Question

The bending stress reduction factor to account for lateral buckling is given by

(a) XLT = 1/{φLT + (φ^2LT – λ^2LT)}

(b) XLT = 1/{φLT  – (φ^2LT + λ^2LT)}

(c) XLT = 1/{φLT  – (φ^2LT + λ^2LT)0.5}

(d) XLT = 1/{φLT + (φ^2LT – λ^2LT)0.5}

The question was posed to me in final exam.

My doubt stems from Design Strength of Laterally Unsupported Beams topic in chapter Design of Beams of Design of Steel Structures

Answer 1

Right choice is (d) XLT = 1/{φLT + (φ^2LT – λ^2LT)0.5}

The best explanation: The bending stress reduction factor to account for lateral buckling is given by XLT = 1/{φLT + (φ^2LT – λ^2LT)0.5}, where φLT depends upon imperfection factor and non dimensional slenderness ratio, λLT is non dimensional slenderness ratio.