Question

Fatigue effect for light and medium duty cranes need not be checked if

(a) Nsc > 10×10^6 [(27/γmft)/γmt].

(b) Nsc < 5×10^6 [(27/γmft)/γmt]^3

(c) Nsc > 5×10^6 [(27/γmft)/γmt]^2

(d) Nsc < 5×10^6 [(27/γmft)γmt].

The question was posed to me in an interview for internship.

This key question is from Gantry Girders & Design of Industrial Buildings in section Gantry Girders, Design of Plate Girders & Industrial Buildings of Design of Steel Structures

Answer 1

Correct answer is (b) Nsc < 5×10^6 [(27/γmft)/γmt]^3

The explanation: Fatigue effect for light and medium duty cranes need not be checked if normal and shear design stress ranges f ≤ (27/γmft) or if actual number of stress cycles, Nsc < 5×10^6 [(27/γmft)/γmt]^3, where f = actual fatigue stress range, γmft = partial safety factor for strength, γmf = partial safety factor for material = 1.10.