Category Archives: column

WHAT IS TOPI & BEAM BOTTOM ?

Good Morning Friends ,

While doing form work for a RCC slab , we start with the beam bottom and then proceed with the topi of the column . This post explains these concepts with easy to follow sketches .

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Calculate Cutting Length for Rings… so easy.

Hi dear friends ,

Good afternoon.

A hearty Welcome to the recently joined followers.

We are now a 585 strong construction team .

Just think , together we can undertake and successfully complete any multi crore project.

By the way , ” Your Question bank ” has been released to many followers on request.

Those who have the desire to obtain a copy , kindly refer to this post :

HOW TO USE THE QUESTION BANK ?:

Today you shall understand the theory and practice behind the stirrups.

Stirrups are also called Links or Rings or Transverse Reinforcement.

These are used for Beams and Columns.

In a Beam , the stirrups are vertical and in a column , these are horizontal.

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RINGS IN A BEAM
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RINGS IN A COLUMN

Each ring has a HOOK at one of the corners which keeps the ring in its shape. The ring shall open if this hook is not given.

Look at this chart to understand about the calculations of the hook length :

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look at this detail usually given in a RCC drawing :

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Now let us solve an example and find out the cutting length for LINKS for a column

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Now let us  take another example :

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Hope you are getting the whole picture :

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Now try your practice with this example.

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Here is the answer :

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Now let us take a complete example :

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Now , let us see what all we need to find out :

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here is the solution :

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Now it is the right time to share with you a simple short cut :

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In case you would like to have a formula that can be used for any cover , any hook length , this is it :

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COLUMN BARS ? ITS DIFFICULT ?

Dear Fellow friends ,

I would like to personally greet the following readers who have  started following this blog since yesterday [ 5th August 2016 ]
1.AMOL AMRUTKAR
2.ANIQUE BIYABANI
3.ABHISHEK DHAMANE
4.KETAN MAHAJAN
5.NITESH VALVI
6.RAJDEEP BISHT
7.SACHIN PAWAR .
Most welcome friends and hope you enjoy reading these posts.

This is the status of the blog as on date :

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Thank you every one for your continuous support to this blog.

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COLUMN BARS ? NO PROBLEM.

Dear Friends ,

This is how you can calculate the cutting length of the main bars of a column .

The junction at the footing is quite typical and hence we shall focus here first.

Let us first look at the photograph :

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Yeah..the Slab is finally cast

Overview:
In this series  we are looking at the various stages in the construction of a building.
So far we have covered from land acquisition up to mobilization and from mass excavation up to columns of the first floor.
This article brings you the intricacies and steps in casting the roof slab.

For the purpose of clarity, the tasks have been grouped under:

A. Pre-concreting care:
B. During concreting care:
C. Post -concreting care:

All the Activities ,however, have been sequenced in a continuous serial nos from 1 to 47.

The activities sequence:

A.Pre-concreting care:

Columns:
1.Columns up to beam bottom
2.Curing of columns
3.marking of beam bottom on columns
4.fixing of runner blocks on columns

Beam bottoms & sides:
5.Fixing of beam bottom
6.Supports below beam bottom
7.Inside face of beam: side fixing

Slab centering:
8.Slab centering in plates
9.Gaps fixing with planks & closing of gaps qith iron strips or masking tape.
10.Fixing of Accrow spans
11.Levelling of centering plates
12.Keeping camber in the slab

Reinforcement laying:
13.laying of beam reinf.
14.Laying of slab reinf.
15.placing chairs below bent up bars

Electrical conduits/ fixtures:
16.Laying electrical conduits/ fan hooks/ down pipes from beams

Sunk portion:
17.Keeping pipe sleeve in the sunk portion for drainage pipe

Securing:
18.Placing cover blocks for beams & slabs
19. Fixing clamps for beams
20.Fixing tie bars in sleeves for deep beams

Joint inspection:
21.Steel measurement and checking
( jointly with clients engineer)
22.Laps counting
23.Extra bars counting

Arrangement for casting:
24.Installing the concrete pump
25.Fixing the pipes for concrete
26.scheduling the transit mixer ( TM)
27.Final checking by consultant
28.pour card approval

B. Care during concreting :

29.Placing concrete
30.Compaction by needle vibrator
31.levelling
32.slab thickness verification
33.finishing
34.Removing excess debris from slab

C.Post concreting care:

35.casting of specimen cubes
36.providing mortar bunds for curing
37.ponding with water
38.striking off beam sides
39. striking off slab centering
40. striking off beam bottom
41.Hacking the concrete surface
42.Sunk portions cleaning
43.waterproofing
44.ponding with water
45.Testing of cubes on 7th & 28th days
46.Reconciliation of materials
47.Bills

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Growing columns in backyard ?

