What is Stirrup?
A reinforcement used to resist shear and diagonal tension stresses in a concrete structural member.
The term stirrups are usually applied to lateral reinforcement in flexural members and the term ties to lateral reinforcement in vertical compression members.
- In uniaxial compression test of concrete, upon reaching the ultimate load failure of concrete occurs where major cracks line up in the vertical direction and the concrete cube would be split up. The development of vertical cracks involves the expansion of concrete in lateral directions. In case the concrete is confined in lateral directions, it was observed that the formation of vertical cracks would be hindered as indicated in past experiments. As a result, the concrete strength is increased with also a rise in failure strain.
- The above theory is often used in the design of bridge columns. Steel stirrups are installed at around the vertical main reinforcement. Other than the function of shear reinforcement, it helps to avoid the lateral deformation of the interior concrete core so that the strength of the concrete column is increased.
- Also, Open stirrups are provided principally to resist shear forces in concrete beams and they are applied in locations in which the effect of torsion is insignificant. U-shaped stirrups are placed in the tension side of concrete beams in which shear cracks would occur. However, when concrete beams are designed to resist a substantial amount of torsion, closed stirrups should be used instead.
- Concrete beams vary in depth. The deeper the beam, the more shear capacity. When the depth is not adequate, steel stirrups must be added to increase the shear capacity of the beam. These stirrups are usually one piece of steel that is bent into a rectangular shape. Often small-diameter steel is used, such as #3 and #4 rebar. The stirrup typically wraps around the bottom and top bars of the beams.
- Too often the stirrup is not prefabricated and the installer tries to make the stirrup in the field after the horizontal bars are already in place. This is usually obvious because the stirrup is constructed from two pieces with inadequate lap splice. It is much easier and efficient to install a stirrup at the same time the horizontal reinforcement is being installed.
In this interesting session of learning, we are going to provide a detailed theoretical and practical demonstration on how to evaluate the cutting length of 4-legged stirrups.
This video tutorial is brought to you by the renowned youtube channel named L & T – Learning Technology. The demonstrator in this video has nicely demonstrated the detailed calculation step by step with no steps skipped.