Why bentup bars provided in slab

The continuous beam, over hanging beam, etc. all faces two types of the bending moments positive and negative so to resist these moments is beams and in slabs we provide bars and give a technical names which we discuss in detail below.

1. Bent-up bars or known as Crank bars. Which we provide in the ends on the top of the slab or also in the top of the mid supports (if any type of mid support is present) to counter the negative moment called (Hogging) which produce at that sections of the slabs and beams.

2. Different Angles on the crank bar (Means bends) is provide in the slabs. In some cases we just provide Straight Bars at the end on the top of the slab and in some cases we provide angles on the crank bars which is 45°. In some cases the 30° bent is provided when shallow beams are present at the end of the slabs.

3. Normally the length of the crank bar are minimum 300 millimeter and the slope or bend on the crank bars (Bent up bars) are 1: 10.

4. it is actually economization of material. normally, for fixed ended beams positive (sagging) moments are present at the mid span and negative (hogging) moments at the supports. So bottom steel is required at the mid span and top steel resists negative moments at the supports. A bent-up is provided to take the steel on the top at supports as bottom steel is not normally required at at the supports (only nominal steel is sufficient).

5. The strength and deformation capacity of alava with bentup bars compared to slabs without bentup bars can be significantly increased. AdditinalAdd, the flexural reinsforreinfcan be decreased wothouw losing punchupu strength, which leads to an evn larger invreain of the the deformation capacity.

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