Caught up in Stirrups ?

Stirrups are an integral part of the reinforcement.

In fact, Beams & columns are incomplete without stirrups.

This article gives you a hands-on information on stirrups

After reading this article, you shall be able to understand the concept of stirrups with ease.

Overview:

What’s a stirrup ?
Stirrup is a ring which binds the bars together. The ring could be square rectangular or circular,depending on the geometry of the beam or column.
Beams shall be mostly rectangular whereas columns could be square rectangular or circular. In case of columns of other shapes likes hexagonal or octagonal, we shall have to take that shape into account.

STIRRUPS ON A PLINTH BEAM
STIRRUPS ON A PLINTH BEAM

What’s the purpose of Stirrups ?
Stirrups are provided in the beam or columns to cater for the transverse shear.

STIRRUPS ON A COLUMN
STIRRUPS ON A COLUMN

Position of stirrups:
Transverse shear shall be vertical in beams and hence the stirrups provided are vertical. Where as in columns, the Transverse shear shall be Horizontal in and hence the stirrups provided are Horizontal .

What’s in the name ?
The fitters invariably call it a ring but all RCC drawings shall mention this as stirrups. Although technically, the stirrups for a circular column or pile should be called as Rings .

CIRCULAR RINGS FOR PILESSTORED  IN THE YARD
CIRCULAR RINGS FOR PILESSTORED IN THE YARD

AUTHOR SHOWING THE PILE REINFORCEMENT  [ NOT YET POSITIONED ] FOR FLYOVER AT PUNE.
AUTHOR SHOWING THE PILE REINFORCEMENT
[ NOT YET POSITIONED ] FOR FLYOVER AT PUNE.
What’s a hook ?
Its the extra length left at the 4th corner so that the stirrup retains its  shape.

Not clear ?
Imagine you have a straight bar and you have to make a square or rectangular stirrup out of it. You bend this bar at 3 junctions and you have a rectangular stirrup with you. But you shall notice that you cannot retain this shape since the stirrup shall open up at the 4th junction.

How much is Hook length ?
Usually this is specified as 9D or 10D where D is the bar diameter to b3 ues

Types of stirrups:

STIRRUPS FOR A SLOPING COLUMN. [Note that each stirrup has to be made of a different length to suit the slope ]
STIRRUPS FOR A SLOPING COLUMN.
[Note that each stirrup has to be made of a different length to suit the slope ]

Full stirrups:
For beams mostly rectangular stirrups are used .For columns ,stirrups can be rectangular or square .

Making of stirrups:
1.ManualThe fitter prepares a wooden or concrete or mild steel stand  ( known as Thiyya or Adda in Hindi ) at the reinforcement yard on the site.
Headless Iron nails or studs are fixed on the base with distances matching with the bends in the given stirrup.
The cut lengths for the stirrups are kept ready. Fitter manually bends  each bar on the stand to make individual stirrup.                                                          

TYPICAL THIYYA OR ADDA [ JIG /FIXTURE ] used by the fitters for the bending of reinforcement bars
TYPICAL THIYYA OR ADDA [ JIG /FIXTURE ] used by the fitters for the bending of reinforcement bars
2.Automatic stirrup forming machine:

The geometry & size of the stirrup is entered into the computer programme.
The stirrup rod in the form of coils is stored on a spool behind the machine.
The material is fwd in the machine. Machine draws the bar,straightens it,cuts it & bends it at the specific locations to make the stirrups.

 Cut links or Cut stirrups:

These give lateral stability to the middle bars of the columns. Cut-links are also provided in a Patli or band beam .

STIRRUPS FOR THE PATLI [ BAND BEAM ]. look at the small square stirrups @ 300 mm c/c.
STIRRUPS FOR THE PATLI [ BAND BEAM ].
look at the small square stirrups @ 300 mm c/c.

Making of cut– links:
Cut links are made with a straight bar with hooks on both side. The hooks are twisted on different sides for better grip.

Patli or band beam on the top of a partition wall .
Patli or band beam on the top of a partition wall .

Cutting length of stirrups:

Steps :
1.Cutting length of the stirrups shall be the periphery of the stirrups plus hook length.
2.For a given cover , we can find out the width & depth of the stirrups
3. find the periphery of the stirrup.
4.Add 120 mm for the hook length.
5.In case the RCC drawing specifies hook length = 10 D , where D is the stirrup bar diameter.
{ for a bar diameter of 8mm , the hook length shall be 10 x 8 = 80 mm.so total hook length shall be 2 x 80 = 160 mm.]
EXAMPLE ;
Beam size : 300 mm x 600 mm.
Stirrup bar size : 10 mm
beam cover : 25 mm.
stirrup size :
width : 300 – ( 25+25 ) =250 mm.
Septh : 600-(25+25 )  = 550 mm.
Periphery of stirrup : 250+250+550+550 = 1600 mm.
Hook length : 2 x 10 x 10 = 200 mm.
Cutting length of stirrup : 1600 +200 = 1800 mm.

Tips:
1.A good fitter will always try to use the scrap bars of specified diameter rather than cutting from fresh bars.

2.good RCC consultant shall specify beam & column sizes in such a way that variations are kept to minimum.

3.It is better to have standard sizes of columns & beams which reduces confusion while binding stirrups and also helps in material planning.

WITH MY MOST IMPORTANT ASSETS , MY MOTIVATORS , MY STUDENTS..  I AM BECAUSE OF YOU
WITH MY MOST IMPORTANT ASSETS ,
MY MOTIVATORS , MY STUDENTS..
I AM BECAUSE OF YOU

Gratitude :The author wishes to thankfully acknowledge for the photographs which have been either captured by students or author himself  at various construction sites at different times. 

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5 thoughts on “Caught up in Stirrups ?”

    1. Hello ,
      Great comment.
      Yeah its true that I have not talked about the elongation reduction in this post.
      I find that discussing about the intricacies of allowance for elongation during the
      preliminary stage of teaching creates a jumbling in the mind of readers .
      However, may be we can add another post on this post.

      Would you like to accept my invitation of writing a guest post for us on this topic ?
      We shall welcome this.
      Do consider this invitation.

      Regards

      Like

  1. your site is really very knowledge full, beacause I searching constantly these things from the previous some month,,,,,,,hope you will collect these things into a form of book; for people like me,

    Like

  2. your site is really very knowledge full, beacause I searching constantly these things from the previous some month,,,,,,,hope you will collect these things into a form of book; for people like me

    Like

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