Definition of clear cover, nominal cover and effective cover
While making the design of reinforced concrete structures, the existing reinforcement is incorporated in the concrete up to a specific distance from the face of the member and it happens due to the following major factors :
The calculation is done based on the following dimensions:-
• Safeguard the reinforcement against the possibility of erosion.
• Enhance the fire resistance capacity of reinforcement.
• Arrange adequate embedded depth to form required stress in reinforcement.
This distance can be calculated in several methods and is measured in different ways and identified by the following terms:-
1. Clear cover: It refers to the distance from the face of the member to the farthest the face of the reinforcement along with shear or torsion Stirrups or links.
2. Nominal cover: It has similarity with clear cover although with other name. This term is applied to the code. It refers to the distance calculated from the face of the member to the farthest face of the reinforcement along with Stirrups or links. It belongs to the dimension demonstrated in drawings and detailing.
3. Effective cover: It refers to the distance that is calculated from the face of the member to the center of area of the main reinforcement i.e. tension or compression reinforcement. It is taken as dimension normally applicable for design calculations.
Effective cover = Clear cover + (Dia of Stirrups/links) + 0.5 * (Dia of main reinforcement bars).
Also,
Effective cover = Overall depth - effective depth.
Given below, the example of the clear cover of a concrete member.
In this example:
In (a):
• x stands for the effective cover.
• t stands for the overall depth.
• d stands for effective depth.
• c stands for clear cover.
In (b):
• d stands for effective depth.
• c stands for clear cover.
• x stands for effective cover.
The effective depth is calculated from the face of the member to the centre of area of main reinforcement. Therefore, Effective cover = Clear cover + (Dia of Stirrups/links) + (Dia of main reinforcement bars) + 0.5*(distance among bars).
