Shear reinforcement and its types
The purpose of shear reinforcement is to withstand shear or diagonal tension stresses. Shear reinforcement is generally arranged in the form of stirrups to retain the longitudinal reinforcement as well as obtain the shear to which the structure is dependent on.
Given below, different types of shear reinforcement which are generally found in construction :-
1. Vertical stirrups
2. Bent up bars along with stirrups.
3. Inclined stirrups.
Vertical Stirrups: These belong to the steel bars which are arranged vertically around the tensile reinforcement at proper distance across the length of the beam. Their diameter fluctuates from 6mm to 16mm. The free ends of the stirrups are fastened in the compression zone of the beam to the anchor bars (hanger bar) or the compressive reinforcement.
Based on the magnitude of the shear force that is used to withstand the vertical stirrups may come in one legged, two legged, four legged. It is recommended to apply narrowly spaced stirrups to resist diagonal cracks in a better way. The distance of stirrups adjacent to the supports is fewer relating to spacing close to the mid span because shear force is highest 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 remains fewer near the supports).
These bent up bars mainly withstand diagonal tension. To keep consistency, identical numbers of bars have to be bent on both sides. The bars are bent up at in excess of one point equally along the length of the beam. These bars are normally bent at 45°.
his system is utilized for greater shear forces. The total shear resistance of the beam is computed with the addition of the contribution of bent up bars and vertical stirrups. The contribution of bent up bars is not over half of the total shear reinforcement.
Inclined Stirrups: Inclined stirrups are normally arranged at 45° for resisting diagonal tension. They are arranged all through the length of the beam.