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.
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.
What’s the purpose of Stirrups ?
Stirrups are provided in the beam or columns to cater for the transverse shear.
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 .
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:
For beams mostly rectangular stirrups are used .For columns ,stirrups can be rectangular or square .
Making of stirrups:
1.Manual: The 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.
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.
These give lateral stability to the middle bars of the columns. Cut-links are also provided in a Patli or band beam .
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.
Cutting length of stirrups:
1.A good fitter will always try to use the scrap bars of specified diameter rather than cutting from fresh bars.
2.A 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.
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.