The following three types of shear reinforcement are used
- Vertical stirrups
- Bent up bars along with stirrups.
- Inclined stirrups.
Vertical Stirrups
These are the steel bars vertically placed around the tensile reinforcement at suitable spacing along the length of the beam. Their diameter varies from 6mm to 16mm. The free ends of the stirrups are anchored in the compression zone of the beam to the anchor bars (hanger bar) or the compressive reinforcement. Depending upon the magnitude of the shear force to be resisted the vertical stirrups may be one legged, two legged, four legged. It is desirable to use closely spaced stirrups for better prevention of the diagonal cracks. The spacing of stirrups near the supports is less as compared to spacing near the midspan since shear force is maximum at the supports.
- Single Legged Stirrup
- Two Legged Stirrup
- Four Legged Stirrup
- Six Legged Stirrup
Bent up Bars along with Vertical Stirrups
Some of the longitudinal bars in a beam can be bent near the supports where they are not required to resist bending moment (Bending Moment is very less near the supports). These bent up bars resist diagonal tension. Equal number of bars are to be bent on both sides to maintain symmetry. The bars can be bent up at more than one point uniformly along the length of the beam. These bars are usually bent at 45°. This system is used for heavier shear forces. The total shear resistance of the beam is calculated by adding the contribution of bent up bars and vertical stirrups. The contribution of bent up bars is not greater than half of the total shear reinforcement.
Inclined Stirrups
Inclined stirrups are also provided generally at 45° for resisting diagonal tension. They are provided throughout the length of the beam.
