UA 100×50×8 BtB - Section Properties

UA 100×50×8 BtB has a mass of 17.9 kg/m, tabulated to BS EN 1993-1-1:2005 / BS EN 10056-1:1999. A 12 m length therefore weighs about 215 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 36.4 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 232 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 3.19 cm about the major axis and iz is 1.73 cm about the minor axis. Column buckling is governed by the SMALLER value: the slenderness is lambda = L_cr / i, so with iz = 1.73 cm a 0.2 m effective length already gives lambda = 100. Minor-axis buckling almost always controls unless the weak axis is restrained.