We know all civil structures are made of concrete, steel, and different other materials. But whenever the structures are made up of concrete there should be included steel in it.
All structures face both compressive as well as the tensile force due to different factors like earthquake, wing, dead load, live load, etc. The structures made with concrete are strong in compression but weak in tension, so to compensate for the tensile force, a steel rod should be included in concrete.
Now, the question is, which resisting power of structure is more? Tensile or compressive? Right, if the structure has more strength in steel then, it will fail due to compression but if the structure has more strength in concrete than steel, then it will fail due to tension force.
Now, you can easily understand the explanation below. Let us see what are Under reinforced section, Over reinforced section, and Balanced section.
Under reinforced section
The RCC section like a beam, column, slab, or strut which are so proportioned that the stress in steel reaches its permissible value earlier than concrete is known as under reinforced section.
- The stress in concrete has lesser than its permissible value.
- Under reinforced sections has a ductile failure i.e The structure does not collapse suddenly, It shows signs of cracks or lines in concrete before complete failure of structural.
- Actual neutral axis shifts above the critical neutral axis.
- Concrete is not subjected to the full value of permissible compression strength.
- It is an inexpensive and economical section.
- Since the failure occurs in steel due to weak in tension, it is also known as primary tension failure or tension failure.
Over reinforced section
The RCC section like a beam, column, slab, or strut which are so proportioned that the stress in concrete reaches its permissible value earlier than steel is known as under reinforced section.
- The stress in steel has lesser than its permissible value.
- Under reinforced sections has brittle failure i.e The structure collapse suddenly, It does not show signs of cracks or lines in concrete before complete failure of structural. So, It is dangerous in nature.
- The actual neutral axis shifts lower the critical neutral axis.
- Steel is not subjected to the full value of permissible compression strength.
- It is costly and uneconomical.
- Since the failure occurs in steel due to weak tension, it is also known as primary compression failure or compression failure.
Balanced section
The RCC section is like a beam, column, slab, or strut which are so proportioned that the stress in steel and concrete reaches its permissible value at the same time.
- The Balance section is also known as the economical section or a critical section.
- The balanced section has a balanced failure i.e the concrete and steel have both equal amounts of strength in tension as well as compression respectively.
I hope this article on “Under reinforced section, Over reinforced section and Balanced section” remains helpful for you.
Happy Learning – Civil Concept
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