Overview:

Previously , we saw how the action went on from land procurement up to the construction of the basement. [ Read posts  :One ..two..three  and ..start & The building grows above plinth ]

We saw how the specimen cubes were cast and tested on 7th & 28th days from the date of casting.
We also spoke about the characteristic strength of concrete.

We went ahead and listed down all tasks that need to be executed in a building.

We also saw 4 different cases of multidisciplinary coordination.[Read post: Progress continued ..upwards ]

Now let’s go ahead and focus on the next activity ..the columns beams slab.

Background:

Basement roof slab has been cast.
Dowel bars are left protruding from the columns .

Further activities shall be undertaken as follows:

Columns above basement roof slab :

1.Dowel bars shall be lapped with new bars of the same diameter so that  the bars reach above the proposed slab .The dowel bars shall extend at least 45 times the bar diameter above the slab.
( If the bar diameter is 12 mm then we must verify that these extend for a minimum of                       45 x 12 = 540 mm above the slab level.Some situations may require that this lapping distance be maintained as 52 times bar diameter. This detail shall be provided in the RCC  drawings.
The lapping between the bars shall be tied together with the binding wire .
Binding wire is mild steel wire of 1.6 mm diameter . Some builders use galvanized binding wire which is resistant to rusting and hence improves the durability  of concrete.
Hand held portable machines are also available for tying the bars with binding wire .

LAPPING OF COLUMN BARS COMPLETED. STIRRUPS ARE BEING TIED UP.
LAPPING OF COLUMN BARS COMPLETED.
STIRRUPS ARE BEING TIED UP.

2.Stirrups shall be inserted in the main bars of the column and shall be fixed at the  spacing specified in the drawing.

COVER BLOCKS WITH BINDING WIRE FOR TYING WITH THE REINF.BARS
COVER BLOCKS WITH BINDING WIRE FOR TYING WITH THE REINF.BARS

Usually the doughnut shaped cover blocks are fixed in the stirrups so that the cover to the reinforcements is maintained.

COLUMN SHUTTERING IN PLACE. PROPERLY CLAMPED WITH SHIKANJA.
COLUMN SHUTTERING IN PLACE.
PROPERLY CLAMPED WITH SHIKANJA.

3.Form work for the column shall now be fixed on the starter.
Starter is a small piece of column which is cast before the main column is cast.
A wooden  box  of internal size exactly matching with  column size is placed in position. The center lines are checked.and concrete of the specified grade is poured in this mould .

STARTER ON THE TOP OF A TRAPEZOIDAL FOOTING
STARTER ON THE TOP OF A TRAPEZOIDAL FOOTING

The advantages of having a starter are:

a.It is easier to establish & verify the center line  of the starter than of that of the column.

b.It is sturdier to fix the column shuttering if the starter is already in place.
c.The chances of column form work becoming skew are eliminated.

4.After erecting the shuttering for column ,Bracing or supports are fixed ,the verticality is checked on two  sides ( adjoining faces ) with a plumb bob and alignment is checked with the help of a cotton or nylon thread.

5. The column shall be cast after all checks are completed with the approved concrete mix.

6.the column shuttering shall be removed next day and the curing shall be taken up. depending on the climate ( temperature and humidity ), the curing can be done either by spraying water at intermediate intervals or by wrapping column with hessian clothe and keeping it wet.

COLUMNS BEING CURED WITH WET HESSIAN CLOTHES [ THE OWNER PROUDLY LOOKS ON ]
COLUMNS BEING CURED WITH WET HESSIAN CLOTHES
[ THE OWNER PROUDLY LOOKS ON ]
Author’s note :

Thank you for reading so far with total attention.

In the next article we shall speak about the entire process involved in the casting of the roof slab.

Till then , bye bye

Take care.

AUTHOR with Construction personnel at a site
AUTHOR with Construction personnel at a site