Bent up bars: Are the main reinforcements bent at a suitable angle to act as shear reinforcements. Reinforcements are bent up to the supports/ends where greater compressive force occurs.
Bars Are Bend Near At Support To
1- To resist shear force.
2-To resist (NBM) adjacent at supports.
3- To increment the strength of RCC in the slab.
4- Bent Up bar can abate the amount of steel.
5- Bent up bars in the slab is more strong form normal slab.
6- Bent up bars sufficiently increase the deformation capacity of slabs as compared to those not having bars bent.
7- By extending bars up to supports, we can also lower the risk of brittle failure due to higher compressive stresses causing the structure to collapse.
There are two patterns to bend the bars
1- Single lattice system
2- Double lattice system
Bent up bars (any type) are always provided with vertical or inclined stirrups.
Bent up bars are used for the economization of material. Normally, for fixed ended Slabs positive moments are present at the mid-span and negative moments at the supports.
1- Bent Bars are provided at the top portion of the supports
2- As per the IS code the bend up bars should not be designed to take more than 50% shear force i.e. The bent up bars can be designed to a maximum of 50% of shear force and the remaining should be taken by the sheer stirrups either inclined or vertical stirrups.