (1 bar should be added for getting the correct number of stirrups.)

= 21 nos.

4. Bending the Bar in Stirrup's Shape

You can use stirrup-making-machine for large project where vast quantity of stirrups are required.

But, we often make stirrups by hand in our project.

For making stirrups by hand you need a stand and a handle.


making column stirrup

See the above image. That is a hand-made stand and a handle. You can make stirrup with these tools.

Just place the rod in the stand and bend the rod with the handle. You have to go for trial and error method to get the desired size of stirrup. Also don't forget to make the hook angle at 135°.

Symbol used in this post
" - inch

' - foot

° - degree

db - diameter of bar

nos - numbers

ø - diameter

c/c - center to center distance


Your Turn
How do you make stirrup bending stand? How do you make the handle? How do you calculate the deduction length for bend of different dia bar?

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10 Easy Steps to Construct a Isolated Footing

There are various types of footing can be constructed for a building. It is structural engineer's responsibility to decide which type of foundation is to be constructed for a building.

As construction professionals, our responsibility is to properly construct footings as designed or suggested in structural drawing.

In this post I'll show you how to construct a isolated footing for a residential building. You can do this in following 10 easy steps.

10 Steps to Construct a Isolated Footing

Follow the steps below to construct a isolated footing.

1. Positioning Footing Location

Footing layout sheet of structural drawing shows dimension related to grid line to place the footing on ground. See the image below.


Mark the footing on ground as shown in the drawing.

2. Earth Excavation

Excavate a trench on earth for the footing. The size of trench should be 1' bigger in both side than the footing size. In the above image we have a footing size of 4' x 5'. For this footing you have to make a trench size of 5' x 6'. It is done for placing and removing shutter easily.

The depth of trench will depend on the earth condition or suggested in the drawing.

3. Preparing the Base

Depending on the soil condition of the base you may require to make brick-flat-soling or cement concrete at footing-base. It is also suggested in the structural drawing.

Read More:
A Checklist for Brick Flat Soling

Sometimes brick-flat-soling isn't suggested in the structural drawing. If you found the base soil isn't suitable enough to construct the footing without brick flat soling then consult with structural designer.

4. Making Form-work

Make form for the footing as specified size. You can use wooden shutter or steel shutter for this purpose. Place the form as showed in the footing layout sheet of structural drawing.

Read More:
Types of Formwork Materials

Check the dimension of form and check if it is properly placed related to grid line. Also make the form-work leakage proof.

5. Placing Reinforcement

I assume you have the required materials for the isolated footing available on the project.

Cut the steel reinforcement as required sizes and provide L-bend  as shown in the structural drawing. You can make the reinforcing net for the footing separately and place in footing position later or you can place the reinforcing bar directly on footing position and bind them there.

One important thing sometimes not shown in the drawing is that - in which direction main reinforcement of footing should be placed - in short direction or in long direction?

In footing, placing main reinforcement doesn't follow the short direction rule. It is related to position of column on footing. Read the following post to know about this.

Placing Main Reinforcement of Footing

6. Providing Cover Block

It is very important to maintain concrete clear cover ont only in footing but also in all RCC members. Provide required cover block in bottom and sides of footing to keep the reinforcing net in position.

7. Placing Column's Reinforcement

Neck column reinforcement should be placed before pouring concrete into footing. Because neck column's reinforcement sits on the bottom reinforcement of footing.

8. Pouring Concrete

Check again the footing and column are properly placed. Check the form of footing is leakage proof. If everything is perfect then move to pouring concrete.

If the concrete volume is large or if you make several footings to cast at a time then you can go for ready-mix concrete. Otherwise you can cast your footing with machine mix concrete. In that case you have to order and stacked the required concrete ingredients on the job-site before.

9. Removing Formwork

On the next day remove the form of footing. If any small honeycomb appears on footing's surface repair those properly. If checked the formwork properly major honeycomb won't appear.

If major honeycomb somehow appeared on the footing then you have to consider breaking the footing and reconstructing.

10. Back Filling

If everything is ok then fill the trench with soil and compact.

Now what? I think, you noticed I back-fill the footing's trench before constructing neck column. Don't do this. Yes. Before back filling you should construct the neck column.

Tour Turn:
If you have anything to say, write it in the comment section below.
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Estimate the Neck Column's Reinforcement With these 8 Easy Steps

For complete estimating and costing solution of a construction project we always use computer aided software like Contractor's office. It is time-saving and accurately deliver us what we want.

