Question

How much percentage increase of permissible stress is allowed when dead load, live load and wind load are considered together in working stress method?

(a) 50%

(b) 33%

(c) 40%

(d) 60%

This question was posed to me in homework.

My doubt is from Design Considerations, Analysis & Methods topic in section Basics of Structural Design of Design of Steel Structures

Answer 1

Right answer is (b) 33%

The explanation: In working stress method, working stress ≤ permissible stress.

Stress due to dead load + live load ≤ permissible stress

Stress due to dead load + wind load ≤ permissible stress

Stress due to dead load + live load + wind load ≤ 1.33 permissible stress.