Question

If a square column section of size 400 mm × 400 mm is reinforced with 4 bars of 25 mm and 4 bars of 16 mm diameter, then the transverse steel should be :
1. 6 mm dia @ 250 mm c/c
2. 6 mm dia @ 300 mm c/c
3. 8 mm dia @ 250 mm c/c
4. 8 mm dia @ 300 mm c/c 

Answer 1

Correct Answer - Option 3 : 8 mm dia @ 250 mm c/c

Explanation

Given,

Reinforcement bars of 25 mm - 4 bars & 16 mm - 4 bars

Column size 400 mm × 400 mm

The maximum longitudinal bar diameter long for compression member is ϕ 25 mm.

Transverse Reinforcement:

i) Diameter (ϕ)

ϕ ≥ Max of \({\frac{{{\phi _{max}}_{longitudinal}}}{4},\;6}\)

ϕ  ≥ Max of \({\frac{{25}}{4},6}\)

⇒  ϕ ≥ 6.25 mm

∴ Adopting ϕ = 8 mm

As in the option dia > 6 mm is 8 mm so it would be the more appropriate answer.

ii) Spacing (s) of the traverse reinforcement:

s ≤ min of \(\left\{ {\begin{array}{*{20}{c}} {least\;lateral\;dimension\;}\\ {16 × {\phi _{{\rm{longitudina}}{{\rm{l}}_{{\rm{min}}}}}}}\\ {300\;mm} \end{array}} \right.\)

s ≤ min of \(\left\{ {\begin{array}{*{20}{c}} {400\;mm}\\ {16 × 16 = 256\;mm}\\ {300\;mm} \end{array}} \right.\)

∴ Adopting spacing (s) = 250 mm

∴ ϕ = 8 mm and S = 250 mm is the right answer.