But for our day to day construction activities, we always do this manually on the project to find the required materials for our tasks.

In this post I'll show how you can estimate the required reinforcement for neck column in 8 easy steps.

As we know a neck column has two types of bars. One is longitudinal bar and another is stirrup.

Longitudinal bars are those which are vertically places in column and stirrup are those which are horizontally provided around longitudinal bars.

So we'll estimate both types of bars in following 8 easy steps.

8 Easy Steps to Estimate Neck Column's Reinforcement

Let's start with the longitudinal bar first.

1. Determining the Number of Longitudinal Bar

Summarise the numbers of same diameter bar separately.

See the image below. There are different diameter of bars in the column section.


estimating, steel reinforcement, neck column
Neck Column: Not scaled and designed

From this image we have found

25mmø bar - 4 nos
20mmø bar - 6 nos

2. Determine the Length of a Longitudinal Bar 

It is not practical to place the longitudinal bar more than 20' long. Another thing to consider is that the full length of a bar is about 40 feet. If you cut them at middle you'll get 20 feet long bar.

So the length of longitudinal bar for the neck column is 20'.

3. Calculating total length of Longitudinal bars

To find the total length of longitudinal bars multiply the length of each bar with the total number of bars of same diameter.

Total number of 25mmø bar = 4 nos
Total numbers of 20mmø bar = 6 nos
Length of each longitudinal bar= 20'

Total length of longitudinal bars 
25mmø bar= 4 x 20' = 80'
20mmø bar= 6 x 20' = 120'

4. Calculating the Weight of Longitudinal Bar

To calculate the weight of bar you should know the unit weight of different diameter bar.

Read the following post to know how to calculate the unit weight of steel reinforcement.

How to Calculate the Unit Weight of Steel Bars

From the above post, we found the unit weight of,

25mmø bar = 1.172 kg/ft, and
20mmø bar = 0.750 kg/ft.

Now multiply the total length of bar with unit weight to find the total weight of bar.

25mmø bar = 80 x 1.172 = 93.76 kg. Say, 94 kg.
20mmø bar =120 x 0.750 = 90 kg.

Now let's move for estimating stirrups of neck column.

5. Determining the Number of Stirrup

To find the number of stirrup you need to know the length of neck column and the spacing of stirrups.

The length of neck column is the distance between the top face of footing and the bottom face of grade beam. Let's assume, neck column length is 5'.

We can find the stirrups specification from the above image. That is 10mmø [email protected]"c/c.

Now divide the neck column's length with the stirrup's spacing.

That means,

=5'/4"+1 (1 additional number should be added)
=16 nos

6. Determine the Length of a Stirrup's Bar

The neck column size we found from the above image is 43" x 23".

That means, the length of column is 43" and width of column is 23".

If we deduct the concrete clear cover from both side, the length of stirrup will be 43"-6"= 37" and width is 23"-6"=17".

The length of bar for a stirrup is,

2 x length of stirrup + 2 x width of stirrups + 2 x hook's length.
= 2 x 37" + 2 x 17" + 2 x 3"
= 114" [12"=1']
=9.5'

7. Calculating Total Length of Bars for Stirrups

To calculate the total length of bars multiply the numbers of stirrups with the bar length of a stirrup.
Total numbers of stirrup = 16 nos
Bar length for a stirrup= 9.5'
Total length of bars = 16 x 9.5 = 152'

8. Calculating the Weight of stirrups

To calculate the weight of stirrup's bar just multiply the unit weight of 10mmø bar with the total length of stirrup's bar.

Unit weight of 10mmø bar = 0.188 kg/ft
Total length of stirrup's bar= 152'
Weight of stirrups bar= 152 x 0.188=28.58 kg, say 29 kg.

So, the required steel reinforcement for the neck column is,

"25mmø bar = 94 kg
20mmø bar = 90 kg
10mmø bar = 29 kg"

Symbol I used in this post
ø - diameter of bar

c/c - center to center distance

' - foot

" - inch

ft - foot

kg - kilogram

nos - numbers

Your Turn:
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How to Place Steel Reinforcement of Neck Column

As neck columns carry the load of whole building those should be constructed with caution.

What is Neck Column?

The column between footing and grade beam is called neck column. It's also called short column.

