Formulas: Lateral-Torsional Buckling

Formula 1

The maximum beam flexural strength, $M_{n}=1.5 M_{y}$, will occur when the theoretical buckling moment, $M_{c r}$, reaches or exceeds $7.7 M_{y} . M_{y}$ is the moment at first yield in Equations F10-2 and F10-3, the same as the $M_{y}$ in Equation F10-1.

Formula 2

Formula 3

(the general expression for the critical moment of an equal-leg angle) with $\theta=-45^{\circ}$ for the condition where the angle tip stress is compressive (see Figure C-F10.3).

Formula 4

Using $\theta=45^{\circ}$ in Equation C-F10-1, the resulting expression is Equation F10-5b with a +1 instead of -1 as the last term.

Formula 5

This is based on $M_{c r}$ given in Equation C-F10-1 with $\theta=0^{\circ}$.

Formula 6

Lateral-torsional buckling will reduce the stress below $1.5 M_{y}$ only for $M_{c r}<7.7 M_{y}$.

Formula 7

For an equal-leg angle bent about its major principal axis, this occurs for $L_{b} / t \geq 3,700 C_{b} / F_{y}$.

Found in

• SINGLE ANGLES