Question

An unstiffened beam of ISMB 300 is subjected to transverse loading. I section is free from shear and torsional-flexural buckling. The yield and ultimate tensile strength of steel are 250 Mpa and 410 MPa respectively. The partial safety factor against yielding and ultimate tensile strength are
${\gamma }_{mo}=1.10and{\gamma }_{m1}=1.25$ respectively. Thickness of web is 7.5 mm and thickness flange is 12.4 mm.
$A=7840m{m}^2;Z_{ez}=573\times {10}^{3}m{m}^3;Z_{pz}=651\times {10}^{3}m{m}^3$.
The design flexural capacity of I section about its major axis is_______ kN-m.

Answer 1

ISMB300
$f_y=250MPa,f_u=410MPa$
${\gamma }_{mo}=1.10,{\gamma }_{m1}=1.25$
$Z_{ez}=573\times {10}^{3}m{m}^3,Z_{pz}=651\times {10}^{3}m{m}^3$
When beam is free from flexural torsional buckling & free from web buckling
Design flexural strength of an I-section is equal to fully plastic moment capacity of a section.
$M_d=Z_{pz}\frac{f_y}{{\gamma }_{mo}}=\frac{651\times {10}^3\times 250}{1.10}=147.9kN-m$