UA 125×75×8 BtB - Section Properties

UA 125×75×8 BtB has a mass of 24.4 kg/m, tabulated to BS EN 1993-1-1:2005 / BS EN 10056-1:1999. A 12 m length therefore weighs about 293 kg, which is the figure to use for a steel take-off or when checking a lift.

The elastic section modulus about the major axis, Wel,y, is 59.2 cm³. Angles are tabulated about their principal (u-u and v-v) axes rather than a plastic major-axis modulus, so the elastic value is the one to design from unless you are working from the principal-axis properties directly.

The second moment of area about the major axis, Iy, is 494 cm⁴. Iy is the value deflection depends on - for a simply supported beam under a uniform load, the midspan deflection is 5wL⁴/384EIy - so on spans where a deflection limit governs rather than strength, this is the number that decides the section.

iy is 4 cm about the major axis and iz is 2.68 cm about the minor axis. Column buckling is governed by the SMALLER value: the slenderness is lambda = L_cr / i, so with iz = 2.68 cm a 0.3 m effective length already gives lambda = 100. Minor-axis buckling almost always controls unless the weak axis is restrained.