When we pour the concrete for the different building structures, we provide sufficient cover for the reinforcement bars, by surrounding them with concrete, which we usually say concrete covers.
Now, let us understand, different terms like clear cover, nominal cover, and effective cover, one by one.
Nominal cover :
As per IS: 456(2000), the distance between the nearest reinforcement bar to the unfinished or exposed concrete surface is said as a nominal cover. As per the guidelines, the nominal cover should not be less than the main reinforcement bar of the concrete structure.
Here the unfinished concrete refers to the naked concrete without plaster of any type or without tiles cladding over it.
Clear cover :
The term clear cover carries the same meaning as the nominal cover. In IS: 456(2000), the clear cover is replaced and defined as the nominal cover.
Now, the term clear cover became obsolete.
Effective cover :
The distance between the exposed or unfinished concrete surface to the center of the main reinforcement bar of that particular structure is said as an effective cover. (see the image below ).
Usually, we use the term effective cover, when we do design calculations of the structural loads.
By observing the above diagrams we can say that
Effective cover = [nominal cover + diameter of the stirrups + 1/2 the diameter of the main bar ( or say radius).]
To understand them clearly, let us go through one example.
Eg. The stirrup diameter of the column = 6mm.
Main reinforcement bar diameter = 16mm.
Nominal cover of the column = 40mm.
Then what will be the effective cover?
Effective cover = [40mm + 6mm + (16mm/2)]
= 54 mm.
If you have any doubts regarding this, then you can ask me in the comment section.
To go through the comparison & difference between the several types of building materials & construction costs, click here.
Thank you for going through this article❤. Have a good day😄.
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