In today's construction world almost all columns of a building are designed as reinforced concrete column and steel reinforcement is the backbone of any reinforced concrete member.

In this post I'll describe how to place steel reinforcement of neck column.

Steel reinforcement also expressed as rebar or MS bar or simply rod. Whatever you call this I'll call this steel reinforcement in this post. So that you don't be confused.

Column is constructed on footing. There are various types of footing. No matter whichever footing you are constructing column on, the procedure is same. In this post I'll construct a column on a isolated footing. After learning this you can place steel reinforcement of neck column on any type of footing.

Steel reinforcement of neck column is placed on the bottom reinforcement of footing. Some footings have two layer of reinforcement. One layer is placed in bottom and another layer is placed on top of the footing. Some footing has only one layer of steel reinforcement that is placed at bottom of the footing. Neck column's reinforcement is directly placed on that bottom reinforcement.

Neck column, steel reinforcement

See the above image. There are 3 footing and 5 grid lines. See how the the footings are shown related to grid line. In structural drawings book there is a sheet titled footing layout. On that drawing you will find the details dimension for placing footing.

In the structural drawing book there is also a column layout drawing sheet. On that drawing you'll see how column is placed related to grid lines.

Ok we studied the drawing. Now let's start the work.

In this post I'll not discuss about how to place the footing reinforcement. I assume you've already placed the bottom reinforcement of footing.

Now we'll place the steel reinforcement of neck column.

Let's take F3 footing for example.

In the image it is clearly showed that how the footing should be placed related to grid line and how the column is placed related to footing. In that we found that column is placed 1'-2" and 1'-4" inside from outer face of footing. Now follow the following steps to place the steel reinforcement of neck column.

steel reinforcement, neck column

Placing Steel Reinforcement of Neck Column

Placing steel reinforcement of neck column involves following three steps -

  1. Positioning a stirrup on footing reinforcement
  2. Binding Column's skeleton separatly
  3. Placing column's skeleton on the Stirrup

  1. Positioning a Stirrup on Footing Reinforcement


  • Make a stirrup of 1'-6½"x 3'-2½" size and place that on the bottom reinforcement of footing as shown in the above image.
  • Here I would like to clear one thing that clear cover for reinforcement is 1½ for the column above ground. But it'll be 3" below ground. In that case the stirrup size should be 1'-5"x3'-1½". But I didn't make that size of stirrup. Why? Because I checked the column dimension for above floor. The column size is not changed for upper. In this case the column size for neck column will be 23"x43" even that isn't specified in the drawing. But the stirrup size will remain unchanged.


To know more about the clear cover of reinforcement read the following post.

Concrete Cover for Reinforcement Bar


  • Now check the dimension. It'll be 1'-5½" from short face of column to short face of footing and 1'-3½" from long face of column to long face of footing. You can also use plumb bob to check the position of that stirrup related to grid line.

2. Binding Column's Skeleton Separatly



  • Now place main reinforcement of column. For that you first have to bind the column's main reinforcement with sstirrups in a separate place.
  • The main reinforcement specified in the drawing (above image) as 30-25mmø bar for the column. You need to bind those main steel reinforcement with the column's stirrups to make skeleton of neck column.
  • The length of steel reinforcement bar we buy from the supplier is about 40 feet. You can't place this so long bar in column. So, cut those rod at middle so that you can place them easily.
  • You have to make 90 degree bend of 1'-6" length at one side of each bar as specified in the drawing (above image).
  • Now tie all the main reinforcement with stirrups in a separate place. Stirrup should provided as per drawing ( I didn't shown them in the image above, you'll find them in the column layout of structural drawing).

3. Placing Column's Skeleton on the Stirrup


  • After completing the binding process you can now place that column's skeleton on the stirrup which we placed on the bottom reinforcement of footing in step-1.
  • Now tie that column's skeleton with the footing reinforcement.
  • Again check the column position related to footing or grid line. It is better to check the column position related to grid-line than related to footing.
  • To keep the skeleton of neck column in its position provide enough support.


Now you can move to next step that is shuttering of column.

You can read the following post to know about the column shuttering procedure.

Basic Construction Process of RCC Column

Neck column positioning is very important because if it is shifted somehow your whole building will be shifted. So check the column position carefully.

Your Turn:
You saw the bend of column's main reinforcements are spread outside. But now-a-days, some structural designers suggest that those should be placed in opposite direction. What do you think about that?
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