WT 10.5X124 - Section Properties

WT 10.5X124 has a mass of 124 lb/ft (184.5 kg/m), tabulated to AISC Shapes Database v16.0. A 12 m length therefore weighs about 2214 kg, which is the figure to use for a steel take-off or when checking a lift.

WT 10.5X124 has a depth of 11.9 in (302.3 mm), a width of 12.8 in (325.1 mm), a web thickness of 1.1 in (27.9 mm), a flange thickness of 1.99 in (50.5 mm), with a cross-sectional area of 37 in² (238.7 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 1,240.5 cm³, and the elastic modulus Wel,y is 660.4 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 440 kNm before any stability check.

The second moment of area about the major axis, Iy, is 15,317 cm⁴, and about the minor axis Iz is 14,526 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 8 cm about the major axis and iz is 7.8 cm about the minor axis. Column buckling is governed by the SMALLER value: the slenderness is lambda = L_cr / i, so with iz = 7.8 cm a 0.8 m effective length already gives lambda = 100. Minor-axis buckling almost always controls unless the weak axis is restrained.

The St Venant torsion constant It is 1,673 cm⁴, and the warping constant Iw is 0.04 dm⁶. Open sections carry torsion mainly by warping rather than uniform torsion, which is why Iw appears in the lateral-torsional buckling resistance - both values feed M_b,Rd.