Question

A grade S450 steel universal column section with designation 254x254x132 is being considered for a column for a office building. Classify the section. Based on the classification, discuss the suitability of the section as a column.

Answer 1

Provided Data

S 450 - Tensile strength of steel = 986 N/mm², while Yield strength = 814 N/mm²

Universal Column section 254 x 254 x 132.

Overall depth of the I section (H) = 267.3 mm, while web depth (d) = 216.7mm, web thickness(t_w) = 15.6mm

Flange width (b) = 261.3 mm, Flange thickness (t_f) = 25.3mm.

Section Classification

Column member is a compression only member.

As the code for the design is not been specified, I have assumed it to be as per European Standard and the formulas provided are as per EN 1993 - 1 - 1 - 2005.

WEB Check : Refer table 5.2 sheet 1

d/ t_w should be less than 42ɛ , wherein ɛ = (250/f_y) ^0.5 for S450, ɛ = 0.72.

d/t_w for our section is = 216.7/15.6 = 13.89 < 42ɛ = 30.24.

The web section is Non slender.

FLANGE Check : Refer table 5.2 sheet 2

b/ t_f should be less than 14ɛ , wherein ɛ = (250/f_y) ^0.5 for S450, ɛ = 0.72.

b/t_f for our section is = 261.3/25.3 = 10.33 < 14ɛ = 10.08.

The flange section is Non slender.

Hence the overall section UC 254 x 254 x 132 is NON SENDER.

Compression members like columns most probably fail by crushing or buckling. Crushing most probably happens because of the material failure, which is quite common in concrete and not steel. Steel columns are likely to fail by buckling and the usage of non slender sections will most probably reduce it's chances of failing at lighter loads and hence it would be safer for an office use.