Limiting Unbraced Length

For the limit state of inelastic lateral-torsional buckling and doubly symmetric I-shaped members

L_{r} = 1.95 \cdot r_{ts} \cdot \frac{E}{0.7 F_{y}} \cdot \sqrt{\frac{J \cdot C}{S_{x} h_{o}} + \sqrt{(^{\frac{Jc}{S_{x} h_{o}}) 2} + 6.76 (^{\frac{0.7 F_{y}}{E}) 2}}}

E	Modulus of elasticity
F_y	Yield strength
J	Torsional constant
S_x	Elastic section modulus taken about the x-axis
h_o	Distance between the flange centroids

Do you have any questions?