WT 5X24.5 - Section Properties

WT 5X24.5 has a mass of 24.5 lb/ft (36.5 kg/m), tabulated to AISC Shapes Database v16.0. A 12 m length therefore weighs about 438 kg, which is the figure to use for a steel take-off or when checking a lift.

WT 5X24.5 has a depth of 4.99 in (126.7 mm), a width of 10 in (254 mm), a web thickness of 0.34 in (8.6 mm), a flange thickness of 0.56 in (14.2 mm), with a cross-sectional area of 7.21 in² (46.5 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 74.07 cm³, and the elastic modulus Wel,y is 39.165 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 26 kNm before any stability check.

The second moment of area about the major axis, Iy, is 416.2 cm⁴, and about the minor axis Iz is 1,944 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 cm about the major axis and iz is 6.45 cm about the minor axis. Column buckling is governed by the SMALLER value: the slenderness is lambda = L_cr / i, so with iz = 6.45 cm a 0.6 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 28.84 cm⁴. Closed sections carry torsion in a shear flow around the perimeter, which makes them far stiffer in torsion than an open section of the same weight and is usually why one is specified.