Correct Answer - Option 3 : 45°
Concept:
Anchorage Length:
Anchorage length is the equivalent length of the reinforcement bar which is considered to be available when a straight bar is bent through some angle. It is provided only at the support. Anchorage length is provided if sufficient development length cannot be provided inside the support.
As per IS 456: 2000:
|
Anchorage Value of Bends & Hooks
|
|
Bends
|
45°
|
4ϕ
|
|
90°
|
8ϕ
|
|
135°
|
12ϕ
|
|
Hooks
|
U type Hook (180°)
|
16ϕ
|
Where, ϕ = nominal diameter of the bar
Development Length:
A development length is the amount of bar length that is needed to be embedded or projected into concrete to create desired bond strength between the two materials and also to develop required stress in steel at that section.
As per IS 456: 2000, clause 26.2.1:
The development length is given by:
\({L_d} = \frac{{\phi {\sigma _s}}}{{4{\tau _{bd}}}}\)
where,
ϕ = Nominal diameter of the bar
σs = Stress in the bar at the section considered at design load
τbd = Design bond stress
