Why crank bars use in RCC beam? Purpose of Crank bars

Hello friends, In this article today I will teach that why crank bars are used in RCC  beam? Really this topic is very important for every civil engineering, and many civil students are confuse in this topic, that what is the main purpose of crank bars in RCC beam. so lets start.

Why Crank Bar’s provide in RCC  Beam?


Bars are bent near the supports at an angle of 45°. The angle bent may also be 30° in shallow beams where the (effective depth< 1.5 breadth).

Crank bars provide to

  1. To resist negative bending moment (hogging)
  2.  To resist shear force which is greater at supports.
  3. To reduce the risk of a brittle failure of slab-column connection.
  4. To increase strength of beam.

Bottom Reinforcement resists the positive bending moment/sagging at the midspan of the beam.

Top Reinforcement resits the negative bending moment at the supports of the beam.

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