The limit of proportionality in the material of a structural steel member, when subjected to simple tension, is 280 N/mm2. The principal stresses in the member are σ1=122 N/mm2 (Tensile) and σ2=60 N/mm2 (Compressive). μ=0.3. According to maximum strain theory, the factor of safety is
σ1−μσ2≤σyF
⇒122−0.3×(−60)≤280F
⇒F≤280140
⇒F≤2