Why Bent Up Bars are provided and Cutting Length of bent up bars

Why Bent Up Bars are Provided in Beam and Slab

“ It is economical of material .normally for fixed beams and slab postive moments (Sagging) momments are mid span and Negateive moments (Hogging) at the Supports

so Bottom Steel is required at mid span and top steel resist negative moment at support "

• To resist negative bending momemt ie Hoggin
• To resist shear forc which is greater at Supports
• To reduce risk of brittle failure of slab and column connection

How much Bent Up Provided

 

1- Continuous slab ­ L/5

2- For End Support ­L/7

Cutting Length of Bent up Bars

• Extra length = d/sin45-d= 0.42d for one bent up

• Extra Length of 2 bent up = 2x0.42d = 0.84d

• d= D – (top+bottom cover)