Question

If the axial load carrying capacity of a column with lateral ties is PT and for column with spiral reinforcement is PS then as per IS 456:2000, how much more does PS have strength over PT?
1. 1%
2. 2%
3. 3%
4. 5%

Answer 1

Correct Answer - Option 4 : 5%

Explanation

As per IS 456:2000, clause 39.4,

Compression Member with Helical Reinforcement

The strength of compression members with helical reinforcement shall be taken as 1.05 times the strength of similar member with lateral ties provided the condition

 \({Volume\; of\; helical\; reinforcement\over Volume\; of\; the\; core}\lt0.36\left( {\frac{{{A_g}}}{{{A_c}}} - 1} \right)\frac{{{f_{ck}}}}{{{f_y}}}\;\)should be satisfied.

where

Ag = gross area of the section

Ac = area of the core of the helically reinforced column measured to the outside diameter of the helix

fck = characteristic compressive strength of the concrete

fy = characteristic strength of the helical reinforcement but not exceeding 415 N/mm2

Hence, the load-carrying capacity of the column with helical reinforcement is increased by 5% due to increased strength as a result of better confinement.