How To Provide Top Extra Bar & Bottom Extra Bar In RCC Beam | अक्सर यह गलती हो जाती है |

Why do we provide top and bottom extra bars in a beam?
Generally,in beams we provide top reinforcement in compression zone and bottom reinforcement in tension zone.

Both top and bottom reinforcements provide resistance to moments since beams are primarily flexural members.

Suppose,if the top and bottom reinforcements are not sufficient to resist the moments of the beam in that case we have to provide additional extra extra bars in top and bottom of the beam according to the requirement.
1) Extra top bar are provided to increase tensile strength of beam ( to control negative moment) at support.

2) To resist diagonal tension stress and in order to prevent inclined cracks to occur by action of maximum shear stresses which concrete fails to resist

A beam with monolethic joint(like in concrete) is having positive moment between supports and negitive moment at supports.

Concrete is having high strength in compression but very week in tension.

Positive moment (bending towards bottom side) creats tention at the bottom and compression at top in between the supports.

On the other hand negtive moment (bending towards top side) creats tention at the top and compression at bottom on the supports.

Bottom bars are provided to increase tensile strenght of beam (to control positive moment) at bottom side in longitudinal direction in between the supports.

Top bars are provided to increase tensile strenght of beam (to control negative moment) at top side in longitudinal direction at the supports.



How To Provide Top Extra Bar & Bottom Extra Bar In RCC Beam | अक्सर यह गलती हो जाती है |

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AVINASH SHARMA

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