2L 4X3-1-2X1-4X3-4SLBB - Section Properties

2L 4X3-1-2X1-4X3-4SLBB has a mass of 12.4 lb/ft (18.5 kg/m), tabulated to AISC Shapes Database v16.0. A 12 m length therefore weighs about 222 kg, which is the figure to use for a steel take-off or when checking a lift.

2L 4X3-1-2X1-4X3-4SLBB has a depth of 3.5 in (88.9 mm), with a cross-sectional area of 3.64 in² (23.5 cm²). These are the nominal dimensions from AISC Shapes Database v16.0; rolling tolerances apply to the delivered section.

The plastic section modulus about the major axis, Wpl,y, is 45.884 cm³, and the elastic modulus Wel,y is 26.055 cm³. Wpl,y is what sets the moment capacity of a Class 1 or 2 section: M_pl,Rd = Wpl,y x f_y / gamma_M0, so at S355 with gamma_M0 = 1.0 this section reaches about 16 kNm before any stability check.

The second moment of area about the major axis, Iy, is 171.9 cm⁴, and about the minor axis Iz is 586.9 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 2.72 cm about the major axis and iz is 5 cm about the minor axis. Column buckling is governed by the SMALLER value: the slenderness is lambda = L_cr / i, so with iz = 5 cm a 0.5 m effective length already gives lambda = 100. Minor-axis buckling almost always controls unless the weak axis is restrained.