- Lateral-torsional buckling of the unsupported length of the beam/member before the cross-section develops the plastic moment Mp.
- Local buckling of the individual plates (flanges and webs) of the cross-section before they develop the compressive yield stress Fy.
Design of Steel Beam:
The development of a plastic stress distribution over the cross-section can be hindered by two different length effects:
Lateral Torsional Buckling
- Beams are generally proportioned such that moment of inertia about the major principal axis is considerably larger than that of minor axis.
- This is done to make
As result they are weak in resistance to TORSION and BENDING about the Minor axis
If bending about Y-axis is not prevented by bracing, the beam will undergo Lateral-Torsional-Buckling before the bending moment capacity of the beam is achieved.
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